1========================== 2Shrinker Debugfs Interface 3========================== 4 5Shrinker debugfs interface provides a visibility into the kernel memory 6shrinkers subsystem and allows to get information about individual shrinkers 7and interact with them. 8 9For each shrinker registered in the system a directory in **<debugfs>/shrinker/** 10is created. The directory's name is composed from the shrinker's name and an 11unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. 12 13Each shrinker directory contains **count** and **scan** files, which allow to 14trigger *count_objects()* and *scan_objects()* callbacks for each memcg and 15numa node (if applicable). 16 17Usage: 18------ 19 201. *List registered shrinkers* 21 22 :: 23 24 $ cd /sys/kernel/debug/shrinker/ 25 $ ls 26 dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42 27 mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43 28 mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44 29 rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49 30 sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13 31 sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36 32 sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19 33 sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10 34 sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9 35 sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37 36 sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38 37 sb-dax-11 sb-proc-45 sb-tmpfs-35 38 sb-debugfs-7 sb-proc-46 sb-tmpfs-40 39 402. *Get information about a specific shrinker* 41 42 :: 43 44 $ cd sb-btrfs\:vda2-24/ 45 $ ls 46 count scan 47 483. *Count objects* 49 50 Each line in the output has the following format:: 51 52 <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... 53 <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... 54 ... 55 56 If there are no objects on all numa nodes, a line is omitted. If there 57 are no objects at all, the output might be empty. 58 59 If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed 60 as cgroup inode id. If the shrinker is not numa-aware, 0's are printed 61 for all nodes except the first one. 62 :: 63 64 $ cat count 65 1 224 2 66 21 98 0 67 55 818 10 68 2367 2 0 69 2401 30 0 70 225 13 0 71 599 35 0 72 939 124 0 73 1041 3 0 74 1075 1 0 75 1109 1 0 76 1279 60 0 77 1313 7 0 78 1347 39 0 79 1381 3 0 80 1449 14 0 81 1483 63 0 82 1517 53 0 83 1551 6 0 84 1585 1 0 85 1619 6 0 86 1653 40 0 87 1687 11 0 88 1721 8 0 89 1755 4 0 90 1789 52 0 91 1823 888 0 92 1857 1 0 93 1925 2 0 94 1959 32 0 95 2027 22 0 96 2061 9 0 97 2469 799 0 98 2537 861 0 99 2639 1 0 100 2707 70 0 101 2775 4 0 102 2877 84 0 103 293 1 0 104 735 8 0 105 1064. *Scan objects* 107 108 The expected input format:: 109 110 <cgroup inode id> <numa id> <number of objects to scan> 111 112 For a non-memcg-aware shrinker or on a system with no memory 113 cgrups **0** should be passed as cgroup id. 114 :: 115 116 $ cd /sys/kernel/debug/shrinker/ 117 $ cd sb-btrfs\:vda2-24/ 118 119 $ cat count | head -n 5 120 1 212 0 121 21 97 0 122 55 802 5 123 2367 2 0 124 225 13 0 125 126 $ echo "55 0 200" > scan 127 128 $ cat count | head -n 5 129 1 212 0 130 21 96 0 131 55 752 5 132 2367 2 0 133 225 13 0 134