From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id DA04F6B0253 for ; Sat, 14 Jan 2017 08:39:25 -0500 (EST) Received: by mail-lf0-f71.google.com with SMTP id v186so31436571lfa.2 for ; Sat, 14 Jan 2017 05:39:25 -0800 (PST) Received: from smtp32.i.mail.ru (smtp32.i.mail.ru. [94.100.177.92]) by mx.google.com with ESMTPS id x18si9881978lja.5.2017.01.14.05.39.24 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sat, 14 Jan 2017 05:39:24 -0800 (PST) Date: Sat, 14 Jan 2017 16:39:18 +0300 From: Vladimir Davydov Subject: Re: [PATCH 6/9] slab: don't put memcg caches on slab_caches list Message-ID: <20170114133918.GE2668@esperanza> References: <20170114055449.11044-1-tj@kernel.org> <20170114055449.11044-7-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170114055449.11044-7-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: 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 Sat, Jan 14, 2017 at 12:54:46AM -0500, 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. > > As the previous patch made it unnecessary to walk slab_caches to > iterate memcg-specific caches, there is no reason to keep memcg caches > on the list. This patch makes slab_caches include only the root > caches. As this makes slab_cache->list unused for memcg caches, > ->memcg_params.children_node is removed and ->list is used instead. > > 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 > --- > include/linux/slab.h | 3 --- > mm/slab.h | 3 +-- > mm/slab_common.c | 58 +++++++++++++++++++++++++--------------------------- > 3 files changed, 29 insertions(+), 35 deletions(-) IIRC the slab_caches list is also used on cpu/mem online/offline, so you have to patch those places to ensure that memcg caches get updated too. Other than that the patch looks good to me. -- 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