cgroup: rename Documentation/cgroups/ to Documentation/cgroup-legacy/

In preparation for adding cgroup2 documentation, rename
Documentation/cgroups/ to Documentation/cgroup-legacy/.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

14 files changed, 0 insertions, 4319 deletions

diff --git a/Documentation/cgroups/00-INDEX b/Documentation/cgroups/00-INDEX
deleted file mode 100644
index 3f5a40f57d4a..000000000000
--- a/Documentation/cgroups/00-INDEX
+++ /dev/null
@@ -1,30 +0,0 @@
-00-INDEX
-	- this file
-blkio-controller.txt
-	- Description for Block IO Controller, implementation and usage details.
-cgroups.txt
-	- Control Groups definition, implementation details, examples and API.
-cpuacct.txt
-	- CPU Accounting Controller; account CPU usage for groups of tasks.
-cpusets.txt
-	- documents the cpusets feature; assign CPUs and Mem to a set of tasks.
-devices.txt
-	- Device Whitelist Controller; description, interface and security.
-freezer-subsystem.txt
-	- checkpointing; rationale to not use signals, interface.
-hugetlb.txt
-	- HugeTLB Controller implementation and usage details.
-memcg_test.txt
-	- Memory Resource Controller; implementation details.
-memory.txt
-	- Memory Resource Controller; design, accounting, interface, testing.
-net_cls.txt
-	- Network classifier cgroups details and usages.
-net_prio.txt
-	- Network priority cgroups details and usages.
-pids.txt
-	- Process number cgroups details and usages.
-resource_counter.txt
-	- Resource Counter API.
-unified-hierarchy.txt
-	- Description the new/next cgroup interface.
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
deleted file mode 100644
index 52fa9f353342..000000000000
--- a/Documentation/cgroups/blkio-controller.txt
+++ /dev/null
@@ -1,455 +0,0 @@
-				Block IO Controller
-				===================
-Overview
-========
-cgroup subsys "blkio" implements the block io controller. There seems to be
-a need of various kinds of IO control policies (like proportional BW, max BW)
-both at leaf nodes as well as at intermediate nodes in a storage hierarchy.
-Plan is to use the same cgroup based management interface for blkio controller
-and based on user options switch IO policies in the background.
-
-Currently two IO control policies are implemented. First one is proportional
-weight time based division of disk policy. It is implemented in CFQ. Hence
-this policy takes effect only on leaf nodes when CFQ is being used. The second
-one is throttling policy which can be used to specify upper IO rate limits
-on devices. This policy is implemented in generic block layer and can be
-used on leaf nodes as well as higher level logical devices like device mapper.
-
-HOWTO
-=====
-Proportional Weight division of bandwidth
------------------------------------------
-You can do a very simple testing of running two dd threads in two different
-cgroups. Here is what you can do.
-
-- Enable Block IO controller
-	CONFIG_BLK_CGROUP=y
-
-- Enable group scheduling in CFQ
-	CONFIG_CFQ_GROUP_IOSCHED=y
-
-- Compile and boot into kernel and mount IO controller (blkio); see
-  cgroups.txt, Why are cgroups needed?.
-
-	mount -t tmpfs cgroup_root /sys/fs/cgroup
-	mkdir /sys/fs/cgroup/blkio
-	mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
-
-- Create two cgroups
-	mkdir -p /sys/fs/cgroup/blkio/test1/ /sys/fs/cgroup/blkio/test2
-
-- Set weights of group test1 and test2
-	echo 1000 > /sys/fs/cgroup/blkio/test1/blkio.weight
-	echo 500 > /sys/fs/cgroup/blkio/test2/blkio.weight
-
-- Create two same size files (say 512MB each) on same disk (file1, file2) and
-  launch two dd threads in different cgroup to read those files.
-
-	sync
-	echo 3 > /proc/sys/vm/drop_caches
-
-	dd if=/mnt/sdb/zerofile1 of=/dev/null &
-	echo $! > /sys/fs/cgroup/blkio/test1/tasks
-	cat /sys/fs/cgroup/blkio/test1/tasks
-
-	dd if=/mnt/sdb/zerofile2 of=/dev/null &
-	echo $! > /sys/fs/cgroup/blkio/test2/tasks
-	cat /sys/fs/cgroup/blkio/test2/tasks
-
-- At macro level, first dd should finish first. To get more precise data, keep
-  on looking at (with the help of script), at blkio.disk_time and
-  blkio.disk_sectors files of both test1 and test2 groups. This will tell how
-  much disk time (in milliseconds), each group got and how many sectors each
-  group dispatched to the disk. We provide fairness in terms of disk time, so
-  ideally io.disk_time of cgroups should be in proportion to the weight.
-
-Throttling/Upper Limit policy
------------------------------
-- Enable Block IO controller
-	CONFIG_BLK_CGROUP=y
-
-- Enable throttling in block layer
-	CONFIG_BLK_DEV_THROTTLING=y
-
-- Mount blkio controller (see cgroups.txt, Why are cgroups needed?)
-        mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
-
-- Specify a bandwidth rate on particular device for root group. The format
-  for policy is "<major>:<minor>  <bytes_per_second>".
-
-        echo "8:16  1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
-
-  Above will put a limit of 1MB/second on reads happening for root group
-  on device having major/minor number 8:16.
-
-- Run dd to read a file and see if rate is throttled to 1MB/s or not.
-
-		# dd if=/mnt/common/zerofile of=/dev/null bs=4K count=1024
-		# iflag=direct
-        1024+0 records in
-        1024+0 records out
-        4194304 bytes (4.2 MB) copied, 4.0001 s, 1.0 MB/s
-
- Limits for writes can be put using blkio.throttle.write_bps_device file.
-
-Hierarchical Cgroups
-====================
-
-Both CFQ and throttling implement hierarchy support; however,
-throttling's hierarchy support is enabled iff "sane_behavior" is
-enabled from cgroup side, which currently is a development option and
-not publicly available.
-
-If somebody created a hierarchy like as follows.
-
-			root
-			/  \
-		     test1 test2
-			|
-		     test3
-
-CFQ by default and throttling with "sane_behavior" will handle the
-hierarchy correctly.  For details on CFQ hierarchy support, refer to
-Documentation/block/cfq-iosched.txt.  For throttling, all limits apply
-to the whole subtree while all statistics are local to the IOs
-directly generated by tasks in that cgroup.
-
-Throttling without "sane_behavior" enabled from cgroup side will
-practically treat all groups at same level as if it looks like the
-following.
-
-				pivot
-			     /  /   \  \
-			root  test1 test2  test3
-
-Various user visible config options
-===================================
-CONFIG_BLK_CGROUP
-	- Block IO controller.
-
-CONFIG_DEBUG_BLK_CGROUP
-	- Debug help. Right now some additional stats file show up in cgroup
-	  if this option is enabled.
-
-CONFIG_CFQ_GROUP_IOSCHED
-	- Enables group scheduling in CFQ. Currently only 1 level of group
-	  creation is allowed.
-
-CONFIG_BLK_DEV_THROTTLING
-	- Enable block device throttling support in block layer.
-
-Details of cgroup files
-=======================
-Proportional weight policy files
---------------------------------
-- blkio.weight
-	- Specifies per cgroup weight. This is default weight of the group
-	  on all the devices until and unless overridden by per device rule.
-	  (See blkio.weight_device).
-	  Currently allowed range of weights is from 10 to 1000.
-
-- blkio.weight_device
-	- One can specify per cgroup per device rules using this interface.
-	  These rules override the default value of group weight as specified
-	  by blkio.weight.
-
-	  Following is the format.
-
-	  # echo dev_maj:dev_minor weight > blkio.weight_device
-	  Configure weight=300 on /dev/sdb (8:16) in this cgroup
-	  # echo 8:16 300 > blkio.weight_device
-	  # cat blkio.weight_device
-	  dev     weight
-	  8:16    300
-
-	  Configure weight=500 on /dev/sda (8:0) in this cgroup
-	  # echo 8:0 500 > blkio.weight_device
-	  # cat blkio.weight_device
-	  dev     weight
-	  8:0     500
-	  8:16    300
-
-	  Remove specific weight for /dev/sda in this cgroup
-	  # echo 8:0 0 > blkio.weight_device
-	  # cat blkio.weight_device
-	  dev     weight
-	  8:16    300
-
-- blkio.leaf_weight[_device]
-	- Equivalents of blkio.weight[_device] for the purpose of
-          deciding how much weight tasks in the given cgroup has while
-          competing with the cgroup's child cgroups. For details,
-          please refer to Documentation/block/cfq-iosched.txt.
-
-- blkio.time
-	- disk time allocated to cgroup per device in milliseconds. First
-	  two fields specify the major and minor number of the device and
-	  third field specifies the disk time allocated to group in
-	  milliseconds.
-
-- blkio.sectors
-	- number of sectors transferred to/from disk by the group. First
-	  two fields specify the major and minor number of the device and
-	  third field specifies the number of sectors transferred by the
-	  group to/from the device.
-
-- blkio.io_service_bytes
-	- Number of bytes transferred to/from the disk by the group. These
-	  are further divided by the type of operation - read or write, sync
-	  or async. First two fields specify the major and minor number of the
-	  device, third field specifies the operation type and the fourth field
-	  specifies the number of bytes.
-
-- blkio.io_serviced
-	- Number of IOs (bio) issued to the disk by the group. These
-	  are further divided by the type of operation - read or write, sync
-	  or async. First two fields specify the major and minor number of the
-	  device, third field specifies the operation type and the fourth field
-	  specifies the number of IOs.
-
-- blkio.io_service_time
-	- Total amount of time between request dispatch and request completion
-	  for the IOs done by this cgroup. This is in nanoseconds to make it
-	  meaningful for flash devices too. For devices with queue depth of 1,
-	  this time represents the actual service time. When queue_depth > 1,
-	  that is no longer true as requests may be served out of order. This
-	  may cause the service time for a given IO to include the service time
-	  of multiple IOs when served out of order which may result in total
-	  io_service_time > actual time elapsed. This time is further divided by
-	  the type of operation - read or write, sync or async. First two fields
-	  specify the major and minor number of the device, third field
-	  specifies the operation type and the fourth field specifies the
-	  io_service_time in ns.
-
-- blkio.io_wait_time
-	- Total amount of time the IOs for this cgroup spent waiting in the
-	  scheduler queues for service. This can be greater than the total time
-	  elapsed since it is cumulative io_wait_time for all IOs. It is not a
-	  measure of total time the cgroup spent waiting but rather a measure of
-	  the wait_time for its individual IOs. For devices with queue_depth > 1
-	  this metric does not include the time spent waiting for service once
-	  the IO is dispatched to the device but till it actually gets serviced
-	  (there might be a time lag here due to re-ordering of requests by the
-	  device). This is in nanoseconds to make it meaningful for flash
-	  devices too. This time is further divided by the type of operation -
-	  read or write, sync or async. First two fields specify the major and
-	  minor number of the device, third field specifies the operation type
-	  and the fourth field specifies the io_wait_time in ns.
-
-- blkio.io_merged
-	- Total number of bios/requests merged into requests belonging to this
-	  cgroup. This is further divided by the type of operation - read or
-	  write, sync or async.
-
-- blkio.io_queued
-	- Total number of requests queued up at any given instant for this
-	  cgroup. This is further divided by the type of operation - read or
-	  write, sync or async.
-
-- blkio.avg_queue_size
-	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
-	  The average queue size for this cgroup over the entire time of this
-	  cgroup's existence. Queue size samples are taken each time one of the
-	  queues of this cgroup gets a timeslice.
-
-- blkio.group_wait_time
-	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
-	  This is the amount of time the cgroup had to wait since it became busy
-	  (i.e., went from 0 to 1 request queued) to get a timeslice for one of
-	  its queues. This is different from the io_wait_time which is the
-	  cumulative total of the amount of time spent by each IO in that cgroup
-	  waiting in the scheduler queue. This is in nanoseconds. If this is
-	  read when the cgroup is in a waiting (for timeslice) state, the stat
-	  will only report the group_wait_time accumulated till the last time it
-	  got a timeslice and will not include the current delta.
-
-- blkio.empty_time
-	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
-	  This is the amount of time a cgroup spends without any pending
-	  requests when not being served, i.e., it does not include any time
-	  spent idling for one of the queues of the cgroup. This is in
-	  nanoseconds. If this is read when the cgroup is in an empty state,
-	  the stat will only report the empty_time accumulated till the last
-	  time it had a pending request and will not include the current delta.
-
-- blkio.idle_time
-	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
-	  This is the amount of time spent by the IO scheduler idling for a
-	  given cgroup in anticipation of a better request than the existing ones
-	  from other queues/cgroups. This is in nanoseconds. If this is read
-	  when the cgroup is in an idling state, the stat will only report the
-	  idle_time accumulated till the last idle period and will not include
-	  the current delta.
-
-- blkio.dequeue
-	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y. This
-	  gives the statistics about how many a times a group was dequeued
-	  from service tree of the device. First two fields specify the major
-	  and minor number of the device and third field specifies the number
-	  of times a group was dequeued from a particular device.
-
-- blkio.*_recursive
-	- Recursive version of various stats. These files show the
-          same information as their non-recursive counterparts but
-          include stats from all the descendant cgroups.
-
-Throttling/Upper limit policy files
------------------------------------
-- blkio.throttle.read_bps_device
-	- Specifies upper limit on READ rate from the device. IO rate is
-	  specified in bytes per second. Rules are per device. Following is
-	  the format.
-
-  echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.throttle.read_bps_device
-
-- blkio.throttle.write_bps_device
-	- Specifies upper limit on WRITE rate to the device. IO rate is
-	  specified in bytes per second. Rules are per device. Following is
-	  the format.
-
-  echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.throttle.write_bps_device
-
-- blkio.throttle.read_iops_device
-	- Specifies upper limit on READ rate from the device. IO rate is
-	  specified in IO per second. Rules are per device. Following is
-	  the format.
-
-  echo "<major>:<minor>  <rate_io_per_second>" > /cgrp/blkio.throttle.read_iops_device
-
-- blkio.throttle.write_iops_device
-	- Specifies upper limit on WRITE rate to the device. IO rate is
-	  specified in io per second. Rules are per device. Following is
-	  the format.
-
-  echo "<major>:<minor>  <rate_io_per_second>" > /cgrp/blkio.throttle.write_iops_device
-
-Note: If both BW and IOPS rules are specified for a device, then IO is
-      subjected to both the constraints.
-
-- blkio.throttle.io_serviced
-	- Number of IOs (bio) issued to the disk by the group. These
-	  are further divided by the type of operation - read or write, sync
-	  or async. First two fields specify the major and minor number of the
-	  device, third field specifies the operation type and the fourth field
-	  specifies the number of IOs.
-
-- blkio.throttle.io_service_bytes
-	- Number of bytes transferred to/from the disk by the group. These
-	  are further divided by the type of operation - read or write, sync
-	  or async. First two fields specify the major and minor number of the
-	  device, third field specifies the operation type and the fourth field
-	  specifies the number of bytes.
-
-Common files among various policies
------------------------------------
-- blkio.reset_stats
-	- Writing an int to this file will result in resetting all the stats
-	  for that cgroup.
-
-CFQ sysfs tunable
-=================
-/sys/block/<disk>/queue/iosched/slice_idle
-------------------------------------------
-On a faster hardware CFQ can be slow, especially with sequential workload.
-This happens because CFQ idles on a single queue and single queue might not
-drive deeper request queue depths to keep the storage busy. In such scenarios
-one can try setting slice_idle=0 and that would switch CFQ to IOPS
-(IO operations per second) mode on NCQ supporting hardware.
-
-That means CFQ will not idle between cfq queues of a cfq group and hence be
-able to driver higher queue depth and achieve better throughput. That also
-means that cfq provides fairness among groups in terms of IOPS and not in
-terms of disk time.
-
-/sys/block/<disk>/queue/iosched/group_idle
-------------------------------------------
-If one disables idling on individual cfq queues and cfq service trees by
-setting slice_idle=0, group_idle kicks in. That means CFQ will still idle
-on the group in an attempt to provide fairness among groups.
-
-By default group_idle is same as slice_idle and does not do anything if
-slice_idle is enabled.
-
-One can experience an overall throughput drop if you have created multiple
-groups and put applications in that group which are not driving enough
-IO to keep disk busy. In that case set group_idle=0, and CFQ will not idle
-on individual groups and throughput should improve.
-
-Writeback
-=========
-
-Page cache is dirtied through buffered writes and shared mmaps and
-written asynchronously to the backing filesystem by the writeback
-mechanism.  Writeback sits between the memory and IO domains and
-regulates the proportion of dirty memory by balancing dirtying and
-write IOs.
-
-On traditional cgroup hierarchies, relationships between different
-controllers cannot be established making it impossible for writeback
-to operate accounting for cgroup resource restrictions and all
-writeback IOs are attributed to the root cgroup.
-
-If both the blkio and memory controllers are used on the v2 hierarchy
-and the filesystem supports cgroup writeback, writeback operations
-correctly follow the resource restrictions imposed by both memory and
-blkio controllers.
-
-Writeback examines both system-wide and per-cgroup dirty memory status
-and enforces the more restrictive of the two.  Also, writeback control
-parameters which are absolute values - vm.dirty_bytes and
-vm.dirty_background_bytes - are distributed across cgroups according
-to their current writeback bandwidth.
-
-There's a peculiarity stemming from the discrepancy in ownership
-granularity between memory controller and writeback.  While memory
-controller tracks ownership per page, writeback operates on inode
-basis.  cgroup writeback bridges the gap by tracking ownership by
-inode but migrating ownership if too many foreign pages, pages which
-don't match the current inode ownership, have been encountered while
-writing back the inode.
-
-This is a conscious design choice as writeback operations are
-inherently tied to inodes making strictly following page ownership
-complicated and inefficient.  The only use case which suffers from
-this compromise is multiple cgroups concurrently dirtying disjoint
-regions of the same inode, which is an unlikely use case and decided
-to be unsupported.  Note that as memory controller assigns page
-ownership on the first use and doesn't update it until the page is
-released, even if cgroup writeback strictly follows page ownership,
-multiple cgroups dirtying overlapping areas wouldn't work as expected.
-In general, write-sharing an inode across multiple cgroups is not well
-supported.
-
-Filesystem support for cgroup writeback
----------------------------------------
-
-A filesystem can make writeback IOs cgroup-aware by updating
-address_space_operations->writepage[s]() to annotate bio's using the
-following two functions.
-
-* wbc_init_bio(@wbc, @bio)
-
-  Should be called for each bio carrying writeback data and associates
-  the bio with the inode's owner cgroup.  Can be called anytime
-  between bio allocation and submission.
-
-* wbc_account_io(@wbc, @page, @bytes)
-
-  Should be called for each data segment being written out.  While
-  this function doesn't care exactly when it's called during the
-  writeback session, it's the easiest and most natural to call it as
-  data segments are added to a bio.
-
-With writeback bio's annotated, cgroup support can be enabled per
-super_block by setting MS_CGROUPWB in ->s_flags.  This allows for
-selective disabling of cgroup writeback support which is helpful when
-certain filesystem features, e.g. journaled data mode, are
-incompatible.
-
-wbc_init_bio() binds the specified bio to its cgroup.  Depending on
-the configuration, the bio may be executed at a lower priority and if
-the writeback session is holding shared resources, e.g. a journal
-entry, may lead to priority inversion.  There is no one easy solution
-for the problem.  Filesystems can try to work around specific problem
-cases by skipping wbc_init_bio() or using bio_associate_blkcg()
-directly.
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
deleted file mode 100644
index c6256ae9885b..000000000000
--- a/Documentation/cgroups/cgroups.txt
+++ /dev/null
@@ -1,682 +0,0 @@
-				CGROUPS
-				-------
-
-Written by Paul Menage <menage@google.com> based on
-Documentation/cgroups/cpusets.txt
-
-Original copyright statements from cpusets.txt:
-Portions Copyright (C) 2004 BULL SA.
-Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.
-Modified by Paul Jackson <pj@sgi.com>
-Modified by Christoph Lameter <clameter@sgi.com>
-
-CONTENTS:
-=========
-
-1. Control Groups
-  1.1 What are cgroups ?
-  1.2 Why are cgroups needed ?
-  1.3 How are cgroups implemented ?
-  1.4 What does notify_on_release do ?
-  1.5 What does clone_children do ?
-  1.6 How do I use cgroups ?
-2. Usage Examples and Syntax
-  2.1 Basic Usage
-  2.2 Attaching processes
-  2.3 Mounting hierarchies by name
-3. Kernel API
-  3.1 Overview
-  3.2 Synchronization
-  3.3 Subsystem API
-4. Extended attributes usage
-5. Questions
-
-1. Control Groups
-=================
-
-1.1 What are cgroups ?
-----------------------
-
-Control Groups provide a mechanism for aggregating/partitioning sets of
-tasks, and all their future children, into hierarchical groups with
-specialized behaviour.
-
-Definitions:
-
-A *cgroup* associates a set of tasks with a set of parameters for one
-or more subsystems.
-
-A *subsystem* is a module that makes use of the task grouping
-facilities provided by cgroups to treat groups of tasks in
-particular ways. A subsystem is typically a "resource controller" that
-schedules a resource or applies per-cgroup limits, but it may be
-anything that wants to act on a group of processes, e.g. a
-virtualization subsystem.
-
-A *hierarchy* is a set of cgroups arranged in a tree, such that
-every task in the system is in exactly one of the cgroups in the
-hierarchy, and a set of subsystems; each subsystem has system-specific
-state attached to each cgroup in the hierarchy.  Each hierarchy has
-an instance of the cgroup virtual filesystem associated with it.
