From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753999AbdA0SH2 (ORCPT ); Fri, 27 Jan 2017 13:07:28 -0500 Received: from smtp42.i.mail.ru ([94.100.177.102]:48321 "EHLO smtp42.i.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753256AbdA0SHG (ORCPT ); Fri, 27 Jan 2017 13:07:06 -0500 Date: Fri, 27 Jan 2017 21:06:56 +0300 From: Vladimir Davydov To: Tejun Heo 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 Message-ID: <20170127180656.GC4332@esperanza> References: <20170117235411.9408-1-tj@kernel.org> <20170117235411.9408-7-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170117235411.9408-7-tj@kernel.org> Authentication-Results: smtp42.i.mail.ru; auth=pass smtp.auth=vdavydov@tarantool.org smtp.mailfrom=vdavydov@tarantool.org X-Mru-Trust-IP: 1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.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 > Reported-by: Jay Vana > Cc: Vladimir Davydov > Cc: Christoph Lameter > Cc: Pekka Enberg > Cc: David Rientjes > Cc: Joonsoo Kim > Cc: Andrew Morton Acked-by: Vladimir Davydov From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Davydov Subject: Re: [PATCH 06/10] slab: implement slab_root_caches list Date: Fri, 27 Jan 2017 21:06:56 +0300 Message-ID: <20170127180656.GC4332@esperanza> References: <20170117235411.9408-1-tj@kernel.org> <20170117235411.9408-7-tj@kernel.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tarantool.org; s=mailru; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date; bh=03CbqwjJAUzysCiREO0x2uujSUb2xohJBc5RYqHokOU=; b=T0Fnnqr4r8UAJRPX3+huZjCDHW4HQ4K/+duBbETj7jeP33S7Mquwlsd6amK5mJiLWtN+4+MzZn35YfM2wkVyejfP3V7s7s3tpkfC0/A2DlBH7NZuDihCVGfVg1YNzCx4WMck++jOro+0x+CMRN016uOL0RCtmke+zSAKZqaB0Zo=; Content-Disposition: inline In-Reply-To: <20170117235411.9408-7-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo 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 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 > Reported-by: Jay Vana > Cc: Vladimir Davydov > Cc: Christoph Lameter > Cc: Pekka Enberg > Cc: David Rientjes > Cc: Joonsoo Kim > Cc: Andrew Morton Acked-by: Vladimir Davydov -- 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