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 B02F86B004D for ; Wed, 9 Sep 2009 19:43:55 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n89Nhw7p031060 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Thu, 10 Sep 2009 08:43:58 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id DDF0A45DE4E for ; Thu, 10 Sep 2009 08:43:57 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id BBEDB45DE51 for ; Thu, 10 Sep 2009 08:43:57 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id A46F71DB8041 for ; Thu, 10 Sep 2009 08:43:57 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 3EB341DB803F for ; Thu, 10 Sep 2009 08:43:57 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [rfc] lru_add_drain_all() vs isolation In-Reply-To: References: <20090909131945.0CF5.A69D9226@jp.fujitsu.com> Message-Id: <20090910083340.9CB7.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Thu, 10 Sep 2009 08:43:56 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: kosaki.motohiro@jp.fujitsu.com, Peter Zijlstra , Mike Galbraith , Ingo Molnar , linux-mm , Oleg Nesterov , lkml List-ID: > On Wed, 9 Sep 2009, KOSAKI Motohiro wrote: > > > Christoph, I'd like to discuss a bit related (and almost unrelated) thing. > > I think page migration don't need lru_add_drain_all() as synchronous, because > > page migration have 10 times retry. > > True this is only an optimization that increases the chance of isolation > being successful. You dont need draining at all. > > > Then asynchronous lru_add_drain_all() cause > > > > - if system isn't under heavy pressure, retry succussfull. > > - if system is under heavy pressure or RT-thread work busy busy loop, retry failure. > > > > I don't think this is problematic bahavior. Also, mlock can use asynchrounous lru drain. > > > > What do you think? > > The retries can be very fast if the migrate pages list is small. The > migrate attempts may be finished before the IPI can be processed by the > other cpus. Ah, I see. Yes, my last proposal is not good. small migration might be fail. How about this? - pass 1-2, lru_add_drain_all_async() - pass 3-10, lru_add_drain_all() this scheme might save RT-thread case and never cause regression. (I think) The last remain problem is, if RT-thread binding cpu's pagevec has migrate targetted page, migration still face the same issue. but we can't solve it... RT-thread must use /proc/sys/vm/drop_caches properly. -- 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