-
-At any one time there may be multiple active hierarchies of task
-cgroups. Each hierarchy is a partition of all tasks in the system.
-
-User-level code may create and destroy cgroups by name in an
-instance of the cgroup virtual file system, specify and query to
-which cgroup a task is assigned, and list the task PIDs assigned to
-a cgroup. Those creations and assignments only affect the hierarchy
-associated with that instance of the cgroup file system.
-
-On their own, the only use for cgroups is for simple job
-tracking. The intention is that other subsystems hook into the generic
-cgroup support to provide new attributes for cgroups, such as
-accounting/limiting the resources which processes in a cgroup can
-access. For example, cpusets (see Documentation/cgroups/cpusets.txt) allow
-you to associate a set of CPUs and a set of memory nodes with the
-tasks in each cgroup.
-
-1.2 Why are cgroups needed ?
-----------------------------
-
-There are multiple efforts to provide process aggregations in the
-Linux kernel, mainly for resource-tracking purposes. Such efforts
-include cpusets, CKRM/ResGroups, UserBeanCounters, and virtual server
-namespaces. These all require the basic notion of a
-grouping/partitioning of processes, with newly forked processes ending
-up in the same group (cgroup) as their parent process.
-
-The kernel cgroup patch provides the minimum essential kernel
-mechanisms required to efficiently implement such groups. It has
-minimal impact on the system fast paths, and provides hooks for
-specific subsystems such as cpusets to provide additional behaviour as
-desired.
-
-Multiple hierarchy support is provided to allow for situations where
-the division of tasks into cgroups is distinctly different for
-different subsystems - having parallel hierarchies allows each
-hierarchy to be a natural division of tasks, without having to handle
-complex combinations of tasks that would be present if several
-unrelated subsystems needed to be forced into the same tree of
-cgroups.
-
-At one extreme, each resource controller or subsystem could be in a
-separate hierarchy; at the other extreme, all subsystems
-would be attached to the same hierarchy.
-
-As an example of a scenario (originally proposed by vatsa@in.ibm.com)
-that can benefit from multiple hierarchies, consider a large
-university server with various users - students, professors, system
-tasks etc. The resource planning for this server could be along the
-following lines:
-
-       CPU :          "Top cpuset"
-                       /       \
-               CPUSet1         CPUSet2
-                  |               |
-               (Professors)    (Students)
-
-               In addition (system tasks) are attached to topcpuset (so
-               that they can run anywhere) with a limit of 20%
-
-       Memory : Professors (50%), Students (30%), system (20%)
-
-       Disk : Professors (50%), Students (30%), system (20%)
-
-       Network : WWW browsing (20%), Network File System (60%), others (20%)
-                               / \
-               Professors (15%)  students (5%)
-
-Browsers like Firefox/Lynx go into the WWW network class, while (k)nfsd goes
-into the NFS network class.
-
-At the same time Firefox/Lynx will share an appropriate CPU/Memory class
-depending on who launched it (prof/student).
-
-With the ability to classify tasks differently for different resources
-(by putting those resource subsystems in different hierarchies),
-the admin can easily set up a script which receives exec notifications
-and depending on who is launching the browser he can
-
-    # echo browser_pid > /sys/fs/cgroup/<restype>/<userclass>/tasks
-
-With only a single hierarchy, he now would potentially have to create
-a separate cgroup for every browser launched and associate it with
-appropriate network and other resource class.  This may lead to
-proliferation of such cgroups.
-
-Also let's say that the administrator would like to give enhanced network
-access temporarily to a student's browser (since it is night and the user
-wants to do online gaming :))  OR give one of the student's simulation
-apps enhanced CPU power.
-
-With ability to write PIDs directly to resource classes, it's just a
-matter of:
-
-       # echo pid > /sys/fs/cgroup/network/<new_class>/tasks
-       (after some time)
-       # echo pid > /sys/fs/cgroup/network/<orig_class>/tasks
-
-Without this ability, the administrator would have to split the cgroup into
-multiple separate ones and then associate the new cgroups with the
-new resource classes.
-
-
-
-1.3 How are cgroups implemented ?
----------------------------------
-
-Control Groups extends the kernel as follows:
-
- - Each task in the system has a reference-counted pointer to a
-   css_set.
-
- - A css_set contains a set of reference-counted pointers to
-   cgroup_subsys_state objects, one for each cgroup subsystem
-   registered in the system. There is no direct link from a task to
-   the cgroup of which it's a member in each hierarchy, but this
-   can be determined by following pointers through the
-   cgroup_subsys_state objects. This is because accessing the
-   subsystem state is something that's expected to happen frequently
-   and in performance-critical code, whereas operations that require a
-   task's actual cgroup assignments (in particular, moving between
-   cgroups) are less common. A linked list runs through the cg_list
-   field of each task_struct using the css_set, anchored at
-   css_set->tasks.
-
- - A cgroup hierarchy filesystem can be mounted for browsing and
-   manipulation from user space.
-
- - You can list all the tasks (by PID) attached to any cgroup.
-
-The implementation of cgroups requires a few, simple hooks
-into the rest of the kernel, none in performance-critical paths:
-
- - in init/main.c, to initialize the root cgroups and initial
-   css_set at system boot.
-
- - in fork and exit, to attach and detach a task from its css_set.
-
-In addition, a new file system of type "cgroup" may be mounted, to
-enable browsing and modifying the cgroups presently known to the
-kernel.  When mounting a cgroup hierarchy, you may specify a
-comma-separated list of subsystems to mount as the filesystem mount
-options.  By default, mounting the cgroup filesystem attempts to
-mount a hierarchy containing all registered subsystems.
-
-If an active hierarchy with exactly the same set of subsystems already
-exists, it will be reused for the new mount. If no existing hierarchy
-matches, and any of the requested subsystems are in use in an existing
-hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy
-is activated, associated with the requested subsystems.
-
-It's not currently possible to bind a new subsystem to an active
-cgroup hierarchy, or to unbind a subsystem from an active cgroup
-hierarchy. This may be possible in future, but is fraught with nasty
-error-recovery issues.
-
-When a cgroup filesystem is unmounted, if there are any
-child cgroups created below the top-level cgroup, that hierarchy
-will remain active even though unmounted; if there are no
-child cgroups then the hierarchy will be deactivated.
-
-No new system calls are added for cgroups - all support for
-querying and modifying cgroups is via this cgroup file system.
-
-Each task under /proc has an added file named 'cgroup' displaying,
-for each active hierarchy, the subsystem names and the cgroup name
-as the path relative to the root of the cgroup file system.
-
-Each cgroup is represented by a directory in the cgroup file system
-containing the following files describing that cgroup:
-
- - tasks: list of tasks (by PID) attached to that cgroup.  This list
-   is not guaranteed to be sorted.  Writing a thread ID into this file
-   moves the thread into this cgroup.
- - cgroup.procs: list of thread group IDs in the cgroup.  This list is
-   not guaranteed to be sorted or free of duplicate TGIDs, and userspace
-   should sort/uniquify the list if this property is required.
-   Writing a thread group ID into this file moves all threads in that
-   group into this cgroup.
- - notify_on_release flag: run the release agent on exit?
- - release_agent: the path to use for release notifications (this file
-   exists in the top cgroup only)
-
-Other subsystems such as cpusets may add additional files in each
-cgroup dir.
-
-New cgroups are created using the mkdir system call or shell
-command.  The properties of a cgroup, such as its flags, are
-modified by writing to the appropriate file in that cgroups
-directory, as listed above.
-
-The named hierarchical structure of nested cgroups allows partitioning
-a large system into nested, dynamically changeable, "soft-partitions".
-
-The attachment of each task, automatically inherited at fork by any
-children of that task, to a cgroup allows organizing the work load
-on a system into related sets of tasks.  A task may be re-attached to
-any other cgroup, if allowed by the permissions on the necessary
-cgroup file system directories.
-
-When a task is moved from one cgroup to another, it gets a new
-css_set pointer - if there's an already existing css_set with the
-desired collection of cgroups then that group is reused, otherwise a new
-css_set is allocated. The appropriate existing css_set is located by
-looking into a hash table.
-
-To allow access from a cgroup to the css_sets (and hence tasks)
-that comprise it, a set of cg_cgroup_link objects form a lattice;
-each cg_cgroup_link is linked into a list of cg_cgroup_links for
-a single cgroup on its cgrp_link_list field, and a list of
-cg_cgroup_links for a single css_set on its cg_link_list.
-
-Thus the set of tasks in a cgroup can be listed by iterating over
-each css_set that references the cgroup, and sub-iterating over
-each css_set's task set.
-
-The use of a Linux virtual file system (vfs) to represent the
-cgroup hierarchy provides for a familiar permission and name space
-for cgroups, with a minimum of additional kernel code.
-
-1.4 What does notify_on_release do ?
-------------------------------------
-
-If the notify_on_release flag is enabled (1) in a cgroup, then
-whenever the last task in the cgroup leaves (exits or attaches to
-some other cgroup) and the last child cgroup of that cgroup
-is removed, then the kernel runs the command specified by the contents
-of the "release_agent" file in that hierarchy's root directory,
-supplying the pathname (relative to the mount point of the cgroup
-file system) of the abandoned cgroup.  This enables automatic
-removal of abandoned cgroups.  The default value of
-notify_on_release in the root cgroup at system boot is disabled
-(0).  The default value of other cgroups at creation is the current
-value of their parents' notify_on_release settings. The default value of
-a cgroup hierarchy's release_agent path is empty.
-
-1.5 What does clone_children do ?
----------------------------------
-
-This flag only affects the cpuset controller. If the clone_children
-flag is enabled (1) in a cgroup, a new cpuset cgroup will copy its
-configuration from the parent during initialization.
-
-1.6 How do I use cgroups ?
---------------------------
-
-To start a new job that is to be contained within a cgroup, using
-the "cpuset" cgroup subsystem, the steps are something like:
-
- 1) mount -t tmpfs cgroup_root /sys/fs/cgroup
- 2) mkdir /sys/fs/cgroup/cpuset
- 3) mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset
- 4) Create the new cgroup by doing mkdir's and write's (or echo's) in
-    the /sys/fs/cgroup/cpuset virtual file system.
- 5) Start a task that will be the "founding father" of the new job.
- 6) Attach that task to the new cgroup by writing its PID to the
-    /sys/fs/cgroup/cpuset tasks file for that cgroup.
- 7) fork, exec or clone the job tasks from this founding father task.
-
-For example, the following sequence of commands will setup a cgroup
-named "Charlie", containing just CPUs 2 and 3, and Memory Node 1,
-and then start a subshell 'sh' in that cgroup:
-
-  mount -t tmpfs cgroup_root /sys/fs/cgroup
-  mkdir /sys/fs/cgroup/cpuset
-  mount -t cgroup cpuset -ocpuset /sys/fs/cgroup/cpuset
-  cd /sys/fs/cgroup/cpuset
-  mkdir Charlie
-  cd Charlie
-  /bin/echo 2-3 > cpuset.cpus
-  /bin/echo 1 > cpuset.mems
-  /bin/echo $$ > tasks
-  sh
-  # The subshell 'sh' is now running in cgroup Charlie
-  # The next line should display '/Charlie'
-  cat /proc/self/cgroup
-
-2. Usage Examples and Syntax
-============================
-
-2.1 Basic Usage
----------------
-
-Creating, modifying, using cgroups can be done through the cgroup
-virtual filesystem.
-
-To mount a cgroup hierarchy with all available subsystems, type:
-# mount -t cgroup xxx /sys/fs/cgroup
-
-The "xxx" is not interpreted by the cgroup code, but will appear in
-/proc/mounts so may be any useful identifying string that you like.
-
-Note: Some subsystems do not work without some user input first.  For instance,
-if cpusets are enabled the user will have to populate the cpus and mems files
-for each new cgroup created before that group can be used.
-
-As explained in section `1.2 Why are cgroups needed?' you should create
-different hierarchies of cgroups for each single resource or group of
-resources you want to control. Therefore, you should mount a tmpfs on
-/sys/fs/cgroup and create directories for each cgroup resource or resource
-group.
-
-# mount -t tmpfs cgroup_root /sys/fs/cgroup
-# mkdir /sys/fs/cgroup/rg1
-
-To mount a cgroup hierarchy with just the cpuset and memory
-subsystems, type:
-# mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1
-
-While remounting cgroups is currently supported, it is not recommend
-to use it. Remounting allows changing bound subsystems and
-release_agent. Rebinding is hardly useful as it only works when the
-hierarchy is empty and release_agent itself should be replaced with
-conventional fsnotify. The support for remounting will be removed in
-the future.
-
-To Specify a hierarchy's release_agent:
-# mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \
-  xxx /sys/fs/cgroup/rg1
-
-Note that specifying 'release_agent' more than once will return failure.
-
-Note that changing the set of subsystems is currently only supported
-when the hierarchy consists of a single (root) cgroup. Supporting
-the ability to arbitrarily bind/unbind subsystems from an existing
-cgroup hierarchy is intended to be implemented in the future.
-
-Then under /sys/fs/cgroup/rg1 you can find a tree that corresponds to the
-tree of the cgroups in the system. For instance, /sys/fs/cgroup/rg1
-is the cgroup that holds the whole system.
-
-If you want to change the value of release_agent:
-# echo "/sbin/new_release_agent" > /sys/fs/cgroup/rg1/release_agent
-
-It can also be changed via remount.
-
-If you want to create a new cgroup under /sys/fs/cgroup/rg1:
-# cd /sys/fs/cgroup/rg1
-# mkdir my_cgroup
-
-Now you want to do something with this cgroup.
-# cd my_cgroup
-
-In this directory you can find several files:
-# ls
-cgroup.procs notify_on_release tasks
-(plus whatever files added by the attached subsystems)
-
-Now attach your shell to this cgroup:
-# /bin/echo $$ > tasks
-
-You can also create cgroups inside your cgroup by using mkdir in this
-directory.
-# mkdir my_sub_cs
-
-To remove a cgroup, just use rmdir:
-# rmdir my_sub_cs
-
-This will fail if the cgroup is in use (has cgroups inside, or
-has processes attached, or is held alive by other subsystem-specific
-reference).
-
-2.2 Attaching processes
------------------------
-
-# /bin/echo PID > tasks
-
-Note that it is PID, not PIDs. You can only attach ONE task at a time.
-If you have several tasks to attach, you have to do it one after another:
-
-# /bin/echo PID1 > tasks
-# /bin/echo PID2 > tasks
-	...
-# /bin/echo PIDn > tasks
-
-You can attach the current shell task by echoing 0:
-
-# echo 0 > tasks
-
-You can use the cgroup.procs file instead of the tasks file to move all
-threads in a threadgroup at once. Echoing the PID of any task in a
-threadgroup to cgroup.procs causes all tasks in that threadgroup to be
-attached to the cgroup. Writing 0 to cgroup.procs moves all tasks
-in the writing task's threadgroup.
-
-Note: Since every task is always a member of exactly one cgroup in each
-mounted hierarchy, to remove a task from its current cgroup you must
-move it into a new cgroup (possibly the root cgroup) by writing to the
-new cgroup's tasks file.
-
-Note: Due to some restrictions enforced by some cgroup subsystems, moving
-a process to another cgroup can fail.
-
-2.3 Mounting hierarchies by name
---------------------------------
-
-Passing the name=<x> option when mounting a cgroups hierarchy
-associates the given name with the hierarchy.  This can be used when
-mounting a pre-existing hierarchy, in order to refer to it by name
-rather than by its set of active subsystems.  Each hierarchy is either
-nameless, or has a unique name.
-
-The name should match [\w.-]+
-
-When passing a name=<x> option for a new hierarchy, you need to
-specify subsystems manually; the legacy behaviour of mounting all
-subsystems when none are explicitly specified is not supported when
-you give a subsystem a name.
-
-The name of the subsystem appears as part of the hierarchy description
-in /proc/mounts and /proc/<pid>/cgroups.
-
-
-3. Kernel API
-=============
-
-3.1 Overview
-------------
-
-Each kernel subsystem that wants to hook into the generic cgroup
-system needs to create a cgroup_subsys object. This contains
-various methods, which are callbacks from the cgroup system, along
-with a subsystem ID which will be assigned by the cgroup system.
-
-Other fields in the cgroup_subsys object include:
-
-- subsys_id: a unique array index for the subsystem, indicating which
-  entry in cgroup->subsys[] this subsystem should be managing.
-
-- name: should be initialized to a unique subsystem name. Should be
-  no longer than MAX_CGROUP_TYPE_NAMELEN.
-
-- early_init: indicate if the subsystem needs early initialization
-  at system boot.
-
-Each cgroup object created by the system has an array of pointers,
-indexed by subsystem ID; this pointer is entirely managed by the
-subsystem; the generic cgroup code will never touch this pointer.
-
-3.2 Synchronization
--------------------
-
-There is a global mutex, cgroup_mutex, used by the cgroup
-system. This should be taken by anything that wants to modify a
-cgroup. It may also be taken to prevent cgroups from being
-modified, but more specific locks may be more appropriate in that
-situation.
-
-See kernel/cgroup.c for more details.
-
-Subsystems can take/release the cgroup_mutex via the functions
-cgroup_lock()/cgroup_unlock().
-
-Accessing a task's cgroup pointer may be done in the following ways:
-- while holding cgroup_mutex
-- while holding the task's alloc_lock (via task_lock())
-- inside an rcu_read_lock() section via rcu_dereference()
-
-3.3 Subsystem API
------------------
-
-Each subsystem should:
-
-- add an entry in linux/cgroup_subsys.h
-- define a cgroup_subsys object called <name>_subsys
-
-If a subsystem can be compiled as a module, it should also have in its
-module initcall a call to cgroup_load_subsys(), and in its exitcall a
-call to cgroup_unload_subsys(). It should also set its_subsys.module =
-THIS_MODULE in its .c file.
-
-Each subsystem may export the following methods. The only mandatory
-methods are css_alloc/free. Any others that are null are presumed to
-be successful no-ops.
-
-struct cgroup_subsys_state *css_alloc(struct cgroup *cgrp)
-(cgroup_mutex held by caller)
-
-Called to allocate a subsystem state object for a cgroup. The
-subsystem should allocate its subsystem state object for the passed
-cgroup, returning a pointer to the new object on success or a
-ERR_PTR() value. On success, the subsystem pointer should point to
-a structure of type cgroup_subsys_state (typically embedded in a
-larger subsystem-specific object), which will be initialized by the
-cgroup system. Note that this will be called at initialization to
-create the root subsystem state for this subsystem; this case can be
-identified by the passed cgroup object having a NULL parent (since
-it's the root of the hierarchy) and may be an appropriate place for
-initialization code.
-
-int css_online(struct cgroup *cgrp)
-(cgroup_mutex held by caller)
-
-Called after @cgrp successfully completed all allocations and made
-visible to cgroup_for_each_child/descendant_*() iterators. The
-subsystem may choose to fail creation by returning -errno. This
-callback can be used to implement reliable state sharing and
-propagation along the hierarchy. See the comment on
-cgroup_for_each_descendant_pre() for details.
-
-void css_offline(struct cgroup *cgrp);
-(cgroup_mutex held by caller)
-
-This is the counterpart of css_online() and called iff css_online()
-has succeeded on @cgrp. This signifies the beginning of the end of
-@cgrp. @cgrp is being removed and the subsystem should start dropping
-all references it's holding on @cgrp. When all references are dropped,
-cgroup removal will proceed to the next step - css_free(). After this
-callback, @cgrp should be considered dead to the subsystem.
-
-void css_free(struct cgroup *cgrp)
-(cgroup_mutex held by caller)
-
-The cgroup system is about to free @cgrp; the subsystem should free
-its subsystem state object. By the time this method is called, @cgrp
-is completely unused; @cgrp->parent is still valid. (Note - can also
-be called for a newly-created cgroup if an error occurs after this
-subsystem's create() method has been called for the new cgroup).
-
-int can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-(cgroup_mutex held by caller)
-
-Called prior to moving one or more tasks into a cgroup; if the
-subsystem returns an error, this will abort the attach operation.
-@tset contains the tasks to be attached and is guaranteed to have at
-least one task in it.
-
-If there are multiple tasks in the taskset, then:
-  - it's guaranteed that all are from the same thread group
-  - @tset contains all tasks from the thread group whether or not
-    they're switching cgroups
-  - the first task is the leader
-
-Each @tset entry also contains the task's old cgroup and tasks which
-aren't switching cgroup can be skipped easily using the
-cgroup_taskset_for_each() iterator. Note that this isn't called on a
-fork. If this method returns 0 (success) then this should remain valid
-while the caller holds cgroup_mutex and it is ensured that either
-attach() or cancel_attach() will be called in future.
-
-void css_reset(struct cgroup_subsys_state *css)
-(cgroup_mutex held by caller)
-
-An optional operation which should restore @css's configuration to the
-initial state.  This is currently only used on the unified hierarchy
-when a subsystem is disabled on a cgroup through
-"cgroup.subtree_control" but should remain enabled because other
-subsystems depend on it.  cgroup core makes such a css invisible by
-removing the associated interface files and invokes this callback so
-that the hidden subsystem can return to the initial neutral state.
-This prevents unexpected resource control from a hidden css and
-ensures that the configuration is in the initial state when it is made
-visible again later.
-
-void cancel_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-(cgroup_mutex held by caller)
-
-Called when a task attach operation has failed after can_attach() has succeeded.
