From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id E96536B00A3 for ; Sun, 24 Oct 2010 23:48:36 -0400 (EDT) Date: Mon, 25 Oct 2010 11:48:33 +0800 From: Wu Fengguang Subject: Re: [PATCH] do_migrate_range: avoid failure as much as possible Message-ID: <20101025034833.GB15933@localhost> References: <1287974851-4064-1-git-send-email-lliubbo@gmail.com> <20101025114017.86ee5e54.kamezawa.hiroyu@jp.fujitsu.com> <20101025025703.GA13858@localhost> <20101025120550.45745c3d.kamezawa.hiroyu@jp.fujitsu.com> <20101025120901.88fdbd17.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101025120901.88fdbd17.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Bob Liu , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "kosaki.motohiro@jp.fujitsu.com" List-ID: On Mon, Oct 25, 2010 at 11:09:01AM +0800, KAMEZAWA Hiroyuki wrote: > On Mon, 25 Oct 2010 12:05:50 +0900 > KAMEZAWA Hiroyuki wrote: > > > This changes behavior. > > > > This "ret" can be > 0 because migrate_page()'s return code is > > "Return: Number of pages not migrated or error code." > > > > Then, > > ret < 0 ===> maybe ebusy > > ret > 0 ===> some pages are not migrated. maybe PG_writeback or some > > ret == 0 ===> ok, all condition green. try next chunk soon. > > > > Then, I added "yield()" and --retrym_max for !ret cases. > ^^^^^^^^ > wrong. > > The code here does > > ret == 0 ==> ok, all condition green, try next chunk. It seems reasonable to remove the drain operations for "ret == 0" case. That would help large NUMA boxes noticeably I guess. > ret > 0 ==> all pages are isolated but some pages cannot be migrated. maybe under I/O > do yield. Don't know how to deal with the possible "migration fail" pages -- sorry I have no idea about that situation at all. Perhaps, OOM while offlining pages? > ret < 0 ==> some pages may not be able to be isolated. reduce retrycount and yield() Makes good sense. Thanks, Fengguang -- 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