Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753388Ab1FOHPG (ORCPT ); Wed, 15 Jun 2011 03:15:06 -0400 Received: from cantor2.suse.de ([195.135.220.15]:41301 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752321Ab1FOHPE (ORCPT ); Wed, 15 Jun 2011 03:15:04 -0400 Date: Wed, 15 Jun 2011 09:15:00 +0200 From: Michal Hocko To: KAMEZAWA Hiroyuki Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" , "bsingharora@gmail.com" , "hannes@cmpxchg.org" , Ying Han Subject: Re: [BUGFIX][PATCH 5/5] memcg: fix percpu cached charge draining frequency Message-ID: <20110615071500.GA31868@tiehlicka.suse.cz> References: <20110613120054.3336e997.kamezawa.hiroyu@jp.fujitsu.com> <20110613121648.3d28afcd.kamezawa.hiroyu@jp.fujitsu.com> <20110614073651.GA21197@tiehlicka.suse.cz> <20110615091245.e3267a6b.kamezawa.hiroyu@jp.fujitsu.com> <20110615101202.fa8e9f76.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110615101202.fa8e9f76.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2552 Lines: 63 On Wed 15-06-11 10:12:02, KAMEZAWA Hiroyuki wrote: > On Wed, 15 Jun 2011 09:12:45 +0900 > KAMEZAWA Hiroyuki wrote: > > > On Tue, 14 Jun 2011 09:36:51 +0200 > > Michal Hocko wrote: > > > > > On Mon 13-06-11 12:16:48, KAMEZAWA Hiroyuki wrote: > > > > From 18b12e53f1cdf6d7feed1f9226c189c34866338c Mon Sep 17 00:00:00 2001 > > > > From: KAMEZAWA Hiroyuki > > > > Date: Mon, 13 Jun 2011 11:25:43 +0900 > > > > Subject: [PATCH 5/5] memcg: fix percpu cached charge draining frequency > > > > > > > > For performance, memory cgroup caches some "charge" from res_counter > > > > into per cpu cache. This works well but because it's cache, > > > > it needs to be flushed in some cases. Typical cases are > > > > 1. when someone hit limit. > > > > 2. when rmdir() is called and need to charges to be 0. > > > > > > > > But "1" has problem. > > > > > > > > Recently, with large SMP machines, we see many kworker runs because > > > > of flushing memcg's cache. Bad things in implementation are > > > > that even if a cpu contains a cache for memcg not related to > > > > a memcg which hits limit, drain code is called. > > > > > > > > This patch does > > > > D) don't call at softlimit reclaim. > > > > > > I think this needs some justification. The decision is not that > > > obvious IMO. I would say that this is a good decision because cached > > > charges will not help to free any memory (at least not directly) during > > > background reclaim. What about something like: > > > " > > > We are not draining per cpu cached charges during soft limit reclaim > > > because background reclaim doesn't care about charges. It tries to free > > > some memory and charges will not give any. > > > Cached charges might influence only selection of the biggest soft limit > > > offender but as the call is done only after the selection has been > > > already done it makes no change. > > > " > > > > > > Anyway, wouldn't it be better to have this change separate from the > > > async draining logic change? > > > > Hmm. I think calling "draining" at softlimit is just a bug. > > > I'll divide patches. Thanks. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/