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Subject[PATCH v4 0/6] mm: introduce shrinker debugfs interface
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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

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