diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/damon/design.rst | 43 | ||||
| -rw-r--r-- | Documentation/vm/damon/faq.rst | 2 | ||||
| -rw-r--r-- | Documentation/vm/page_owner.rst | 75 |
3 files changed, 88 insertions, 32 deletions
diff --git a/Documentation/vm/damon/design.rst b/Documentation/vm/damon/design.rst index 210f0f50efd8..0cff6fac6b7e 100644 --- a/Documentation/vm/damon/design.rst +++ b/Documentation/vm/damon/design.rst @@ -13,12 +13,13 @@ primitives that dependent on and optimized for the target address space. On the other hand, the accuracy and overhead tradeoff mechanism, which is the core of DAMON, is in the pure logic space. DAMON separates the two parts in different layers and defines its interface to allow various low level -primitives implementations configurable with the core logic. +primitives implementations configurable with the core logic. We call the low +level primitives implementations monitoring operations. Due to this separated design and the configurable interface, users can extend -DAMON for any address space by configuring the core logics with appropriate low -level primitive implementations. If appropriate one is not provided, users can -implement the primitives on their own. +DAMON for any address space by configuring the core logics with appropriate +monitoring operations. If appropriate one is not provided, users can implement +the operations on their own. For example, physical memory, virtual memory, swap space, those for specific processes, NUMA nodes, files, and backing memory devices would be supportable. @@ -26,25 +27,24 @@ Also, if some architectures or devices support special optimized access check primitives, those will be easily configurable. -Reference Implementations of Address Space Specific Primitives -============================================================== +Reference Implementations of Address Space Specific Monitoring Operations +========================================================================= -The low level primitives for the fundamental access monitoring are defined in -two parts: +The monitoring operations are defined in two parts: 1. Identification of the monitoring target address range for the address space. 2. Access check of specific address range in the target space. -DAMON currently provides the implementations of the primitives for the physical +DAMON currently provides the implementations of the operations for the physical and virtual address spaces. Below two subsections describe how those work. VMA-based Target Address Range Construction ------------------------------------------- -This is only for the virtual address space primitives implementation. That for -the physical address space simply asks users to manually set the monitoring -target address ranges. +This is only for the virtual address space monitoring operations +implementation. That for the physical address space simply asks users to +manually set the monitoring target address ranges. Only small parts in the super-huge virtual address space of the processes are mapped to the physical memory and accessed. Thus, tracking the unmapped @@ -84,9 +84,10 @@ table having a mapping to the address. In this way, the implementations find and clear the bit(s) for next sampling target address and checks whether the bit(s) set again after one sampling period. This could disturb other kernel subsystems using the Accessed bits, namely Idle page tracking and the reclaim -logic. To avoid such disturbances, DAMON makes it mutually exclusive with Idle -page tracking and uses ``PG_idle`` and ``PG_young`` page flags to solve the -conflict with the reclaim logic, as Idle page tracking does. +logic. DAMON does nothing to avoid disturbing Idle page tracking, so handling +the interference is the responsibility of sysadmins. However, it solves the +conflict with the reclaim logic using ``PG_idle`` and ``PG_young`` page flags, +as Idle page tracking does. Address Space Independent Core Mechanisms @@ -94,8 +95,8 @@ Address Space Independent Core Mechanisms Below four sections describe each of the DAMON core mechanisms and the five monitoring attributes, ``sampling interval``, ``aggregation interval``, -``regions update interval``, ``minimum number of regions``, and ``maximum -number of regions``. +``update interval``, ``minimum number of regions``, and ``maximum number of +regions``. Access Frequency Monitoring @@ -168,6 +169,8 @@ The monitoring target address range could dynamically changed. For example, virtual memory could be dynamically mapped and unmapped. Physical memory could be hot-plugged. -As the changes could be quite frequent in some cases, DAMON checks the dynamic -memory mapping changes and applies it to the abstracted target area only for -each of a user-specified time interval (``regions update interval``). +As the changes could be quite frequent in some cases, DAMON allows the +monitoring operations to check