Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752787AbZIGKLa (ORCPT ); Mon, 7 Sep 2009 06:11:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752727AbZIGKLa (ORCPT ); Mon, 7 Sep 2009 06:11:30 -0400 Received: from lon1-post-1.mail.demon.net ([195.173.77.148]:47197 "EHLO lon1-post-1.mail.demon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752616AbZIGKL3 (ORCPT ); Mon, 7 Sep 2009 06:11:29 -0400 Subject: Re: [RFC PATCH] v2 mm: balance_dirty_pages. reduce calls to global_page_state to reduce cache references From: Richard Kennedy To: Jens Axboe Cc: Andrew Morton , Wu Fengguang , "chris.mason" , linux-mm , lkml , Peter Zijlstra , linux-fsdevel In-Reply-To: <20090906184214.GL18599@kernel.dk> References: <1252062330.2271.61.camel@castor> <20090906184214.GL18599@kernel.dk> Content-Type: text/plain Date: Mon, 07 Sep 2009 11:11:30 +0100 Message-Id: <1252318290.2348.20.camel@castor> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1451 Lines: 39 On Sun, 2009-09-06 at 20:42 +0200, Jens Axboe wrote: > On Fri, Sep 04 2009, Richard Kennedy wrote: > > Reducing the number of times balance_dirty_pages calls global_page_state > > reduces the cache references and so improves write performance on a > > variety of workloads. > > > > 'perf stats' of simple fio write tests shows the reduction in cache > > access. > > Where the test is fio 'write,mmap,600Mb,pre_read' on AMD AthlonX2 with > > 3Gb memory (dirty_threshold approx 600 Mb) > > running each test 10 times, dropping the fasted & slowest values then > > taking > > the average & standard deviation > > > > average (s.d.) in millions (10^6) > > 2.6.31-rc8 648.6 (14.6) > > +patch 620.1 (16.5) > > This patch looks good to me, I have workloads too here where up to 10% > of the time is spent in balance_dirty_pages() because of this. I'll give > this patch a go on the box and test in question tomorrow, but it looks > promising. > Thanks Jens, It will be interesting to see how it works on different hardware & workload. How many cores are you going to run it on? wow 10% in balance_dirty_pages! Is that on a large server? or do you think its peculiar to your workload? regards Richard -- 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/