Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754749AbZGONlS (ORCPT ); Wed, 15 Jul 2009 09:41:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754711AbZGONlR (ORCPT ); Wed, 15 Jul 2009 09:41:17 -0400 Received: from mx2.redhat.com ([66.187.237.31]:36841 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754482AbZGONlQ (ORCPT ); Wed, 15 Jul 2009 09:41:16 -0400 From: Jeff Moyer To: Jan Kara Cc: Chris Mason , Mike Galbraith , Diego Calleja , Andrew Morton , LKML , jens.axboe@oracle.com, linux-ext4@vger.kernel.org Subject: Re: Performance regressions in 2.6.30-rc7? References: <20090529210718.bef7a9c1.akpm@linux-foundation.org> <200905301851.47708.diegocg@gmail.com> <20090603195806.GA9571@atrey.karlin.mff.cuni.cz> <1244100382.7131.12.camel@marge.simson.net> <20090604112109.GC2859@duck.suse.cz> <1244142795.5731.31.camel@marge.simson.net> <20090609103208.GB9235@duck.suse.cz> <20090609184818.GD9556@think> <20090610091211.GA13692@duck.suse.cz> <20090715104319.GC25458@duck.suse.cz> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 15 Jul 2009 09:41:02 -0400 In-Reply-To: <20090715104319.GC25458@duck.suse.cz> (Jan Kara's message of "Wed, 15 Jul 2009 12:43:19 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5748 Lines: 115 Jan Kara writes: > On Wed 10-06-09 18:12:50, Jeff Moyer wrote: >> Jan Kara writes: >> >> > On Tue 09-06-09 14:48:18, Chris Mason wrote: >> >> On Tue, Jun 09, 2009 at 12:32:08PM +0200, Jan Kara wrote: >> >> > On Thu 04-06-09 21:13:15, Mike Galbraith wrote: >> >> > > On Thu, 2009-06-04 at 13:21 +0200, Jan Kara wrote: >> >> > > >> >> > > > > Sequential Writes >> >> > > > > 2.6.30-smp-ordered 6000 65536 32 50.16 508.9% 31.996 45595.78 0.64965 0.02402 10 >> >> > > > > 2.6.29.4-smp-ordered 6000 65536 32 52.70 543.2% 33.658 23794.92 0.71754 0.00836 10 >> >> > > > > >> >> > > > > 2.6.30-smp-writeback 6000 65536 32 47.82 525.4% 35.003 32588.84 0.56192 0.02298 9 >> >> > > > > 2.6.29.4-smp-writeback 6000 65536 32 52.52 467.6% 32.397 12972.78 0.53580 0.00522 11 >> >> > > > > >> >> > > > > 2.6.30-smp-ordered 6000 65536 16 56.08 254.9% 15.463 33000.68 0.39687 0.00521 22 >> >> > > > > 2.6.29.4-smp-ordered 6000 65536 16 62.40 308.4% 14.701 13455.02 0.13125 0.00208 20 >> >> > > > > >> >> > > > > 2.6.30-smp-writeback 6000 65536 16 51.90 281.4% 17.098 12869.85 0.36771 0.00104 18 >> >> > > > > 2.6.29.4-smp-writeback 6000 65536 16 60.53 272.6% 14.977 8637.08 0.21146 0.00000 22 >> >> > > > > >> >> > > > > 2.6.30-smp-ordered 6000 65536 8 51.09 113.4% 8.700 14856.55 0.06771 0.00417 45 >> >> > > > > 2.6.29.4-smp-ordered 6000 65536 8 56.13 130.6% 8.098 8400.45 0.03958 0.00000 43 >> >> > > > > >> >> > > > > 2.6.30-smp-writeback 6000 65536 8 50.19 131.7% 8.680 16821.04 0.11979 0.00208 38 >> >> > > > > 2.6.29.4-smp-writeback 6000 65536 8 54.90 130.7% 8.244 4925.48 0.10000 0.00000 42 >> >> > > > It really seems write has some problems... There's consistently lower >> >> > > > throughput and it also seems some writes take really long. I'll try to >> >> > > > reproduce it here. >> >> > > >> >> > > Looked "pretty solid" to me. I haven't observed enough to ~trust. >> >> > OK, I did a few runs