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

From: Vladimir Davydov
Date: Fri Apr 18 2014 - 04:08:35 EST


On 04/18/2014 12:04 PM, Vladimir Davydov wrote:
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.

v1 can be found here: https://lkml.org/lkml/2014/4/9/298

Changes in v2:
- substitute per memcg slab_caches_mutex's with the global
memcg_slab_mutex and re-split the set.


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(-)

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