-A subsystem whose can_attach() has some side-effects should provide this
-function, so that the subsystem can implement a rollback. If not, not necessary.
-This will be called only about subsystems whose can_attach() operation have
-succeeded. The parameters are identical to can_attach().
-
-void attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-(cgroup_mutex held by caller)
-
-Called after the task has been attached to the cgroup, to allow any
-post-attachment activity that requires memory allocations or blocking.
-The parameters are identical to can_attach().
-
-void fork(struct task_struct *task)
-
-Called when a task is forked into a cgroup.
-
-void exit(struct task_struct *task)
-
-Called during task exit.
-
-void free(struct task_struct *task)
-
-Called when the task_struct is freed.
-
-void bind(struct cgroup *root)
-(cgroup_mutex held by caller)
-
-Called when a cgroup subsystem is rebound to a different hierarchy
-and root cgroup. Currently this will only involve movement between
-the default hierarchy (which never has sub-cgroups) and a hierarchy
-that is being created/destroyed (and hence has no sub-cgroups).
-
-4. Extended attribute usage
-===========================
-
-cgroup filesystem supports certain types of extended attributes in its
-directories and files.  The current supported types are:
-	- Trusted (XATTR_TRUSTED)
-	- Security (XATTR_SECURITY)
-
-Both require CAP_SYS_ADMIN capability to set.
-
-Like in tmpfs, the extended attributes in cgroup filesystem are stored
-using kernel memory and it's advised to keep the usage at minimum.  This
-is the reason why user defined extended attributes are not supported, since
-any user can do it and there's no limit in the value size.
-
-The current known users for this feature are SELinux to limit cgroup usage
-in containers and systemd for assorted meta data like main PID in a cgroup
-(systemd creates a cgroup per service).
-
-5. Questions
-============
-
-Q: what's up with this '/bin/echo' ?
-A: bash's builtin 'echo' command does not check calls to write() against
-   errors. If you use it in the cgroup file system, you won't be
-   able to tell whether a command succeeded or failed.
-
-Q: When I attach processes, only the first of the line gets really attached !
-A: We can only return one error code per call to write(). So you should also
-   put only ONE PID.
-
diff --git a/Documentation/cgroups/cpuacct.txt b/Documentation/cgroups/cpuacct.txt
deleted file mode 100644
index 9d73cc0cadb9..000000000000
--- a/Documentation/cgroups/cpuacct.txt
+++ /dev/null
@@ -1,49 +0,0 @@
-CPU Accounting Controller
--------------------------
-
-The CPU accounting controller is used to group tasks using cgroups and
-account the CPU usage of these groups of tasks.
-
-The CPU accounting controller supports multi-hierarchy groups. An accounting
-group accumulates the CPU usage of all of its child groups and the tasks
-directly present in its group.
-
-Accounting groups can be created by first mounting the cgroup filesystem.
-
-# mount -t cgroup -ocpuacct none /sys/fs/cgroup
-
-With the above step, the initial or the parent accounting group becomes
-visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in
-the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup.
-/sys/fs/cgroup/cpuacct.usage gives the CPU time (in nanoseconds) obtained
-by this group which is essentially the CPU time obtained by all the tasks
-in the system.
-
-New accounting groups can be created under the parent group /sys/fs/cgroup.
-
-# cd /sys/fs/cgroup
-# mkdir g1
-# echo $$ > g1/tasks
-
-The above steps create a new group g1 and move the current shell
-process (bash) into it. CPU time consumed by this bash and its children
-can be obtained from g1/cpuacct.usage and the same is accumulated in
-/sys/fs/cgroup/cpuacct.usage also.
-
-cpuacct.stat file lists a few statistics which further divide the
-CPU time obtained by the cgroup into user and system times. Currently
-the following statistics are supported:
-
-user: Time spent by tasks of the cgroup in user mode.
-system: Time spent by tasks of the cgroup in kernel mode.
-
-user and system are in USER_HZ unit.
-
-cpuacct controller uses percpu_counter interface to collect user and
-system times. This has two side effects:
-
-- It is theoretically possible to see wrong values for user and system times.
-  This is because percpu_counter_read() on 32bit systems isn't safe
-  against concurrent writes.
-- It is possible to see slightly outdated values for user and system times
-  due to the batch processing nature of percpu_counter.
diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
deleted file mode 100644
index fdf7dff3f607..000000000000
--- a/Documentation/cgroups/cpusets.txt
+++ /dev/null
@@ -1,839 +0,0 @@
-				CPUSETS
-				-------
-
-Copyright (C) 2004 BULL SA.
-Written by Simon.Derr@bull.net
-
-Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.
-Modified by Paul Jackson <pj@sgi.com>
-Modified by Christoph Lameter <clameter@sgi.com>
-Modified by Paul Menage <menage@google.com>
-Modified by Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
-
-CONTENTS:
-=========
-
-1. Cpusets
-  1.1 What are cpusets ?
-  1.2 Why are cpusets needed ?
-  1.3 How are cpusets implemented ?
-  1.4 What are exclusive cpusets ?
-  1.5 What is memory_pressure ?
-  1.6 What is memory spread ?
-  1.7 What is sched_load_balance ?
-  1.8 What is sched_relax_domain_level ?
-  1.9 How do I use cpusets ?
-2. Usage Examples and Syntax
-  2.1 Basic Usage
-  2.2 Adding/removing cpus
-  2.3 Setting flags
-  2.4 Attaching processes
-3. Questions
-4. Contact
-
-1. Cpusets
-==========
-
-1.1 What are cpusets ?
-----------------------
-
-Cpusets provide a mechanism for assigning a set of CPUs and Memory
-Nodes to a set of tasks.   In this document "Memory Node" refers to
-an on-line node that contains memory.
-
-Cpusets constrain the CPU and Memory placement of tasks to only
-the resources within a task's current cpuset.  They form a nested
-hierarchy visible in a virtual file system.  These are the essential
-hooks, beyond what is already present, required to manage dynamic
-job placement on large systems.
-
-Cpusets use the generic cgroup subsystem described in
-Documentation/cgroups/cgroups.txt.
-
-Requests by a task, using the sched_setaffinity(2) system call to
-include CPUs in its CPU affinity mask, and using the mbind(2) and
-set_mempolicy(2) system calls to include Memory Nodes in its memory
-policy, are both filtered through that task's cpuset, filtering out any
-CPUs or Memory Nodes not in that cpuset.  The scheduler will not
-schedule a task on a CPU that is not allowed in its cpus_allowed
-vector, and the kernel page allocator will not allocate a page on a
-node that is not allowed in the requesting task's mems_allowed vector.
-
-User level code may create and destroy cpusets by name in the cgroup
-virtual file system, manage the attributes and permissions of these
-cpusets and which CPUs and Memory Nodes are assigned to each cpuset,
-specify and query to which cpuset a task is assigned, and list the
-task pids assigned to a cpuset.
-
-
-1.2 Why are cpusets needed ?
-----------------------------
-
-The management of large computer systems, with many processors (CPUs),
-complex memory cache hierarchies and multiple Memory Nodes having
-non-uniform access times (NUMA) presents additional challenges for
-the efficient scheduling and memory placement of processes.
-
-Frequently more modest sized systems can be operated with adequate
-efficiency just by letting the operating system automatically share
-the available CPU and Memory resources amongst the requesting tasks.
-
-But larger systems, which benefit more from careful processor and
-memory placement to reduce memory access times and contention,
-and which typically represent a larger investment for the customer,
-can benefit from explicitly placing jobs on properly sized subsets of
-the system.
-
-This can be especially valuable on:
-
-    * Web Servers running multiple instances of the same web application,
-    * Servers running different applications (for instance, a web server
-      and a database), or
-    * NUMA systems running large HPC applications with demanding
-      performance characteristics.
-
-These subsets, or "soft partitions" must be able to be dynamically
-adjusted, as the job mix changes, without impacting other concurrently
-executing jobs. The location of the running jobs pages may also be moved
-when the memory locations are changed.
-
-The kernel cpuset patch provides the minimum essential kernel
-mechanisms required to efficiently implement such subsets.  It
-leverages existing CPU and Memory Placement facilities in the Linux
-kernel to avoid any additional impact on the critical scheduler or
-memory allocator code.
-
-
-1.3 How are cpusets implemented ?
----------------------------------
-
-Cpusets provide a Linux kernel mechanism to constrain which CPUs and
-Memory Nodes are used by a process or set of processes.
-
-The Linux kernel already has a pair of mechanisms to specify on which
-CPUs a task may be scheduled (sched_setaffinity) and on which Memory
-Nodes it may obtain memory (mbind, set_mempolicy).
-
-Cpusets extends these two mechanisms as follows:
-
- - Cpusets are sets of allowed CPUs and Memory Nodes, known to the
-   kernel.
- - Each task in the system is attached to a cpuset, via a pointer
-   in the task structure to a reference counted cgroup structure.
- - Calls to sched_setaffinity are filtered to just those CPUs
-   allowed in that task's cpuset.
- - Calls to mbind and set_mempolicy are filtered to just
-   those Memory Nodes allowed in that task's cpuset.
- - The root cpuset contains all the systems CPUs and Memory
-   Nodes.
- - For any cpuset, one can define child cpusets containing a subset
-   of the parents CPU and Memory Node resources.
- - The hierarchy of cpusets can be mounted at /dev/cpuset, for
-   browsing and manipulation from user space.
- - A cpuset may be marked exclusive, which ensures that no other
-   cpuset (except direct ancestors and descendants) may contain
-   any overlapping CPUs or Memory Nodes.
- - You can list all the tasks (by pid) attached to any cpuset.
-
-The implementation of cpusets requires a few, simple hooks
-into the rest of the kernel, none in performance critical paths:
-
- - in init/main.c, to initialize the root cpuset at system boot.
- - in fork and exit, to attach and detach a task from its cpuset.
- - in sched_setaffinity, to mask the requested CPUs by what's
-   allowed in that task's cpuset.
- - in sched.c migrate_live_tasks(), to keep migrating tasks within
-   the CPUs allowed by their cpuset, if possible.
- - in the mbind and set_mempolicy system calls, to mask the requested
-   Memory Nodes by what's allowed in that task's cpuset.
- - in page_alloc.c, to restrict memory to allowed nodes.
- - in vmscan.c, to restrict page recovery to the current cpuset.
-
-You should mount the "cgroup" filesystem type in order to enable
-browsing and modifying the cpusets presently known to the kernel.  No
-new system calls are added for cpusets - all support for querying and
-modifying cpusets is via this cpuset file system.
-
-The /proc/<pid>/status file for each task has four added lines,
-displaying the task's cpus_allowed (on which CPUs it may be scheduled)
-and mems_allowed (on which Memory Nodes it may obtain memory),
-in the two formats seen in the following example:
-
-  Cpus_allowed:   ffffffff,ffffffff,ffffffff,ffffffff
-  Cpus_allowed_list:      0-127
-  Mems_allowed:   ffffffff,ffffffff
-  Mems_allowed_list:      0-63
-
-Each cpuset is represented by a directory in the cgroup file system
-containing (on top of the standard cgroup files) the following
-files describing that cpuset:
-
- - cpuset.cpus: list of CPUs in that cpuset
- - cpuset.mems: list of Memory Nodes in that cpuset
- - cpuset.memory_migrate flag: if set, move pages to cpusets nodes
- - cpuset.cpu_exclusive flag: is cpu placement exclusive?
- - cpuset.mem_exclusive flag: is memory placement exclusive?
- - cpuset.mem_hardwall flag:  is memory allocation hardwalled
- - cpuset.memory_pressure: measure of how much paging pressure in cpuset
- - cpuset.memory_spread_page flag: if set, spread page cache evenly on allowed nodes
- - cpuset.memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
- - cpuset.sched_load_balance flag: if set, load balance within CPUs on that cpuset
- - cpuset.sched_relax_domain_level: the searching range when migrating tasks
-
-In addition, only the root cpuset has the following file:
- - cpuset.memory_pressure_enabled flag: compute memory_pressure?
-
-New cpusets are created using the mkdir system call or shell
-command.  The properties of a cpuset, such as its flags, allowed
-CPUs and Memory Nodes, and attached tasks, are modified by writing
-to the appropriate file in that cpusets directory, as listed above.
-
-The named hierarchical structure of nested cpusets allows partitioning
-a large system into nested, dynamically changeable, "soft-partitions".
-
-The attachment of each task, automatically inherited at fork by any
-children of that task, to a cpuset allows organizing the work load
-on a system into related sets of tasks such that each set is constrained
-to using the CPUs and Memory Nodes of a particular cpuset.  A task
-may be re-attached to any other cpuset, if allowed by the permissions
-on the necessary cpuset file system directories.
-
-Such management of a system "in the large" integrates smoothly with
-the detailed placement done on individual tasks and memory regions
-using the sched_setaffinity, mbind and set_mempolicy system calls.
-
-The following rules apply to each cpuset:
-
- - Its CPUs and Memory Nodes must be a subset of its parents.
- - It can't be marked exclusive unless its parent is.
- - If its cpu or memory is exclusive, they may not overlap any sibling.
-
-These rules, and the natural hierarchy of cpusets, enable efficient
-enforcement of the exclusive guarantee, without having to scan all
-cpusets every time any of them change to ensure nothing overlaps a
-exclusive cpuset.  Also, the use of a Linux virtual file system (vfs)
-to represent the cpuset hierarchy provides for a familiar permission
-and name space for cpusets, with a minimum of additional kernel code.
-
-The cpus and mems files in the root (top_cpuset) cpuset are
-read-only.  The cpus file automatically tracks the value of
-cpu_online_mask using a CPU hotplug notifier, and the mems file
-automatically tracks the value of node_states[N_MEMORY]--i.e.,
-nodes with memory--using the cpuset_track_online_nodes() hook.
-
-
-1.4 What are exclusive cpusets ?
---------------------------------
-
-If a cpuset is cpu or mem exclusive, no other cpuset, other than
-a direct ancestor or descendant, may share any of the same CPUs or
-Memory Nodes.
-
-A cpuset that is cpuset.mem_exclusive *or* cpuset.mem_hardwall is "hardwalled",
-i.e. it restricts kernel allocations for page, buffer and other data
-commonly shared by the kernel across multiple users.  All cpusets,
-whether hardwalled or not, restrict allocations of memory for user
-space.  This enables configuring a system so that several independent
-jobs can share common kernel data, such as file system pages, while
-isolating each job's user allocation in its own cpuset.  To do this,
-construct a large mem_exclusive cpuset to hold all the jobs, and
-construct child, non-mem_exclusive cpusets for each individual job.
-Only a small amount of typical kernel memory, such as requests from
-interrupt handlers, is allowed to be taken outside even a
-mem_exclusive cpuset.
-
-
-1.5 What is memory_pressure ?
------------------------------
-The memory_pressure of a cpuset provides a simple per-cpuset metric
-of the rate that the tasks in a cpuset are attempting to free up in
-use memory on the nodes of the cpuset to satisfy additional memory
-requests.
-
-This enables batch managers monitoring jobs running in dedicated
-cpusets to efficiently detect what level of memory pressure that job
-is causing.
-
-This is useful both on tightly managed systems running a wide mix of
-submitted jobs, which may choose to terminate or re-prioritize jobs that
-are trying to use more memory than allowed on the nodes assigned to them,
-and with tightly coupled, long running, massively parallel scientific
-computing jobs that will dramatically fail to meet required performance
-goals if they start to use more memory than allowed to them.
-
-This mechanism provides a very economical way for the batch manager
-to monitor a cpuset for signs of memory pressure.  It's up to the
-batch manager or other user code to decide what to do about it and
-take action.
-
-==> Unless this feature is enabled by writing "1" to the special file
-    /dev/cpuset/memory_pressure_enabled, the hook in the rebalance
-    code of __alloc_pages() for this metric reduces to simply noticing
-    that the cpuset_memory_pressure_enabled flag is zero.  So only
-    systems that enable this feature will compute the metric.
-
-Why a per-cpuset, running average:
-
-    Because this meter is per-cpuset, rather than per-task or mm,
-    the system load imposed by a batch scheduler monitoring this
-    metric is sharply reduced on large systems, because a scan of
-    the tasklist can be avoided on each set of queries.
-
-    Because this meter is a running average, instead of an accumulating
-    counter, a batch scheduler can detect memory pressure with a
-    single read, instead of having to read and accumulate results
-    for a period of time.
-
-    Because this meter is per-cpuset rather than per-task or mm,
-    the batch scheduler can obtain the key information, memory
-    pressure in a cpuset, with a single read, rather than having to
-    query and accumulate results over all the (dynamically changing)
-    set of tasks in the cpuset.
-
-A per-cpuset simple digital filter (requires a spinlock and 3 words
-of data per-cpuset) is kept, and updated by any task attached to that
-cpuset, if it enters the synchronous (direct) page reclaim code.
-
-A per-cpuset file provides an integer number representing the recent
-(half-life of 10 seconds) rate of direct page reclaims caused by
-the tasks in the cpuset, in units of reclaims attempted per second,
-times 1000.
-
-
-1.6 What is memory spread ?
----------------------------
-There are two boolean flag files per cpuset that control where the
-kernel allocates pages for the file system buffers and related in
-kernel data structures.  They are called 'cpuset.memory_spread_page' and
-'cpuset.memory_spread_slab'.
-
-If the per-cpuset boolean flag file 'cpuset.memory_spread_page' is set, then
-the kernel will spread the file system buffers (page cache) evenly
-over all the nodes that the faulting task is allowed to use, instead
-of preferring to put those pages on the node where the task is running.
-
-If the per-cpuset boolean flag file 'cpuset.memory_spread_slab' is set,
-then the kernel will spread some file system related slab caches,
-such as for inodes and dentries evenly over all the nodes that the
-faulting task is allowed to use, instead of preferring to put those
-pages on the node where the task is running.
-
-The setting of these flags does not affect anonymous data segment or
-stack segment pages of a task.
-
-By default, both kinds of memory spreading are off, and memory
-pages are allocated on the node local to where the task is running,
-except perhaps as modified by the task's NUMA mempolicy or cpuset
-configuration, so long as sufficient free memory pages are available.
-
-When new cpusets are created, they inherit the memory spread settings
-of their parent.
-
-Setting memory spreading causes allocations for the affected page
-or slab caches to ignore the task's NUMA mempolicy and be spread
-instead.    Tasks using mbind() or set_mempolicy() calls to set NUMA
-mempolicies will not notice any change in these calls as a result of
-their containing task's memory spread settings.  If memory spreading
-is turned off, then the currently specified NUMA mempolicy once again
-applies to memory page allocations.
-
-Both 'cpuset.memory_spread_page' and 'cpuset.memory_spread_slab' are boolean flag
-files.  By default they contain "0", meaning that the feature is off
-for that cpuset.  If a "1" is written to that file, then that turns
-the named feature on.
-
-The implementation is simple.
-
-Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag
-PFA_SPREAD_PAGE for each task that is in that cpuset or subsequently
-joins that cpuset.  The page allocation calls for the page cache
-is modified to perform an inline check for this PFA_SPREAD_PAGE task
-flag, and if set, a call to a new routine cpuset_mem_spread_node()
-returns the node to prefer for the allocation.
-
-Similarly, setting 'cpuset.memory_spread_slab' turns on the flag
-PFA_SPREAD_SLAB, and appropriately marked slab caches will allocate
-pages from the node returned by cpuset_mem_spread_node().
-
-The cpuset_mem_spread_node() routine is also simple.  It uses the
-value of a per-task rotor cpuset_mem_spread_rotor to select the next
-node in the current task's mems_allowed to prefer for the allocation.
-
-This memory placement policy is also known (in other contexts) as
-round-robin or interleave.
-
-This policy can provide substantial improvements for jobs that need
-to place thread local data on the corresponding node, but that need
-to access large file system data sets that need to be spread across
-the several nodes in the jobs cpuset in order to fit.  Without this
-policy, especially for jobs that might have one thread reading in the
-data set, the memory allocation across the nodes in the jobs cpuset
-can become very uneven.
-
-1.7 What is sched_load_balance ?
---------------------------------
-
-The kernel scheduler (kernel/sched/core.c) automatically load balances
-tasks.  If one CPU is underutilized, kernel code running on that
-CPU will look for tasks on other more overloaded CPUs and move those
-tasks to itself, within the constraints of such placement mechanisms
-as cpusets and sched_setaffinity.
-
-The algorithmic cost of load balancing and its impact on key shared
-kernel data structures such as the task list increases more than
-linearly with the number of CPUs being balanced.  So the scheduler
-has support to partition the systems CPUs into a number of sched
-domains such that it only load balances within each sched domain.
-Each sched domain covers some subset of the CPUs in the system;
-no two sched domains overlap; some CPUs might not be in any sched
-domain and hence won't be load balanced.
-
-Put simply, it costs less to balance between two smaller sched domains
-than one big one, but doing so means that overloads in one of the
-two domains won't be load balanced to the other one.
-
-By default, there is one sched domain covering all CPUs, including those
-marked isolated using the kernel boot time "isolcpus=" argument. However,
-the isolated CPUs will not participate in load balancing, and will not
-have tasks running on them unless explicitly assigned.
-
-This default load balancing across all CPUs is not well suited for
-the following two situations:
- 1) On large systems, load balancing across many CPUs is expensive.
-    If the system is managed using cpusets to place independent jobs
-    on separate sets of CPUs, full load balancing is unnecessary.
- 2) Systems supporting realtime on some CPUs need to minimize
-    system overhead on those CPUs, including avoiding task load
-    balancing if that is not needed.
