Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754437Ab1FOBTC (ORCPT ); Tue, 14 Jun 2011 21:19:02 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:47473 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754206Ab1FOBTB (ORCPT ); Tue, 14 Jun 2011 21:19:01 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 15 Jun 2011 10:12:02 +0900 From: KAMEZAWA Hiroyuki To: KAMEZAWA Hiroyuki Cc: Michal Hocko , "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: <20110615101202.fa8e9f76.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20110615091245.e3267a6b.kamezawa.hiroyu@jp.fujitsu.com> 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> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.1.1 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2315 Lines: 56 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, -kame -- 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/