From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 0A0A96B007E for ; Tue, 8 Sep 2009 10:20:05 -0400 (EDT) Subject: Re: [rfc] lru_add_drain_all() vs isolation From: Peter Zijlstra 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 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: KOSAKI Motohiro , Mike Galbraith , Ingo Molnar , linux-mm , Oleg Nesterov , lkml List-ID: 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, 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