-
-When the per-cpuset flag "cpuset.sched_load_balance" is enabled (the default
-setting), it requests that all the CPUs in that cpusets allowed 'cpuset.cpus'
-be contained in a single sched domain, ensuring that load balancing
-can move a task (not otherwised pinned, as by sched_setaffinity)
-from any CPU in that cpuset to any other.
-
-When the per-cpuset flag "cpuset.sched_load_balance" is disabled, then the
-scheduler will avoid load balancing across the CPUs in that cpuset,
---except-- in so far as is necessary because some overlapping cpuset
-has "sched_load_balance" enabled.
-
-So, for example, if the top cpuset has the flag "cpuset.sched_load_balance"
-enabled, then the scheduler will have one sched domain covering all
-CPUs, and the setting of the "cpuset.sched_load_balance" flag in any other
-cpusets won't matter, as we're already fully load balancing.
-
-Therefore in the above two situations, the top cpuset flag
-"cpuset.sched_load_balance" should be disabled, and only some of the smaller,
-child cpusets have this flag enabled.
-
-When doing this, you don't usually want to leave any unpinned tasks in
-the top cpuset that might use non-trivial amounts of CPU, as such tasks
-may be artificially constrained to some subset of CPUs, depending on
-the particulars of this flag setting in descendant cpusets.  Even if
-such a task could use spare CPU cycles in some other CPUs, the kernel
-scheduler might not consider the possibility of load balancing that
-task to that underused CPU.
-
-Of course, tasks pinned to a particular CPU can be left in a cpuset
-that disables "cpuset.sched_load_balance" as those tasks aren't going anywhere
-else anyway.
-
-There is an impedance mismatch here, between cpusets and sched domains.
-Cpusets are hierarchical and nest.  Sched domains are flat; they don't
-overlap and each CPU is in at most one sched domain.
-
-It is necessary for sched domains to be flat because load balancing
-across partially overlapping sets of CPUs would risk unstable dynamics
-that would be beyond our understanding.  So if each of two partially
-overlapping cpusets enables the flag 'cpuset.sched_load_balance', then we
-form a single sched domain that is a superset of both.  We won't move
-a task to a CPU outside its cpuset, but the scheduler load balancing
-code might waste some compute cycles considering that possibility.
-
-This mismatch is why there is not a simple one-to-one relation
-between which cpusets have the flag "cpuset.sched_load_balance" enabled,
-and the sched domain configuration.  If a cpuset enables the flag, it
-will get balancing across all its CPUs, but if it disables the flag,
-it will only be assured of no load balancing if no other overlapping
-cpuset enables the flag.
-
-If two cpusets have partially overlapping 'cpuset.cpus' allowed, and only
-one of them has this flag enabled, then the other may find its
-tasks only partially load balanced, just on the overlapping CPUs.
-This is just the general case of the top_cpuset example given a few
-paragraphs above.  In the general case, as in the top cpuset case,
-don't leave tasks that might use non-trivial amounts of CPU in
-such partially load balanced cpusets, as they may be artificially
-constrained to some subset of the CPUs allowed to them, for lack of
-load balancing to the other CPUs.
-
-CPUs in "cpuset.isolcpus" were excluded from load balancing by the
-isolcpus= kernel boot option, and will never be load balanced regardless
-of the value of "cpuset.sched_load_balance" in any cpuset.
-
-1.7.1 sched_load_balance implementation details.
-------------------------------------------------
-
-The per-cpuset flag 'cpuset.sched_load_balance' defaults to enabled (contrary
-to most cpuset flags.)  When enabled for a cpuset, the kernel will
-ensure that it can load balance across all the CPUs in that cpuset
-(makes sure that all the CPUs in the cpus_allowed of that cpuset are
-in the same sched domain.)
-
-If two overlapping cpusets both have 'cpuset.sched_load_balance' enabled,
-then they will be (must be) both in the same sched domain.
-
-If, as is the default, the top cpuset has 'cpuset.sched_load_balance' enabled,
-then by the above that means there is a single sched domain covering
-the whole system, regardless of any other cpuset settings.
-
-The kernel commits to user space that it will avoid load balancing
-where it can.  It will pick as fine a granularity partition of sched
-domains as it can while still providing load balancing for any set
-of CPUs allowed to a cpuset having 'cpuset.sched_load_balance' enabled.
-
-The internal kernel cpuset to scheduler interface passes from the
-cpuset code to the scheduler code a partition of the load balanced
-CPUs in the system. This partition is a set of subsets (represented
-as an array of struct cpumask) of CPUs, pairwise disjoint, that cover
-all the CPUs that must be load balanced.
-
-The cpuset code builds a new such partition and passes it to the
-scheduler sched domain setup code, to have the sched domains rebuilt
-as necessary, whenever:
- - the 'cpuset.sched_load_balance' flag of a cpuset with non-empty CPUs changes,
- - or CPUs come or go from a cpuset with this flag enabled,
- - or 'cpuset.sched_relax_domain_level' value of a cpuset with non-empty CPUs
-   and with this flag enabled changes,
- - or a cpuset with non-empty CPUs and with this flag enabled is removed,
- - or a cpu is offlined/onlined.
-
-This partition exactly defines what sched domains the scheduler should
-setup - one sched domain for each element (struct cpumask) in the
-partition.
-
-The scheduler remembers the currently active sched domain partitions.
-When the scheduler routine partition_sched_domains() is invoked from
-the cpuset code to update these sched domains, it compares the new
-partition requested with the current, and updates its sched domains,
-removing the old and adding the new, for each change.
-
-
-1.8 What is sched_relax_domain_level ?
---------------------------------------
-
-In sched domain, the scheduler migrates tasks in 2 ways; periodic load
-balance on tick, and at time of some schedule events.
-
-When a task is woken up, scheduler try to move the task on idle CPU.
-For example, if a task A running on CPU X activates another task B
-on the same CPU X, and if CPU Y is X's sibling and performing idle,
-then scheduler migrate task B to CPU Y so that task B can start on
-CPU Y without waiting task A on CPU X.
-
-And if a CPU run out of tasks in its runqueue, the CPU try to pull
-extra tasks from other busy CPUs to help them before it is going to
-be idle.
-
-Of course it takes some searching cost to find movable tasks and/or
-idle CPUs, the scheduler might not search all CPUs in the domain
-every time.  In fact, in some architectures, the searching ranges on
-events are limited in the same socket or node where the CPU locates,
-while the load balance on tick searches all.
-
-For example, assume CPU Z is relatively far from CPU X.  Even if CPU Z
-is idle while CPU X and the siblings are busy, scheduler can't migrate
-woken task B from X to Z since it is out of its searching range.
-As the result, task B on CPU X need to wait task A or wait load balance
-on the next tick.  For some applications in special situation, waiting
-1 tick may be too long.
-
-The 'cpuset.sched_relax_domain_level' file allows you to request changing
-this searching range as you like.  This file takes int value which
-indicates size of searching range in levels ideally as follows,
-otherwise initial value -1 that indicates the cpuset has no request.
-
-  -1  : no request. use system default or follow request of others.
-   0  : no search.
-   1  : search siblings (hyperthreads in a core).
-   2  : search cores in a package.
-   3  : search cpus in a node [= system wide on non-NUMA system]
-   4  : search nodes in a chunk of node [on NUMA system]
-   5  : search system wide [on NUMA system]
-
-The system default is architecture dependent.  The system default
-can be changed using the relax_domain_level= boot parameter.
-
-This file is per-cpuset and affect the sched domain where the cpuset
-belongs to.  Therefore if the flag 'cpuset.sched_load_balance' of a cpuset
-is disabled, then 'cpuset.sched_relax_domain_level' have no effect since
-there is no sched domain belonging the cpuset.
-
-If multiple cpusets are overlapping and hence they form a single sched
-domain, the largest value among those is used.  Be careful, if one
-requests 0 and others are -1 then 0 is used.
-
-Note that modifying this file will have both good and bad effects,
-and whether it is acceptable or not depends on your situation.
-Don't modify this file if you are not sure.
-
-If your situation is:
- - The migration costs between each cpu can be assumed considerably
-   small(for you) due to your special application's behavior or
-   special hardware support for CPU cache etc.
- - The searching cost doesn't have impact(for you) or you can make
-   the searching cost enough small by managing cpuset to compact etc.
- - The latency is required even it sacrifices cache hit rate etc.
-then increasing 'sched_relax_domain_level' would benefit you.
-
-
-1.9 How do I use cpusets ?
---------------------------
-
-In order to minimize the impact of cpusets on critical kernel
-code, such as the scheduler, and due to the fact that the kernel
-does not support one task updating the memory placement of another
-task directly, the impact on a task of changing its cpuset CPU
-or Memory Node placement, or of changing to which cpuset a task
-is attached, is subtle.
-
-If a cpuset has its Memory Nodes modified, then for each task attached
-to that cpuset, the next time that the kernel attempts to allocate
-a page of memory for that task, the kernel will notice the change
-in the task's cpuset, and update its per-task memory placement to
-remain within the new cpusets memory placement.  If the task was using
-mempolicy MPOL_BIND, and the nodes to which it was bound overlap with
-its new cpuset, then the task will continue to use whatever subset
-of MPOL_BIND nodes are still allowed in the new cpuset.  If the task
-was using MPOL_BIND and now none of its MPOL_BIND nodes are allowed
-in the new cpuset, then the task will be essentially treated as if it
-was MPOL_BIND bound to the new cpuset (even though its NUMA placement,
-as queried by get_mempolicy(), doesn't change).  If a task is moved
-from one cpuset to another, then the kernel will adjust the task's
-memory placement, as above, the next time that the kernel attempts
-to allocate a page of memory for that task.
-
-If a cpuset has its 'cpuset.cpus' modified, then each task in that cpuset
-will have its allowed CPU placement changed immediately.  Similarly,
-if a task's pid is written to another cpusets 'cpuset.tasks' file, then its
-allowed CPU placement is changed immediately.  If such a task had been
-bound to some subset of its cpuset using the sched_setaffinity() call,
-the task will be allowed to run on any CPU allowed in its new cpuset,
-negating the effect of the prior sched_setaffinity() call.
-
-In summary, the memory placement of a task whose cpuset is changed is
-updated by the kernel, on the next allocation of a page for that task,
-and the processor placement is updated immediately.
-
-Normally, once a page is allocated (given a physical page
-of main memory) then that page stays on whatever node it
-was allocated, so long as it remains allocated, even if the
-cpusets memory placement policy 'cpuset.mems' subsequently changes.
-If the cpuset flag file 'cpuset.memory_migrate' is set true, then when
-tasks are attached to that cpuset, any pages that task had
-allocated to it on nodes in its previous cpuset are migrated
-to the task's new cpuset. The relative placement of the page within
-the cpuset is preserved during these migration operations if possible.
-For example if the page was on the second valid node of the prior cpuset
-then the page will be placed on the second valid node of the new cpuset.
-
-Also if 'cpuset.memory_migrate' is set true, then if that cpuset's
-'cpuset.mems' file is modified, pages allocated to tasks in that
-cpuset, that were on nodes in the previous setting of 'cpuset.mems',
-will be moved to nodes in the new setting of 'mems.'
-Pages that were not in the task's prior cpuset, or in the cpuset's
-prior 'cpuset.mems' setting, will not be moved.
-
-There is an exception to the above.  If hotplug functionality is used
-to remove all the CPUs that are currently assigned to a cpuset,
-then all the tasks in that cpuset will be moved to the nearest ancestor
-with non-empty cpus.  But the moving of some (or all) tasks might fail if
-cpuset is bound with another cgroup subsystem which has some restrictions
-on task attaching.  In this failing case, those tasks will stay
-in the original cpuset, and the kernel will automatically update
-their cpus_allowed to allow all online CPUs.  When memory hotplug
-functionality for removing Memory Nodes is available, a similar exception
-is expected to apply there as well.  In general, the kernel prefers to
-violate cpuset placement, over starving a task that has had all
-its allowed CPUs or Memory Nodes taken offline.
-
-There is a second exception to the above.  GFP_ATOMIC requests are
-kernel internal allocations that must be satisfied, immediately.
-The kernel may drop some request, in rare cases even panic, if a
-GFP_ATOMIC alloc fails.  If the request cannot be satisfied within
-the current task's cpuset, then we relax the cpuset, and look for
-memory anywhere we can find it.  It's better to violate the cpuset
-than stress the kernel.
-
-To start a new job that is to be contained within a cpuset, the steps are:
-
- 1) mkdir /sys/fs/cgroup/cpuset
- 2) mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset
- 3) Create the new cpuset by doing mkdir's and write's (or echo's) in
-    the /sys/fs/cgroup/cpuset virtual file system.
- 4) Start a task that will be the "founding father" of the new job.
- 5) Attach that task to the new cpuset by writing its pid to the
-    /sys/fs/cgroup/cpuset tasks file for that cpuset.
- 6) fork, exec or clone the job tasks from this founding father task.
-
-For example, the following sequence of commands will setup a cpuset
-named "Charlie", containing just CPUs 2 and 3, and Memory Node 1,
-and then start a subshell 'sh' in that cpuset:
-
-  mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset
-  cd /sys/fs/cgroup/cpuset
-  mkdir Charlie
-  cd Charlie
-  /bin/echo 2-3 > cpuset.cpus
-  /bin/echo 1 > cpuset.mems
-  /bin/echo $$ > tasks
-  sh
-  # The subshell 'sh' is now running in cpuset Charlie
-  # The next line should display '/Charlie'
-  cat /proc/self/cpuset
-
-There are ways to query or modify cpusets:
- - via the cpuset file system directly, using the various cd, mkdir, echo,
-   cat, rmdir commands from the shell, or their equivalent from C.
- - via the C library libcpuset.
- - via the C library libcgroup.
-   (http://sourceforge.net/projects/libcg/)
- - via the python application cset.
-   (http://code.google.com/p/cpuset/)
-
-The sched_setaffinity calls can also be done at the shell prompt using
-SGI's runon or Robert Love's taskset.  The mbind and set_mempolicy
-calls can be done at the shell prompt using the numactl command
-(part of Andi Kleen's numa package).
-
-2. Usage Examples and Syntax
-============================
-
-2.1 Basic Usage
----------------
-
-Creating, modifying, using the cpusets can be done through the cpuset
-virtual filesystem.
-
-To mount it, type:
-# mount -t cgroup -o cpuset cpuset /sys/fs/cgroup/cpuset
-
-Then under /sys/fs/cgroup/cpuset you can find a tree that corresponds to the
-tree of the cpusets in the system. For instance, /sys/fs/cgroup/cpuset
-is the cpuset that holds the whole system.
-
-If you want to create a new cpuset under /sys/fs/cgroup/cpuset:
-# cd /sys/fs/cgroup/cpuset
-# mkdir my_cpuset
-
-Now you want to do something with this cpuset.
-# cd my_cpuset
-
-In this directory you can find several files:
-# ls
-cgroup.clone_children  cpuset.memory_pressure
-cgroup.event_control   cpuset.memory_spread_page
-cgroup.procs           cpuset.memory_spread_slab
-cpuset.cpu_exclusive   cpuset.mems
-cpuset.cpus            cpuset.sched_load_balance
-cpuset.mem_exclusive   cpuset.sched_relax_domain_level
-cpuset.mem_hardwall    notify_on_release
-cpuset.memory_migrate  tasks
-
-Reading them will give you information about the state of this cpuset:
-the CPUs and Memory Nodes it can use, the processes that are using
-it, its properties.  By writing to these files you can manipulate
-the cpuset.
-
-Set some flags:
-# /bin/echo 1 > cpuset.cpu_exclusive
-
-Add some cpus:
-# /bin/echo 0-7 > cpuset.cpus
-
-Add some mems:
-# /bin/echo 0-7 > cpuset.mems
-
-Now attach your shell to this cpuset:
-# /bin/echo $$ > tasks
-
-You can also create cpusets inside your cpuset by using mkdir in this
-directory.
-# mkdir my_sub_cs
-
-To remove a cpuset, just use rmdir:
-# rmdir my_sub_cs
-This will fail if the cpuset is in use (has cpusets inside, or has
-processes attached).
-
-Note that for legacy reasons, the "cpuset" filesystem exists as a
-wrapper around the cgroup filesystem.
-
-The command
-
-mount -t cpuset X /sys/fs/cgroup/cpuset
-
-is equivalent to
-
-mount -t cgroup -ocpuset,noprefix X /sys/fs/cgroup/cpuset
-echo "/sbin/cpuset_release_agent" > /sys/fs/cgroup/cpuset/release_agent
-
-2.2 Adding/removing cpus
-------------------------
-
-This is the syntax to use when writing in the cpus or mems files
-in cpuset directories:
-
-# /bin/echo 1-4 > cpuset.cpus		-> set cpus list to cpus 1,2,3,4
-# /bin/echo 1,2,3,4 > cpuset.cpus	-> set cpus list to cpus 1,2,3,4
-
-To add a CPU to a cpuset, write the new list of CPUs including the
-CPU to be added. To add 6 to the above cpuset:
-
-# /bin/echo 1-4,6 > cpuset.cpus	-> set cpus list to cpus 1,2,3,4,6
-
-Similarly to remove a CPU from a cpuset, write the new list of CPUs
-without the CPU to be removed.
-
-To remove all the CPUs:
-
-# /bin/echo "" > cpuset.cpus		-> clear cpus list
-
-2.3 Setting flags
------------------
-
-The syntax is very simple:
-
-# /bin/echo 1 > cpuset.cpu_exclusive 	-> set flag 'cpuset.cpu_exclusive'
-# /bin/echo 0 > cpuset.cpu_exclusive 	-> unset flag 'cpuset.cpu_exclusive'
-
-2.4 Attaching processes
------------------------
-
-# /bin/echo PID > tasks
-
-Note that it is PID, not PIDs. You can only attach ONE task at a time.
-If you have several tasks to attach, you have to do it one after another:
-
-# /bin/echo PID1 > tasks
-# /bin/echo PID2 > tasks
-	...
-# /bin/echo PIDn > tasks
-
-
-3. Questions
-============
-
-Q: what's up with this '/bin/echo' ?
-A: bash's builtin 'echo' command does not check calls to write() against
-   errors. If you use it in the cpuset file system, you won't be
-   able to tell whether a command succeeded or failed.
-
-Q: When I attach processes, only the first of the line gets really attached !
-A: We can only return one error code per call to write(). So you should also
-   put only ONE pid.
-
-4. Contact
-==========
-
-Web: http://www.bullopensource.org/cpuset
diff --git a/Documentation/cgroups/devices.txt b/Documentation/cgroups/devices.txt
deleted file mode 100644
index 3c1095ca02ea..000000000000
--- a/Documentation/cgroups/devices.txt
+++ /dev/null
@@ -1,116 +0,0 @@
-Device Whitelist Controller
-
-1. Description:
-
-Implement a cgroup to track and enforce open and mknod restrictions
-on device files.  A device cgroup associates a device access
-whitelist with each cgroup.  A whitelist entry has 4 fields.
-'type' is a (all), c (char), or b (block).  'all' means it applies
-to all types and all major and minor numbers.  Major and minor are
-either an integer or * for all.  Access is a composition of r
-(read), w (write), and m (mknod).
-
-The root device cgroup starts with rwm to 'all'.  A child device
-cgroup gets a copy of the parent.  Administrators can then remove
-devices from the whitelist or add new entries.  A child cgroup can
-never receive a device access which is denied by its parent.
-
-2. User Interface
-
-An entry is added using devices.allow, and removed using
-devices.deny.  For instance
-
-	echo 'c 1:3 mr' > /sys/fs/cgroup/1/devices.allow
-
-allows cgroup 1 to read and mknod the device usually known as
-/dev/null.  Doing
-
-	echo a > /sys/fs/cgroup/1/devices.deny
-
-will remove the default 'a *:* rwm' entry. Doing
-
-	echo a > /sys/fs/cgroup/1/devices.allow
-
-will add the 'a *:* rwm' entry to the whitelist.
-
-3. Security
-
-Any task can move itself between cgroups.  This clearly won't
-suffice, but we can decide the best way to adequately restrict
-movement as people get some experience with this.  We may just want
-to require CAP_SYS_ADMIN, which at least is a separate bit from
-CAP_MKNOD.  We may want to just refuse moving to a cgroup which
-isn't a descendant of the current one.  Or we may want to use
-CAP_MAC_ADMIN, since we really are trying to lock down root.
-
-CAP_SYS_ADMIN is needed to modify the whitelist or move another
-task to a new cgroup.  (Again we'll probably want to change that).
-
-A cgroup may not be granted more permissions than the cgroup's
-parent has.
-
-4. Hierarchy
-
-device cgroups maintain hierarchy by making sure a cgroup never has more
-access permissions than its parent.  Every time an entry is written to
-a cgroup's devices.deny file, all its children will have that entry removed
-from their whitelist and all the locally set whitelist entries will be
-re-evaluated.  In case one of the locally set whitelist entries would provide
-more access than the cgroup's parent, it'll be removed from the whitelist.
-
-Example:
-      A
-     / \
-        B
-
-    group        behavior	exceptions
-    A            allow		"b 8:* rwm", "c 116:1 rw"
-    B            deny		"c 1:3 rwm", "c 116:2 rwm", "b 3:* rwm"
-
-If a device is denied in group A:
-	# echo "c 116:* r" > A/devices.deny
-it'll propagate down and after revalidating B's entries, the whitelist entry
-"c 116:2 rwm" will be removed:
-
-    group        whitelist entries                        denied devices
-    A            all                                      "b 8:* rwm", "c 116:* rw"
-    B            "c 1:3 rwm", "b 3:* rwm"                 all the rest
-
-In case parent's exceptions change and local exceptions are not allowed
-anymore, they'll be deleted.
