Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752774AbZG3WnK (ORCPT ); Thu, 30 Jul 2009 18:43:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751745AbZG3WnJ (ORCPT ); Thu, 30 Jul 2009 18:43:09 -0400 Received: from brick.kernel.dk ([93.163.65.50]:51468 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbZG3WnI (ORCPT ); Thu, 30 Jul 2009 18:43:08 -0400 Date: Fri, 31 Jul 2009 00:43:08 +0200 From: Jens Axboe To: Martin Bligh Cc: Chad Talbott , linux-kernel@vger.kernel.org, linux-mm@kvack.org, wfg@mail.ustc.edu.cn, Michael Rubin , Andrew Morton , sandeen@redhat.com Subject: Re: Bug in kernel 2.6.31, Slow wb_kupdate writeout Message-ID: <20090730224308.GJ12579@kernel.dk> References: <1786ab030907281211x6e432ba6ha6afe9de73f24e0c@mail.gmail.com> <20090730213956.GH12579@kernel.dk> <33307c790907301501v4c605ea8oe57762b21d414445@mail.gmail.com> <20090730221727.GI12579@kernel.dk> <33307c790907301534v64c08f59o66fbdfbd3174ff5f@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <33307c790907301534v64c08f59o66fbdfbd3174ff5f@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 35 On Thu, Jul 30 2009, Martin Bligh wrote: > > The test case above on a 4G machine is only generating 1G of dirty data. > > I ran the same test case on the 16G, resulting in only background > > writeout. The relevant bit here being that the background writeout > > finished quickly, writing at disk speed. > > > > I re-ran the same test, but using 300 100MB files instead. While the > > dd's are running, we are going at ~80MB/sec (this is disk speed, it's an > > x25-m). When the dd's are done, it continues doing 80MB/sec for 10 > > seconds or so. Then the remainder (about 2G) is written in bursts at > > disk speeds, but with some time in between. > > OK, I think the test case is sensitive to how many files you have - if > we punt them to the back of the list, and yet we still have 299 other > ones, it may well be able to keep the disk spinning despite the bug > I outlined.Try using 30 1GB files? If this disk starts spinning, then we have bigger bugs :-) > > Though it doesn't seem to happen with just one dd streamer, and > I don't see why the bug doesn't trigger in that case either. > > I believe the bugfix is correct independent of any bdi changes? Yeah I think so too, I'll run some more tests on this tomorrow and verify it there as well. -- Jens Axboe -- 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/