From: Mel Gorman <mel@csn.ul.ie>
To: Martin Knoblauch <spamtrap@knobisoft.de>
Cc: Fengguang Wu <wfg@mail.ustc.edu.cn>,
Mike Snitzer <snitzer@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
jplatte@naasa.net, Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
James.Bottomley@steeleye.com
Subject: Re: regression: 100% io-wait with 2.6.24-rcX
Date: Thu, 17 Jan 2008 22:12:21 +0000 [thread overview]
Message-ID: <20080117221220.GC25975@csn.ul.ie> (raw)
In-Reply-To: <169450.15299.qm@web32606.mail.mud.yahoo.com>
On (17/01/08 13:50), Martin Knoblauch didst pronounce:
> > <mail manglement snipped>
>
> The effect is defintely depending on the IO hardware. I performed the same tests
> on a different box with an AACRAID controller and there things look different.
I take it different also means it does not show this odd performance
behaviour and is similar whether the patch is applied or not?
> Basically
> the "offending" commit helps seingle stream performance on that box, while dual/triple
> stream are not affected. So I suspect that the CCISS is just not behaving well.
>
> And yes, the tests are usually done on a freshly booted box. Of course, I repeat them
> a few times. On the CCISS box the numbers are very constant. On the AACRAID box
> they vary quite a bit.
>
> I can certainly stress the box before doing the tests. Please define "many" for the kernel
> compiles :-)
>
With 8GiB of RAM, try making 24 copies of the kernel and compiling them
all simultaneously. Running that for for 20-30 minutes should be enough to
randomise the freelists affecting what color of page is used for the dd test.
> > > OK, the change happened between rc5 and rc6. Just following a
> > > gut feeling, I reverted
> > >
> > > #commit 81eabcbe0b991ddef5216f30ae91c4b226d54b6d
> > > #Author: Mel Gorman
> > > #Date: Mon Dec 17 16:20:05 2007 -0800
> > > #
>
> > >
> > > This has brought back the good results I observed and reported.
> > > I do not know what to make out of this. At least on the systems
> > > I care about (HP/DL380g4, dual CPUs, HT-enabled, 8 GB Memory,
> > > SmartaArray6i controller with 4x72GB SCSI disks as RAID5 (battery
> > > protected writeback cache enabled) and gigabit networking (tg3)) this
> > > optimisation is a dissaster.
> > >
> >
> > That patch was not an optimisation, it was a regression fix
> > against 2.6.23 and I don't believe reverting it is an option. Other IO
> > hardware benefits from having the allocator supply pages in PFN order.
>
> I think this late in the 2.6.24 game we just should leave things as they are. But
> we should try to find a way to make CCISS faster, as it apparently can be faster.
>
> > Your controller would seem to suffer when presented with the same situation
> > but I don't know why that is. I've added James to the cc in case he has seen this
> > sort of situation before.
> >
> > > On the other hand, it is not a regression against 2.6.22/23. Those
> >
> > had bad IO scaling to. It would just be a shame to loose an apparently
> >
> > great performance win.
> >
> > Could you try running your tests again when the system has been
> > stressed with some other workload first?
> >
>
> Will do.