-
-Notice that new whitelist entries will not be propagated:
-      A
-     / \
-        B
-
-    group        whitelist entries                        denied devices
-    A            "c 1:3 rwm", "c 1:5 r"                   all the rest
-    B            "c 1:3 rwm", "c 1:5 r"                   all the rest
-
-when adding "c *:3 rwm":
-	# echo "c *:3 rwm" >A/devices.allow
-
-the result:
-    group        whitelist entries                        denied devices
-    A            "c *:3 rwm", "c 1:5 r"                   all the rest
-    B            "c 1:3 rwm", "c 1:5 r"                   all the rest
-
-but now it'll be possible to add new entries to B:
-	# echo "c 2:3 rwm" >B/devices.allow
-	# echo "c 50:3 r" >B/devices.allow
-or even
-	# echo "c *:3 rwm" >B/devices.allow
-
-Allowing or denying all by writing 'a' to devices.allow or devices.deny will
-not be possible once the device cgroups has children.
-
-4.1 Hierarchy (internal implementation)
-
-device cgroups is implemented internally using a behavior (ALLOW, DENY) and a
-list of exceptions.  The internal state is controlled using the same user
-interface to preserve compatibility with the previous whitelist-only
-implementation.  Removal or addition of exceptions that will reduce the access
-to devices will be propagated down the hierarchy.
-For every propagated exception, the effective rules will be re-evaluated based
-on current parent's access rules.
diff --git a/Documentation/cgroups/freezer-subsystem.txt b/Documentation/cgroups/freezer-subsystem.txt
deleted file mode 100644
index e831cb2b8394..000000000000
--- a/Documentation/cgroups/freezer-subsystem.txt
+++ /dev/null
@@ -1,123 +0,0 @@
-The cgroup freezer is useful to batch job management system which start
-and stop sets of tasks in order to schedule the resources of a machine
-according to the desires of a system administrator. This sort of program
-is often used on HPC clusters to schedule access to the cluster as a
-whole. The cgroup freezer uses cgroups to describe the set of tasks to
-be started/stopped by the batch job management system. It also provides
-a means to start and stop the tasks composing the job.
-
-The cgroup freezer will also be useful for checkpointing running groups
-of tasks. The freezer allows the checkpoint code to obtain a consistent
-image of the tasks by attempting to force the tasks in a cgroup into a
-quiescent state. Once the tasks are quiescent another task can
-walk /proc or invoke a kernel interface to gather information about the
-quiesced tasks. Checkpointed tasks can be restarted later should a
-recoverable error occur. This also allows the checkpointed tasks to be
-migrated between nodes in a cluster by copying the gathered information
-to another node and restarting the tasks there.
-
-Sequences of SIGSTOP and SIGCONT are not always sufficient for stopping
-and resuming tasks in userspace. Both of these signals are observable
-from within the tasks we wish to freeze. While SIGSTOP cannot be caught,
-blocked, or ignored it can be seen by waiting or ptracing parent tasks.
-SIGCONT is especially unsuitable since it can be caught by the task. Any
-programs designed to watch for SIGSTOP and SIGCONT could be broken by
-attempting to use SIGSTOP and SIGCONT to stop and resume tasks. We can
-demonstrate this problem using nested bash shells:
-
-	$ echo $$
-	16644
-	$ bash
-	$ echo $$
-	16690
-
-	From a second, unrelated bash shell:
-	$ kill -SIGSTOP 16690
-	$ kill -SIGCONT 16690
-
-	<at this point 16690 exits and causes 16644 to exit too>
-
-This happens because bash can observe both signals and choose how it
-responds to them.
-
-Another example of a program which catches and responds to these
-signals is gdb. In fact any program designed to use ptrace is likely to
-have a problem with this method of stopping and resuming tasks.
-
-In contrast, the cgroup freezer uses the kernel freezer code to
-prevent the freeze/unfreeze cycle from becoming visible to the tasks
-being frozen. This allows the bash example above and gdb to run as
-expected.
-
-The cgroup freezer is hierarchical. Freezing a cgroup freezes all
-tasks belonging to the cgroup and all its descendant cgroups. Each
-cgroup has its own state (self-state) and the state inherited from the
-parent (parent-state). Iff both states are THAWED, the cgroup is
-THAWED.
-
-The following cgroupfs files are created by cgroup freezer.
-
-* freezer.state: Read-write.
-
-  When read, returns the effective state of the cgroup - "THAWED",
-  "FREEZING" or "FROZEN". This is the combined self and parent-states.
-  If any is freezing, the cgroup is freezing (FREEZING or FROZEN).
-
-  FREEZING cgroup transitions into FROZEN state when all tasks
-  belonging to the cgroup and its descendants become frozen. Note that
-  a cgroup reverts to FREEZING from FROZEN after a new task is added
-  to the cgroup or one of its descendant cgroups until the new task is
-  frozen.
-
-  When written, sets the self-state of the cgroup. Two values are
-  allowed - "FROZEN" and "THAWED". If FROZEN is written, the cgroup,
-  if not already freezing, enters FREEZING state along with all its
-  descendant cgroups.
-
-  If THAWED is written, the self-state of the cgroup is changed to
-  THAWED.  Note that the effective state may not change to THAWED if
-  the parent-state is still freezing. If a cgroup's effective state
-  becomes THAWED, all its descendants which are freezing because of
-  the cgroup also leave the freezing state.
-
-* freezer.self_freezing: Read only.
-
-  Shows the self-state. 0 if the self-state is THAWED; otherwise, 1.
-  This value is 1 iff the last write to freezer.state was "FROZEN".
-
-* freezer.parent_freezing: Read only.
-
-  Shows the parent-state.  0 if none of the cgroup's ancestors is
-  frozen; otherwise, 1.
-
-The root cgroup is non-freezable and the above interface files don't
-exist.
-
-* Examples of usage :
-
-   # mkdir /sys/fs/cgroup/freezer
-   # mount -t cgroup -ofreezer freezer /sys/fs/cgroup/freezer
-   # mkdir /sys/fs/cgroup/freezer/0
-   # echo $some_pid > /sys/fs/cgroup/freezer/0/tasks
-
-to get status of the freezer subsystem :
-
-   # cat /sys/fs/cgroup/freezer/0/freezer.state
-   THAWED
-
-to freeze all tasks in the container :
-
-   # echo FROZEN > /sys/fs/cgroup/freezer/0/freezer.state
-   # cat /sys/fs/cgroup/freezer/0/freezer.state
-   FREEZING
-   # cat /sys/fs/cgroup/freezer/0/freezer.state
-   FROZEN
-
-to unfreeze all tasks in the container :
-
-   # echo THAWED > /sys/fs/cgroup/freezer/0/freezer.state
-   # cat /sys/fs/cgroup/freezer/0/freezer.state
-   THAWED
-
-This is the basic mechanism which should do the right thing for user space task
-in a simple scenario.
diff --git a/Documentation/cgroups/hugetlb.txt b/Documentation/cgroups/hugetlb.txt
deleted file mode 100644
index 106245c3aecc..000000000000
--- a/Documentation/cgroups/hugetlb.txt
+++ /dev/null
@@ -1,45 +0,0 @@
-HugeTLB Controller
--------------------
-
-The HugeTLB controller allows to limit the HugeTLB usage per control group and
-enforces the controller limit during page fault. Since HugeTLB doesn't
-support page reclaim, enforcing the limit at page fault time implies that,
-the application will get SIGBUS signal if it tries to access HugeTLB pages
-beyond its limit. This requires the application to know beforehand how much
-HugeTLB pages it would require for its use.
-
-HugeTLB controller can be created by first mounting the cgroup filesystem.
-
-# mount -t cgroup -o hugetlb none /sys/fs/cgroup
-
-With the above step, the initial or the parent HugeTLB group becomes
-visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in
-the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup.
-
-New groups can be created under the parent group /sys/fs/cgroup.
-
-# cd /sys/fs/cgroup
-# mkdir g1
-# echo $$ > g1/tasks
-
-The above steps create a new group g1 and move the current shell
-process (bash) into it.
-
-Brief summary of control files
-
- hugetlb.<hugepagesize>.limit_in_bytes     # set/show limit of "hugepagesize" hugetlb usage
- hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb  usage recorded
- hugetlb.<hugepagesize>.usage_in_bytes     # show current usage for "hugepagesize" hugetlb
- hugetlb.<hugepagesize>.failcnt		   # show the number of allocation failure due to HugeTLB limit
-
-For a system supporting two hugepage size (16M and 16G) the control
-files include:
-
-hugetlb.16GB.limit_in_bytes
-hugetlb.16GB.max_usage_in_bytes
-hugetlb.16GB.usage_in_bytes
-hugetlb.16GB.failcnt
-hugetlb.16MB.limit_in_bytes
-hugetlb.16MB.max_usage_in_bytes
-hugetlb.16MB.usage_in_bytes
-hugetlb.16MB.failcnt
diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt
deleted file mode 100644
index 8870b0212150..000000000000
--- a/Documentation/cgroups/memcg_test.txt
+++ /dev/null
@@ -1,280 +0,0 @@
-Memory Resource Controller(Memcg)  Implementation Memo.
-Last Updated: 2010/2
-Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34).
-
-Because VM is getting complex (one of reasons is memcg...), memcg's behavior
-is complex. This is a document for memcg's internal behavior.
-Please note that implementation details can be changed.
-
-(*) Topics on API should be in Documentation/cgroups/memory.txt)
-
-0. How to record usage ?
-   2 objects are used.
-
-   page_cgroup ....an object per page.
-	Allocated at boot or memory hotplug. Freed at memory hot removal.
-
-   swap_cgroup ... an entry per swp_entry.
-	Allocated at swapon(). Freed at swapoff().
-
-   The page_cgroup has USED bit and double count against a page_cgroup never
-   occurs. swap_cgroup is used only when a charged page is swapped-out.
-
-1. Charge
-
-   a page/swp_entry may be charged (usage += PAGE_SIZE) at
-
-	mem_cgroup_try_charge()
-
-2. Uncharge
-  a page/swp_entry may be uncharged (usage -= PAGE_SIZE) by
-
-	mem_cgroup_uncharge()
-	  Called when a page's refcount goes down to 0.
-
-	mem_cgroup_uncharge_swap()
-	  Called when swp_entry's refcnt goes down to 0. A charge against swap
-	  disappears.
-
-3. charge-commit-cancel
-	Memcg pages are charged in two steps:
-		mem_cgroup_try_charge()
-		mem_cgroup_commit_charge() or mem_cgroup_cancel_charge()
-
-	At try_charge(), there are no flags to say "this page is charged".
-	at this point, usage += PAGE_SIZE.
-
-	At commit(), the page is associated with the memcg.
-
-	At cancel(), simply usage -= PAGE_SIZE.
-
-Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
-
-4. Anonymous
-	Anonymous page is newly allocated at
-		  - page fault into MAP_ANONYMOUS mapping.
-		  - Copy-On-Write.
-
-	4.1 Swap-in.
-	At swap-in, the page is taken from swap-cache. There are 2 cases.
-
-	(a) If the SwapCache is newly allocated and read, it has no charges.
-	(b) If the SwapCache has been mapped by processes, it has been
-	    charged already.
-
-	4.2 Swap-out.
-	At swap-out, typical state transition is below.
-
-	(a) add to swap cache. (marked as SwapCache)
-	    swp_entry's refcnt += 1.
-	(b) fully unmapped.
-	    swp_entry's refcnt += # of ptes.
-	(c) write back to swap.
-	(d) delete from swap cache. (remove from SwapCache)
-	    swp_entry's refcnt -= 1.
-
-
-	Finally, at task exit,
-	(e) zap_pte() is called and swp_entry's refcnt -=1 -> 0.
-
-5. Page Cache
-   	Page Cache is charged at
-	- add_to_page_cache_locked().
-
-	The logic is very clear. (About migration, see below)
-	Note: __remove_from_page_cache() is called by remove_from_page_cache()
-	and __remove_mapping().
-
-6. Shmem(tmpfs) Page Cache
-	The best way to understand shmem's page state transition is to read
-	mm/shmem.c.
-	But brief explanation of the behavior of memcg around shmem will be
-	helpful to understand the logic.
-
-	Shmem's page (just leaf page, not direct/indirect block) can be on
-		- radix-tree of shmem's inode.
-		- SwapCache.
-		- Both on radix-tree and SwapCache. This happens at swap-in
-		  and swap-out,
-
-	It's charged when...
-	- A new page is added to shmem's radix-tree.
-	- A swp page is read. (move a charge from swap_cgroup to page_cgroup)
-
-7. Page Migration
-
-	mem_cgroup_migrate()
-
-8. LRU
-        Each memcg has its own private LRU. Now, its handling is under global
-	VM's control (means that it's handled under global zone->lru_lock).
-	Almost all routines around memcg's LRU is called by global LRU's
-	list management functions under zone->lru_lock().
-
-	A special function is mem_cgroup_isolate_pages(). This scans
-	memcg's private LRU and call __isolate_lru_page() to extract a page
-	from LRU.
-	(By __isolate_lru_page(), the page is removed from both of global and
-	 private LRU.)
-
-
-9. Typical Tests.
-
- Tests for racy cases.
-
- 9.1 Small limit to memcg.
-	When you do test to do racy case, it's good test to set memcg's limit
-	to be very small rather than GB. Many races found in the test under
-	xKB or xxMB limits.
-	(Memory behavior under GB and Memory behavior under MB shows very
-	 different situation.)
-
- 9.2 Shmem
-	Historically, memcg's shmem handling was poor and we saw some amount
-	of troubles here. This is because shmem is page-cache but can be
-	SwapCache. Test with shmem/tmpfs is always good test.
-
- 9.3 Migration
-	For NUMA, migration is an another special case. To do easy test, cpuset
-	is useful. Following is a sample script to do migration.
-
-	mount -t cgroup -o cpuset none /opt/cpuset
-
-	mkdir /opt/cpuset/01
-	echo 1 > /opt/cpuset/01/cpuset.cpus
-	echo 0 > /opt/cpuset/01/cpuset.mems
-	echo 1 > /opt/cpuset/01/cpuset.memory_migrate
-	mkdir /opt/cpuset/02
-	echo 1 > /opt/cpuset/02/cpuset.cpus
-	echo 1 > /opt/cpuset/02/cpuset.mems
-	echo 1 > /opt/cpuset/02/cpuset.memory_migrate
-
-	In above set, when you moves a task from 01 to 02, page migration to
-	node 0 to node 1 will occur. Following is a script to migrate all
-	under cpuset.
-	--
-	move_task()
-	{
-	for pid in $1
-        do
-                /bin/echo $pid >$2/tasks 2>/dev/null
-		echo -n $pid
-		echo -n " "
-        done
-	echo END
-	}
-
-	G1_TASK=`cat ${G1}/tasks`
-	G2_TASK=`cat ${G2}/tasks`
-	move_task "${G1_TASK}" ${G2} &
-	--
- 9.4 Memory hotplug.
-	memory hotplug test is one of good test.
-	to offline memory, do following.
-	# echo offline > /sys/devices/system/memory/memoryXXX/state
-	(XXX is the place of memory)
-	This is an easy way to test page migration, too.
-
- 9.5 mkdir/rmdir
-	When using hierarchy, mkdir/rmdir test should be done.
-	Use tests like the following.
-
-	echo 1 >/opt/cgroup/01/memory/use_hierarchy
-	mkdir /opt/cgroup/01/child_a
-	mkdir /opt/cgroup/01/child_b
-
-	set limit to 01.
-	add limit to 01/child_b
-	run jobs under child_a and child_b
-
-	create/delete following groups at random while jobs are running.
-	/opt/cgroup/01/child_a/child_aa
-	/opt/cgroup/01/child_b/child_bb
-	/opt/cgroup/01/child_c
-
-	running new jobs in new group is also good.
-
- 9.6 Mount with other subsystems.
-	Mounting with other subsystems is a good test because there is a
-	race and lock dependency with other cgroup subsystems.
-
-	example)
-	# mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices
-
-	and do task move, mkdir, rmdir etc...under this.
-
- 9.7 swapoff.
-	Besides management of swap is one of complicated parts of memcg,
-	call path of swap-in at swapoff is not same as usual swap-in path..
-	It's worth to be tested explicitly.
-
-	For example, test like following is good.
-	(Shell-A)
-	# mount -t cgroup none /cgroup -o memory
-	# mkdir /cgroup/test
-	# echo 40M > /cgroup/test/memory.limit_in_bytes
-	# echo 0 > /cgroup/test/tasks
-	Run malloc(100M) program under this. You'll see 60M of swaps.
-	(Shell-B)
-	# move all tasks in /cgroup/test to /cgroup
-	# /sbin/swapoff -a
-	# rmdir /cgroup/test
-	# kill malloc task.
-
-	Of course, tmpfs v.s. swapoff test should be tested, too.
-
- 9.8 OOM-Killer
-	Out-of-memory caused by memcg's limit will kill tasks under
-	the memcg. When hierarchy is used, a task under hierarchy
-	will be killed by the kernel.
-	In this case, panic_on_oom shouldn't be invoked and tasks
-	in other groups shouldn't be killed.
-
-	It's not difficult to cause OOM under memcg as following.
-	Case A) when you can swapoff
-	#swapoff -a
-	#echo 50M > /memory.limit_in_bytes
-	run 51M of malloc
-
-	Case B) when you use mem+swap limitation.
-	#echo 50M > memory.limit_in_bytes
-	#echo 50M > memory.memsw.limit_in_bytes
-	run 51M of malloc
-
- 9.9 Move charges at task migration
-	Charges associated with a task can be moved along with task migration.
-
-	(Shell-A)
-	#mkdir /cgroup/A
-	#echo $$ >/cgroup/A/tasks
-	run some programs which uses some amount of memory in /cgroup/A.
-
-	(Shell-B)
-	#mkdir /cgroup/B
-	#echo 1 >/cgroup/B/memory.move_charge_at_immigrate
-	#echo "pid of the program running in group A" >/cgroup/B/tasks
-
-	You can see charges have been moved by reading *.usage_in_bytes or
-	memory.stat of both A and B.
-	See 8.2 of Documentation/cgroups/memory.txt to see what value should be
-	written to move_charge_at_immigrate.
-
- 9.10 Memory thresholds
-	Memory controller implements memory thresholds using cgroups notification
-	API. You can use tools/cgroup/cgroup_event_listener.c to test it.
-
-	(Shell-A) Create cgroup and run event listener
-	# mkdir /cgroup/A
-	# ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M
-
-	(Shell-B) Add task to cgroup and try to allocate and free memory
-	# echo $$ >/cgroup/A/tasks
-	# a="$(dd if=/dev/zero bs=1M count=10)"
-	# a=
-
-	You will see message from cgroup_event_listener every time you cross
-	the thresholds.
-
-	Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds.
-
-	It's good idea to test root cgroup as well.
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
deleted file mode 100644
index ff71e16cc752..000000000000
--- a/Documentation/cgroups/memory.txt
+++ /dev/null
@@ -1,876 +0,0 @@
-Memory Resource Controller
-
-NOTE: This document is hopelessly outdated and it asks for a complete
-      rewrite. It still contains a useful information so we are keeping it
-      here but make sure to check the current code if you need a deeper
-      understanding.
-
-NOTE: The Memory Resource Controller has generically been referred to as the
-      memory controller in this document. Do not confuse memory controller
-      used here with the memory controller that is used in hardware.
-
-(For editors)
-In this document:
-      When we mention a cgroup (cgroupfs's directory) with memory controller,
-      we call it "memory cgroup". When you see git-log and source code, you'll
-      see patch's title and function names tend to use "memcg".
-      In this document, we avoid using it.
-
-Benefits and Purpose of the memory controller
-
-The memory controller isolates the memory behaviour of a group of tasks
-from the rest of the system. The article on LWN [12] mentions some probable
-uses of the memory controller. The memory controller can be used to
-
-a. Isolate an application or a group of applications
-   Memory-hungry applications can be isolated and limited to a smaller
-   amount of memory.
-b. Create a cgroup with a limited amount of memory; this can be used
-   as a good alternative to booting with mem=XXXX.
-c. Virtualization solutions can control the amount of memory they want
-   to assign to a virtual machine instance.
-d. A CD/DVD burner could control the amount of memory used by the
-   rest of the system to ensure that burning does not fail due to lack
-   of available memory.
-e. There are several other use cases; find one or use the controller just
-   for fun (to learn and hack on the VM subsystem).
-
-Current Status: linux-2.6.34-mmotm(development version of 2010/April)
-
-Features:
- - accounting anonymous pages, file caches, swap caches usage and limiting them.
- - pages are linked to per-memcg LRU exclusively, and there is no global LRU.
- - optionally, memory+swap usage can be accounted and limited.
- - hierarchical accounting
- - soft limit
- - moving (recharging) account at moving a task is selectable.
- - usage threshold notifier
- - memory pressure notifier
- - oom-killer disable knob and oom-notifier
- - Root cgroup has no limit controls.
-
- Kernel memory support is a work in progress, and the current version provides
- basically functionality. (See Section 2.7)
-
-Brief summary of control files.
