| Commit message (Collapse) | Author | Age | Files | Lines |
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Patch series "HWPOISON: soft offlining for non-lru movable page", v6.
After Minchan's commit bda807d44454 ("mm: migrate: support non-lru
movable page migration"), some type of non-lru page like zsmalloc and
virtio-balloon page also support migration.
Therefore, we can:
1) soft offlining no-lru movable pages, which means when memory
corrected errors occur on a non-lru movable page, we can stop to use
it by migrating data onto another page and disable the original
(maybe half-broken) one.
2) enable memory hotplug for non-lru movable pages, i.e. we may offline
blocks, which include such pages, by using non-lru page migration.
This patchset is heavily dependent on non-lru movable page migration.
This patch (of 4):
Change the return type of isolate_movable_page() from bool to int. It
will return 0 when isolate movable page successfully, and return -EBUSY
when it isolates failed.
There is no functional change within this patch but prepare for later
patch.
[xieyisheng1@huawei.com: v6]
Link: http://lkml.kernel.org/r/1486108770-630-2-git-send-email-xieyisheng1@huawei.com
Link: http://lkml.kernel.org/r/1485867981-16037-2-git-send-email-ysxie@foxmail.com
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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With both coming and already present locking optimizations, introducing
kref to reference-count z3fold objects is the right thing to do.
Moreover, it makes buddied list no longer necessary, and allows for a
simpler handling of headless pages.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170131214650.8ea78033d91ded233f552bc0@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Most of z3fold operations are in-page, such as modifying z3fold page
header or moving z3fold objects within a page. Taking per-pool spinlock
to protect per-page objects is therefore suboptimal, and the idea of
having a per-page spinlock (or rwlock) has been around for some time.
This patch implements spinlock-based per-page locking mechanism which is
lightweight enough to normally fit ok into the z3fold header.
Link: http://lkml.kernel.org/r/20170131214438.433e0a5fda908337b63206d3@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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z3fold_compact_page() currently only handles the situation when there's
a single middle chunk within the z3fold page. However it may be worth
it to move middle chunk closer to either first or last chunk, whichever
is there, if the gap between them is big enough.
This patch adds the relevant code, using BIG_CHUNK_GAP define as a
threshold for middle chunk to be worth moving.
Link: http://lkml.kernel.org/r/20170131214334.c4f3eac9a477af0fa9a22c46@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Currently the whole kernel build will be stopped if the size of struct
z3fold_header is greater than the size of one chunk, which is 64 bytes
by default. This patch instead defines the offset for z3fold objects as
the size of the z3fold header in chunks.
Fixed also are the calculation of num_free_chunks() and the address to
move the middle chunk to in case of in-page compaction in
z3fold_compact_page().
Link: http://lkml.kernel.org/r/20170131214057.d98677032bc7b1c6c59a80c9@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Convert pages_nr per-pool counter to atomic64_t.
Link: http://lkml.kernel.org/r/20170131213946.b828676ab17bbea42022c213@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A new unit test for the device-dax 1GB enabling currently fails with
this warning before hanging the test thread:
WARNING: CPU: 0 PID: 21 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0
percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic
[..]
CPU: 0 PID: 21 Comm: rcuos/1 Tainted: G O 4.10.0-rc7-next-20170207+ #944
[..]
Call Trace:
dump_stack+0x86/0xc3
__warn+0xcb/0xf0
warn_slowpath_fmt+0x5f/0x80
? rcu_nocb_kthread+0x27a/0x510
? dax_pmem_percpu_exit+0x50/0x50 [dax_pmem]
percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0
? percpu_ref_exit+0x60/0x60
rcu_nocb_kthread+0x339/0x510
? rcu_nocb_kthread+0x27a/0x510
kthread+0x101/0x140
The get_user_pages() path needs to arrange for references to be taken
against the dev_pagemap instance backing the pud mapping. Refactor the
existing __gup_device_huge_pmd() to also account for the pud case.
Link: http://lkml.kernel.org/r/148653181153.38226.9605457830505509385.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Since the introduction of FAULT_FLAG_SIZE to the vm_fault flag, it has
been somewhat painful with getting the flags set and removed at the
correct locations. More than one kernel oops was introduced due to
difficulties of getting the placement correctly.
Remove the flag values and introduce an input parameter to huge_fault
that indicates the size of the page entry. This makes the code easier
to trace and should avoid the issues we see with the fault flags where
removal of the flag was necessary in the fallback paths.
Link: http://lkml.kernel.org/r/148615748258.43180.1690152053774975329.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add transparent huge PUD pages support for device DAX by adding a
pud_fault handler.
Link: http://lkml.kernel.org/r/148545060002.17912.6765687780007547551.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The current transparent hugepage code only supports PMDs. This patch
adds support for transparent use of PUDs with DAX. It does not include
support for anonymous pages. x86 support code also added.
Most of this patch simply parallels the work that was done for huge
PMDs. The only major difference is how the new ->pud_entry method in
mm_walk works. The ->pmd_entry method replaces the ->pte_entry method,
whereas the ->pud_entry method works along with either ->pmd_entry or
->pte_entry. The pagewalk code takes care of locking the PUD before
calling ->pud_walk, so handlers do not need to worry whether the PUD is
stable.
[dave.jiang@intel.com: fix SMP x86 32bit build for native_pud_clear()]
Link: http://lkml.kernel.org/r/148719066814.31111.3239231168815337012.stgit@djiang5-desk3.ch.intel.com
[dave.jiang@intel.com: native_pud_clear missing on i386 build]
Link: http://lkml.kernel.org/r/148640375195.69754.3315433724330910314.stgit@djiang5-desk3.ch.intel.com
Link: http://lkml.kernel.org/r/148545059381.17912.8602162635537598445.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Alexander Kapshuk <alexander.kapshuk@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "1G transparent hugepage support for device dax", v2.
The following series implements support for 1G trasparent hugepage on
x86 for device dax. The bulk of the code was written by Mathew Wilcox a
while back supporting transparent 1G hugepage for fs DAX. I have
forward ported the relevant bits to 4.10-rc. The current submission has
only the necessary code to support device DAX.
Comments from Dan Williams: So the motivation and intended user of this
functionality mirrors the motivation and users of 1GB page support in
hugetlbfs. Given expected capacities of persistent memory devices an
in-memory database may want to reduce tlb pressure beyond what they can
already achieve with 2MB mappings of a device-dax file. We have
customer feedback to that effect as Willy mentioned in his previous
version of these patches [1].
[1]: https://lkml.org/lkml/2016/1/31/52
Comments from Nilesh @ Oracle:
There are applications which have a process model; and if you assume
10,000 processes attempting to mmap all the 6TB memory available on a
server; we are looking at the following:
processes : 10,000
memory : 6TB
pte @ 4k page size: 8 bytes / 4K of memory * #processes = 6TB / 4k * 8 * 10000 = 1.5GB * 80000 = 120,000GB
pmd @ 2M page size: 120,000 / 512 = ~240GB
pud @ 1G page size: 240GB / 512 = ~480MB
As you can see with 2M pages, this system will use up an exorbitant
amount of DRAM to hold the page tables; but the 1G pages finally brings
it down to a reasonable level. Memory sizes will keep increasing; so
this number will keep increasing.
An argument can be made to convert the applications from process model
to thread model, but in the real world that may not be always practical.
Hopefully this helps explain the use case where this is valuable.
This patch (of 3):
In preparation for adding the ability to handle PUD pages, convert
vm_operations_struct.pmd_fault to vm_operations_struct.huge_fault. The
vm_fault structure is extended to include a union of the different page
table pointers that may be needed, and three flag bits are reserved to
indicate which type of pointer is in the union.
