Commit 7507f099 authored by Roman Gushchin's avatar Roman Gushchin Committed by Andrew Morton
Browse files

mm: docs: document shrinker debugfs 

Add a document describing the shrinker debugfs interface.

Link: https://lkml.kernel.org/r/20220601032227.4076670-5-roman.gushchin@linux.dev


Signed-off-by: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e33c267a

Documentation/admin-guide/mm/index.rst

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@@ -36,6 +36,7 @@ the Linux memory management. 
   numa_memory_policy

   numaperf

   pagemap

   shrinker_debugfs

   soft-dirty

   swap_numa

   transhuge

Documentation/admin-guide/mm/shrinker_debugfs.rst

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.. _shrinker_debugfs:



==========================

Shrinker Debugfs Interface

==========================



Shrinker debugfs interface provides a visibility into the kernel memory

shrinkers subsystem and allows to get information about individual shrinkers.



For each shrinker registered in the system a directory in **<debugfs>/shrinker/**

is created. The directory's name is composed from the shrinker's name and an

unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*.



Each shrinker directory contains the **count** file, which allows to trigger

the *count_objects()* callback for each memcg and numa node (if applicable).



Usage:

------



1. *List registered shrinkers*



  ::



    $ cd /sys/kernel/debug/shrinker/

    $ ls

    dquota-cache-16     sb-devpts-28     sb-proc-47       sb-tmpfs-42

    mm-shadow-18        sb-devtmpfs-5    sb-proc-48       sb-tmpfs-43

    mm-zspool:zram0-34  sb-hugetlbfs-17  sb-pstore-31     sb-tmpfs-44

    rcu-kfree-0         sb-hugetlbfs-33  sb-rootfs-2      sb-tmpfs-49

    sb-aio-20           sb-iomem-12      sb-securityfs-6  sb-tracefs-13

    sb-anon_inodefs-15  sb-mqueue-21     sb-selinuxfs-22  sb-xfs:vda1-36

    sb-bdev-3           sb-nsfs-4        sb-sockfs-8      sb-zsmalloc-19

    sb-bpf-32           sb-pipefs-14     sb-sysfs-26      thp-deferred_split-10

    sb-btrfs:vda2-24    sb-proc-25       sb-tmpfs-1       thp-zero-9

    sb-cgroup2-30       sb-proc-39       sb-tmpfs-27      xfs-buf:vda1-37

    sb-configfs-23      sb-proc-41       sb-tmpfs-29      xfs-inodegc:vda1-38

    sb-dax-11           sb-proc-45       sb-tmpfs-35

    sb-debugfs-7        sb-proc-46       sb-tmpfs-40



2. *Get information about a specific shrinker*



  ::



    $ cd sb-btrfs\:vda2-24/

    $ ls

    count



3. *Count objects*



  Each line in the output has the following format::



    <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ...

    <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ...

    ...



  If there are no objects on all numa nodes, a line is omitted. If there

  are no objects at all, the output might be empty.



  If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed

  as cgroup inode id. If the shrinker is not numa-aware, 0's are printed

  for all nodes except the first one.

  ::



    $ cat count

    1 224 2

    21 98 0

    55 818 10

    2367 2 0

    2401 30 0

    225 13 0

    599 35 0

    939 124 0

    1041 3 0

    1075 1 0

    1109 1 0

    1279 60 0

    1313 7 0

    1347 39 0

    1381 3 0

    1449 14 0

    1483 63 0

    1517 53 0

    1551 6 0

    1585 1 0

    1619 6 0

    1653 40 0

    1687 11 0

    1721 8 0

    1755 4 0

    1789 52 0

    1823 888 0

    1857 1 0

    1925 2 0

    1959 32 0

    2027 22 0

    2061 9 0

    2469 799 0

    2537 861 0

    2639 1 0

    2707 70 0

    2775 4 0

    2877 84 0

    293 1 0

    735 8 0