From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 8/8] slab: remove slub sysfs interface files early for empty memcg caches Date: Sat, 14 Jan 2017 13:48:34 -0500 Message-ID: <20170114184834.8658-9-tj@kernel.org> References: <20170114184834.8658-1-tj@kernel.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=b58WZKhpVuCKIvTedPdY3rv1/qB/Het50ubLSax32FU=; b=A/4OgMfSNrM1qLrUCAwo2g0v5Q2v6iyGPp3wUGzZH/SDofsGDrHDHV3+VPYvssWtjw V9BMpbe564onog+8bX7p+3xHDriQD6zw3sAV63UtTG5h0YtpVotbj48iVYCRD8DK/q2j kua3EglIYQlDDhvacGaL5DzRqv+5KbftEv1FEPFAo8x1HpTnDqWFnazmLnmV/pHs41Hy nFEplME8PAnKWBrXvarMuv2CP6ywVZ0vS6og2ASRgfM+upEN8hw61gQAB7g376naM8Nc H8oHrWGJLPGhFHYNQOJEvetLmQr2c+YWVLDmHNxeGdPmd6ozFibGpUnmuDPkb9BgJKQJ 0zRQ== In-Reply-To: <20170114184834.8658-1-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: vdavydov.dev@gmail.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Cc: jsvana@fb.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@fb.com, Tejun Heo 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. Each cache has a number of sysfs interface files under /sys/kernel/slab. On a system with a lot of memory and transient memcgs, the number of interface files which have to be removed once memory reclaim kicks in can reach millions. Signed-off-by: Tejun Heo Reported-by: Jay Vana Acked-by: Vladimir Davydov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton --- mm/slub.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 184f80b..5bffa1f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3951,8 +3951,20 @@ int __kmem_cache_shrink(struct kmem_cache *s) #ifdef CONFIG_MEMCG static void kmemcg_cache_deact_after_rcu(struct kmem_cache *s) { - /* called with all the locks held after a sched RCU grace period */ - __kmem_cache_shrink(s); + /* + * Called with all the locks held after a sched RCU grace period. + * Even if @s becomes empty after shrinking, we can't know that @s + * doesn't have allocations already in-flight and thus can't + * destroy @s until the associated memcg is released. + * + * However, let's remove the sysfs files for empty caches here. + * Each cache has a lot of interface files which aren't + * particularly useful for empty draining caches; otherwise, we can + * easily end up with millions of unnecessary sysfs files on + * systems which have a lot of memory and transient cgroups. + */ + if (!__kmem_cache_shrink(s)) + sysfs_slab_remove(s); } void __kmemcg_cache_deactivate(struct kmem_cache *s) @@ -5651,6 +5663,15 @@ static void sysfs_slab_remove(struct kmem_cache *s) */ return; + if (!s->kobj.state_in_sysfs) + /* + * For a memcg cache, this may be called during + * deactivation and again on shutdown. Remove only once. + * A cache is never shut down before deactivation is + * complete, so no need to worry about synchronization. + */ + return; + #ifdef CONFIG_MEMCG kset_unregister(s->memcg_kset); #endif -- 2.9.3 -- 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: email@kvack.org