[ross.zwisler@linux.intel.com: remove unused function ext4_dax_huge_fault()]
Link: http://lkml.kernel.org/r/1485813172-7284-1-git-send-email-ross.zwisler@linux.intel.com
[dave.jiang@intel.com: clear PMD or PUD size flags when in fall through path]
Link: http://lkml.kernel.org/r/148589842696.5820.16078080610311444794.stgit@djiang5-desk3.ch.intel.com
Link: http://lkml.kernel.org/r/148545058784.17912.6353162518188733642.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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As suggested by Vlastimil Babka and Tejun Heo, this patch uses a static
work_struct to co-ordinate the draining of per-cpu pages on the
workqueue. Only one task can drain at a time but this is better than
the previous scheme that allowed multiple tasks to send IPIs at a time.
One consideration is whether parallel requests should synchronise
against each other. This patch does not synchronise for a global drain
as the common case for such callers is expected to be multiple parallel
direct reclaimers competing for pages when the watermark is close to
min. Draining the per-cpu list is unlikely to make much progress and
serialising the drain is of dubious merit. Drains are synchonrised for
callers such as memory hotplug and CMA that care about the drain being
complete when the function returns.
Link: http://lkml.kernel.org/r/20170125083038.rzb5f43nptmk7aed@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Suggested-by: Tejun Heo <tj@kernel.org>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Since commit 682a3385e773 ("mm, page_alloc: inline the fast path of the
zonelist iterator") we replace a NULL nodemask with
cpuset_current_mems_allowed in the fast path, so that
get_page_from_freelist() filters nodes allowed by the cpuset via
for_next_zone_zonelist_nodemask().
In that case it's pointless to additionaly check __cpuset_zone_allowed()
in each iteration, which we can avoid by not adding ALLOC_CPUSET to
alloc_flags in that scenario.
This saves some cycles in the allocator fast path on systems with one or
more non-root cpuset configured. In the slow path, ALLOC_CPUSET is
reset according to __alloc_pages_slowpath(). Without configured
cpusets, this code is disabled by a static key.
Link: http://lkml.kernel.org/r/20170124150511.5710-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The allocation fast path contains two similar checks for zoneref->zone
being NULL, where zoneref points either to the first zone in the
zonelist, or to the preferred zone. These can be NULL either due to
empty zonelist, or no zone being compatible with given nodemask or
task's cpuset.
These checks are unnecessary, because the zonelist walks in
first_zones_zonelist() and get_page_from_freelist() handle a NULL
starting zoneref->zone or preferred_zoneref->zone safely. It's safe to
fallback to __alloc_pages_slowpath() where we also have the check early
enough.
Link: http://lkml.kernel.org/r/20170124150511.5710-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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zram_reset_device() waits for ongoing writepage pages to be completed by
zram->refcount logic. However, it's pointless because before the reset,
we prevent further opening of zram by zram->claim and flush all of
pending IO by fsync_bdev so there should be no pending IO at the
zram_reset_device().
So let's remove that code which is even broken due to the lack of
wake_up elsewhere.
Link: http://lkml.kernel.org/r/1485145031-11661-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mmap_init() is no longer associated with VMA slab. So fix it.
Link: http://lkml.kernel.org/r/1485182601-9294-1-git-send-email-iamyooon@gmail.com
Signed-off-by: seokhoon.yoon <iamyooon@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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->fault(), ->page_mkwrite(), and ->pfn_mkwrite() calls do not need to
take a vma and vmf parameter when the vma already resides in vmf.
Remove the vma parameter to simplify things.
[arnd@arndb.de: fix ARM build]
Link: http://lkml.kernel.org/r/20170125223558.1451224-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/148521301778.19116.10840599906674778980.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Many workloads that allocate pages are not handling an interrupt at a
time. As allocation requests may be from IRQ context, it's necessary to
disable/enable IRQs for every page allocation. This cost is the bulk of
the free path but also a significant percentage of the allocation path.
This patch alters the locking and checks such that only irq-safe
allocation requests use the per-cpu allocator. All others acquire the
irq-safe zone->lock and allocate from the buddy allocator. It relies on
disabling preemption to safely access the per-cpu structures. It could
be slightly modified to avoid soft IRQs using it but it's not clear it's
worthwhile.
This modification may slow allocations from IRQ context slightly but the
main gain from the per-cpu allocator is that it scales better for
allocations from multiple contexts. There is an implicit assumption
that intensive allocations from IRQ contexts on multiple CPUs from a
single NUMA node are rare and that the fast majority of scaling issues
are encountered in !IRQ contexts such as page faulting. It's worth
noting that this patch is not required for a bulk page allocator but it
significantly reduces the overhead.
The following is results from a page allocator micro-benchmark. Only
order-0 is interesting as higher orders do not use the per-cpu allocator
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
This is the alloc, free and total overhead of allocating order-0 pages
in batches of 1 page up to 16384 pages. Avoiding disabling/enabling
overhead massively reduces overhead. Alloc overhead is roughly reduced
by 14-20% in most cases. The free path is reduced by 26-46% and the
total reduction is significant.
Many users require zeroing of pages from the page allocator which is the
vast cost of allocation. Hence, the impact on a basic page faulting
benchmark is not that significant
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Hmean page_test 656632.98 ( 0.00%) 675536.13 ( 2.88%)
Hmean brk_test 3845502.67 ( 0.00%) 3867186.94 ( 0.56%)
Stddev page_test 10543.29 ( 0.00%) 4104.07 ( 61.07%)
Stddev brk_test 33472.36 ( 0.00%) 15538.39 ( 53.58%)
CoeffVar page_test 1.61 ( 0.00%) 0.61 ( 62.15%)
CoeffVar brk_test 0.87 ( 0.00%) 0.40 ( 53.84%)
Max page_test 666513.33 ( 0.00%) 678640.00 ( 1.82%)
Max brk_test 3882800.00 ( 0.00%) 3887008.66 ( 0.11%)
This is from aim9 and the most notable outcome is that fault variability
is reduced by the patch. The headline improvement is small as the
overall fault cost, zeroing, page table insertion etc dominate relative
to disabling/enabling IRQs in the per-cpu allocator.
Similarly, little benefit was seen on networking benchmarks both
localhost and between physical server/clients where other costs
dominate. It's possible that this will only be noticable on very high
speed networks.
Jesper Dangaard Brouer independently tested this with a separate
microbenchmark from
https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench
Micro-benchmarked with [1] page_bench02:
modprobe page_bench02 page_order=0 run_flags=$((2#010)) loops=$((10**8)); \
rmmod page_bench02 ; dmesg --notime | tail -n 4
Compared to baseline: 213 cycles(tsc) 53.417 ns
- against this : 184 cycles(tsc) 46.056 ns
- Saving : -29 cycles
- Very close to expected 27 cycles saving [see below [2]]
Micro benchmarking via time_bench_sample[3], we get the cost of these
operations:
time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.232 ns (step:0)
time_bench: Type:spin_lock_unlock Per elem: 33 cycles(tsc) 8.334 ns (step:0)
time_bench: Type:spin_lock_unlock_irqsave Per elem: 62 cycles(tsc) 15.607 ns (step:0)
time_bench: Type:irqsave_before_lock Per elem: 57 cycles(tsc) 14.344 ns (step:0)
time_bench: Type:spin_lock_unlock_irq Per elem: 34 cycles(tsc) 8.560 ns (step:0)
time_bench: Type:simple_irq_disable_before_lock Per elem: 37 cycles(tsc) 9.289 ns (step:0)
time_bench: Type:local_BH_disable_enable Per elem: 19 cycles(tsc) 4.920 ns (step:0)
time_bench: Type:local_IRQ_disable_enable Per elem: 7 cycles(tsc) 1.864 ns (step:0)
time_bench: Type:local_irq_save_restore Per elem: 38 cycles(tsc) 9.665 ns (step:0)
[Mel's patch removes a ^^^^^^^^^^^^^^^^] ^^^^^^^^^ expected saving - preempt cost
time_bench: Type:preempt_disable_enable Per elem: 11 cycles(tsc) 2.794 ns (step:0)
[adds a preempt ^^^^^^^^^^^^^^^^^^^^^^] ^^^^^^^^^ adds this cost
time_bench: Type:funcion_call_cost Per elem: 6 cycles(tsc) 1.689 ns (step:0)
time_bench: Type:func_ptr_call_cost Per elem: 11 cycles(tsc) 2.767 ns (step:0)
time_bench: Type:page_alloc_put Per elem: 211 cycles(tsc) 52.803 ns (step:0)
Thus, expected improvement is: 38-11 = 27 cycles.
