Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752271Ab1FIBkm (ORCPT ); Wed, 8 Jun 2011 21:40:42 -0400 Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:49454 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751246Ab1FIBkl (ORCPT ); Wed, 8 Jun 2011 21:40:41 -0400 Date: Thu, 9 Jun 2011 10:30:23 +0900 From: Daisuke Nishimura To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , Michal Hocko , "bsingharora@gmail.com" , Ying Han , Daisuke Nishimura Subject: Re: [BUGFIX][PATCH v3] memcg: fix behavior of per cpu charge cache draining. Message-Id: <20110609103023.4c4deaf2.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20110609093045.1f969d30.kamezawa.hiroyu@jp.fujitsu.com> References: <20110609093045.1f969d30.kamezawa.hiroyu@jp.fujitsu.com> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 3.1.0 (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: 2011 Lines: 50 On Thu, 9 Jun 2011 09:30:45 +0900 KAMEZAWA Hiroyuki wrote: > From 0ebd8a90a91d50c512e7c63e5529a22e44e84c42 Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki > Date: Wed, 8 Jun 2011 13:51:11 +0900 > Subject: [PATCH] Fix behavior of per-cpu charge cache draining in memcg. > > 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 many kworker runs because > of flushing memcg's cache. Bad things in implementation are > > a) it's called before calling try_to_free_mem_cgroup_pages() > so, it's called immidiately when a task hit limit. > (I though it was better to avoid to run into memory reclaim. > But it was wrong decision.) > > b) Even if a cpu contains a cache for memcg not related to > a memcg which hits limit, drain code is called. > > This patch fixes a) and b) by > > A) delay calling of flushing until one run of try_to_free... > Then, the number of calling is decreased. > B) check percpu cache contains a useful data or not. > plus > C) check asynchronous percpu draining doesn't run. > > BTW, why this patch relpaces atomic_t counter with mutex is > to guarantee a memcg which is pointed by stock->cacne is > not destroyed while we check css_id. > > Reported-by: Ying Han > Reviewed-by: Michal Hocko > Signed-off-by: KAMEZAWA Hiroyuki > Acked-by: Daisuke Nishimura -- 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/