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 85B016B004D for ; Sat, 1 Aug 2009 01:03:27 -0400 (EDT) Date: Sat, 1 Aug 2009 13:03:54 +0800 From: Wu Fengguang Subject: Re: Bug in kernel 2.6.31, Slow wb_kupdate writeout Message-ID: <20090801050354.GA16648@localhost> References: <1786ab030907281211x6e432ba6ha6afe9de73f24e0c@mail.gmail.com> <20090730213956.GH12579@kernel.dk> <33307c790907301501v4c605ea8oe57762b21d414445@mail.gmail.com> <20090730221727.GI12579@kernel.dk> <33307c790907301534v64c08f59o66fbdfbd3174ff5f@mail.gmail.com> <20090730224308.GJ12579@kernel.dk> <33307c790907301548t2ef1bb72k4adbe81865d2bde9@mail.gmail.com> <20090801040313.GB13291@localhost> <20090801045345.GA16011@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090801045345.GA16011@localhost> Sender: owner-linux-mm@kvack.org To: Martin Bligh Cc: Jens Axboe , Chad Talbott , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michael Rubin , sandeen@redhat.com, Andrew Morton , Peter Zijlstra List-ID: On Sat, Aug 01, 2009 at 12:53:46PM +0800, Wu Fengguang wrote: > On Sat, Aug 01, 2009 at 12:03:13PM +0800, Wu Fengguang wrote: > I can see the growth when I increased the dd size to 2GB, > and the dd throughput decreased from 82.5MB/s to 60.9MB/s. The raw disk write throughput seems to be 60MB/s: wfg ~% dd if=/dev/zero of=/opt/vm/200M bs=1M count=200 oflag=direct 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 3.48137 s, 60.2 MB/s read throughput is a bit better: wfg ~% dd of=/dev/null if=/opt/vm/200M bs=1M count=200 iflag=direct 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 2.66606 s, 78.7 MB/s # hdparm -tT /dev/hda /dev/hda: Timing cached reads: 10370 MB in 1.99 seconds = 5213.70 MB/sec Timing buffered disk reads: 216 MB in 3.03 seconds = 71.22 MB/sec And sync writes are pretty slow: wfg ~% dd if=/dev/zero of=/opt/vm/200M bs=1M count=200 oflag=sync 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 10.4741 s, 20.0 MB/s Thanks, Fengguang -- 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