[mgorman@techsingularity.net: s/preempt_enable_no_resched/preempt_enable/]
Link: http://lkml.kernel.org/r/20170208143128.25ahymqlyspjcixu@techsingularity.net
Link: http://lkml.kernel.org/r/20170123153906.3122-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Dmitry has reported the following lockdep splat
lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3753
__mutex_lock_common kernel/locking/mutex.c:521 [inline]
mutex_lock_nested+0x24e/0xff0 kernel/locking/mutex.c:621
pcpu_alloc+0xbda/0x1280 mm/percpu.c:896
__alloc_percpu+0x24/0x30 mm/percpu.c:1075
smpcfd_prepare_cpu+0x73/0xd0 kernel/smp.c:44
cpuhp_invoke_callback+0x254/0x1480 kernel/cpu.c:136
cpuhp_up_callbacks+0x81/0x2a0 kernel/cpu.c:493
_cpu_up+0x1e3/0x2a0 kernel/cpu.c:1057
do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
cpu_up+0x18/0x20 kernel/cpu.c:1095
smp_init+0xe9/0xee kernel/smp.c:564
kernel_init_freeable+0x439/0x690 init/main.c:1010
kernel_init+0x13/0x180 init/main.c:941
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
cpu_hotplug_begin
cpu_hotplug.lock
pcpu_alloc
pcpu_alloc_mutex
get_online_cpus+0x62/0x90 kernel/cpu.c:248
drain_all_pages+0xf8/0x710 mm/page_alloc.c:2385
__alloc_pages_direct_reclaim mm/page_alloc.c:3440 [inline]
__alloc_pages_slowpath+0x8fd/0x2370 mm/page_alloc.c:3778
__alloc_pages_nodemask+0x8f5/0xc60 mm/page_alloc.c:3980
__alloc_pages include/linux/gfp.h:426 [inline]
__alloc_pages_node include/linux/gfp.h:439 [inline]
alloc_pages_node include/linux/gfp.h:453 [inline]
pcpu_alloc_pages mm/percpu-vm.c:93 [inline]
pcpu_populate_chunk+0x1e1/0x900 mm/percpu-vm.c:282
pcpu_alloc+0xe01/0x1280 mm/percpu.c:998
__alloc_percpu_gfp+0x27/0x30 mm/percpu.c:1062
bpf_array_alloc_percpu kernel/bpf/arraymap.c:34 [inline]
array_map_alloc+0x532/0x710 kernel/bpf/arraymap.c:99
find_and_alloc_map kernel/bpf/syscall.c:34 [inline]
map_create kernel/bpf/syscall.c:188 [inline]
SYSC_bpf kernel/bpf/syscall.c:870 [inline]
SyS_bpf+0xd64/0x2500 kernel/bpf/syscall.c:827
entry_SYSCALL_64_fastpath+0x1f/0xc2
pcpu_alloc
pcpu_alloc_mutex
drain_all_pages
get_online_cpus
cpu_hotplug.lock
cpu_hotplug_begin+0x206/0x2e0 kernel/cpu.c:304
_cpu_up+0xca/0x2a0 kernel/cpu.c:1011
do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
cpu_up+0x18/0x20 kernel/cpu.c:1095
smp_init+0xe9/0xee kernel/smp.c:564
kernel_init_freeable+0x439/0x690 init/main.c:1010
kernel_init+0x13/0x180 init/main.c:941
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
cpu_hotplug_begin
cpu_hotplug.lock
Pulling cpu hotplug locks inside the page allocator is just too
dangerous. Let's remove the dependency by dropping get_online_cpus()
from drain_all_pages. This is not so simple though because now we do
not have a protection against cpu hotplug which means 2 things:
- the work item might be executed on a different cpu in worker from
unbound pool so it doesn't run on pinned on the cpu
- we have to make sure that we do not race with page_alloc_cpu_dead
calling drain_pages_zone
Disabling preemption in drain_local_pages_wq will solve the first
problem drain_local_pages will determine its local CPU from the WQ
context which will be stable after that point, page_alloc_cpu_dead is
pinned to the CPU already. The later condition is achieved by disabling
IRQs in drain_pages_zone.
Fixes: mm, page_alloc: drain per-cpu pages from workqueue context
Link: http://lkml.kernel.org/r/20170207201950.20482-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The per-cpu page allocator can be drained immediately via
drain_all_pages() which sends IPIs to every CPU. In the next patch, the
per-cpu allocator will only be used for interrupt-safe allocations which
prevents draining it from IPI context. This patch uses workqueues to
drain the per-cpu lists instead.
This is slower but no slowdown during intensive reclaim was measured and
the paths that use drain_all_pages() are not that sensitive to
performance. This is particularly true as the path would only be
triggered when reclaim is failing. It also makes a some sense to avoid
storming a machine with IPIs when it's under memory pressure. Arguably,
it should be further adjusted so that only one caller at a time is
draining pages but it's beyond the scope of the current patch.
Link: http://lkml.kernel.org/r/20170123153906.3122-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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alloc_pages_nodemask does a number of preperation steps that determine
what zones can be used for the allocation depending on a variety of
factors. This is fine but a hypothetical caller that wanted multiple
order-0 pages has to do the preparation steps multiple times. This
patch structures __alloc_pages_nodemask such that it's relatively easy
to build a bulk order-0 page allocator. There is no functional change.
Link: http://lkml.kernel.org/r/20170123153906.3122-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "Use per-cpu allocator for !irq requests and prepare for a
bulk allocator", v5.
This series is motivated by a conversation led by Jesper Dangaard Brouer
at the last LSF/MM proposing a generic page pool for DMA-coherent pages.
Part of his motivation was due to the overhead of allocating multiple
order-0 that led some drivers to use high-order allocations and
splitting them. This is very slow in some cases.
The first two patches in this series restructure the page allocator such
that it is relatively easy to introduce an order-0 bulk page allocator.
A patch exists to do that and has been handed over to Jesper until an
in-kernel users is created. The third patch prevents the per-cpu
allocator being drained from IPI context as that can potentially corrupt
the list after patch four is merged. The final patch alters the per-cpu
alloctor to make it exclusive to !irq requests. This cuts
allocation/free overhead by roughly 30%.
Performance tests from both Jesper and me are included in the patch.
This patch (of 4):
buffered_rmqueue removes a page from a given zone and uses the per-cpu
list for order-0. This is fine but a hypothetical caller that wanted
multiple order-0 pages has to disable/reenable interrupts multiple
times. This patch structures buffere_rmqueue such that it's relatively
easy to build a bulk order-0 page allocator. There is no functional
change.
