From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id D91086B0055 for ; Tue, 9 Jun 2009 05:14:33 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n599jYhi003076 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Tue, 9 Jun 2009 18:45:36 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 0220245DE7A for ; Tue, 9 Jun 2009 18:45:32 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id CC32045DE70 for ; Tue, 9 Jun 2009 18:45:31 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 983F41DB803B for ; Tue, 9 Jun 2009 18:45:31 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 4ECD81DB8042 for ; Tue, 9 Jun 2009 18:45:30 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA In-Reply-To: <20090609094231.GM18380@csn.ul.ie> References: <20090609173011.DD7F.A69D9226@jp.fujitsu.com> <20090609094231.GM18380@csn.ul.ie> Message-Id: <20090609184422.DD8B.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 9 Jun 2009 18:45:29 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Rik van Riel , Christoph Lameter , yanmin.zhang@intel.com, Wu Fengguang , linuxram@us.ibm.com, linux-mm , LKML List-ID: > > > Here it is just recording the jiffies value. The real smarts with the counter > > > use time_before() which I assumed could handle jiffie wrap-arounds. Even > > > if it doesn't, the consequence is that one scan will occur that could have > > > been avoided around the time of the jiffie wraparound. The value will then > > > be reset and it will be fine. > > > > time_before() assume two argument are enough nearly time. > > if we use 32bit cpu and HZ=1000, about jiffies wraparound about one month. > > > > Then, > > > > 1. zone reclaim failure occur > > 2. system works fine for one month > > 3. jiffies wrap and time_before() makes mis-calculation. > > > > And the scan occurs uselessly and zone_reclaim_failure gets set again. > I believe the one useless scan is not significant enough to warrent dealing > with jiffie wraparound. Thank you for kindful explanation. I fully agreed. -- 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