All of lore.kernel.org
 help / color / mirror / Atom feed
From: Vladimir Davydov <vdavydov@tarantool.org>
To: Tejun Heo <tj@kernel.org>
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
	iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, jsvana@fb.com,
	hannes@cmpxchg.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 03/10] slab: remove synchronous rcu_barrier() call in memcg cache release path
Date: Fri, 27 Jan 2017 21:03:05 +0300	[thread overview]
Message-ID: <20170127180305.GB4332@esperanza> (raw)
In-Reply-To: <20170117235411.9408-4-tj@kernel.org>

On Tue, Jan 17, 2017 at 03:54:04PM -0800, Tejun Heo wrote:
> With kmem cgroup support enabled, kmem_caches can be created and
> destroyed frequently and a great number of near empty kmem_caches can
> accumulate if there are a lot of transient cgroups and the system is
> not under memory pressure.  When memory reclaim starts under such
> conditions, it can lead to consecutive deactivation and destruction of
> many kmem_caches, easily hundreds of thousands on moderately large
> systems, exposing scalability issues in the current slab management
> code.  This is one of the patches to address the issue.
> 
> SLAB_DESTORY_BY_RCU caches need to flush all RCU operations before
> destruction because slab pages are freed through RCU and they need to
> be able to dereference the associated kmem_cache.  Currently, it's
> done synchronously with rcu_barrier().  As rcu_barrier() is expensive
> time-wise, slab implements a batching mechanism so that rcu_barrier()
> can be done for multiple caches at the same time.
> 
> Unfortunately, the rcu_barrier() is in synchronous path which is
> called while holding cgroup_mutex and the batching is too limited to
> be actually helpful.
> 
> This patch updates the cache release path so that the batching is
> asynchronous and global.  All SLAB_DESTORY_BY_RCU caches are queued
> globally and a work item consumes the list.  The work item calls
> rcu_barrier() only once for all caches that are currently queued.
> 
> * release_caches() is removed and shutdown_cache() now either directly
>   release the cache or schedules a RCU callback to do that.  This
>   makes the cache inaccessible once shutdown_cache() is called and
>   makes it impossible for shutdown_memcg_caches() to do memcg-specific
>   cleanups afterwards.  Move memcg-specific part into a helper,
>   unlink_memcg_cache(), and make shutdown_cache() call it directly.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: Jay Vana <jsvana@fb.com>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Vladimir Davydov <vdavydov@tarantool.org>

WARNING: multiple messages have this Message-ID (diff)
From: Vladimir Davydov <vdavydov@tarantool.org>
To: Tejun Heo <tj@kernel.org>
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
	iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, jsvana@fb.com,
	hannes@cmpxchg.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 03/10] slab: remove synchronous rcu_barrier() call in memcg cache release path
Date: Fri, 27 Jan 2017 21:03:05 +0300	[thread overview]
Message-ID: <20170127180305.GB4332@esperanza> (raw)
In-Reply-To: <20170117235411.9408-4-tj@kernel.org>

On Tue, Jan 17, 2017 at 03:54:04PM -0800, Tejun Heo wrote:
> With kmem cgroup support enabled, kmem_caches can be created and
> destroyed frequently and a great number of near empty kmem_caches can
> accumulate if there are a lot of transient cgroups and the system is
> not under memory pressure.  When memory reclaim starts under such
> conditions, it can lead to consecutive deactivation and destruction of
> many kmem_caches, easily hundreds of thousands on moderately large
> systems, exposing scalability issues in the current slab management
> code.  This is one of the patches to address the issue.
> 
> SLAB_DESTORY_BY_RCU caches need to flush all RCU operations before
> destruction because slab pages are freed through RCU and they need to
> be able to dereference the associated kmem_cache.  Currently, it's
> done synchronously with rcu_barrier().  As rcu_barrier() is expensive
> time-wise, slab implements a batching mechanism so that rcu_barrier()
> can be done for multiple caches at the same time.
> 
> Unfortunately, the rcu_barrier() is in synchronous path which is
> called while holding cgroup_mutex and the batching is too limited to
> be actually helpful.
> 
> This patch updates the cache release path so that the batching is
> asynchronous and global.  All SLAB_DESTORY_BY_RCU caches are queued
> globally and a work item consumes the list.  The work item calls
> rcu_barrier() only once for all caches that are currently queued.
> 
> * release_caches() is removed and shutdown_cache() now either directly
>   release the cache or schedules a RCU callback to do that.  This
>   makes the cache inaccessible once shutdown_cache() is called and
>   makes it impossible for shutdown_memcg_caches() to do memcg-specific
>   cleanups afterwards.  Move memcg-specific part into a helper,
>   unlink_memcg_cache(), and make shutdown_cache() call it directly.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: Jay Vana <jsvana@fb.com>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Vladimir Davydov <vdavydov@tarantool.org>

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply	other threads:[~2017-01-27 18:22 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-17 23:54 [PATCHSET v3] slab: make memcg slab destruction scalable Tejun Heo
2017-01-17 23:54 ` Tejun Heo
2017-01-17 23:54 ` [PATCH 01/10] Revert "slub: move synchronize_sched out of slab_mutex on shrink" Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 02/10] slub: separate out sysfs_slab_release() from sysfs_slab_remove() Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-23 22:54   ` [PATCH v2 " Tejun Heo
2017-01-23 22:54     ` Tejun Heo
2017-01-23 22:54     ` Tejun Heo
2017-01-27 18:00     ` Vladimir Davydov
2017-01-27 18:00       ` Vladimir Davydov
2017-01-17 23:54 ` [PATCH 03/10] slab: remove synchronous rcu_barrier() call in memcg cache release path Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-27 18:03   ` Vladimir Davydov [this message]
2017-01-27 18:03     ` Vladimir Davydov
2017-01-17 23:54 ` [PATCH 04/10] slab: reorganize memcg_cache_params Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 05/10] slab: link memcg kmem_caches on their associated memory cgroup Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 06/10] slab: implement slab_root_caches list Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-27 18:06   ` Vladimir Davydov
2017-01-27 18:06     ` Vladimir Davydov
2017-01-17 23:54 ` [PATCH 07/10] slab: introduce __kmemcg_cache_deactivate() Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 08/10] slab: remove synchronous synchronize_sched() from memcg cache deactivation path Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 09/10] slab: remove slub sysfs interface files early for empty memcg caches Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-17 23:54 ` [PATCH 10/10] slab: use memcg_kmem_cache_wq for slab destruction operations Tejun Heo
2017-01-17 23:54   ` Tejun Heo
2017-01-29 16:04   ` Vladimir Davydov
2017-01-29 16:04     ` Vladimir Davydov
2017-02-03 17:43 ` [PATCHSET v3] slab: make memcg slab destruction scalable Tejun Heo
2017-02-03 17:43   ` Tejun Heo

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170127180305.GB4332@esperanza \
    --to=vdavydov@tarantool.org \
    --cc=akpm@linux-foundation.org \
    --cc=cgroups@vger.kernel.org \
    --cc=cl@linux.com \
    --cc=hannes@cmpxchg.org \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=jsvana@fb.com \
    --cc=kernel-team@fb.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=tj@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.