[mgorman@techsingularity.net: failed per-cpu refill may blow up]
Link: http://lkml.kernel.org/r/20170124112723.mshmgwq2ihxku2um@techsingularity.net
Link: http://lkml.kernel.org/r/20170123153906.3122-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We noticed a performance regression when moving hadoop workloads from
3.10 kernels to 4.0 and 4.6. This is accompanied by increased pageout
activity initiated by kswapd as well as frequent bursts of allocation
stalls and direct reclaim scans. Even lowering the dirty ratios to the
equivalent of less than 1% of memory would not eliminate the issue,
suggesting that dirty pages concentrate where the scanner is looking.
This can be traced back to recent efforts of thrash avoidance. Where
3.10 would not detect refaulting pages and continuously supply clean
cache to the inactive list, a thrashing workload on 4.0+ will detect and
activate refaulting pages right away, distilling used-once pages on the
inactive list much more effectively. This is by design, and it makes
sense for clean cache. But for the most part our workload's cache
faults are refaults and its use-once cache is from streaming writes. We
end up with most of the inactive list dirty, and we don't go after the
active cache as long as we have use-once pages around.
But waiting for writes to avoid reclaiming clean cache that *might*
refault is a bad trade-off. Even if the refaults happen, reads are
faster than writes. Before getting bogged down on writeback, reclaim
should first look at *all* cache in the system, even active cache.
To accomplish this, activate pages that are dirty or under writeback
when they reach the end of the inactive LRU. The pages are marked for
immediate reclaim, meaning they'll get moved back to the inactive LRU
tail as soon as they're written back and become reclaimable. But in the
meantime, by reducing the inactive list to only immediately reclaimable
pages, we allow the scanner to deactivate and refill the inactive list
with clean cache from the active list tail to guarantee forward
progress.
[hannes@cmpxchg.org: update comment]
Link: http://lkml.kernel.org/r/20170202191957.22872-8-hannes@cmpxchg.org
Link: http://lkml.kernel.org/r/20170123181641.23938-6-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Dirty pages can easily reach the end of the LRU while there are still
clean pages to reclaim around. Don't let kswapd write them back just
because there are a lot of them. It costs more CPU to find the clean
pages, but that's almost certainly better than to disrupt writeback from
the flushers with LRU-order single-page writes from reclaim. And the
flushers have been woken up by that point, so we spend IO capacity on
flushing and CPU capacity on finding the clean cache.
Only start writing dirty pages if they have cycled around the LRU twice
now and STILL haven't been queued on the IO device. It's possible that
the dirty pages are so sparsely distributed across different bdis,
inodes, memory cgroups, that the flushers take forever to get to the
ones we want reclaimed. Once we see them twice on the LRU, we know
that's the quicker way to find them, so do LRU writeback.
Link: http://lkml.kernel.org/r/20170123181641.23938-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Direct reclaim has been replaced by kswapd reclaim in pretty much all
common memory pressure situations, so this code most likely doesn't
accomplish the described effect anymore. The previous patch wakes up
flushers for all reclaimers when we encounter dirty pages at the tail
end of the LRU. Remove the crufty old direct reclaim invocation.
Link: http://lkml.kernel.org/r/20170123181641.23938-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Memory pressure can put dirty pages at the end of the LRU without
anybody running into dirty limits. Don't start writing individual pages
from kswapd while the flushers might be asleep.
Unlike the old direct reclaim flusher wakeup (removed in the next patch)
that flushes the number of pages just scanned, this patch wakes the
flushers for all outstanding dirty pages. That seemed to perform better
in a synthetic test that pushes dirty pages to the end of the LRU and
into reclaim, because we know LRU aging outstrips writeback already, and
this way we give younger dirty pages a headstart rather than wait until
reclaim runs into them as well. It also means less plugging and risk of
exhausting the struct request pool from reclaim.
There is a concern that this will cause temporary files that used to get
dirtied and truncated before writeback to now get written to disk under
memory pressure. If this turns out to be a real problem, we'll have to
revisit this and tame the reclaim flusher wakeups.
[hannes@cmpxchg.org: mention dirty expiration as a condition]
Link: http://lkml.kernel.org/r/20170126174739.GA30636@cmpxchg.org
Link: http://lkml.kernel.org/r/20170123181641.23938-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "mm: vmscan: fix kswapd writeback regression".
We noticed a regression on multiple hadoop workloads when moving from
3.10 to 4.0 and 4.6, which involves kswapd getting tangled up in page
writeout, causing direct reclaim herds that also don't make progress.
I tracked it down to the thrash avoidance efforts after 3.10 that make
the kernel better at keeping use-once cache and use-many cache sorted on
the inactive and active list, with more aggressive protection of the
active list as long as there is inactive cache. Unfortunately, our
workload's use-once cache is mostly from streaming writes. Waiting for
writes to avoid potential reloads in the future is not a good tradeoff.
These patches do the following:
1. Wake the flushers when kswapd sees a lump of dirty pages. It's
possible to be below the dirty background limit and still have cache
velocity push them through the LRU. So start a-flushin'.
2. Let kswapd only write pages that have been rotated twice. This makes
sure we really tried to get all the clean pages on the inactive list
before resorting to horrible LRU-order writeback.
3. Move rotating dirty pages off the inactive list. Instead of churning
or waiting on page writeback, we'll go after clean active cache. This
might lead to thrashing, but in this state memory demand outstrips IO
speed anyway, and reads are faster than writes.
Mel backported the series to 4.10-rc5 with one minor conflict and ran a
couple of tests on it. Mix of read/write random workload didn't show
anything interesting. Write-only database didn't show much difference
in performance but there were slight reductions in IO -- probably in the
noise.
simoop did show big differences although not as big as Mel expected.
This is Chris Mason's workload that similate the VM activity of hadoop.
Mel won't go through the full details but over the samples measured
during an hour it reported
4.10.0-rc5 4.10.0-rc5
vanilla johannes-v1r1
Amean p50-Read 21346531.56 ( 0.00%) 21697513.24 ( -1.64%)
Amean p95-Read 24700518.40 ( 0.00%) 25743268.98 ( -4.22%)
Amean p99-Read 27959842.13 ( 0.00%) 28963271.11 ( -3.59%)
Amean p50-Write 1138.04 ( 0.00%) 989.82 ( 13.02%)
Amean p95-Write 1106643.48 ( 0.00%) 12104.00 ( 98.91%)
Amean p99-Write 1569213.22 ( 0.00%) 36343.38 ( 97.68%)
Amean p50-Allocation 85159.82 ( 0.00%) 79120.70 ( 7.09%)
Amean p95-Allocation 204222.58 ( 0.00%) 129018.43 ( 36.82%)
Amean p99-Allocation 278070.04 ( 0.00%) 183354.43 ( 34.06%)
Amean final-p50-Read 21266432.00 ( 0.00%) 21921792.00 ( -3.08%)
Amean final-p95-Read 24870912.00 ( 0.00%) 26116096.00 ( -5.01%)
Amean final-p99-Read 28147712.00 ( 0.00%) 29523968.00 ( -4.89%)
Amean final-p50-Write 1130.00 ( 0.00%) 977.00 ( 13.54%)
Amean final-p95-Write 1033216.00 ( 0.00%) 2980.00 ( 99.71%)
Amean final-p99-Write 1517568.00 ( 0.00%) 32672.00 ( 97.85%)
Amean final-p50-Allocation 86656.00 ( 0.00%) 78464.00 ( 9.45%)
Amean final-p95-Allocation 211712.00 ( 0.00%) 116608.00 ( 44.92%)
Amean final-p99-Allocation 287232.00 ( 0.00%) 168704.00 ( 41.27%)
The latencies are actually completely horrific in comparison to 4.4 (and
4.10-rc5 is worse than 4.9 according to historical data for reasons Mel
hasn't analysed yet).
