Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751013AbZIHOUL (ORCPT ); Tue, 8 Sep 2009 10:20:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750881AbZIHOUK (ORCPT ); Tue, 8 Sep 2009 10:20:10 -0400 Received: from viefep17-int.chello.at ([62.179.121.37]:15188 "EHLO viefep17-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbZIHOUJ (ORCPT ); Tue, 8 Sep 2009 10:20:09 -0400 X-SourceIP: 213.93.53.227 Subject: Re: [rfc] lru_add_drain_all() vs isolation From: Peter Zijlstra To: Christoph Lameter Cc: KOSAKI Motohiro , Mike Galbraith , Ingo Molnar , linux-mm , Oleg Nesterov , lkml In-Reply-To: References: <20090908190148.0CC9.A69D9226@jp.fujitsu.com> <1252405209.7746.38.camel@twins> <20090908193712.0CCF.A69D9226@jp.fujitsu.com> <1252411520.7746.68.camel@twins> Content-Type: text/plain Date: Tue, 08 Sep 2009 16:20:02 +0200 Message-Id: <1252419602.7746.73.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 30 On Tue, 2009-09-08 at 10:03 -0400, Christoph Lameter wrote: > On Tue, 8 Sep 2009, Peter Zijlstra wrote: > > > This is about avoiding work when there is non, clearly when an > > application does use the kernel it creates work. > > Hmmm. The lru draining in page migration is to reduce the number of pages > that are not on the lru to increase the chance of page migration to be > successful. A page on a per cpu list cannot be drained. > > Reducing the number of cpus where we perform the drain results in > increased likelyhood that we cannot migrate a page because its on the per > cpu lists of a cpu not covered. Did you even read the patch? There is _no_ functional difference between before and after, except less wakeups on cpus that don't have any __lru_cache_add activity. If there's pages on the per cpu lru_add_pvecs list it will be present in the mask and will be send a drain request. If its not, then it won't be send. -- 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/