Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756012AbXKFXbx (ORCPT ); Tue, 6 Nov 2007 18:31:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754865AbXKFXbn (ORCPT ); Tue, 6 Nov 2007 18:31:43 -0500 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:57743 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754767AbXKFXbm (ORCPT ); Tue, 6 Nov 2007 18:31:42 -0500 Date: Wed, 7 Nov 2007 10:31:14 +1100 From: David Chinner To: Torsten Kaiser Cc: Fengguang Wu , Peter Zijlstra , Maxim Levitsky , linux-kernel@vger.kernel.org, Andrew Morton , David Chinner , linux-fsdevel@vger.kernel.org Subject: Re: writeout stalls in current -git Message-ID: <20071106233114.GB995458@sgi.com> References: <393060478.03650@ustc.edu.cn> <64bb37e0710310822r5ca6b793p8fd97db2f72a8655@mail.gmail.com> <393903856.06449@ustc.edu.cn> <64bb37e0711011120i63cdfe3ci18995d57b6649a8@mail.gmail.com> <64bb37e0711011200n228e708eg255640388f83da22@mail.gmail.com> <1193998532.27652.343.camel@twins> <64bb37e0711021222q7d12c825mc62d433c4fe19e8@mail.gmail.com> <394340668.31055@ustc.edu.cn> <64bb37e0711061353g4a8b881cgd78fef3a11378b9c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64bb37e0711061353g4a8b881cgd78fef3a11378b9c@mail.gmail.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1814 Lines: 42 On Tue, Nov 06, 2007 at 10:53:25PM +0100, Torsten Kaiser wrote: > On 11/6/07, David Chinner wrote: > > Rather than vmstat, can you use something like iostat to show how busy your > > disks are? i.e. are we seeing RMW cycles in the raid5 or some such issue. > > Both "vmstat 10" and "iostat -x 10" output from this test: > procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- > r b swpd free buff cache si so bi bo in cs us sy id wa > 2 0 0 3700592 0 85424 0 0 31 83 108 244 2 1 95 1 > -> emerge reads something, don't knwo for sure what... > 1 0 0 3665352 0 87940 0 0 239 2 343 585 2 1 97 0 .... > > The last 20% of the btrace look more or less completely like this, no > other programs do any IO... > > 253,0 3 104626 526.293450729 974 C WS 79344288 + 8 [0] > 253,0 3 104627 526.293455078 974 C WS 79344296 + 8 [0] > 253,0 1 36469 444.513863133 1068 Q WS 154998480 + 8 [xfssyncd] > 253,0 1 36470 444.513863135 1068 Q WS 154998488 + 8 [xfssyncd] ^^ Apparently we are doing synchronous writes. That would explain why it is slow. We shouldn't be doing synchronous writes here. I'll see if I can reproduce this. Yes, I can reproduce the sync writes coming out of xfssyncd. I'll look into this further and send a patch when I have something concrete. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - 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/