Still, 95% of write latency (p95-write) is halved by the series and
allocation latency is way down. Direct reclaim activity is one fifth of
what it was according to vmstats. Kswapd activity is higher but this is
not necessarily surprising. Kswapd efficiency is unchanged at 99% (99%
of pages scanned were reclaimed) but direct reclaim efficiency went from
77% to 99%
In the vanilla kernel, 627MB of data was written back from reclaim
context. With the series, no data was written back. With or without
the patch, pages are being immediately reclaimed after writeback
completes. However, with the patch, only 1/8th of the pages are
reclaimed like this.
This patch (of 5):
We have an elaborate dirty/writeback throttling mechanism inside the
reclaim scanner, but for that to work the pages have to go through
shrink_page_list() and get counted for what they are. Otherwise, we
mess up the LRU order and don't match reclaim speed to writeback.
Especially during deactivation, there is never a reason to skip dirty
pages; nothing is even trying to write them out from there. Don't mess
up the LRU order for nothing, shuffle these pages along.
Link: http://lkml.kernel.org/r/20170123181641.23938-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Now when madvise(MADV_REMOVE) notifies uffd reader, we should verify
that appliciation actually sees zeros at the removed range.
Link: http://lkml.kernel.org/r/1484814154-1557-4-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When a page is removed from a shared mapping, the uffd reader should be
notified, so that it won't attempt to handle #PF events for the removed
pages.
We can reuse the UFFD_EVENT_REMOVE because from the uffd monitor point
of view, the semantices of madvise(MADV_DONTNEED) and
madvise(MADV_REMOVE) is exactly the same.
Link: http://lkml.kernel.org/r/1484814154-1557-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "userfaultfd: non-cooperative: add madvise() event for
MADV_REMOVE request".
These patches add notification of madvise(MADV_REMOVE) event to
non-cooperative userfaultfd monitor.
The first pacth renames EVENT_MADVDONTNEED to EVENT_REMOVE along with
relevant functions and structures. Using _REMOVE instead of
_MADVDONTNEED describes the event semantics more clearly and I hope it's
not too late for such change in the ABI.
This patch (of 3):
The UFFD_EVENT_MADVDONTNEED purpose is to notify uffd monitor about
removal of certain range from address space tracked by userfaultfd.
Hence, UFFD_EVENT_REMOVE seems to better reflect the operation
semantics. Respectively, 'madv_dn' field of uffd_msg is renamed to
'remove' and the madvise_userfault_dontneed callback is renamed to
userfaultfd_remove.
Link: http://lkml.kernel.org/r/1484814154-1557-2-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Provide the name of each memblock type with struct memblock_type. This
allows to get rid of the function memblock_type_name() and duplicating
the type names in __memblock_dump_all().
The only memblock_type usage out of mm/memblock.c seems to be
arch/s390/kernel/crash_dump.c. While at it, give it a name.
Link: http://lkml.kernel.org/r/20170120123456.46508-4-heiko.carstens@de.ibm.com
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Since commit 70210ed950b5 ("mm/memblock: add physical memory list") the
memblock structure knows about a physical memory list.
The physical memory list should also be dumped if memblock_dump_all() is
called in case memblock_debug is switched on. This makes debugging a
bit easier.
Link: http://lkml.kernel.org/r/20170120123456.46508-3-heiko.carstens@de.ibm.com
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Since commit 70210ed950b5 ("mm/memblock: add physical memory list") the
memblock structure knows about a physical memory list.
memblock_type_name() should return "physmem" instead of "unknown" if the
name of the physmem memblock_type is being asked for.
Link: http://lkml.kernel.org/r/20170120123456.46508-2-heiko.carstens@de.ibm.com
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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It has no modular callers.
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mem_hotplug_begin() assumes that it can set mem_hotplug.active_writer
and run the hotplug process without racing another thread. Validate
this assumption with a lockdep assertion.
Link: http://lkml.kernel.org/r/148693886229.16345.1770484669403334689.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The mem_hotplug_{begin,done} lock coordinates with {get,put}_online_mems()
to hold off "readers" of the current state of memory from new hotplug
actions. mem_hotplug_begin() expects exclusive access, via the
device_hotplug lock, to set mem_hotplug.active_writer. Calling
mem_hotplug_begin() without locking device_hotplug can lead to
corrupting mem_hotplug.refcount and missed wakeups / soft lockups.
[dan.j.williams@intel.com: v2]
Link: http://lkml.kernel.org/r/148728203365.38457.17804568297887708345.stgit@dwillia2-desk3.amr.corp.intel.com
Link: http://lkml.kernel.org/r/148693885680.16345.17802627926777862337.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: f931ab479dd2 ("mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit 82e7d3abec86 ("oom: print nodemask in the oom report") implicitly
sets the allocation nodemask to cpuset_current_mems_allowed when there
is no effective mempolicy. cpuset_current_mems_allowed is only
effective when cpusets are enabled, which is also printed by
dump_header(), so setting the nodemask to cpuset_current_mems_allowed is
redundant and prevents debugging issues where ac->nodemask is not set
properly in the page allocator.
This provides better debugging output since
cpuset_print_current_mems_allowed() is already provided.
[rientjes@google.com: newline per Hillf]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701200158300.88321@chino.kir.corp.google.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701191454470.2381@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Some architectures have a set of zero pages (coloured zero pages)
instead of only one zero page, in order to improve the cache
performance. In those cases, the kernel samepage merger (KSM) would
merge all the allocated pages that happen to be filled with zeroes to
the same deduplicated page, thus losing all the advantages of coloured
zero pages.
This behaviour is noticeable when a process accesses large arrays of
allocated pages containing zeroes. A test I conducted on s390 shows
that there is a speed penalty when KSM merges such pages, compared to
not merging them or using actual zero pages from the start without
breaking the COW.
This patch fixes this behaviour. When coloured zero pages are present,
the checksum of a zero page is calculated during initialisation, and
compared with the checksum of the current canditate during merging. In
case of a match, the normal merging routine is used to merge the page
with the correct coloured zero page, which ensures the candidate page is
checked to be equal to the target zero page.
A sysfs entry is also added to toggle this behaviour, since it can
potentially introduce performance regressions, especially on
architectures without coloured zero pages. The default value is
disabled, for backwards compatibility.
With this patch, the performance with KSM is the same as with non
COW-broken actual zero pages, which is also the same as without KSM.
[akpm@linux-foundation.org: make zero_checksum and ksm_use_zero_pages __read_mostly, per Andrea]
[imbrenda@linux.vnet.ibm.com: documentation for coloured zero pages deduplication]
Link: http://lkml.kernel.org/r/1484927522-1964-1-git-send-email-imbrenda@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1484850953-23941-1-git-send-email-imbrenda@linux.vnet.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Given that the arch does not add its own implementations, simply use the
asm-generic/current.h (generic-y) header instead of duplicating code.
Link: http://lkml.kernel.org/r/1485992878-4780-3-git-send-email-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace updates from Eric Biederman:
"There is a lot here. A lot of these changes result in subtle user
visible differences in kernel behavior. I don't expect anything will
care but I will revert/fix things immediately if any regressions show
up.
From Seth Forshee there is a continuation of the work to make the vfs
ready for unpriviled mounts. We had thought the previous changes
prevented the creation of files outside of s_user_ns of a filesystem,
but it turns we missed the O_CREAT path. Ooops.
