From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 228866B003D for ; Fri, 13 Mar 2009 03:17:30 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n2D7HR3u008166 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Fri, 13 Mar 2009 16:17:27 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 841F945DD81 for ; Fri, 13 Mar 2009 16:17:27 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 5C07745DD7F for ; Fri, 13 Mar 2009 16:17:27 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 1DE4FE08009 for ; Fri, 13 Mar 2009 16:17:27 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id B4336E08004 for ; Fri, 13 Mar 2009 16:17:26 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 4/4] Memory controller soft limit reclaim on contention (v5) In-Reply-To: <20090313070340.GI16897@balbir.in.ibm.com> References: <20090313145032.AF4D.A69D9226@jp.fujitsu.com> <20090313070340.GI16897@balbir.in.ibm.com> Message-Id: <20090313160632.683D.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 13 Mar 2009 16:17:25 +0900 (JST) Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, YAMAMOTO Takashi , lizf@cn.fujitsu.com, Rik van Riel , Andrew Morton , KAMEZAWA Hiroyuki List-ID: > > hm > > I read past discussion. so, I think we discuss many aspect at once. > > So, my current thinking is below, > > > > (1) if the group don't have any soft limit shrinking page, > > mem_cgroup_soft_limit_reclaim() spent time unnecessary. > > -> right. > > If the soft limit RB tree is empty, we don't spend any time at all. > Are you referring to something else? Am I missing something? The tree > will be empty if no group is over the soft limit. maybe, I am missing anything. May I ask your following paragraph meaning? > I experimented a *lot* with zone reclaim and found it to be not so > effective. Here is why > > 1. We have no control over priority or how much to scan, that is > controlled by balance_pgdat(). If we find that we are unable to scan > anything, we continue scanning with the scan > 0 check, but we scan > the same pages and the same number, because shrink_zone does scan >> > priority. I thought this sentense mean soft-limit-shrinking spent a lot of time. if not, could you please tell me what makes so slower? and, you wrote: > > Yes, I sent that reason out as comments to Kame's patches. kswapd or > balance_pgdat controls the zones, priority and in effect how many > pages we scan while doing reclaim. I did lots of experiments and found > that if soft limit reclaim occurred from kswapd, soft_limit_reclaim > would almost always fail and shrink_zone() would succeed, since it > looks at the whole zone and is always able to find some pages at all > priority levels. It also does not allow for targetted reclaim based on > how much we exceed the soft limit by. but, if "soft_limit_reclaim fail and shrink_zone() succeed" don't cause any performance degression, I don't find why kswapd is wrong. I guess you and kamezawa-san know it detail. but my understanding don't reach it. Could you please tell me what so slowness. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org