From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 3DBE06B009A for ; Mon, 7 Sep 2009 06:11:29 -0400 (EDT) Subject: Re: [RFC PATCH] v2 mm: balance_dirty_pages. reduce calls to global_page_state to reduce cache references From: Richard Kennedy 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 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Jens Axboe Cc: Andrew Morton , Wu Fengguang , "chris.mason" , linux-mm , lkml , Peter Zijlstra , linux-fsdevel List-ID: 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, 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