Pavel Tikhomirov and Oleg Nesterov worked together to fix a long
standing bug in the implemenation of PR_SET_CHILD_SUBREAPER where only
children that are forked after the prctl are considered and not
children forked before the prctl. The only known user of this prctl
systemd forks all children after the prctl. So no userspace
regressions will occur. Holding earlier forked children to the same
rules as later forked children creates a semantic that is sane enough
to allow checkpoing of processes that use this feature.
There is a long delayed change by Nikolay Borisov to limit inotify
instances inside a user namespace.
Michael Kerrisk extends the API for files used to maniuplate
namespaces with two new trivial ioctls to allow discovery of the
hierachy and properties of namespaces.
Konstantin Khlebnikov with the help of Al Viro adds code that when a
network namespace exits purges it's sysctl entries from the dcache. As
in some circumstances this could use a lot of memory.
Vivek Goyal fixed a bug with stacked filesystems where the permissions
on the wrong inode were being checked.
I continue previous work on ptracing across exec. Allowing a file to
be setuid across exec while being ptraced if the tracer has enough
credentials in the user namespace, and if the process has CAP_SETUID
in it's own namespace. Proc files for setuid or otherwise undumpable
executables are now owned by the root in the user namespace of their
mm. Allowing debugging of setuid applications in containers to work
better.
A bug I introduced with permission checking and automount is now
fixed. The big change is to mark the mounts that the kernel initiates
as a result of an automount. This allows the permission checks in sget
to be safely suppressed for this kind of mount. As the permission
check happened when the original filesystem was mounted.
Finally a special case in the mount namespace is removed preventing
unbounded chains in the mount hash table, and making the semantics
simpler which benefits CRIU.
The vfs fix along with related work in ima and evm I believe makes us
ready to finish developing and merge fully unprivileged mounts of the
fuse filesystem. The cleanups of the mount namespace makes discussing
how to fix the worst case complexity of umount. The stacked filesystem
fixes pave the way for adding multiple mappings for the filesystem
uids so that efficient and safer containers can be implemented"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
proc/sysctl: Don't grab i_lock under sysctl_lock.
vfs: Use upper filesystem inode in bprm_fill_uid()
proc/sysctl: prune stale dentries during unregistering
mnt: Tuck mounts under others instead of creating shadow/side mounts.
prctl: propagate has_child_subreaper flag to every descendant
introduce the walk_process_tree() helper
nsfs: Add an ioctl() to return owner UID of a userns
fs: Better permission checking for submounts
exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction
vfs: open() with O_CREAT should not create inodes with unknown ids
nsfs: Add an ioctl() to return the namespace type
proc: Better ownership of files for non-dumpable tasks in user namespaces
exec: Remove LSM_UNSAFE_PTRACE_CAP
exec: Test the ptracer's saved cred to see if the tracee can gain caps
exec: Don't reset euid and egid when the tracee has CAP_SETUID
inotify: Convert to using per-namespace limits
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Konstantin Khlebnikov <khlebnikov@yandex-team.ru> writes:
> This patch has locking problem. I've got lockdep splat under LTP.
>
> [ 6633.115456] ======================================================
> [ 6633.115502] [ INFO: possible circular locking dependency detected ]
> [ 6633.115553] 4.9.10-debug+ #9 Tainted: G L
> [ 6633.115584] -------------------------------------------------------
> [ 6633.115627] ksm02/284980 is trying to acquire lock:
> [ 6633.115659] (&sb->s_type->i_lock_key#4){+.+...}, at: [<ffffffff816bc1ce>] igrab+0x1e/0x80
> [ 6633.115834] but task is already holding lock:
> [ 6633.115882] (sysctl_lock){+.+...}, at: [<ffffffff817e379b>] unregister_sysctl_table+0x6b/0x110
> [ 6633.116026] which lock already depends on the new lock.
> [ 6633.116026]
> [ 6633.116080]
> [ 6633.116080] the existing dependency chain (in reverse order) is:
> [ 6633.116117]
> -> #2 (sysctl_lock){+.+...}:
> -> #1 (&(&dentry->d_lockref.lock)->rlock){+.+...}:
> -> #0 (&sb->s_type->i_lock_key#4){+.+...}:
>
> d_lock nests inside i_lock
> sysctl_lock nests inside d_lock in d_compare
>
> This patch adds i_lock nesting inside sysctl_lock.
Al Viro <viro@ZenIV.linux.org.uk> replied:
> Once ->unregistering is set, you can drop sysctl_lock just fine. So I'd
> try something like this - use rcu_read_lock() in proc_sys_prune_dcache(),
> drop sysctl_lock() before it and regain after. Make sure that no inodes
> are added to the list ones ->unregistering has been set and use RCU list
> primitives for modifying the inode list, with sysctl_lock still used to
> serialize its modifications.
>
> Freeing struct inode is RCU-delayed (see proc_destroy_inode()), so doing
> igrab() is safe there. Since we don't drop inode reference until after we'd
> passed beyond it in the list, list_for_each_entry_rcu() should be fine.
I agree with Al Viro's analsysis of the situtation.
Fixes: d6cffbbe9a7e ("proc/sysctl: prune stale dentries during unregistering")
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Tested-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Right now bprm_fill_uid() uses inode fetched from file_inode(bprm->file).
This in turn returns inode of lower filesystem (in a stacked filesystem
setup).
I was playing with modified patches of shiftfs posted by james bottomley
and realized that through shiftfs setuid bit does not take effect. And
reason being that we fetch uid/gid from inode of lower fs (and not from
shiftfs inode). And that results in following checks failing.
/* We ignore suid/sgid if there are no mappings for them in the ns */
if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
!kgid_has_mapping(bprm->cred->user_ns, gid))
return;
uid/gid fetched from lower fs inode might not be mapped inside the user
namespace of container. So we need to look at uid/gid fetched from
upper filesystem (shiftfs in this particular case) and these should be
mapped and setuid bit can take affect.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Currently unregistering sysctl table does not prune its dentries.
Stale dentries could slowdown sysctl operations significantly.
For example, command:
# for i in {1..100000} ; do unshare -n -- sysctl -a &> /dev/null ; done
creates a millions of stale denties around sysctls of loopback interface:
# sysctl fs.dentry-state
fs.dentry-state = 25812579 24724135 45 0 0 0
All of them have matching names thus lookup have to scan though whole
hash chain and call d_compare (proc_sys_compare) which checks them
under system-wide spinlock (sysctl_lock).
# time sysctl -a > /dev/null
real 1m12.806s
user 0m0.016s
sys 1m12.400s
Currently only memory reclaimer could remove this garbage.
But without significant memory pressure this never happens.
This patch collects sysctl inodes into list on sysctl table header and
prunes all their dentries once that table unregisters.
Konstantin Khlebnikov <khlebnikov@yandex-team.ru> writes:
> On 10.02.2017 10:47, Al Viro wrote:
>> how about >> the matching stats *after* that patch?
>
> dcache size doesn't grow endlessly, so stats are fine
>
> # sysctl fs.dentry-state
> fs.dentry-state = 92712 58376 45 0 0 0
>
> # time sysctl -a &>/dev/null
>
> real 0m0.013s
> user 0m0.004s
> sys 0m0.008s
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Ever since mount propagation was introduced in cases where a mount in
propagated to parent mount mountpoint pair that is already in use the
code has placed the new mount behind the old mount in the mount hash
table.
This implementation detail is problematic as it allows creating
arbitrary length mount hash chains.
