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Date: Mon, 8 Jun 2009 22:45:44 +0200 From: Ingo Molnar <mingo@...e.hu> To: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Linus Torvalds <torvalds@...ux-foundation.org>, Jens Axboe <jens.axboe@...cle.com> Cc: linux-kernel@...r.kernel.org, Thomas Pilarski <thomas.pi@...or.de>, Christoph Hellwig <hch@....de>, akpm@...ux-foundation.org Subject: Re: (forw) [bugzilla-daemon@...zilla.kernel.org: [Bug 12309] Large I/O operations result in slow performance and high iowait times] (Cc:-ed Linus and Jens too) * Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote: > Thomas have done a very thorough bissection job and have made some very > interesting findings. Just in case everyone is ignoring this now huge > bugzilla thread, I'm forwarding his email to LKML so people can have a > closer look at the offending commits. > > I'm glad you are so persistent on figuring out the source of these > long-lasting regressions Thomas, thanks a lot ! > > Mathieu > > ----- Forwarded message from bugzilla-daemon@...zilla.kernel.org ----- > > Date: Fri, 5 Jun 2009 21:55:16 GMT > To: mathieu.desnoyers@...ymtl.ca > From: bugzilla-daemon@...zilla.kernel.org > Subject: [Bug 12309] Large I/O operations result in slow performance and high > iowait times > > http://bugzilla.kernel.org/show_bug.cgi?id=12309 > > > > > > --- Comment #360 from Thomas Pilarski <thomas.pi@...or.de> 2009-06-05 21:55:05 --- > Created an attachment (id=21774) > --> (http://bugzilla.kernel.org/attachment.cgi?id=21774) > Test patch against heavy io bug > > I have made an bisection and got these two patches. Reverting these patches > improves the desktop responsiveness on my notebook enormous. I have tested it > on a 2.6.28 non smp kernel (my heavy io testing installation) during four > concurrent read and write operations, while working with two VMs. It's only a > Core2 @2.4GHz system. I can even start new application during heavy io. > > I have added the patch, which I have applied to my test installation. Use it > with care, as I am not a kernel developer and does not know the dependencies in > the cfq scheduler. > > I have reverted theses two patches: > > 07db59bd6b0f279c31044cba6787344f63be87ea is first bad commit > commit 07db59bd6b0f279c31044cba6787344f63be87ea > Author: Linus Torvalds <torvalds@...dy.linux-foundation.org> > Date: Fri Apr 27 09:10:47 2007 -0700 > > Change default dirty-writeback limits > > Do this really early in the 2.6.22-rc series, so that we'll get > feedback. And don't change by half measures. Just cut the default > dirty limit to a quarter of what it was, and see if anybody even > notices. > > Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org> > > :040000 040000 b63eb9faf5b9a42a1cdad901a5f18d6cceb7fdf6 > 2b8b4117ca34077cb0b817c77595aa6c9e34253a M mm > > a993800655ee516b6f6a6fc4c2ee13fedfb0590b is first bad commit > commit a993800655ee516b6f6a6fc4c2ee13fedfb0590b > Author: Jens Axboe <jens.axboe@...cle.com> > Date: Fri Apr 20 08:55:52 2007 +0200 > > cfq-iosched: fix sequential write regression > > We have a 10-15% performance regression for sequential writes on TCQ/NCQ > enabled drives in 2.6.21-rcX after the CFQ update went in. It has been > reported by Valerie Clement <valerie.clement@...l.net> and the Intel > testing folks. The regression is because of CFQ's now more aggressive > queue control, limiting the depth available to the device. > > This patches fixes that regression by allowing a greater depth when only > one queue is busy. It has been tested to not impact sync-vs-async > workloads too much - we still do a lot better than 2.6.20. > > Signed-off-by: Jens Axboe <jens.axboe@...cle.com> > Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org> > > :040000 040000 07c48a6930ce62d36540b6650e3ea0563bd7ec59 > 95fc11105fe3339c90c4e7bebb66a820f7084601 M block > > > Here the fsync result on my machine: > > ************************************************************************** > Without patch > Linux balrog 2.6.28 #2 Mon Mar 23 11:19:13 CET 2009 x86_64 GNU/Linux > > fsync time: 7.8282 > fsync time: 17.3598 > fsync time: 24.0352 > fsync time: 19.7307 > fsync time: 21.9559 > fsync time: 21.0571 > 5000+0 Datensätze ein > 5000+0 Datensätze aus > 5242880000 Bytes (5,2 GB) kopiert, 129,286 s, 40,6 MB/s > fsync time: 21.8491 > fsync time: 0.0430 > fsync time: 0.0448 > fsync time: 0.0451 > fsync time: 0.0451 > fsync time: 0.0451 > fsync time: 0.0452 > > > > ************************************************************************** > With patch > Linux balrog 2.6.28 #5 Fri Jun 5 22:23:54 CEST 2009 x86_64 GNU/Linux > > fsync time: 2.8409 > fsync time: 2.3345 > fsync time: 2.8423 > fsync time: 0.0851 > fsync time: 1.2497 > fsync time: 0.9981 > fsync time: 0.9494 > fsync time: 2.7094 > fsync time: 2.9753 > fsync time: 2.8886 > fsync time: 2.9894 > fsync time: 1.2673 > fsync time: 2.6728 > fsync time: 1.3408 > 5000+0 Datensätze ein > 5000+0 Datensätze aus > 5242880000 Bytes (5,2 GB) kopiert, 117,388 s, 44,7 MB/s > fsync time: 85.1461 > fsync time: 23.5310 > fsync time: 0.0317 > fsync time: 0.0337 > fsync time: 0.0338 > fsync time: 0.0338 > > -- > Configure bugmail: http://bugzilla.kernel.org/userprefs.cgi?tab=email > ------- You are receiving this mail because: ------- > You are on the CC list for the bug. > > ----- End forwarded message ----- > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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