1.. _shrinker_debugfs: 2 3========================== 4Shrinker Debugfs Interface 5========================== 6 7Shrinker debugfs interface provides a visibility into the kernel memory 8shrinkers subsystem and allows to get information about individual shrinkers 9and interact with them. 10 11For each shrinker registered in the system a directory in **<debugfs>/shrinker/** 12is created. The directory's name is composed from the shrinker's name and an 13unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. 14 15Each shrinker directory contains **count** and **scan** files, which allow to 16trigger *count_objects()* and *scan_objects()* callbacks for each memcg and 17numa node (if applicable). 18 19Usage: 20------ 21 221. *List registered shrinkers* 23 24 :: 25 26 $ cd /sys/kernel/debug/shrinker/ 27 $ ls 28 dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42 29 mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43 30 mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44 31 rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49 32 sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13 33 sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36 34 sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19 35 sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10 36 sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9 37 sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37 38 sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38 39 sb-dax-11 sb-proc-45 sb-tmpfs-35 40 sb-debugfs-7 sb-proc-46 sb-tmpfs-40 41 422. *Get information about a specific shrinker* 43 44 :: 45 46 $ cd sb-btrfs\:vda2-24/ 47 $ ls 48 count scan 49 503. *Count objects* 51 52 Each line in the output has the following format:: 53 54 <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... 55 <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... 56 ... 57 58 If there are no objects on all numa nodes, a line is omitted. If there 59 are no objects at all, the output might be empty. 60 61 If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed 62 as cgroup inode id. If the shrinker is not numa-aware, 0's are printed 63 for all nodes except the first one. 64 :: 65 66 $ cat count 67 1 224 2 68 21 98 0 69 55 818 10 70 2367 2 0 71 2401 30 0 72 225 13 0 73 599 35 0 74 939 124 0 75 1041 3 0 76 1075 1 0 77 1109 1 0 78 1279 60 0 79 1313 7 0 80 1347 39 0 81 1381 3 0 82 1449 14 0 83 1483 63 0 84 1517 53 0 85 1551 6 0 86 1585 1 0 87 1619 6 0 88 1653 40 0 89 1687 11 0 90 1721 8 0 91 1755 4 0 92 1789 52 0 93 1823 888 0 94 1857 1 0 95 1925 2 0 96 1959 32 0 97 2027 22 0 98 2061 9 0 99 2469 799 0 100 2537 861 0 101 2639 1 0 102 2707 70 0 103 2775 4 0 104 2877 84 0 105 293 1 0 106 735 8 0 107 1084. *Scan objects* 109 110 The expected input format:: 111 112 <cgroup inode id> <numa id> <number of objects to scan> 113 114 For a non-memcg-aware shrinker or on a system with no memory 115 cgrups **0** should be passed as cgroup id. 116 :: 117 118 $ cd /sys/kernel/debug/shrinker/ 119 $ cd sb-btrfs\:vda2-24/ 120 121 $ cat count | head -n 5 122 1 212 0 123 21 97 0 124 55 802 5 125 2367 2 0 126 225 13 0 127 128 $ echo "55 0 200" > scan 129 130 $ cat count | head -n 5 131 1 212 0 132 21 96 0 133 55 752 5 134 2367 2 0 135 225 13 0 136