Furthermore it invalidates the constraint maintained elsewhere in the
mount code that a parent mount and a mountpoint pair will have exactly
one mount upon them. Making it hard to deal with and to talk about
this special case in the mount code.
Modify mount propagation to notice when there is already a mount at
the parent mount and mountpoint where a new mount is propagating to
and place that preexisting mount on top of the new mount.
Modify unmount propagation to notice when a mount that is being
unmounted has another mount on top of it (and no other children), and
to replace the unmounted mount with the mount on top of it.
Move the MNT_UMUONT test from __lookup_mnt_last into
__propagate_umount as that is the only call of __lookup_mnt_last where
MNT_UMOUNT may be set on any mount visible in the mount hash table.
These modifications allow:
- __lookup_mnt_last to be removed.
- attach_shadows to be renamed __attach_mnt and its shadow
handling to be removed.
- commit_tree to be simplified
- copy_tree to be simplified
The result is an easier to understand tree of mounts that does not
allow creation of arbitrary length hash chains in the mount hash table.
The result is also a very slight userspace visible difference in semantics.
The following two cases now behave identically, where before order
mattered:
case 1: (explicit user action)
B is a slave of A
mount something on A/a , it will propagate to B/a
and than mount something on B/a
case 2: (tucked mount)
B is a slave of A
mount something on B/a
and than mount something on A/a
Histroically umount A/a would fail in case 1 and succeed in case 2.
Now umount A/a succeeds in both configurations.
This very small change in semantics appears if anything to be a bug
fix to me and my survey of userspace leads me to believe that no programs
will notice or care of this subtle semantic change.
v2: Updated to mnt_change_mountpoint to not call dput or mntput
and instead to decrement the counts directly. It is guaranteed
that there will be other references when mnt_change_mountpoint is
called so this is safe.
v3: Moved put_mountpoint under mount_lock in attach_recursive_mnt
As the locking in fs/namespace.c changed between v2 and v3.
v4: Reworked the logic in propagate_mount_busy and __propagate_umount
that detects when a mount completely covers another mount.
v5: Removed unnecessary tests whose result is alwasy true in
find_topper and attach_recursive_mnt.
v6: Document the user space visible semantic difference.
Cc: stable@vger.kernel.org
Fixes: b90fa9ae8f51 ("[PATCH] shared mount handling: bind and rbind")
Tested-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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If process forks some children when it has is_child_subreaper
flag enabled they will inherit has_child_subreaper flag - first
group, when is_child_subreaper is disabled forked children will
not inherit it - second group. So child-subreaper does not reparent
all his descendants when their parents die. Having these two
differently behaving groups can lead to confusion. Also it is
a problem for CRIU, as when we restore process tree we need to
somehow determine which descendants belong to which group and
much harder - to put them exactly to these group.
To simplify these we can add a propagation of has_child_subreaper
flag on PR_SET_CHILD_SUBREAPER, walking all descendants of child-
subreaper to setup has_child_subreaper flag.
In common cases when process like systemd first sets itself to
be a child-subreaper and only after that forks its services, we will
have zero-length list of descendants to walk. Testing with binary
subtree of 2^15 processes prctl took < 0.007 sec and has shown close
to linear dependency(~0.2 * n * usec) on lower numbers of processes.
Moreover, I doubt someone intentionaly pre-forks the children whitch
should reparent to init before becoming subreaper, because some our
ancestor migh have had is_child_subreaper flag while forking our
sub-tree and our childs will all inherit has_child_subreaper flag,
and we have no way to influence it. And only way to check if we have
no has_child_subreaper flag is to create some childs, kill them and
see where they will reparent to.
Using walk_process_tree helper to walk subtree, thanks to Oleg! Timing
seems to be the same.
Optimize:
a) When descendant already has has_child_subreaper flag all his subtree
has it too already.
* for a) to be true need to move has_child_subreaper inheritance under
the same tasklist_lock with adding task to its ->real_parent->children
as without it process can inherit zero has_child_subreaper, then we
set 1 to it's parent flag, check that parent has no more children, and
only after child with wrong flag is added to the tree.
* Also make these inheritance more clear by using real_parent instead of
current, as on clone(CLONE_PARENT) if current has is_child_subreaper
and real_parent has no is_child_subreaper or has_child_subreaper, child
will have has_child_subreaper flag set without actually having a
subreaper in it's ancestors.
b) When some descendant is child_reaper, it's subtree is in different
pidns from us(original child-subreaper) and processes from other pidns
will never reparent to us.
So we can skip their(a,b) subtree from walk.
v2: switch to walk_process_tree() general helper, move
has_child_subreaper inheritance
v3: remove csr_descendant leftover, change current to real_parent
in has_child_subreaper inheritance
v4: small commit message fix
Fixes: ebec18a6d3aa ("prctl: add PR_{SET,GET}_CHILD_SUBREAPER to allow simple process supervision")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Add the new helper to walk the process tree, the next patch adds a user.
Note that it visits the group leaders only, proc_visitor can do
for_each_thread itself or we can trivially extend walk_process_tree() to
do this.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Michael Kerrisk <<mtk.manpages@gmail.com> writes:
I would like to write code that discovers the namespace setup on a live
system. The NS_GET_PARENT and NS_GET_USERNS ioctl() operations added in
Linux 4.9 provide much of what I want, but there are still a couple of
small pieces missing. Those pieces are added with this patch series.
Here's an example program that makes use of the new ioctl() operations.
8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---
/* ns_capable.c
(C) 2016 Michael Kerrisk, <mtk.manpages@gmail.com>
Licensed under the GNU General Public License v2 or later.
Test whether a process (identified by PID) might (subject to LSM checks)
have capabilities in a namespace (identified by a /proc/PID/ns/xxx file).
