Per memcg slab shrinkers

Hi,

Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do.

Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup.

Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does.

As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy.

Changes in v3:
- Removed extra walk over all memory cgroups for shrinking per memcg slab caches; shrink_slab is now called per memcg from the loop in shrink_zone, as suggested by Johannes
- Reworked list_lru per memcg arrays init/destroy/update functions, hopefully making them more readable
- Rebased on top of v3.19-rc3-mmotm-2015-01-07-17-07

v2: https://lkml.org/lkml/2014/10/24/219
v1: https://lkml.org/lkml/2014/9/21/64

The patch set is organized as follows:

- Patches 1-3 implement per-memcg shrinker core with patches 1 and 2 preparing list_lru users for upcoming changes and patch 3 tuning shrink_slab.

- Patches 4 and 5 cleanup handling of max memcg_cache_id in the memcg core.

- Patch 6 gets rid of the useless list_lru->active_nodes, and patch 7 links all list_lrus to a list, which is required by memcg.

- Patch 8 adds per-memcg lrus to the list_lru structure, and finally patch 9 marks fs shrinkers as memcg aware.

Thanks,

Vladimir Davydov (9):
list_lru: introduce list_lru_shrink_{count,walk}
fs: consolidate {nr,free}_cached_objects args in shrink_control
vmscan: per memory cgroup slab shrinkers
memcg: rename some cache id related variables
memcg: add rwsem to synchronize against memcg_caches arrays
relocation
list_lru: get rid of ->active_nodes
list_lru: organize all list_lrus to list
list_lru: introduce per-memcg lists
fs: make shrinker memcg aware

 fs/dcache.c                |   14 +-
 fs/drop_caches.c           |   14 --
 fs/gfs2/quota.c            |    6 +-
 fs/inode.c                 |    7 +-
 fs/internal.h              |    7 +-
 fs/super.c                 |   44 +++--
 fs/xfs/xfs_buf.c           |    7 +-
 fs/xfs/xfs_qm.c            |    7 +-
 fs/xfs/xfs_super.c         |    7 +-
 include/linux/fs.h         |    6 +-
 include/linux/list_lru.h   |   70 ++++++--
 include/linux/memcontrol.h |   37 +++-
 include/linux/mm.h         |    5 +-
 include/linux/shrinker.h   |    6 +-
 mm/list_lru.c              |  412 +++++++++++++++++++++++++++++++++++++++++---
 mm/memcontrol.c            |   68 +++++---
 mm/memory-failure.c        |   11 +-
 mm/slab_common.c           |   13 +-
 mm/vmscan.c                |   86 ++++++---
 mm/workingset.c            |    6 +-
 20 files changed, 657 insertions(+), 176 deletions(-)

1.7.10.4