From: Vladimir Davydov <vdavydov@parallels.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>, Greg Thelen <gthelen@google.com>,
Dave Chinner <david@fromorbit.com>,
Glauber Costa <glommer@gmail.com>,
Suleiman Souhlal <suleiman@google.com>,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Tejun Heo <tj@kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-mm@kvack.org>, <cgroups@vger.kernel.org>
Subject: Re: [PATCH -mm 00/14] Per memcg slab shrinkers
Date: Mon, 29 Sep 2014 11:02:53 +0400 [thread overview]
Message-ID: <20140929070252.GA16447@esperanza> (raw)
In-Reply-To: <cover.1411301245.git.vdavydov@parallels.com>
ping
On Sun, Sep 21, 2014 at 07:14:32PM +0400, Vladimir Davydov wrote:
> 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.
>
> The main difference of this patch set from my previous attempts to push
> memcg aware shrinkers is in how it handles css offline. Now we don't let
> list_lrus corresponding to dead memory cgroups hang around till all
> objects are freed. Instead we move lru items to the parent cgroup's lru
> list. This is really important, because this allows us to release
> memcg_cache_id used for indexing in per-memcg arrays. If we don't do
> this, the arrays will grow uncontrollably, which is really bad. Note, in
> comparison to user memory reparenting, which Johannes is going to get
> rid of, it's not racy and much easier to implement although it does
> impose some limitations on how list_lru locking can be implemented.
> Another difference is that it doesn't reparent charges, only list_lru
> entries - the css will be dangling until the last kmem object is freed.
>
> 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, it
> will probably require a sort of soft limit to work properly. I'm leaving
> this for future work.
>
> The patch set basically consists of three main parts and 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 4-10 make memcg core release cache ids on offline doing a bit
> of cleanup in the meanwhile. This is easy, because kmem_caches don't
> need the cache id after css offline since there can't be allocations
> going from a dead memcg. Note that most of these patches (namely 4-6,
> and 8) were once merged, but then I decided to drop them, because I
> didn't know how to deal with list_lrus at that time (see
> https://lkml.org/lkml/2014/7/23/218).
>
> - Finally patches 11-14 make list_lru per-memcg and mark FS shrinkers
> as memcg-aware. This is the most difficult part of this patch set
> with patch 13 (unlucky :-) doing the most important work.
>
> Reviews are more than welcome.
prev parent reply other threads:[~2014-09-29 7:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-21 15:14 [PATCH -mm 00/14] Per memcg slab shrinkers Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 01/14] list_lru: introduce list_lru_shrink_{count,walk} Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 02/14] fs: consolidate {nr,free}_cached_objects args in shrink_control Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 03/14] vmscan: shrink slab on memcg pressure Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 04/14] memcg: use mem_cgroup_id for per memcg cache naming Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 05/14] memcg: add pointer to owner cache to memcg_cache_params Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 06/14] memcg: keep all children of each root cache on a list Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 07/14] memcg: update memcg_caches array entries on the slab side Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 08/14] memcg: release memcg_cache_id on css offline Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 09/14] memcg: rename some cache id related variables Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 10/14] memcg: add rwsem to sync against memcg_caches arrays relocation Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 11/14] list_lru: get rid of ->active_nodes Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 12/14] list_lru: organize all list_lrus to list Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 13/14] list_lru: introduce per-memcg lists Vladimir Davydov
2014-09-21 15:14 ` [PATCH -mm 14/14] fs: make shrinker memcg aware Vladimir Davydov
2014-09-21 16:00 ` [PATCH -mm 00/14] Per memcg slab shrinkers Tejun Heo
2014-09-22 7:04 ` Vladimir Davydov
2014-09-29 7:02 ` Vladimir Davydov [this message]
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