136 lines
3.3 KiB
ReStructuredText
136 lines
3.3 KiB
ReStructuredText
.. _shrinker_debugfs:
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==========================
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Shrinker Debugfs Interface
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==========================
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Shrinker debugfs interface provides a visibility into the kernel memory
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shrinkers subsystem and allows to get information about individual shrinkers
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and interact with them.
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For each shrinker registered in the system a directory in **<debugfs>/shrinker/**
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is created. The directory's name is composed from the shrinker's name and an
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unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*.
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Each shrinker directory contains **count** and **scan** files, which allow to
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trigger *count_objects()* and *scan_objects()* callbacks for each memcg and
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numa node (if applicable).
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Usage:
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------
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1. *List registered shrinkers*
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::
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$ cd /sys/kernel/debug/shrinker/
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$ ls
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dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42
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mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43
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mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44
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rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49
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sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13
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sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36
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sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19
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sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10
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sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9
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sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37
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sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38
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sb-dax-11 sb-proc-45 sb-tmpfs-35
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sb-debugfs-7 sb-proc-46 sb-tmpfs-40
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2. *Get information about a specific shrinker*
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::
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$ cd sb-btrfs\:vda2-24/
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$ ls
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count scan
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3. *Count objects*
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Each line in the output has the following format::
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<cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ...
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<cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ...
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...
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If there are no objects on all numa nodes, a line is omitted. If there
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are no objects at all, the output might be empty.
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If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed
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as cgroup inode id. If the shrinker is not numa-aware, 0's are printed
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for all nodes except the first one.
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::
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$ cat count
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1 224 2
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21 98 0
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55 818 10
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2367 2 0
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2401 30 0
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225 13 0
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599 35 0
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939 124 0
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1041 3 0
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1075 1 0
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1109 1 0
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1279 60 0
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1313 7 0
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1347 39 0
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1381 3 0
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1449 14 0
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1483 63 0
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1517 53 0
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1551 6 0
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1585 1 0
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1619 6 0
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1653 40 0
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1687 11 0
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1721 8 0
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1755 4 0
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1789 52 0
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1823 888 0
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1857 1 0
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1925 2 0
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1959 32 0
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2027 22 0
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2061 9 0
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2469 799 0
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2537 861 0
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2639 1 0
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2707 70 0
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2775 4 0
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2877 84 0
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293 1 0
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735 8 0
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4. *Scan objects*
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The expected input format::
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<cgroup inode id> <numa id> <number of objects to scan>
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For a non-memcg-aware shrinker or on a system with no memory
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cgrups **0** should be passed as cgroup id.
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::
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$ cd /sys/kernel/debug/shrinker/
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$ cd sb-btrfs\:vda2-24/
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$ cat count | head -n 5
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1 212 0
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21 97 0
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55 802 5
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2367 2 0
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225 13 0
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$ echo "55 0 200" > scan
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$ cat count | head -n 5
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1 212 0
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21 96 0
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55 752 5
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2367 2 0
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225 13 0
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