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 BA7B06B007E for ; Wed, 9 Sep 2009 00:27:14 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n894RL38010858 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 9 Sep 2009 13:27:21 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 6D18745DE51 for ; Wed, 9 Sep 2009 13:27:21 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 3420345DE52 for ; Wed, 9 Sep 2009 13:27:21 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id E9F31E08005 for ; Wed, 9 Sep 2009 13:27:19 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 9FE28E08010 for ; Wed, 9 Sep 2009 13:27:18 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [rfc] lru_add_drain_all() vs isolation In-Reply-To: References: Message-Id: <20090909131945.0CF5.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 9 Sep 2009 13:27:17 +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: > The usefulness of a scheme like this requires: > > 1. There are cpus that continually execute user space code > without system interaction. > > 2. There are repeated VM activities that require page isolation / > migration. > > The first page isolation activity will then clear the lru caches of the > processes doing number crunching in user space (and therefore the first > isolation will still interrupt). The second and following isolation will > then no longer interrupt the processes. > > 2. is rare. So the question is if the additional code in the LRU handling > can be justified. If lru handling is not time sensitive then yes. 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. 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? -- 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