dynamic changes including memory mapping changes +and applies it to monitoring operations-related data structures such as the +abstracted monitoring target memory area only for each of a user-specified time +interval (``update interval``). diff --git a/Documentation/vm/damon/faq.rst b/Documentation/vm/damon/faq.rst index 11aea40eb328..dde7e2414ee6 100644 --- a/Documentation/vm/damon/faq.rst +++ b/Documentation/vm/damon/faq.rst @@ -31,7 +31,7 @@ Does DAMON support virtual memory only? ======================================= No. The core of the DAMON is address space independent. The address space -specific low level primitive parts including monitoring target regions +specific monitoring operations including monitoring target regions constructions and actual access checks can be implemented and configured on the DAMON core by the users. In this way, DAMON users can monitor any address space with any access check technique. diff --git a/Documentation/vm/page_owner.rst b/Documentation/vm/page_owner.rst index 9837fc8147dd..c4de6f8dabe9 100644 --- a/Documentation/vm/page_owner.rst +++ b/Documentation/vm/page_owner.rst @@ -26,9 +26,9 @@ fragmentation statistics can be obtained through gfp flag information of each page. It is already implemented and activated if page owner is enabled. Other usages are more than welcome. -page owner is disabled in default. So, if you'd like to use it, you need -to add "page_owner=on" into your boot cmdline. If the kernel is built -with page owner and page owner is disabled in runtime due to no enabling +page owner is disabled by default. So, if you'd like to use it, you need +to add "page_owner=on" to your boot cmdline. If the kernel is built +with page owner and page owner is disabled in runtime due to not enabling boot option, runtime overhead is marginal. If disabled in runtime, it doesn't require memory to store owner information, so there is no runtime memory overhead. And, page owner inserts just two unlikely branches into @@ -78,33 +78,86 @@ Usage 2) Enable page owner: add "page_owner=on" to boot cmdline. -3) Do the job what you want to debug +3) Do the job that you want to debug. 4) Analyze information from page owner:: cat /sys/kernel/debug/page_owner > page_owner_full.txt ./page_owner_sort page_owner_full.txt sorted_page_owner.txt - The general output of ``page_owner_full.txt`` is as follows: + The general output of ``page_owner_full.txt`` is as follows:: Page allocated via order XXX, ... PFN XXX ... - // Detailed stack + // Detailed stack Page allocated via order XXX, ... PFN XXX ... - // Detailed stack + // Detailed stack The ``page_owner_sort`` tool ignores ``PFN`` rows, puts the remaining rows in buf, uses regexp to extract the page order value, counts the times - and pages of buf, and finally sorts them according to the times. + and pages of buf, and finally sorts them according to the parameter(s). See the result about who allocated each page - in the ``sorted_page_owner.txt``. General output: + in the ``sorted_page_owner.txt``. General output:: XXX times, XXX pages: Page allocated via order XXX, ... - // Detailed stack + // Detailed stack By default, ``page_owner_sort`` is sorted according to the times of buf. - If you want to sort by the pages nums of buf, use the ``-m`` parameter. + If you want to sort by the page nums of buf, use the ``-m`` parameter. + The detailed parameters are: + + fundamental function: + + Sort: + -a Sort by memory allocation time. + -m Sort by total memory. + -p Sort by pid. + -P Sort by tgid. + -n Sort by task command name. + -r Sort by memory release time. + -s Sort by stack trace. + -t Sort by times (default). + + additional function: + + Cull: + -c Cull by comparing stacktrace instead of total block. + --cull <rules> + Specify culling rules.Culling syntax is key[,key[,...]].Choose a + multi-letter key from the **STANDARD FORMAT SPECIFIERS** section. + + + <rules> is a single argument in the form of a comma-separated list, + which offers a way to specify individual culling rules. The recognized + keywords are described in the **STANDARD FORMAT SPECIFIERS** section below. + <rules> can be specified by the sequence of keys k1,k2, ..., as described in + the STANDARD SORT KEYS section below. Mixed use of abbreviated and + complete-form of keys is allowed. + + + Examples: + ./page_owner_sort <input> <output> --cull=stacktrace + ./page_owner_sort <input> <output> --cull=st,pid,name + ./page_owner_sort <input> <output> --cull=n,f + + Filter: + -f Filter out the information of blocks whose memory has been released. + + Select: + --pid <PID> Select by pid. + --tgid <TGID> Select by tgid. + --name <command> Select by task command name. + +STANDARD FORMAT SPECIFIERS +========================== + + KEY LONG DESCRIPTION + p pid process ID + tg tgid thread group ID + n name task command name + f free whether the page has been released or not + st stacktrace stace trace of the page allocation |