-
- tasks				 # attach a task(thread) and show list of threads
- cgroup.procs			 # show list of processes
- cgroup.event_control		 # an interface for event_fd()
- memory.usage_in_bytes		 # show current usage for memory
-				 (See 5.5 for details)
- memory.memsw.usage_in_bytes	 # show current usage for memory+Swap
-				 (See 5.5 for details)
- memory.limit_in_bytes		 # set/show limit of memory usage
- memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage
- memory.failcnt			 # show the number of memory usage hits limits
- memory.memsw.failcnt		 # show the number of memory+Swap hits limits
- memory.max_usage_in_bytes	 # show max memory usage recorded
- memory.memsw.max_usage_in_bytes # show max memory+Swap usage recorded
- memory.soft_limit_in_bytes	 # set/show soft limit of memory usage
- memory.stat			 # show various statistics
- memory.use_hierarchy		 # set/show hierarchical account enabled
- memory.force_empty		 # trigger forced move charge to parent
- memory.pressure_level		 # set memory pressure notifications
- memory.swappiness		 # set/show swappiness parameter of vmscan
-				 (See sysctl's vm.swappiness)
- memory.move_charge_at_immigrate # set/show controls of moving charges
- memory.oom_control		 # set/show oom controls.
- memory.numa_stat		 # show the number of memory usage per numa node
-
- memory.kmem.limit_in_bytes      # set/show hard limit for kernel memory
- memory.kmem.usage_in_bytes      # show current kernel memory allocation
- memory.kmem.failcnt             # show the number of kernel memory usage hits limits
- memory.kmem.max_usage_in_bytes  # show max kernel memory usage recorded
-
- memory.kmem.tcp.limit_in_bytes  # set/show hard limit for tcp buf memory
- memory.kmem.tcp.usage_in_bytes  # show current tcp buf memory allocation
- memory.kmem.tcp.failcnt            # show the number of tcp buf memory usage hits limits
- memory.kmem.tcp.max_usage_in_bytes # show max tcp buf memory usage recorded
-
-1. History
-
-The memory controller has a long history. A request for comments for the memory
-controller was posted by Balbir Singh [1]. At the time the RFC was posted
-there were several implementations for memory control. The goal of the
-RFC was to build consensus and agreement for the minimal features required
-for memory control. The first RSS controller was posted by Balbir Singh[2]
-in Feb 2007. Pavel Emelianov [3][4][5] has since posted three versions of the
-RSS controller. At OLS, at the resource management BoF, everyone suggested
-that we handle both page cache and RSS together. Another request was raised
-to allow user space handling of OOM. The current memory controller is
-at version 6; it combines both mapped (RSS) and unmapped Page
-Cache Control [11].
-
-2. Memory Control
-
-Memory is a unique resource in the sense that it is present in a limited
-amount. If a task requires a lot of CPU processing, the task can spread
-its processing over a period of hours, days, months or years, but with
-memory, the same physical memory needs to be reused to accomplish the task.
-
-The memory controller implementation has been divided into phases. These
-are:
-
-1. Memory controller
-2. mlock(2) controller
-3. Kernel user memory accounting and slab control
-4. user mappings length controller
-
-The memory controller is the first controller developed.
-
-2.1. Design
-
-The core of the design is a counter called the page_counter. The
-page_counter tracks the current memory usage and limit of the group of
-processes associated with the controller. Each cgroup has a memory controller
-specific data structure (mem_cgroup) associated with it.
-
-2.2. Accounting
-
-		+--------------------+
-		|  mem_cgroup        |
-		|  (page_counter)    |
-		+--------------------+
-		 /            ^      \
-		/             |       \
-           +---------------+  |        +---------------+
-           | mm_struct     |  |....    | mm_struct     |
-           |               |  |        |               |
-           +---------------+  |        +---------------+
-                              |
-                              + --------------+
-                                              |
-           +---------------+           +------+--------+
-           | page          +---------->  page_cgroup|
-           |               |           |               |
-           +---------------+           +---------------+
-
-             (Figure 1: Hierarchy of Accounting)
-
-
-Figure 1 shows the important aspects of the controller
-
-1. Accounting happens per cgroup
-2. Each mm_struct knows about which cgroup it belongs to
-3. Each page has a pointer to the page_cgroup, which in turn knows the
-   cgroup it belongs to
-
-The accounting is done as follows: mem_cgroup_charge_common() is invoked to
-set up the necessary data structures and check if the cgroup that is being
-charged is over its limit. If it is, then reclaim is invoked on the cgroup.
-More details can be found in the reclaim section of this document.
-If everything goes well, a page meta-data-structure called page_cgroup is
-updated. page_cgroup has its own LRU on cgroup.
-(*) page_cgroup structure is allocated at boot/memory-hotplug time.
-
-2.2.1 Accounting details
-
-All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
-Some pages which are never reclaimable and will not be on the LRU
-are not accounted. We just account pages under usual VM management.
-
-RSS pages are accounted at page_fault unless they've already been accounted
-for earlier. A file page will be accounted for as Page Cache when it's
-inserted into inode (radix-tree). While it's mapped into the page tables of
-processes, duplicate accounting is carefully avoided.
-
-An RSS page is unaccounted when it's fully unmapped. A PageCache page is
-unaccounted when it's removed from radix-tree. Even if RSS pages are fully
-unmapped (by kswapd), they may exist as SwapCache in the system until they
-are really freed. Such SwapCaches are also accounted.
-A swapped-in page is not accounted until it's mapped.
-
-Note: The kernel does swapin-readahead and reads multiple swaps at once.
-This means swapped-in pages may contain pages for other tasks than a task
-causing page fault. So, we avoid accounting at swap-in I/O.
-
-At page migration, accounting information is kept.
-
-Note: we just account pages-on-LRU because our purpose is to control amount
-of used pages; not-on-LRU pages tend to be out-of-control from VM view.
-
-2.3 Shared Page Accounting
-
-Shared pages are accounted on the basis of the first touch approach. The
-cgroup that first touches a page is accounted for the page. The principle
-behind this approach is that a cgroup that aggressively uses a shared
-page will eventually get charged for it (once it is uncharged from
-the cgroup that brought it in -- this will happen on memory pressure).
-
-But see section 8.2: when moving a task to another cgroup, its pages may
-be recharged to the new cgroup, if move_charge_at_immigrate has been chosen.
-
-Exception: If CONFIG_MEMCG_SWAP is not used.
-When you do swapoff and make swapped-out pages of shmem(tmpfs) to
-be backed into memory in force, charges for pages are accounted against the
-caller of swapoff rather than the users of shmem.
-
-2.4 Swap Extension (CONFIG_MEMCG_SWAP)
-
-Swap Extension allows you to record charge for swap. A swapped-in page is
-charged back to original page allocator if possible.
-
-When swap is accounted, following files are added.
- - memory.memsw.usage_in_bytes.
- - memory.memsw.limit_in_bytes.
-
-memsw means memory+swap. Usage of memory+swap is limited by
-memsw.limit_in_bytes.
-
-Example: Assume a system with 4G of swap. A task which allocates 6G of memory
-(by mistake) under 2G memory limitation will use all swap.
-In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap.
-By using the memsw limit, you can avoid system OOM which can be caused by swap
-shortage.
-
-* why 'memory+swap' rather than swap.
-The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
-to move account from memory to swap...there is no change in usage of
-memory+swap. In other words, when we want to limit the usage of swap without
-affecting global LRU, memory+swap limit is better than just limiting swap from
-an OS point of view.
-
-* What happens when a cgroup hits memory.memsw.limit_in_bytes
-When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do swap-out
-in this cgroup. Then, swap-out will not be done by cgroup routine and file
-caches are dropped. But as mentioned above, global LRU can do swapout memory
-from it for sanity of the system's memory management state. You can't forbid
-it by cgroup.
-
-2.5 Reclaim
-
-Each cgroup maintains a per cgroup LRU which has the same structure as
-global VM. When a cgroup goes over its limit, we first try
-to reclaim memory from the cgroup so as to make space for the new
-pages that the cgroup has touched. If the reclaim is unsuccessful,
-an OOM routine is invoked to select and kill the bulkiest task in the
-cgroup. (See 10. OOM Control below.)
-
-The reclaim algorithm has not been modified for cgroups, except that
-pages that are selected for reclaiming come from the per-cgroup LRU
-list.
-
-NOTE: Reclaim does not work for the root cgroup, since we cannot set any
-limits on the root cgroup.
-
-Note2: When panic_on_oom is set to "2", the whole system will panic.
-
-When oom event notifier is registered, event will be delivered.
-(See oom_control section)
-
-2.6 Locking
-
-   lock_page_cgroup()/unlock_page_cgroup() should not be called under
-   mapping->tree_lock.
-
-   Other lock order is following:
-   PG_locked.
-   mm->page_table_lock
-       zone->lru_lock
-	  lock_page_cgroup.
-  In many cases, just lock_page_cgroup() is called.
-  per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
-  zone->lru_lock, it has no lock of its own.
-
-2.7 Kernel Memory Extension (CONFIG_MEMCG_KMEM)
-
-With the Kernel memory extension, the Memory Controller is able to limit
-the amount of kernel memory used by the system. Kernel memory is fundamentally
-different than user memory, since it can't be swapped out, which makes it
-possible to DoS the system by consuming too much of this precious resource.
-
-Kernel memory won't be accounted at all until limit on a group is set. This
-allows for existing setups to continue working without disruption.  The limit
-cannot be set if the cgroup have children, or if there are already tasks in the
-cgroup. Attempting to set the limit under those conditions will return -EBUSY.
-When use_hierarchy == 1 and a group is accounted, its children will
-automatically be accounted regardless of their limit value.
-
-After a group is first limited, it will be kept being accounted until it
-is removed. The memory limitation itself, can of course be removed by writing
--1 to memory.kmem.limit_in_bytes. In this case, kmem will be accounted, but not
-limited.
-
-Kernel memory limits are not imposed for the root cgroup. Usage for the root
-cgroup may or may not be accounted. The memory used is accumulated into
-memory.kmem.usage_in_bytes, or in a separate counter when it makes sense.
-(currently only for tcp).
-The main "kmem" counter is fed into the main counter, so kmem charges will
-also be visible from the user counter.
-
-Currently no soft limit is implemented for kernel memory. It is future work
-to trigger slab reclaim when those limits are reached.
-
-2.7.1 Current Kernel Memory resources accounted
-
-* stack pages: every process consumes some stack pages. By accounting into
-kernel memory, we prevent new processes from being created when the kernel
-memory usage is too high.
-
-* slab pages: pages allocated by the SLAB or SLUB allocator are tracked. A copy
-of each kmem_cache is created every time the cache is touched by the first time
-from inside the memcg. The creation is done lazily, so some objects can still be
-skipped while the cache is being created. All objects in a slab page should
-belong to the same memcg. This only fails to hold when a task is migrated to a
-different memcg during the page allocation by the cache.
-
-* sockets memory pressure: some sockets protocols have memory pressure
-thresholds. The Memory Controller allows them to be controlled individually
-per cgroup, instead of globally.
-
-* tcp memory pressure: sockets memory pressure for the tcp protocol.
-
-2.7.2 Common use cases
-
-Because the "kmem" counter is fed to the main user counter, kernel memory can
-never be limited completely independently of user memory. Say "U" is the user
-limit, and "K" the kernel limit. There are three possible ways limits can be
-set:
-
-    U != 0, K = unlimited:
-    This is the standard memcg limitation mechanism already present before kmem
-    accounting. Kernel memory is completely ignored.
-
-    U != 0, K < U:
-    Kernel memory is a subset of the user memory. This setup is useful in
-    deployments where the total amount of memory per-cgroup is overcommited.
-    Overcommiting kernel memory limits is definitely not recommended, since the
-    box can still run out of non-reclaimable memory.
-    In this case, the admin could set up K so that the sum of all groups is
-    never greater than the total memory, and freely set U at the cost of his
-    QoS.
-    WARNING: In the current implementation, memory reclaim will NOT be
-    triggered for a cgroup when it hits K while staying below U, which makes
-    this setup impractical.
-
-    U != 0, K >= U:
-    Since kmem charges will also be fed to the user counter and reclaim will be
-    triggered for the cgroup for both kinds of memory. This setup gives the
-    admin a unified view of memory, and it is also useful for people who just
-    want to track kernel memory usage.
-
-3. User Interface
-
-3.0. Configuration
-
-a. Enable CONFIG_CGROUPS
-b. Enable CONFIG_MEMCG
-c. Enable CONFIG_MEMCG_SWAP (to use swap extension)
-d. Enable CONFIG_MEMCG_KMEM (to use kmem extension)
-
-3.1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
-# mount -t tmpfs none /sys/fs/cgroup
-# mkdir /sys/fs/cgroup/memory
-# mount -t cgroup none /sys/fs/cgroup/memory -o memory
-
-3.2. Make the new group and move bash into it
-# mkdir /sys/fs/cgroup/memory/0
-# echo $$ > /sys/fs/cgroup/memory/0/tasks
-
-Since now we're in the 0 cgroup, we can alter the memory limit:
-# echo 4M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes
-
-NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
-mega or gigabytes. (Here, Kilo, Mega, Giga are Kibibytes, Mebibytes, Gibibytes.)
-
-NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
-NOTE: We cannot set limits on the root cgroup any more.
-
-# cat /sys/fs/cgroup/memory/0/memory.limit_in_bytes
-4194304
-
-We can check the usage:
-# cat /sys/fs/cgroup/memory/0/memory.usage_in_bytes
-1216512
-
-A successful write to this file does not guarantee a successful setting of
-this limit to the value written into the file. This can be due to a
-number of factors, such as rounding up to page boundaries or the total
-availability of memory on the system. The user is required to re-read
-this file after a write to guarantee the value committed by the kernel.
-
-# echo 1 > memory.limit_in_bytes
-# cat memory.limit_in_bytes
-4096
-
-The memory.failcnt field gives the number of times that the cgroup limit was
-exceeded.
-
-The memory.stat file gives accounting information. Now, the number of
-caches, RSS and Active pages/Inactive pages are shown.
-
-4. Testing
-
-For testing features and implementation, see memcg_test.txt.
-
-Performance test is also important. To see pure memory controller's overhead,
-testing on tmpfs will give you good numbers of small overheads.
-Example: do kernel make on tmpfs.
-
-Page-fault scalability is also important. At measuring parallel
-page fault test, multi-process test may be better than multi-thread
-test because it has noise of shared objects/status.
-
-But the above two are testing extreme situations.
-Trying usual test under memory controller is always helpful.
-
-4.1 Troubleshooting
-
-Sometimes a user might find that the application under a cgroup is
-terminated by the OOM killer. There are several causes for this:
-
-1. The cgroup limit is too low (just too low to do anything useful)
-2. The user is using anonymous memory and swap is turned off or too low
-
-A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of
-some of the pages cached in the cgroup (page cache pages).
-
-To know what happens, disabling OOM_Kill as per "10. OOM Control" (below) and
-seeing what happens will be helpful.
-
-4.2 Task migration
-
-When a task migrates from one cgroup to another, its charge is not
-carried forward by default. The pages allocated from the original cgroup still
-remain charged to it, the charge is dropped when the page is freed or
-reclaimed.
-
-You can move charges of a task along with task migration.
-See 8. "Move charges at task migration"
-
-4.3 Removing a cgroup
-
-A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
-cgroup might have some charge associated with it, even though all
-tasks have migrated away from it. (because we charge against pages, not
-against tasks.)
-
-We move the stats to root (if use_hierarchy==0) or parent (if
-use_hierarchy==1), and no change on the charge except uncharging
-from the child.
-
-Charges recorded in swap information is not updated at removal of cgroup.
-Recorded information is discarded and a cgroup which uses swap (swapcache)
-will be charged as a new owner of it.
-
-About use_hierarchy, see Section 6.
-
-5. Misc. interfaces.
-
-5.1 force_empty
-  memory.force_empty interface is provided to make cgroup's memory usage empty.
-  When writing anything to this
-
-  # echo 0 > memory.force_empty
-
-  the cgroup will be reclaimed and as many pages reclaimed as possible.
-
-  The typical use case for this interface is before calling rmdir().
-  Because rmdir() moves all pages to parent, some out-of-use page caches can be
-  moved to the parent. If you want to avoid that, force_empty will be useful.
-
-  Also, note that when memory.kmem.limit_in_bytes is set the charges due to
-  kernel pages will still be seen. This is not considered a failure and the
-  write will still return success. In this case, it is expected that
-  memory.kmem.usage_in_bytes == memory.usage_in_bytes.
-
-  About use_hierarchy, see Section 6.
-
-5.2 stat file
-
-memory.stat file includes following statistics
-
-# per-memory cgroup local status
-cache		- # of bytes of page cache memory.
-rss		- # of bytes of anonymous and swap cache memory (includes
-		transparent hugepages).
-rss_huge	- # of bytes of anonymous transparent hugepages.
-mapped_file	- # of bytes of mapped file (includes tmpfs/shmem)
-pgpgin		- # of charging events to the memory cgroup. The charging
-		event happens each time a page is accounted as either mapped
-		anon page(RSS) or cache page(Page Cache) to the cgroup.
-pgpgout		- # of uncharging events to the memory cgroup. The uncharging
-		event happens each time a page is unaccounted from the cgroup.
-swap		- # of bytes of swap usage
-dirty		- # of bytes that are waiting to get written back to the disk.
-writeback	- # of bytes of file/anon cache that are queued for syncing to
-		disk.
-inactive_anon	- # of bytes of anonymous and swap cache memory on inactive
-		LRU list.
-active_anon	- # of bytes of anonymous and swap cache memory on active
-		LRU list.
-inactive_file	- # of bytes of file-backed memory on inactive LRU list.
-active_file	- # of bytes of file-backed memory on active LRU list.
-unevictable	- # of bytes of memory that cannot be reclaimed (mlocked etc).
-
-# status considering hierarchy (see memory.use_hierarchy settings)
-
-hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
-			under which the memory cgroup is
-hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
-			hierarchy under which memory cgroup is.
-
-total_<counter>		- # hierarchical version of <counter>, which in
-			addition to the cgroup's own value includes the
-			sum of all hierarchical children's values of
-			<counter>, i.e. total_cache
-
-# The following additional stats are dependent on CONFIG_DEBUG_VM.
-
-recent_rotated_anon	- VM internal parameter. (see mm/vmscan.c)
-recent_rotated_file	- VM internal parameter. (see mm/vmscan.c)
-recent_scanned_anon	- VM internal parameter. (see mm/vmscan.c)
-recent_scanned_file	- VM internal parameter. (see mm/vmscan.c)
-
-Memo:
-	recent_rotated means recent frequency of LRU rotation.
-	recent_scanned means recent # of scans to LRU.
-	showing for better debug please see the code for meanings.
-
-Note:
-	Only anonymous and swap cache memory is listed as part of 'rss' stat.
-	This should not be confused with the true 'resident set size' or the
-	amount of physical memory used by the cgroup.
-	'rss + file_mapped" will give you resident set size of cgroup.
-	(Note: file and shmem may be shared among other cgroups. In that case,
-	 file_mapped is accounted only when the memory cgroup is owner of page
-	 cache.)
-
-5.3 swappiness
-
-Overrides /proc/sys/vm/swappiness for the particular group. The tunable
-in the root cgroup corresponds to the global swappiness setting.
-
-Please note that unlike during the global reclaim, limit reclaim
-enforces that 0 swappiness really prevents from any swapping even if
-there is a swap storage available. This might lead to memcg OOM killer
-if there are no file pages to reclaim.
-
-5.4 failcnt
-
-A memory cgroup provides memory.failcnt and memory.memsw.failcnt files.
-This failcnt(== failure count) shows the number of times that a usage counter
-hit its limit. When a memory cgroup hits a limit, failcnt increases and
-memory under it will be reclaimed.
-
-You can reset failcnt by writing 0 to failcnt file.
-# echo 0 > .../memory.failcnt
-
-5.5 usage_in_bytes
-
-For efficiency, as other kernel components, memory cgroup uses some optimization
-to avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the
-method and doesn't show 'exact' value of memory (and swap) usage, it's a fuzz
-value for efficient access. (Of course, when necessary, it's synchronized.)
-If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP)
-value in memory.stat(see 5.2).
-
-5.6 numa_stat
-
-This is similar to numa_maps but operates on a per-memcg basis.  This is
-useful for providing visibility into the numa locality information within
-an memcg since the pages are allowed to be allocated from any physical
-node.  One of the use cases is evaluating application performance by
-combining this information with the application's CPU allocation.
-
-Each memcg's numa_stat file includes "total", "file", "anon" and "unevictable"
-per-node page counts including "hierarchical_<counter>" which sums up all
-hierarchical children's values in addition to the memcg's own value.
-
-The output format of memory.numa_stat is:
-
-total=<total pages> N0=<node 0 pages> N1=<node 1 pages> ...
-file=<total file pages> N0=<node 0 pages> N1=<node 1 pages> ...
-anon=<total anon pages> N0=<node 0 pages> N1=<node 1 pages> ...
-unevictable=<total anon pages> N0=<node 0 pages> N1=<node 1 pages> ...
-hierarchical_<counter>=<counter pages> N0=<node 0 pages> N1=<node 1 pages> ...
-
-The "total" count is sum of file + anon + unevictable.
-
-6. Hierarchy support
-
-The memory controller supports a deep hierarchy and hierarchical accounting.
-The hierarchy is created by creating the appropriate cgroups in the
-cgroup filesystem. Consider for example, the following cgroup filesystem
-hierarchy
-
-	       root
-	     /  |   \
-            /	|    \
-	   a	b     c
-		      | \
-		      |  \
-		      d   e
-
-In the diagram above, with hierarchical accounting enabled, all memory
-usage of e, is accounted to its ancestors up until the root (i.e, c and root),
-that has memory.use_hierarchy enabled. If one of the ancestors goes over its
-limit, the reclaim algorithm reclaims from the tasks in the ancestor and the
-children of the ancestor.
