[PATCH RFC -mm v2 0/3] kmemcg: simplify work-flow (was "memcg-vs-slab cleanup")

[Vladimir Davydov <vdavydov@parallels.com>]

Hi Michal, Johannes,

This patch-set is a part of preparations for kmemcg re-parenting. It
targets at simplifying kmemcg work-flows and synchronization.

First, it removes async per memcg cache destruction (see patches 1, 2).
Now caches are only destroyed on memcg offline. That means the caches
that are not empty on memcg offline will be leaked. However, they are
already leaked, because memcg_cache_params::nr_pages normally never
drops to 0 so the destruction work is never scheduled except
kmem_cache_shrink is called explicitly. In the future I'm planning
reaping such dead caches on vmpressure or periodically.

Second, it substitutes per memcg slab_caches_mutex's with the global
memcg_slab_mutex, which should be taken during the whole per memcg cache
creation/destruction path before the slab_mutex (see patch 3). This
greatly simplifies synchronization among various per memcg cache
creation/destruction paths.

I really need your help, because I'm far not sure if what I'm doing here
is right. So I would appreciate if you could look through the patches
and share your thoughts about the design changes they introduce.

Thanks,

Vladimir Davydov (3):
  memcg, slab: do not schedule cache destruction when last page goes
    away
  memcg, slab: merge memcg_{bind,release}_pages to
    memcg_{un}charge_slab
  memcg, slab: simplify synchronization scheme

 include/linux/memcontrol.h |   15 +--
 include/linux/slab.h       |    8 +-
 mm/memcontrol.c            |  231 +++++++++++++++-----------------------------
 mm/slab.c                  |    2 -
 mm/slab.h                  |   28 +-----
 mm/slab_common.c           |   22 ++---
 mm/slub.c                  |    2 -
 7 files changed, 92 insertions(+), 216 deletions(-)

-- 
1.7.10.4

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