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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 06/10] slab: implement slab_root_caches list
Date: Fri, 27 Jan 2017 21:06:56 +0300	[thread overview]
Message-ID: <20170127180656.GC4332@esperanza> (raw)
In-Reply-To: <20170117235411.9408-7-tj@kernel.org>

On Tue, Jan 17, 2017 at 03:54:07PM -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_caches currently lists all caches including root and memcg ones.
> This is the only data structure which lists the root caches and
> iterating root caches can only be done by walking the list while
> skipping over memcg caches.  As there can be a huge number of memcg
> caches, this can become very expensive.
> 
> This also can make /proc/slabinfo behave very badly.  seq_file
> processes reads in 4k chunks and seeks to the previous Nth position on
> slab_caches list to resume after each chunk.  With a lot of memcg
> cache churns on the list, reading /proc/slabinfo can become very slow
> and its content often ends up with duplicate and/or missing entries.
> 
> This patch adds a new list slab_root_caches which lists only the root
> caches.  When memcg is not enabled, it becomes just an alias of
> slab_caches.  memcg specific list operations are collected into
> memcg_[un]link_cache().
> 
> 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 06/10] slab: implement slab_root_caches list
Date: Fri, 27 Jan 2017 21:06:56 +0300	[thread overview]
Message-ID: <20170127180656.GC4332@esperanza> (raw)
In-Reply-To: <20170117235411.9408-7-tj@kernel.org>

On Tue, Jan 17, 2017 at 03:54:07PM -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_caches currently lists all caches including root and memcg ones.
> This is the only data structure which lists the root caches and
> iterating root caches can only be done by walking the list while
> skipping over memcg caches.  As there can be a huge number of memcg
> caches, this can become very expensive.
> 
> This also can make /proc/slabinfo behave very badly.  seq_file
> processes reads in 4k chunks and seeks to the previous Nth position on
> slab_caches list to resume after each chunk.  With a lot of memcg
> cache churns on the list, reading /proc/slabinfo can become very slow
> and its content often ends up with duplicate and/or missing entries.
> 
> This patch adds a new list slab_root_caches which lists only the root
> caches.  When memcg is not enabled, it becomes just an alias of
> slab_caches.  memcg specific list operations are collected into
> memcg_[un]link_cache().
> 
> 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>

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  reply	other threads:[~2017-01-27 18:07 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
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 [this message]
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

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