From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755288AbaIDUuh (ORCPT ); Thu, 4 Sep 2014 16:50:37 -0400 Received: from www.sr71.net ([198.145.64.142]:48236 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753271AbaIDUug (ORCPT ); Thu, 4 Sep 2014 16:50:36 -0400 Message-ID: <5408D09A.5030000@sr71.net> Date: Thu, 04 Sep 2014 13:50:34 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Johannes Weiner CC: Michal Hocko , Hugh Dickins , Tejun Heo , Vladimir Davydov , Linus Torvalds , Andrew Morton , LKML , Linux-MM Subject: Re: regression caused by cgroups optimization in 3.17-rc2 References: <54061505.8020500@sr71.net> <20140902221814.GA18069@cmpxchg.org> <5406466D.1020000@sr71.net> <20140903001009.GA25970@cmpxchg.org> <5406612E.8040802@sr71.net> <20140904150846.GA10794@cmpxchg.org> In-Reply-To: <20140904150846.GA10794@cmpxchg.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/04/2014 08:08 AM, Johannes Weiner wrote: > Dave Hansen reports a massive scalability regression in an uncontained > page fault benchmark with more than 30 concurrent threads, which he > bisected down to 05b843012335 ("mm: memcontrol: use root_mem_cgroup > res_counter") and pin-pointed on res_counter spinlock contention. > > That change relied on the per-cpu charge caches to mostly swallow the > res_counter costs, but it's apparent that the caches don't scale yet. > > Revert memcg back to bypassing res_counters on the root level in order > to restore performance for uncontained workloads. A quick sniff test shows performance coming back to what it was around 3.16 with this patch. I'll run a more thorough set of tests and verify that it's working well.