-
-6.1 Enabling hierarchical accounting and reclaim
-
-A memory cgroup by default disables the hierarchy feature. Support
-can be enabled by writing 1 to memory.use_hierarchy file of the root cgroup
-
-# echo 1 > memory.use_hierarchy
-
-The feature can be disabled by
-
-# echo 0 > memory.use_hierarchy
-
-NOTE1: Enabling/disabling will fail if either the cgroup already has other
-       cgroups created below it, or if the parent cgroup has use_hierarchy
-       enabled.
-
-NOTE2: When panic_on_oom is set to "2", the whole system will panic in
-       case of an OOM event in any cgroup.
-
-7. Soft limits
-
-Soft limits allow for greater sharing of memory. The idea behind soft limits
-is to allow control groups to use as much of the memory as needed, provided
-
-a. There is no memory contention
-b. They do not exceed their hard limit
-
-When the system detects memory contention or low memory, control groups
-are pushed back to their soft limits. If the soft limit of each control
-group is very high, they are pushed back as much as possible to make
-sure that one control group does not starve the others of memory.
-
-Please note that soft limits is a best-effort feature; it comes with
-no guarantees, but it does its best to make sure that when memory is
-heavily contended for, memory is allocated based on the soft limit
-hints/setup. Currently soft limit based reclaim is set up such that
-it gets invoked from balance_pgdat (kswapd).
-
-7.1 Interface
-
-Soft limits can be setup by using the following commands (in this example we
-assume a soft limit of 256 MiB)
-
-# echo 256M > memory.soft_limit_in_bytes
-
-If we want to change this to 1G, we can at any time use
-
-# echo 1G > memory.soft_limit_in_bytes
-
-NOTE1: Soft limits take effect over a long period of time, since they involve
-       reclaiming memory for balancing between memory cgroups
-NOTE2: It is recommended to set the soft limit always below the hard limit,
-       otherwise the hard limit will take precedence.
-
-8. Move charges at task migration
-
-Users can move charges associated with a task along with task migration, that
-is, uncharge task's pages from the old cgroup and charge them to the new cgroup.
-This feature is not supported in !CONFIG_MMU environments because of lack of
-page tables.
-
-8.1 Interface
-
-This feature is disabled by default. It can be enabled (and disabled again) by
-writing to memory.move_charge_at_immigrate of the destination cgroup.
-
-If you want to enable it:
-
-# echo (some positive value) > memory.move_charge_at_immigrate
-
-Note: Each bits of move_charge_at_immigrate has its own meaning about what type
-      of charges should be moved. See 8.2 for details.
-Note: Charges are moved only when you move mm->owner, in other words,
-      a leader of a thread group.
-Note: If we cannot find enough space for the task in the destination cgroup, we
-      try to make space by reclaiming memory. Task migration may fail if we
-      cannot make enough space.
-Note: It can take several seconds if you move charges much.
-
-And if you want disable it again:
-
-# echo 0 > memory.move_charge_at_immigrate
-
-8.2 Type of charges which can be moved
-
-Each bit in move_charge_at_immigrate has its own meaning about what type of
-charges should be moved. But in any case, it must be noted that an account of
-a page or a swap can be moved only when it is charged to the task's current
-(old) memory cgroup.
-
-  bit | what type of charges would be moved ?
- -----+------------------------------------------------------------------------
-   0  | A charge of an anonymous page (or swap of it) used by the target task.
-      | You must enable Swap Extension (see 2.4) to enable move of swap charges.
- -----+------------------------------------------------------------------------
-   1  | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory)
-      | and swaps of tmpfs file) mmapped by the target task. Unlike the case of
-      | anonymous pages, file pages (and swaps) in the range mmapped by the task
-      | will be moved even if the task hasn't done page fault, i.e. they might
-      | not be the task's "RSS", but other task's "RSS" that maps the same file.
-      | And mapcount of the page is ignored (the page can be moved even if
-      | page_mapcount(page) > 1). You must enable Swap Extension (see 2.4) to
-      | enable move of swap charges.
-
-8.3 TODO
-
-- All of moving charge operations are done under cgroup_mutex. It's not good
-  behavior to hold the mutex too long, so we may need some trick.
-
-9. Memory thresholds
-
-Memory cgroup implements memory thresholds using the cgroups notification
-API (see cgroups.txt). It allows to register multiple memory and memsw
-thresholds and gets notifications when it crosses.
-
-To register a threshold, an application must:
-- create an eventfd using eventfd(2);
-- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
-- write string like "<event_fd> <fd of memory.usage_in_bytes> <threshold>" to
-  cgroup.event_control.
-
-Application will be notified through eventfd when memory usage crosses
-threshold in any direction.
-
-It's applicable for root and non-root cgroup.
-
-10. OOM Control
-
-memory.oom_control file is for OOM notification and other controls.
-
-Memory cgroup implements OOM notifier using the cgroup notification
-API (See cgroups.txt). It allows to register multiple OOM notification
-delivery and gets notification when OOM happens.
-
-To register a notifier, an application must:
- - create an eventfd using eventfd(2)
- - open memory.oom_control file
- - write string like "<event_fd> <fd of memory.oom_control>" to
-   cgroup.event_control
-
-The application will be notified through eventfd when OOM happens.
-OOM notification doesn't work for the root cgroup.
-
-You can disable the OOM-killer by writing "1" to memory.oom_control file, as:
-
-	#echo 1 > memory.oom_control
-
-If OOM-killer is disabled, tasks under cgroup will hang/sleep
-in memory cgroup's OOM-waitqueue when they request accountable memory.
-
-For running them, you have to relax the memory cgroup's OOM status by
-	* enlarge limit or reduce usage.
-To reduce usage,
-	* kill some tasks.
-	* move some tasks to other group with account migration.
-	* remove some files (on tmpfs?)
-
-Then, stopped tasks will work again.
-
-At reading, current status of OOM is shown.
-	oom_kill_disable 0 or 1 (if 1, oom-killer is disabled)
-	under_oom	 0 or 1 (if 1, the memory cgroup is under OOM, tasks may
-				 be stopped.)
-
-11. Memory Pressure
-
-The pressure level notifications can be used to monitor the memory
-allocation cost; based on the pressure, applications can implement
-different strategies of managing their memory resources. The pressure
-levels are defined as following:
-
-The "low" level means that the system is reclaiming memory for new
-allocations. Monitoring this reclaiming activity might be useful for
-maintaining cache level. Upon notification, the program (typically
-"Activity Manager") might analyze vmstat and act in advance (i.e.
-prematurely shutdown unimportant services).
-
-The "medium" level means that the system is experiencing medium memory
-pressure, the system might be making swap, paging out active file caches,
-etc. Upon this event applications may decide to further analyze
-vmstat/zoneinfo/memcg or internal memory usage statistics and free any
-resources that can be easily reconstructed or re-read from a disk.
-
-The "critical" level means that the system is actively thrashing, it is
-about to out of memory (OOM) or even the in-kernel OOM killer is on its
-way to trigger. Applications should do whatever they can to help the
-system. It might be too late to consult with vmstat or any other
-statistics, so it's advisable to take an immediate action.
-
-The events are propagated upward until the event is handled, i.e. the
-events are not pass-through. Here is what this means: for example you have
-three cgroups: A->B->C. Now you set up an event listener on cgroups A, B
-and C, and suppose group C experiences some pressure. In this situation,
-only group C will receive the notification, i.e. groups A and B will not
-receive it. This is done to avoid excessive "broadcasting" of messages,
-which disturbs the system and which is especially bad if we are low on
-memory or thrashing. So, organize the cgroups wisely, or propagate the
-events manually (or, ask us to implement the pass-through events,
-explaining why would you need them.)
-
-The file memory.pressure_level is only used to setup an eventfd. To
-register a notification, an application must:
-
-- create an eventfd using eventfd(2);
-- open memory.pressure_level;
-- write string like "<event_fd> <fd of memory.pressure_level> <level>"
-  to cgroup.event_control.
-
-Application will be notified through eventfd when memory pressure is at
-the specific level (or higher). Read/write operations to
-memory.pressure_level are no implemented.
-
-Test:
-
-   Here is a small script example that makes a new cgroup, sets up a
-   memory limit, sets up a notification in the cgroup and then makes child
-   cgroup experience a critical pressure:
-
-   # cd /sys/fs/cgroup/memory/
-   # mkdir foo
-   # cd foo
-   # cgroup_event_listener memory.pressure_level low &
-   # echo 8000000 > memory.limit_in_bytes
-   # echo 8000000 > memory.memsw.limit_in_bytes
-   # echo $$ > tasks
-   # dd if=/dev/zero | read x
-
-   (Expect a bunch of notifications, and eventually, the oom-killer will
-   trigger.)
-
-12. TODO
-
-1. Make per-cgroup scanner reclaim not-shared pages first
-2. Teach controller to account for shared-pages
-3. Start reclamation in the background when the limit is
-   not yet hit but the usage is getting closer
-
-Summary
-
-Overall, the memory controller has been a stable controller and has been
-commented and discussed quite extensively in the community.
-
-References
-
-1. Singh, Balbir. RFC: Memory Controller, http://lwn.net/Articles/206697/
-2. Singh, Balbir. Memory Controller (RSS Control),
-   http://lwn.net/Articles/222762/
-3. Emelianov, Pavel. Resource controllers based on process cgroups
-   http://lkml.org/lkml/2007/3/6/198
-4. Emelianov, Pavel. RSS controller based on process cgroups (v2)
-   http://lkml.org/lkml/2007/4/9/78
-5. Emelianov, Pavel. RSS controller based on process cgroups (v3)
-   http://lkml.org/lkml/2007/5/30/244
-6. Menage, Paul. Control Groups v10, http://lwn.net/Articles/236032/
-7. Vaidyanathan, Srinivasan, Control Groups: Pagecache accounting and control
-   subsystem (v3), http://lwn.net/Articles/235534/
-8. Singh, Balbir. RSS controller v2 test results (lmbench),
-   http://lkml.org/lkml/2007/5/17/232
-9. Singh, Balbir. RSS controller v2 AIM9 results
-   http://lkml.org/lkml/2007/5/18/1
-10. Singh, Balbir. Memory controller v6 test results,
-    http://lkml.org/lkml/2007/8/19/36
-11. Singh, Balbir. Memory controller introduction (v6),
-    http://lkml.org/lkml/2007/8/17/69
-12. Corbet, Jonathan, Controlling memory use in cgroups,
-    http://lwn.net/Articles/243795/
diff --git a/Documentation/cgroups/net_cls.txt b/Documentation/cgroups/net_cls.txt
deleted file mode 100644
index ec182346dea2..000000000000
--- a/Documentation/cgroups/net_cls.txt
+++ /dev/null
@@ -1,39 +0,0 @@
-Network classifier cgroup
--------------------------
-
-The Network classifier cgroup provides an interface to
-tag network packets with a class identifier (classid).
-
-The Traffic Controller (tc) can be used to assign
-different priorities to packets from different cgroups.
-Also, Netfilter (iptables) can use this tag to perform
-actions on such packets.
-
-Creating a net_cls cgroups instance creates a net_cls.classid file.
-This net_cls.classid value is initialized to 0.
-
-You can write hexadecimal values to net_cls.classid; the format for these
-values is 0xAAAABBBB; AAAA is the major handle number and BBBB
-is the minor handle number.
-Reading net_cls.classid yields a decimal result.
-
-Example:
-mkdir /sys/fs/cgroup/net_cls
-mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls
-mkdir /sys/fs/cgroup/net_cls/0
-echo 0x100001 >  /sys/fs/cgroup/net_cls/0/net_cls.classid
-	- setting a 10:1 handle.
-
-cat /sys/fs/cgroup/net_cls/0/net_cls.classid
-1048577
-
-configuring tc:
-tc qdisc add dev eth0 root handle 10: htb
-
-tc class add dev eth0 parent 10: classid 10:1 htb rate 40mbit
- - creating traffic class 10:1
-
-tc filter add dev eth0 parent 10: protocol ip prio 10 handle 1: cgroup
-
-configuring iptables, basic example:
-iptables -A OUTPUT -m cgroup ! --cgroup 0x100001 -j DROP
diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt
deleted file mode 100644
index a82cbd28ea8a..000000000000
--- a/Documentation/cgroups/net_prio.txt
+++ /dev/null
@@ -1,55 +0,0 @@
-Network priority cgroup
--------------------------
-
-The Network priority cgroup provides an interface to allow an administrator to
-dynamically set the priority of network traffic generated by various
-applications
-
-Nominally, an application would set the priority of its traffic via the
-SO_PRIORITY socket option.  This however, is not always possible because:
-
-1) The application may not have been coded to set this value
-2) The priority of application traffic is often a site-specific administrative
-   decision rather than an application defined one.
-
-This cgroup allows an administrator to assign a process to a group which defines
-the priority of egress traffic on a given interface. Network priority groups can
-be created by first mounting the cgroup filesystem.
-
-# mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio
-
-With the above step, the initial group acting as the parent accounting group
-becomes visible at '/sys/fs/cgroup/net_prio'.  This group includes all tasks in
-the system. '/sys/fs/cgroup/net_prio/tasks' lists the tasks in this cgroup.
-
-Each net_prio cgroup contains two files that are subsystem specific
-
-net_prio.prioidx
-This file is read-only, and is simply informative.  It contains a unique integer
-value that the kernel uses as an internal representation of this cgroup.
-
-net_prio.ifpriomap
-This file contains a map of the priorities assigned to traffic originating from
-processes in this group and egressing the system on various interfaces. It
-contains a list of tuples in the form <ifname priority>.  Contents of this file
-can be modified by echoing a string into the file using the same tuple format.
-for example:
-
-echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomap
-
-This command would force any traffic originating from processes belonging to the
-iscsi net_prio cgroup and egressing on interface eth0 to have the priority of
-said traffic set to the value 5. The parent accounting group also has a
-writeable 'net_prio.ifpriomap' file that can be used to set a system default
-priority.
-
-Priorities are set immediately prior to queueing a frame to the device
-queueing discipline (qdisc) so priorities will be assigned prior to the hardware
-queue selection being made.
-
-One usage for the net_prio cgroup is with mqprio qdisc allowing application
-traffic to be steered to hardware/driver based traffic classes. These mappings
-can then be managed by administrators or other networking protocols such as
-DCBX.
-
-A new net_prio cgroup inherits the parent's configuration.
diff --git a/Documentation/cgroups/pids.txt b/Documentation/cgroups/pids.txt
deleted file mode 100644
index 1a078b5d281a..000000000000
--- a/Documentation/cgroups/pids.txt
+++ /dev/null
@@ -1,85 +0,0 @@
-						   Process Number Controller
-						   =========================
-
-Abstract
---------
-
-The process number controller is used to allow a cgroup hierarchy to stop any
-new tasks from being fork()'d or clone()'d after a certain limit is reached.
-
-Since it is trivial to hit the task limit without hitting any kmemcg limits in
-place, PIDs are a fundamental resource. As such, PID exhaustion must be
-preventable in the scope of a cgroup hierarchy by allowing resource limiting of
-the number of tasks in a cgroup.
-
-Usage
------
-
-In order to use the `pids` controller, set the maximum number of tasks in
-pids.max (this is not available in the root cgroup for obvious reasons). The
-number of processes currently in the cgroup is given by pids.current.
-
-Organisational operations are not blocked by cgroup policies, so it is possible
-to have pids.current > pids.max. This can be done by either setting the limit to
-be smaller than pids.current, or attaching enough processes to the cgroup such
-that pids.current > pids.max. However, it is not possible to violate a cgroup
-policy through fork() or clone(). fork() and clone() will return -EAGAIN if the
-creation of a new process would cause a cgroup policy to be violated.
-
-To set a cgroup to have no limit, set pids.max to "max". This is the default for
-all new cgroups (N.B. that PID limits are hierarchical, so the most stringent
-limit in the hierarchy is followed).
-
-pids.current tracks all child cgroup hierarchies, so parent/pids.current is a
-superset of parent/child/pids.current.
-
-Example
--------
-
-First, we mount the pids controller:
-# mkdir -p /sys/fs/cgroup/pids
-# mount -t cgroup -o pids none /sys/fs/cgroup/pids
-
-Then we create a hierarchy, set limits and attach processes to it:
-# mkdir -p /sys/fs/cgroup/pids/parent/child
-# echo 2 > /sys/fs/cgroup/pids/parent/pids.max
-# echo $$ > /sys/fs/cgroup/pids/parent/cgroup.procs
-# cat /sys/fs/cgroup/pids/parent/pids.current
-2
-#
-
-It should be noted that attempts to overcome the set limit (2 in this case) will
-fail:
-
-# cat /sys/fs/cgroup/pids/parent/pids.current
-2
-# ( /bin/echo "Here's some processes for you." | cat )
-sh: fork: Resource temporary unavailable
-#
-
-Even if we migrate to a child cgroup (which doesn't have a set limit), we will
-not be able to overcome the most stringent limit in the hierarchy (in this case,
-parent's):
-
-# echo $$ > /sys/fs/cgroup/pids/parent/child/cgroup.procs
-# cat /sys/fs/cgroup/pids/parent/pids.current
-2
-# cat /sys/fs/cgroup/pids/parent/child/pids.current
-2
-# cat /sys/fs/cgroup/pids/parent/child/pids.max
-max
-# ( /bin/echo "Here's some processes for you." | cat )
-sh: fork: Resource temporary unavailable
-#
-
-We can set a limit that is smaller than pids.current, which will stop any new
-processes from being forked at all (note that the shell itself counts towards
-pids.current):
-
-# echo 1 > /sys/fs/cgroup/pids/parent/pids.max
-# /bin/echo "We can't even spawn a single process now."
-sh: fork: Resource temporary unavailable
-# echo 0 > /sys/fs/cgroup/pids/parent/pids.max
-# /bin/echo "We can't even spawn a single process now."
-sh: fork: Resource temporary unavailable
-#
diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
deleted file mode 100644
index c1f0e8780960..000000000000
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ /dev/null
@@ -1,645 +0,0 @@
-
-Cgroup unified hierarchy
-
-April, 2014		Tejun Heo <tj@kernel.org>
-
-This document describes the changes made by unified hierarchy and
-their rationales.  It will eventually be merged into the main cgroup
-documentation.
-
-CONTENTS
-
-1. Background
-2. Basic Operation
-  2-1. Mounting
-  2-2. cgroup.subtree_control
-  2-3. cgroup.controllers
-3. Structural Constraints
-  3-1. Top-down
-  3-2. No internal tasks
-4. Delegation
-  4-1. Model of delegation
-  4-2. Common ancestor rule
-5. Other Changes
-  5-1. [Un]populated Notification
-  5-2. Other Core Changes
-  5-3. Controller File Conventions
-    5-3-1. Format
-    5-3-2. Control Knobs
-  5-4. Per-Controller Changes
-    5-4-1. io
-    5-4-2. cpuset
-    5-4-3. memory
-6. Planned Changes
-  6-1. CAP for resource control
-
-
-1. Background
-
-cgroup allows an arbitrary number of hierarchies and each hierarchy
-can host any number of controllers.  While this seems to provide a
-high level of flexibility, it isn't quite useful in practice.
-
-For example, as there is only one instance of each controller, utility
-type controllers such as freezer which can be useful in all
-hierarchies can only be used in one.  The issue is exacerbated by the
-fact that controllers can't be moved around once hierarchies are
-populated.  Another issue is that all controllers bound to a hierarchy
-are forced to have exactly the same view of the hierarchy.  It isn't
-possible to vary the granularity depending on the specific controller.
-
-In practice, these issues heavily limit which controllers can be put
-on the same hierarchy and most configurations resort to putting each
-controller on its own hierarchy.  Only closely related ones, such as
-the cpu and cpuacct controllers, make sense to put on the same
-hierarchy.  This often means that userland ends up managing multiple
-similar hierarchies repeating the same steps on each hierarchy
-whenever a hierarchy management operation is necessary.
-
-Unfortunately, support for multiple hierarchies comes at a steep cost.
-Internal implementation in cgroup core proper is dazzlingly
-complicated but more importantly the support for multiple hierarchies
-restricts how cgroup is used in general and what controllers can do.
-
-There's no limit on how many hierarchies there may be, which means
-that a task's cgroup membership can't be described in finite length.
-The key may contain any varying number of entries and is unlimited in
-length, which makes it highly awkward to handle and leads to addition
-of controllers which exist only to identify membership, which in turn
-exacerbates the original problem.
-
-Also, as a controller can't have any expectation regarding what shape
-of hierarchies other controllers would be on, each controller has to
-assume that all other controllers are operating on completely
-orthogonal hierarchies.  This makes it impossible, or at least very
-cumbersome, for controllers to cooperate with each other.
-
-In most use cases, putting controllers on hierarchies which are
-completely orthogonal to each other isn't necessary.  What usually is
-called for is the ability to have differing levels of granularity
-depending on the specific controller.  In other words, hierarchy may
-be collapsed from leaf towards root when viewed from specific
-controllers.  For example, a given configuration might not care about
-how memory is distributed beyond a certain level while still wanting
-to control how CPU cycles are distributed.
-
-Unified hierarchy is the next version of cgroup interface.  It aims to
-address the aforementioned issues by having more structure while
-retaining enough flexibility for most use cases.  Various other
-general and controller-specific interface issues are also addressed in
-the process.