>
Thanks
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
next prev parent reply other threads:[~2008-01-17 22:12 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-17 21:50 regression: 100% io-wait with 2.6.24-rcX Martin Knoblauch
2008-01-17 22:12 ` Mel Gorman [this message]
-- strict thread matches above, loose matches on Subject: below --
2008-01-23 11:12 Martin Knoblauch
2008-01-22 18:51 Martin Knoblauch
2008-01-22 15:25 Martin Knoblauch
2008-01-22 23:40 ` Alasdair G Kergon
2008-01-19 10:24 Martin Knoblauch
2008-01-18 8:19 Martin Knoblauch
2008-01-18 16:01 ` Mel Gorman
2008-01-18 17:46 ` Linus Torvalds
2008-01-18 19:01 ` Martin Knoblauch
2008-01-18 19:23 ` Linus Torvalds
2008-01-22 14:39 ` Alasdair G Kergon
2008-01-18 20:00 ` Mike Snitzer
2008-01-18 22:47 ` Mike Snitzer
2008-01-17 17:51 Martin Knoblauch
2008-01-17 17:44 Martin Knoblauch
2008-01-17 20:23 ` Mel Gorman
2008-01-17 13:52 Martin Knoblauch
2008-01-17 16:11 ` Mike Snitzer
2008-01-16 14:15 Martin Knoblauch
2008-01-16 16:27 ` Mike Snitzer
2008-01-16 9:26 Martin Knoblauch
[not found] ` <E1JF6w8-0000vs-HM@localhost.localdomain>
2008-01-16 12:00 ` Fengguang Wu
2008-01-07 10:51 Joerg Platte
2008-01-07 11:19 ` Ingo Molnar
2008-01-07 13:24 ` Joerg Platte
2008-01-07 13:32 ` Peter Zijlstra
2008-01-07 13:40 ` Joerg Platte
[not found] ` <E1JCRbA-0002bh-3c@localhost.localdomain>
2008-01-09 3:27 ` Fengguang Wu
2008-01-09 6:13 ` Joerg Platte
[not found] ` <E1JCZg2-0001DE-RP@localhost.localdomain>
2008-01-09 12:04 ` Fengguang Wu
2008-01-09 12:22 ` Joerg Platte
[not found] ` <E1JCaUd-0001Ko-Tt@localhost.localdomain>
2008-01-09 12:57 ` Fengguang Wu
2008-01-09 13:04 ` Joerg Platte
[not found] ` <E1JCrMj-0001HR-SZ@localhost.localdomain>
2008-01-10 6:58 ` Fengguang Wu
[not found] ` <E1JCrsE-0000v4-Dz@localhost.localdomain>
2008-01-10 7:30 ` Fengguang Wu
[not found] ` <20080110073046.GA3432@mail.ustc.edu.cn>
[not found] ` <E1JCsDr-0002cl-0e@localhost.localdomain>
2008-01-10 7:53 ` Fengguang Wu
2008-01-10 8:37 ` Joerg Platte
[not found] ` <E1JCt0n-00048n-AD@localhost.localdomain>
2008-01-10 8:43 ` Fengguang Wu
2008-01-10 10:03 ` Joerg Platte
[not found] ` <E1JDBk4-0000UF-03@localhost.localdomain>
2008-01-11 4:43 ` Fengguang Wu
2008-01-11 5:29 ` Joerg Platte
2008-01-11 6:41 ` Joerg Platte
2008-01-12 23:32 ` Joerg Platte
[not found] ` <E1JDwaA-00017Q-W6@localhost.localdomain>
2008-01-13 6:44 ` Fengguang Wu
2008-01-13 8:05 ` Joerg Platte
[not found] ` <E1JDy5a-0001al-Tk@localhost.localdomain>
2008-01-13 8:21 ` Fengguang Wu
2008-01-13 9:49 ` Joerg Platte
[not found] ` <E1JE1Uz-0002w5-6z@localhost.localdomain>
2008-01-13 11:59 ` Fengguang Wu
[not found] ` <20080113115933.GA11045@mail.ustc.edu.cn>
[not found] ` <E1JEGPH-0001uw-Df@localhost.localdomain>
2008-01-14 3:54 ` Fengguang Wu
[not found] ` <20080114035439.GA7330@mail.ustc.edu.cn>
[not found] ` <E1JEM2I-00010S-5U@localhost.localdomain>
2008-01-14 9:55 ` Fengguang Wu
2008-01-14 11:30 ` Joerg Platte
2008-01-14 11:41 ` Peter Zijlstra
[not found] ` <E1JEOmD-0001Ap-U7@localhost.localdomain>
2008-01-14 12:50 ` Fengguang Wu
2008-01-15 21:13 ` Mike Snitzer
[not found] ` <E1JF0m1-000101-OK@localhost.localdomain>
2008-01-16 5:25 ` Fengguang Wu
2008-01-15 21:42 ` Ingo Molnar
[not found] ` <E1JF0bJ-0000zU-FG@localhost.localdomain>
2008-01-16 5:14 ` Fengguang Wu
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