of tiobench here and I can confirm that I see about >> >> > 6% performance regression in Sequential Write throughput between 2.6.29 >> >> > and 2.6.30-rc8. I'll try to find what's causing it. >> >> >> >> My first guess would be the WRITE_SYNC style changes. Is the regression >> >> still there with noop? >> > Thanks for the hint. I was guessing that as well. And experiments show >> > it's definitely connected. To be more precise with the data: >> > The test machine is 2 CPU, 2 GB ram, simple lowend SATA disk. Tiobench run >> > with: >> > tiobench/tiobench.pl -b 65536 -t 16 -t 8 -d /local/scratch -s 4096 >> > which means 4GB testfile, writes happen in 64k chunks, test done with 16 >> > and 8 threads. /local/scratch is a separate partition always cleaned and >> > umounted + mounted before each test. The results are (always 3 runs): >> > 2.6.29+CFQ: Avg StdDev >> > 8 38.01 40.26 39.69 -> 39.32 0.955092 >> > 16 40.09 38.18 40.05 -> 39.44 0.891104 >> > >> > 2.6.30-rc8+CFQ: >> > 8 36.67 36.81 38.20 -> 37.23 0.69062 >> > 16 37.45 36.47 37.46 -> 37.13 0.464351 >> > >> > 2.6.29+NOOP: >> > 8 38.67 38.66 37.55 -> 38.29 0.525632 >> > 16 39.59 39.15 39.19 -> 39.31 0.198662 >> > >> > 2.6.30-rc8+NOOP: >> > 8 38.31 38.47 38.16 -> 38.31 0.126579 >> > 16 39.08 39.25 39.13 -> 39.15 0.0713364 >> >> I ran the same test on a bigger system: 8GB ram (so I used a 16GB size >> for the test) and a 4 disk stripe hanging off of a CCISS controller. >> All the runs used ext3 in data=ordered mode and CFQ as the I/O scheduler. >> >> 2.6.29.3-140.fc11 Avg StdDev >> 8 158.72 152.72 148.24 153.227 5.25834 >> 16 176.06 174.91 176.27 175.747 0.73214 >> >> 2.6.30-rc7 >> 8 147.89 144.57 144.99 145.817 1.8078 >> 16 121.37 119.56 111.85 117.593 5.05553 >> >> Jan, let me know if you want any help tracking this down. > OK, so I've found time to follow-up on this. I've checked that > congestion_wait fixes Jens sent recently didn't change anything. Also I've > verified that backing out WRITE_SYNC related changes didn't help. Finally, > I've verified that when I back out all the changes that went to CFQ between > 2.6.29 and 2.6.30 and the WRITE_SYNC changes, then the performance is back > to original values. > Jens / Jeff, what to do next? I can try to bisect through CFQ changes but > that's going to be rather tedious and the result is uncertain since I > expect performance to jump up and down as various changes took place. So > I'd rather spend my time with something that has a higher chance to > succeed... > Looking through the changelogs, I most suspect this: commit 2f5cb7381b737e24c8046fd4aeab571fb71315f5 Author: Jens Axboe Date: Tue Apr 7 08:51:19 2009 +0200 cfq-iosched: change dispatch logic to deal with single requests at the time We had one other regression that bisected to this change, though I don't claim to fully understand why just yet. Take a look at this bug: http://bugzilla.kernel.org/show_bug.cgi?id=13401 Try Jens' test patch posted there: http://bugzilla.kernel.org/attachment.cgi?id=21650 and let us know how that fares. Thanks for looking into this! -Jeff -- 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/