Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751687AbZIIE1T (ORCPT ); Wed, 9 Sep 2009 00:27:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751445AbZIIE1S (ORCPT ); Wed, 9 Sep 2009 00:27:18 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:40690 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432AbZIIE1S (ORCPT ); Wed, 9 Sep 2009 00:27:18 -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: Message-Id: <20090909131945.0CF5.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: Wed, 9 Sep 2009 13:27:17 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1389 Lines: 35 > 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 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/