Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762011AbZDAJLv (ORCPT ); Wed, 1 Apr 2009 05:11:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760207AbZDAJL2 (ORCPT ); Wed, 1 Apr 2009 05:11:28 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:49083 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760120AbZDAJL1 (ORCPT ); Wed, 1 Apr 2009 05:11:27 -0400 From: KOSAKI Motohiro To: KAMEZAWA Hiroyuki Subject: Re: [PATCH] vmscan: memcg needs may_swap (Re: [patch] vmscan: rename sc.may_swap to may_unmap) Cc: kosaki.motohiro@jp.fujitsu.com, Johannes Weiner , Minchan Kim , Daisuke Nishimura , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , "Rafael J. Wysocki" , Rik van Riel , Balbir Singh In-Reply-To: <20090401180445.80b11d90.kamezawa.hiroyu@jp.fujitsu.com> References: <20090401040951.GA1548@cmpxchg.org> <20090401180445.80b11d90.kamezawa.hiroyu@jp.fujitsu.com> Message-Id: <20090401180756.B1F1.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50 [ja] Date: Wed, 1 Apr 2009 18:11:20 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 40 > memory cgroup has 2 calls to this shrink_zone. > 1. memory usage hits the limit. > 2. mem+swap usage hits the limit. > > At "2", swap-out doesn't decrease the usage of mem+swap, then set may_swap=0. > So, we want to kick out only file caches. > But, we can reclaim file cache and "unmap file cache and reclaim it!" is > necessary even if may_swap=0. > > Then, scanning only FILE LRU makes sense at may_swap=0 *if* memcg is > the only user of may_swap=0. > > Let's see others. > > - __zone_reclaim sets may_unmap to be 0 when they don't want swap-out. > .....can be replaced with may_swap. > > - shrink_all_memory sets may_swap to be 0. Is this called by hibernation ? > If you don't want to unmap file caches while hibernation, adding may_unmap > as *new* paramter makes sense, I think. > > The change you proposed is for dropping unused SwapCache pages. Right ? > But this will be dropped by kswapd if necessary. > > As far as memcg concerns, scanning ANON LRU even when may_swap=0 is just > a waste of cpu time. this sentence just explain my intention. 1. memcg, zone_reclaim scanning ANON LRU is just waste of cpu. 2. kswapd and normal direct reclaim can reclaim stealed swapcache anyway. then above trick don't cause any system hang-up and performance degression. -- 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/