Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754703AbZIIXoD (ORCPT ); Wed, 9 Sep 2009 19:44:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754574AbZIIXoA (ORCPT ); Wed, 9 Sep 2009 19:44:00 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:38252 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754597AbZIIXn6 (ORCPT ); Wed, 9 Sep 2009 19:43:58 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Christoph Lameter Subject: Re: [rfc] lru_add_drain_all() vs isolation Cc: kosaki.motohiro@jp.fujitsu.com, Peter Zijlstra , Mike Galbraith , Ingo Molnar , linux-mm , Oleg Nesterov , lkml 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 X-Mailer: Becky! ver. 2.50.07 [ja] Date: Thu, 10 Sep 2009 08:43:56 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1579 Lines: 42 > 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 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/