*/
} while (0)
exit(EXIT_FAILURE); } while (0)
/* Display capabilities sets of process with specified PID */
static void
show_cap(pid_t pid)
{
cap_t caps;
char *cap_string;
caps = cap_get_pid(pid);
if (caps == NULL)
errExit("cap_get_proc");
cap_string = cap_to_text(caps, NULL);
if (cap_string == NULL)
errExit("cap_to_text");
printf("Capabilities: %s\n", cap_string);
}
/* Obtain the effective UID pf the process 'pid' by
scanning its /proc/PID/file */
static uid_t
get_euid_of_process(pid_t pid)
{
char path[PATH_MAX];
char line[1024];
int uid;
snprintf(path, sizeof(path), "/proc/%ld/status", (long) pid);
FILE *fp;
fp = fopen(path, "r");
if (fp == NULL)
errExit("fopen-/proc/PID/status");
for (;;) {
if (fgets(line, sizeof(line), fp) == NULL) {
/* Should never happen... */
fprintf(stderr, "Failure scanning %s\n", path);
exit(EXIT_FAILURE);
}
if (strstr(line, "Uid:") == line) {
sscanf(line, "Uid: %*d %d %*d %*d", &uid);
return uid;
}
}
}
int
main(int argc, char *argv[])
{
int ns_fd, userns_fd, pid_userns_fd;
int nstype;
int next_fd;
struct stat pid_stat;
struct stat target_stat;
char *pid_str;
pid_t pid;
char path[PATH_MAX];
if (argc < 2) {
fprintf(stderr, "Usage: %s PID [ns-file]\n", argv[0]);
fprintf(stderr, "\t'ns-file' is a /proc/PID/ns/xxxx file; "
"if omitted, use the namespace\n"
"\treferred to by standard input "
"(file descriptor 0)\n");
exit(EXIT_FAILURE);
}
pid_str = argv[1];
pid = atoi(pid_str);
if (argc <= 2) {
ns_fd = STDIN_FILENO;
} else {
ns_fd = open(argv[2], O_RDONLY);
if (ns_fd == -1)
errExit("open-ns-file");
}
/* Get the relevant user namespace FD, which is 'ns_fd' if 'ns_fd' refers
to a user namespace, otherwise the user namespace that owns 'ns_fd' */
nstype = ioctl(ns_fd, NS_GET_NSTYPE);
if (nstype == -1)
errExit("ioctl-NS_GET_NSTYPE");
if (nstype == CLONE_NEWUSER) {
userns_fd = ns_fd;
} else {
userns_fd = ioctl(ns_fd, NS_GET_USERNS);
if (userns_fd == -1)
errExit("ioctl-NS_GET_USERNS");
}
/* Obtain 'stat' info for the user namespace of the specified PID */
snprintf(path, sizeof(path), "/proc/%s/ns/user", pid_str);
pid_userns_fd = open(path, O_RDONLY);
if (pid_userns_fd == -1)
errExit("open-PID");
if (fstat(pid_userns_fd, &pid_stat) == -1)
errExit("fstat-PID");
/* Get 'stat' info for the target user namesapce */
if (fstat(userns_fd, &target_stat) == -1)
errExit("fstat-PID");
/* If the PID is in the target user namespace, then it has
whatever capabilities are in its sets. */
if (pid_stat.st_dev == target_stat.st_dev &&
pid_stat.st_ino == target_stat.st_ino) {
printf("PID is in target namespace\n");
printf("Subject to LSM checks, it has the following capabilities\n");
show_cap(pid);
exit(EXIT_SUCCESS);
}
/* Otherwise, we need to walk through the ancestors of the target
user namespace to see if PID is in an ancestor namespace */
for (;;) {
int f;
next_fd = ioctl(userns_fd, NS_GET_PARENT);
if (next_fd == -1) {
/* The error here should be EPERM... */
if (errno != EPERM)
errExit("ioctl-NS_GET_PARENT");
printf("PID is not in an ancestor namespace\n");
printf("It has no capabilities in the target namespace\n");
exit(EXIT_SUCCESS);
}
if (fstat(next_fd, &target_stat) == -1)
errExit("fstat-PID");
/* If the 'stat' info for this user namespace matches the 'stat'
* info for 'next_fd', then the PID is in an ancestor namespace */
if (pid_stat.st_dev == target_stat.st_dev &&
pid_stat.st_ino == target_stat.st_ino)
break;
/* Next time round, get the next parent */
f = userns_fd;
userns_fd = next_fd;
close(f);
}
/* At this point, we found that PID is in an ancestor of the target
user namespace, and 'userns_fd' refers to the immediate descendant
user namespace of PID in the chain of user namespaces from PID to
the target user namespace. If the effective UID of PID matches the
owner UID of descendant user namespace, then PID has all
capabilities in the descendant namespace(s); otherwise, it just has
the capabilities that are in its sets. */
uid_t owner_uid, uid;
if (ioctl(userns_fd, NS_GET_OWNER_UID, &owner_uid) == -1) {
perror("ioctl-NS_GET_OWNER_UID");
exit(EXIT_FAILURE);
}
uid = get_euid_of_process(pid);
printf("PID is in an ancestor namespace\n");
if (owner_uid == uid) {
printf("And its effective UID matches the owner "
"of the namespace\n");
printf("Subject to LSM checks, PID has all capabilities in "
"that namespace!\n");
} else {
printf("But its effective UID does not match the owner "
"of the namespace\n");
printf("Subject to LSM checks, it has the following capabilities\n");
show_cap(pid);
}
exit(EXIT_SUCCESS);
}
8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---
Michael Kerrisk (2):
nsfs: Add an ioctl() to return the namespace type
nsfs: Add an ioctl() to return owner UID of a userns
fs/nsfs.c | 13 +++++++++++++
include/uapi/linux/nsfs.h | 9 +++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
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I'd like to write code that discovers the user namespace hierarchy on a
running system, and also shows who owns the various user namespaces.
Currently, there is no way of getting the owner UID of a user namespace.
Therefore, this patch adds a new NS_GET_CREATOR_UID ioctl() that fetches
the UID (as seen in the user namespace of the caller) of the creator of
the user namespace referred to by the specified file descriptor.
If the supplied file descriptor does not refer to a user namespace,
the operation fails with the error EINVAL. If the owner UID does
not have a mapping in the caller's user namespace return the
overflow UID as that appears easier to deal with in practice
in user-space applications.
-- EWB Changed the handling of unmapped UIDs from -EOVERFLOW
back to the overflow uid. Per conversation with
Michael Kerrisk after examining his test code.
Acked-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Michael Kerrisk <mtk-manpages@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Linux 4.9 added two ioctl() operations that can be used to discover:
* the parental relationships for hierarchical namespaces (user and PID)
[NS_GET_PARENT]
* the user namespaces that owns a specified non-user-namespace
[NS_GET_USERNS]
For no good reason that I can glean, NS_GET_USERNS was made synonymous
with NS_GET_PARENT for user namespaces. It might have been better if
NS_GET_USERNS had returned an error if the supplied file descriptor
referred to a user namespace, since it suggests that the caller may be
confused. More particularly, if it had generated an error, then I wouldn't
need the new ioctl() operation proposed here. (On the other hand, what
I propose here may be more generally useful.)
I would like to write code that discovers namespace relationships for
the purpose of understanding the namespace setup on a running system.
In particular, given a file descriptor (or pathname) for a namespace,
N, I'd like to obtain the corresponding user namespace. Namespace N
might be a user namespace (in which case my code would just use N) or
a non-user namespace (in which case my code will use NS_GET_USERNS to
get the user namespace associated with N). The problem is that there
is no way to tell the difference by looking at the file descriptor
(and if I try to use NS_GET_USERNS on an N that is a user namespace, I
get the parent user namespace of N, which is not what I want).
This patch therefore adds a new ioctl(), NS_GET_NSTYPE, which, given
a file descriptor that refers to a user namespace, returns the
namespace type (one of the CLONE_NEW* constants).
Signed-off-by: Michael Kerrisk <mtk-manpages@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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To support unprivileged users mounting filesystems two permission
checks have to be performed: a test to see if the user allowed to
create a mount in the mount namespace, and a test to see if
the user is allowed to access the specified filesystem.
The automount case is special in that mounting the original filesystem
grants permission to mount the sub-filesystems, to any user who
happens to stumble across the their mountpoint and satisfies the
ordinary filesystem permission checks.
Attempting to handle the automount case by using override_creds
almost works. It preserves the idea that permission to mount
the original filesystem is permission to mount the sub-filesystem.
Unfortunately using override_creds messes up the filesystems
ordinary permission checks.
Solve this by being explicit that a mount is a submount by introducing
vfs_submount, and using it where appropriate.
vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let
sget and friends know that a mount is a submount so they can take appropriate
action.
sget and sget_userns are modified to not perform any permission checks
on submounts.
follow_automount is modified to stop using override_creds as that
has proven problemantic.
do_mount is modified to always remove the new MS_SUBMOUNT flag so
that we know userspace will never by able to specify it.
autofs4 is modified to stop using current_real_cred that was put in
there to handle the previous version of submount permission checking.
cifs is modified to pass the mountpoint all of the way down to vfs_submount.
debugfs is modified to pass the mountpoint all of the way down to
trace_automount by adding a new parameter. To make this change easier
a new typedef debugfs_automount_t is introduced to capture the type of
the debugfs automount function.
Cc: stable@vger.kernel.org
Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid")
Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds")
Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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