The only existing debugging mechanism is a couple of tracepoints in do_shrink_slab(): mm_shrink_slab_start and mm_shrink_slab_end. They aren't covering everything though: shrinkers which report 0 objects will never show up, there is no support for memcg-aware shrinkers. Shrinkers are identified by their scan function, which is not always enough (e.g. hard to guess which super block's shrinker it is having only "super_cache_scan"). To provide a better visibility and debug options for memory shrinkers this patchset introduces a /sys/kernel/debug/shrinker interface, to some extent similar to /sys/kernel/slab. For each shrinker registered in the system a directory is created. As now, the directory will contain only a "scan" file, which allows to get the number of managed objects for each memory cgroup (for memcg-aware shrinkers) and each numa node (for numa-aware shrinkers on a numa machine). Other interfaces might be added in the future. To make debugging more pleasant, the patchset also names all shrinkers, so that debugfs entries can have meaningful names. v4: 1) multiple shrinkers naming enhancements, by Kent and Dave 2) multiple minor fixes/optimizations, by Muchun v3: 1) separated the "scan" part into a separate patch, by Dave 2) merged *_memcg, *_node and *_memcg_node interfaces, by Dave 3) shrinkers naming enhancements, by Christophe and Dave 4) added signal_pending() check, by Hillf 5) enabled by default, by Dave v2: 1) switched to debugfs, suggested by Mike, Andrew, Greg and others 2) switched to seq_file API for output, no PAGE_SIZE limit anymore, by Andrew 3) switched to down_read_killable(), suggested by Hillf 4) dropped stateful filtering and "freed" returning, by Kent 5) added docs, by Andrew 6) added memcg_shrinker.py tool rfc: https://lwn.net/Articles/891542/ Roman Gushchin (6): mm: memcontrol: introduce mem_cgroup_ino() and mem_cgroup_get_from_ino() mm: shrinkers: introduce debugfs interface for memory shrinkers mm: shrinkers: provide shrinkers with names mm: docs: document shrinker debugfs tools: add memcg_shrinker.py mm: shrinkers: add scan interface for shrinker debugfs Documentation/admin-guide/mm/index.rst | 1 + .../admin-guide/mm/shrinker_debugfs.rst | 131 ++++++++ arch/x86/kvm/mmu/mmu.c | 2 +- drivers/android/binder_alloc.c | 2 +- drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 3 +- drivers/gpu/drm/msm/msm_gem_shrinker.c | 2 +- .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 2 +- drivers/gpu/drm/ttm/ttm_pool.c | 2 +- drivers/md/bcache/btree.c | 2 +- drivers/md/dm-bufio.c | 3 +- drivers/md/dm-zoned-metadata.c | 4 +- drivers/md/raid5.c | 2 +- drivers/misc/vmw_balloon.c | 2 +- drivers/virtio/virtio_balloon.c | 2 +- drivers/xen/xenbus/xenbus_probe_backend.c | 2 +- fs/btrfs/super.c | 2 + fs/erofs/utils.c | 2 +- fs/ext4/extents_status.c | 3 +- fs/f2fs/super.c | 2 +- fs/gfs2/glock.c | 2 +- fs/gfs2/main.c | 2 +- fs/jbd2/journal.c | 3 +- fs/mbcache.c | 2 +- fs/nfs/nfs42xattr.c | 7 +- fs/nfs/super.c | 2 +- fs/nfsd/filecache.c | 2 +- fs/nfsd/nfscache.c | 3 +- fs/quota/dquot.c | 2 +- fs/super.c | 6 +- fs/ubifs/super.c | 2 +- fs/xfs/xfs_buf.c | 3 +- fs/xfs/xfs_icache.c | 2 +- fs/xfs/xfs_qm.c | 3 +- include/linux/memcontrol.h | 21 ++ include/linux/shrinker.h | 31 +- kernel/rcu/tree.c | 2 +- lib/Kconfig.debug | 9 + mm/Makefile | 1 + mm/huge_memory.c | 4 +- mm/memcontrol.c | 23 ++ mm/shrinker_debug.c | 285 ++++++++++++++++++ mm/vmscan.c | 64 +++- mm/workingset.c | 2 +- mm/zsmalloc.c | 3 +- net/sunrpc/auth.c | 2 +- tools/cgroup/memcg_shrinker.py | 71 +++++ 46 files changed, 684 insertions(+), 46 deletions(-) create mode 100644 Documentation/admin-guide/mm/shrinker_debugfs.rst create mode 100644 mm/shrinker_debug.c create mode 100755 tools/cgroup/memcg_shrinker.py -- 2.35.3