-
-
-2. Basic Operation
-
-2-1. Mounting
-
-Unified hierarchy can be mounted with the following mount command.
-
- mount -t cgroup2 none $MOUNT_POINT
-
-All controllers which support the unified hierarchy and are not bound
-to other hierarchies are automatically bound to unified hierarchy and
-show up at the root of it.  Controllers which are enabled only in the
-root of unified hierarchy can be bound to other hierarchies.  This
-allows mixing unified hierarchy with the traditional multiple
-hierarchies in a fully backward compatible way.
-
-A controller can be moved across hierarchies only after the controller
-is no longer referenced in its current hierarchy.  Because per-cgroup
-controller states are destroyed asynchronously and controllers may
-have lingering references, a controller may not show up immediately on
-the unified hierarchy after the final umount of the previous
-hierarchy.  Similarly, a controller should be fully disabled to be
-moved out of the unified hierarchy and it may take some time for the
-disabled controller to become available for other hierarchies;
-furthermore, due to dependencies among controllers, other controllers
-may need to be disabled too.
-
-While useful for development and manual configurations, dynamically
-moving controllers between the unified and other hierarchies is
-strongly discouraged for production use.  It is recommended to decide
-the hierarchies and controller associations before starting using the
-controllers.
-
-
-2-2. cgroup.subtree_control
-
-All cgroups on unified hierarchy have a "cgroup.subtree_control" file
-which governs which controllers are enabled on the children of the
-cgroup.  Let's assume a hierarchy like the following.
-
-  root - A - B - C
-               \ D
-
-root's "cgroup.subtree_control" file determines which controllers are
-enabled on A.  A's on B.  B's on C and D.  This coincides with the
-fact that controllers on the immediate sub-level are used to
-distribute the resources of the parent.  In fact, it's natural to
-assume that resource control knobs of a child belong to its parent.
-Enabling a controller in a "cgroup.subtree_control" file declares that
-distribution of the respective resources of the cgroup will be
-controlled.  Note that this means that controller enable states are
-shared among siblings.
-
-When read, the file contains a space-separated list of currently
-enabled controllers.  A write to the file should contain a
-space-separated list of controllers with '+' or '-' prefixed (without
-the quotes).  Controllers prefixed with '+' are enabled and '-'
-disabled.  If a controller is listed multiple times, the last entry
-wins.  The specific operations are executed atomically - either all
-succeed or fail.
-
-
-2-3. cgroup.controllers
-
-Read-only "cgroup.controllers" file contains a space-separated list of
-controllers which can be enabled in the cgroup's
-"cgroup.subtree_control" file.
-
-In the root cgroup, this lists controllers which are not bound to
-other hierarchies and the content changes as controllers are bound to
-and unbound from other hierarchies.
-
-In non-root cgroups, the content of this file equals that of the
-parent's "cgroup.subtree_control" file as only controllers enabled
-from the parent can be used in its children.
-
-
-3. Structural Constraints
-
-3-1. Top-down
-
-As it doesn't make sense to nest control of an uncontrolled resource,
-all non-root "cgroup.subtree_control" files can only contain
-controllers which are enabled in the parent's "cgroup.subtree_control"
-file.  A controller can be enabled only if the parent has the
-controller enabled and a controller can't be disabled if one or more
-children have it enabled.
-
-
-3-2. No internal tasks
-
-One long-standing issue that cgroup faces is the competition between
-tasks belonging to the parent cgroup and its children cgroups.  This
-is inherently nasty as two different types of entities compete and
-there is no agreed-upon obvious way to handle it.  Different
-controllers are doing different things.
-
-The cpu controller considers tasks and cgroups as equivalents and maps
-nice levels to cgroup weights.  This works for some cases but falls
-flat when children should be allocated specific ratios of CPU cycles
-and the number of internal tasks fluctuates - the ratios constantly
-change as the number of competing entities fluctuates.  There also are
-other issues.  The mapping from nice level to weight isn't obvious or
-universal, and there are various other knobs which simply aren't
-available for tasks.
-
-The io controller implicitly creates a hidden leaf node for each
-cgroup to host the tasks.  The hidden leaf has its own copies of all
-the knobs with "leaf_" prefixed.  While this allows equivalent control
-over internal tasks, it's with serious drawbacks.  It always adds an
-extra layer of nesting which may not be necessary, makes the interface
-messy and significantly complicates the implementation.
-
-The memory controller currently doesn't have a way to control what
-happens between internal tasks and child cgroups and the behavior is
-not clearly defined.  There have been attempts to add ad-hoc behaviors
-and knobs to tailor the behavior to specific workloads.  Continuing
-this direction will lead to problems which will be extremely difficult
-to resolve in the long term.
-
-Multiple controllers struggle with internal tasks and came up with
-different ways to deal with it; unfortunately, all the approaches in
-use now are severely flawed and, furthermore, the widely different
-behaviors make cgroup as whole highly inconsistent.
-
-It is clear that this is something which needs to be addressed from
-cgroup core proper in a uniform way so that controllers don't need to
-worry about it and cgroup as a whole shows a consistent and logical
-behavior.  To achieve that, unified hierarchy enforces the following
-structural constraint:
-
- Except for the root, only cgroups which don't contain any task may
- have controllers enabled in their "cgroup.subtree_control" files.
-
-Combined with other properties, this guarantees that, when a
-controller is looking at the part of the hierarchy which has it
-enabled, tasks are always only on the leaves.  This rules out
-situations where child cgroups compete against internal tasks of the
-parent.
-
-There are two things to note.  Firstly, the root cgroup is exempt from
-the restriction.  Root contains tasks and anonymous resource
-consumption which can't be associated with any other cgroup and
-requires special treatment from most controllers.  How resource
-consumption in the root cgroup is governed is up to each controller.
-
-Secondly, the restriction doesn't take effect if there is no enabled
-controller in the cgroup's "cgroup.subtree_control" file.  This is
-important as otherwise it wouldn't be possible to create children of a
-populated cgroup.  To control resource distribution of a cgroup, the
-cgroup must create children and transfer all its tasks to the children
-before enabling controllers in its "cgroup.subtree_control" file.
-
-
-4. Delegation
-
-4-1. Model of delegation
-
-A cgroup can be delegated to a less privileged user by granting write
-access of the directory and its "cgroup.procs" file to the user.  Note
-that the resource control knobs in a given directory concern the
-resources of the parent and thus must not be delegated along with the
-directory.
-
-Once delegated, the user can build sub-hierarchy under the directory,
-organize processes as it sees fit and further distribute the resources
-it got from the parent.  The limits and other settings of all resource
-controllers are hierarchical and regardless of what happens in the
-delegated sub-hierarchy, nothing can escape the resource restrictions
-imposed by the parent.
-
-Currently, cgroup doesn't impose any restrictions on the number of
-cgroups in or nesting depth of a delegated sub-hierarchy; however,
-this may in the future be limited explicitly.
-
-
-4-2. Common ancestor rule
-
-On the unified hierarchy, to write to a "cgroup.procs" file, in
-addition to the usual write permission to the file and uid match, the
-writer must also have write access to the "cgroup.procs" file of the
-common ancestor of the source and destination cgroups.  This prevents
-delegatees from smuggling processes across disjoint sub-hierarchies.
-
-Let's say cgroups C0 and C1 have been delegated to user U0 who created
-C00, C01 under C0 and C10 under C1 as follows.
-
- ~~~~~~~~~~~~~ - C0 - C00
- ~ cgroup    ~      \ C01
- ~ hierarchy ~
- ~~~~~~~~~~~~~ - C1 - C10
-
-C0 and C1 are separate entities in terms of resource distribution
-regardless of their relative positions in the hierarchy.  The
-resources the processes under C0 are entitled to are controlled by
-C0's ancestors and may be completely different from C1.  It's clear
-that the intention of delegating C0 to U0 is allowing U0 to organize
-the processes under C0 and further control the distribution of C0's
-resources.
-
-On traditional hierarchies, if a task has write access to "tasks" or
-"cgroup.procs" file of a cgroup and its uid agrees with the target, it
-can move the target to the cgroup.  In the above example, U0 will not
-only be able to move processes in each sub-hierarchy but also across
-the two sub-hierarchies, effectively allowing it to violate the
-organizational and resource restrictions implied by the hierarchical
-structure above C0 and C1.
-
-On the unified hierarchy, let's say U0 wants to write the pid of a
-process which has a matching uid and is currently in C10 into
-"C00/cgroup.procs".  U0 obviously has write access to the file and
-migration permission on the process; however, the common ancestor of
-the source cgroup C10 and the destination cgroup C00 is above the
-points of delegation and U0 would not have write access to its
-"cgroup.procs" and thus be denied with -EACCES.
-
-
-5. Other Changes
-
-5-1. [Un]populated Notification
-
-cgroup users often need a way to determine when a cgroup's
-subhierarchy becomes empty so that it can be cleaned up.  cgroup
-currently provides release_agent for it; unfortunately, this mechanism
-is riddled with issues.
-
-- It delivers events by forking and execing a userland binary
-  specified as the release_agent.  This is a long deprecated method of
-  notification delivery.  It's extremely heavy, slow and cumbersome to
-  integrate with larger infrastructure.
-
-- There is single monitoring point at the root.  There's no way to
-  delegate management of a subtree.
-
-- The event isn't recursive.  It triggers when a cgroup doesn't have
-  any tasks or child cgroups.  Events for internal nodes trigger only
-  after all children are removed.  This again makes it impossible to
-  delegate management of a subtree.
-
-- Events are filtered from the kernel side.  A "notify_on_release"
-  file is used to subscribe to or suppress release events.  This is
-  unnecessarily complicated and probably done this way because event
-  delivery itself was expensive.
-
-Unified hierarchy implements "populated" field in "cgroup.events"
-interface file which can be used to monitor whether the cgroup's
-subhierarchy has tasks in it or not.  Its value is 0 if there is no
-task in the cgroup and its descendants; otherwise, 1.  poll and
-[id]notify events are triggered when the value changes.
-
-This is significantly lighter and simpler and trivially allows
-delegating management of subhierarchy - subhierarchy monitoring can
-block further propagation simply by putting itself or another process
-in the subhierarchy and monitor events that it's interested in from
-there without interfering with monitoring higher in the tree.
-
-In unified hierarchy, the release_agent mechanism is no longer
-supported and the interface files "release_agent" and
-"notify_on_release" do not exist.
-
-
-5-2. Other Core Changes
-
-- None of the mount options is allowed.
-
-- remount is disallowed.
-
-- rename(2) is disallowed.
-
-- The "tasks" file is removed.  Everything should at process
-  granularity.  Use the "cgroup.procs" file instead.
-
-- The "cgroup.procs" file is not sorted.  pids will be unique unless
-  they got recycled in-between reads.
-
-- The "cgroup.clone_children" file is removed.
-
-- /proc/PID/cgroup keeps reporting the cgroup that a zombie belonged
-  to before exiting.  If the cgroup is removed before the zombie is
-  reaped, " (deleted)" is appeneded to the path.
-
-
-5-3. Controller File Conventions
-
-5-3-1. Format
-
-In general, all controller files should be in one of the following
-formats whenever possible.
-
-- Values only files
-
-  VAL0 VAL1...\n
-
-- Flat keyed files
-
-  KEY0 VAL0\n
-  KEY1 VAL1\n
-  ...
-
-- Nested keyed files
-
-  KEY0 SUB_KEY0=VAL00 SUB_KEY1=VAL01...
-  KEY1 SUB_KEY0=VAL10 SUB_KEY1=VAL11...
-  ...
-
-For a writeable file, the format for writing should generally match
-reading; however, controllers may allow omitting later fields or
-implement restricted shortcuts for most common use cases.
-
-For both flat and nested keyed files, only the values for a single key
-can be written at a time.  For nested keyed files, the sub key pairs
-may be specified in any order and not all pairs have to be specified.
-
-
-5-3-2. Control Knobs
-
-- Settings for a single feature should generally be implemented in a
-  single file.
-
-- In general, the root cgroup should be exempt from resource control
-  and thus shouldn't have resource control knobs.
-
-- If a controller implements ratio based resource distribution, the
-  control knob should be named "weight" and have the range [1, 10000]
-  and 100 should be the default value.  The values are chosen to allow
-  enough and symmetric bias in both directions while keeping it
-  intuitive (the default is 100%).
-
-- If a controller implements an absolute resource guarantee and/or
-  limit, the control knobs should be named "min" and "max"
-  respectively.  If a controller implements best effort resource
-  gurantee and/or limit, the control knobs should be named "low" and
-  "high" respectively.
-
-  In the above four control files, the special token "max" should be
-  used to represent upward infinity for both reading and writing.
-
-- If a setting has configurable default value and specific overrides,
-  the default settings should be keyed with "default" and appear as
-  the first entry in the file.  Specific entries can use "default" as
-  its value to indicate inheritance of the default value.
-
-- For events which are not very high frequency, an interface file
-  "events" should be created which lists event key value pairs.
-  Whenever a notifiable event happens, file modified event should be
-  generated on the file.
-
-
-5-4. Per-Controller Changes
-
-5-4-1. io
-
-- blkio is renamed to io.  The interface is overhauled anyway.  The
-  new name is more in line with the other two major controllers, cpu
-  and memory, and better suited given that it may be used for cgroup
-  writeback without involving block layer.
-
-- Everything including stat is always hierarchical making separate
-  recursive stat files pointless and, as no internal node can have
-  tasks, leaf weights are meaningless.  The operation model is
-  simplified and the interface is overhauled accordingly.
-
-  io.stat
-
-	The stat file.  The reported stats are from the point where
-	bio's are issued to request_queue.  The stats are counted
-	independent of which policies are enabled.  Each line in the
-	file follows the following format.  More fields may later be
-	added at the end.
-
-	  $MAJ:$MIN rbytes=$RBYTES wbytes=$WBYTES rios=$RIOS wrios=$WIOS
-
-  io.weight
-
-	The weight setting, currently only available and effective if
-	cfq-iosched is in use for the target device.  The weight is
-	between 1 and 10000 and defaults to 100.  The first line
-	always contains the default weight in the following format to
-	use when per-device setting is missing.
-
-	  default $WEIGHT
-
-	Subsequent lines list per-device weights of the following
-	format.
-
-	  $MAJ:$MIN $WEIGHT
-
-	Writing "$WEIGHT" or "default $WEIGHT" changes the default
-	setting.  Writing "$MAJ:$MIN $WEIGHT" sets per-device weight
-	while "$MAJ:$MIN default" clears it.
-
-	This file is available only on non-root cgroups.
-
-  io.max
-
-	The maximum bandwidth and/or iops setting, only available if
-	blk-throttle is enabled.  The file is of the following format.
-
-	  $MAJ:$MIN rbps=$RBPS wbps=$WBPS riops=$RIOPS wiops=$WIOPS
-
-	${R|W}BPS are read/write bytes per second and ${R|W}IOPS are
-	read/write IOs per second.  "max" indicates no limit.  Writing
-	to the file follows the same format but the individual
-	settings may be omitted or specified in any order.
-
-	This file is available only on non-root cgroups.
-
-
-5-4-2. cpuset
-
-- Tasks are kept in empty cpusets after hotplug and take on the masks
-  of the nearest non-empty ancestor, instead of being moved to it.
-
-- A task can be moved into an empty cpuset, and again it takes on the
-  masks of the nearest non-empty ancestor.
-
-
-5-4-3. memory
-
-- use_hierarchy is on by default and the cgroup file for the flag is
-  not created.
-
-- The original lower boundary, the soft limit, is defined as a limit
-  that is per default unset.  As a result, the set of cgroups that
-  global reclaim prefers is opt-in, rather than opt-out.  The costs
-  for optimizing these mostly negative lookups are so high that the
-  implementation, despite its enormous size, does not even provide the
-  basic desirable behavior.  First off, the soft limit has no
-  hierarchical meaning.  All configured groups are organized in a
-  global rbtree and treated like equal peers, regardless where they
-  are located in the hierarchy.  This makes subtree delegation
-  impossible.  Second, the soft limit reclaim pass is so aggressive
-  that it not just introduces high allocation latencies into the
-  system, but also impacts system performance due to overreclaim, to
-  the point where the feature becomes self-defeating.
-
-  The memory.low boundary on the other hand is a top-down allocated
-  reserve.  A cgroup enjoys reclaim protection when it and all its
-  ancestors are below their low boundaries, which makes delegation of
-  subtrees possible.  Secondly, new cgroups have no reserve per
-  default and in the common case most cgroups are eligible for the
-  preferred reclaim pass.  This allows the new low boundary to be
-  efficiently implemented with just a minor addition to the generic
-  reclaim code, without the need for out-of-band data structures and
-  reclaim passes.  Because the generic reclaim code considers all
-  cgroups except for the ones running low in the preferred first
-  reclaim pass, overreclaim of individual groups is eliminated as
-  well, resulting in much better overall workload performance.
-
-- The original high boundary, the hard limit, is defined as a strict
-  limit that can not budge, even if the OOM killer has to be called.
-  But this generally goes against the goal of making the most out of
-  the available memory.  The memory consumption of workloads varies
-  during runtime, and that requires users to overcommit.  But doing
-  that with a strict upper limit requires either a fairly accurate
-  prediction of the working set size or adding slack to the limit.
-  Since working set size estimation is hard and error prone, and
-  getting it wrong results in OOM kills, most users tend to err on the
-  side of a looser limit and end up wasting precious resources.
-
-  The memory.high boundary on the other hand can be set much more
-  conservatively.  When hit, it throttles allocations by forcing them
-  into direct reclaim to work off the excess, but it never invokes the
-  OOM killer.  As a result, a high boundary that is chosen too
-  aggressively will not terminate the processes, but instead it will
-  lead to gradual performance degradation.  The user can monitor this
-  and make corrections until the minimal memory footprint that still
-  gives acceptable performance is found.
-
-  In extreme cases, with many concurrent allocations and a complete
-  breakdown of reclaim progress within the group, the high boundary
-  can be exceeded.  But even then it's mostly better to satisfy the
-  allocation from the slack available in other groups or the rest of
-  the system than killing the group.  Otherwise, memory.max is there
-  to limit this type of spillover and ultimately contain buggy or even
-  malicious applications.
-
-- The original control file names are unwieldy and inconsistent in
-  many different ways.  For example, the upper boundary hit count is
-  exported in the memory.failcnt file, but an OOM event count has to
-  be manually counted by listening to memory.oom_control events, and
-  lower boundary / soft limit events have to be counted by first
-  setting a threshold for that value and then counting those events.
-  Also, usage and limit files encode their units in the filename.
-  That makes the filenames very long, even though this is not
-  information that a user needs to be reminded of every time they type
-  out those names.
-
-  To address these naming issues, as well as to signal clearly that
-  the new interface carries a new configuration model, the naming
-  conventions in it necessarily differ from the old interface.
-
-- The original limit files indicate the state of an unset limit with a
-  Very High Number, and a configured limit can be unset by echoing -1
-  into those files.  But that very high number is implementation and
-  architecture dependent and not very descriptive.  And while -1 can
-  be understood as an underflow into the highest possible value, -2 or
-  -10M etc. do not work, so it's not consistent.
-
-  memory.low, memory.high, and memory.max will use the string "max" to
-  indicate and set the highest possible value.
-
-6. Planned Changes
-
-6-1. CAP for resource control
-
-Unified hierarchy will require one of the capabilities(7), which is
-yet to be decided, for all resource control related knobs.  Process
-organization operations - creation of sub-cgroups and migration of
-processes in sub-hierarchies may be delegated by changing the
-ownership and/or permissions on the cgroup directory and
-"cgroup.procs" interface file; however, all operations which affect
-resource control - writes to a "cgroup.subtree_control" file or any
-controller-specific knobs - will require an explicit CAP privilege.
-
-This, in part, is to prevent the cgroup interface from being
-inadvertently promoted to programmable API used by non-privileged
-binaries.  cgroup exposes various aspects of the system in ways which
-aren't properly abstracted for direct consumption by regular programs.
-This is an administration interface much closer to sysctl knobs than
-system calls.  Even the basic access model, being filesystem path
-based, isn't suitable for direct consumption.  There's no way to
-access "my cgroup" in a race-free way or make multiple operations
-atomic against migration to another cgroup.
-
-Another aspect is that, for better or for worse, the cgroup interface
-goes through far less scrutiny than regular interfaces for
-unprivileged userland.  The upside is that cgroup is able to expose
-useful features which may not be suitable for general consumption in a
-reasonable time frame.  It provides a relatively short path between
-internal details and userland-visible interface.  Of course, this
-shortcut comes with high risk.  We go through what we go through for
-general kernel APIs for good reasons.  It may end up leaking internal
-details in a way which can exert significant pain by locking the
-kernel into a contract that can't be maintained in a reasonable
-manner.
-
-Also, due to the specific nature, cgroup and its controllers don't
-tend to attract attention from a wide scope of developers.  cgroup's
-short history is already fraught with severely mis-designed
-interfaces, unnecessary commitments to and exposing of internal
-details, broken and dangerous implementations of various features.
-
-Keeping cgroup as an administration interface is both advantageous for
-its role and imperative given its nature.  Some of the cgroup features
-may make sense for unprivileged access.  If deemed justified, those
-must be further abstracted and implemented as a different interface,
-be it a system call or process-private filesystem, and survive through
-the scrutiny that any interface for general consumption is required to
-go through.
-
-Requiring CAP is not a complete solution but should serve as a
-significant deterrent against spraying cgroup usages in non-privileged
-programs.