From: NeilBrown <neilb@suse.de>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: linux-mm@kvack.org, linux-raid@vger.kernel.org
Subject: Re: mdraid write performance in different kernels up to 3.0, 3.0 shows huge improvement
Date: Thu, 10 Nov 2011 08:58:03 +1100 [thread overview]
Message-ID: <20111110085803.3f60c2d6@notabene.brown> (raw)
In-Reply-To: <alpine.DEB.2.00.1111081019010.19721@uplift.swm.pp.se>
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On Tue, 8 Nov 2011 10:28:57 +0100 (CET) Mikael Abrahamsson <swmike@swm.pp.se>
wrote:
>
> Hello.
>
> I have been running mdraid->cryptsetup/LUKS->lvm->xfs on Ubuntu AMD64 with
> RAID5 and now RAID6 for quite some time, dating back to 2.6.27. Around
> 2.6.32 I saw quite a bit of regression in write performance (probably the
> implementation of barriers), 2.6.35 was acceptable, 2.6.38 was really
> really bad, and 3.0 is like a rocket. Best of them all.
>
> I'm talking about 10-20x in different in write performance on my workload,
> in combination with the older kernels throwing me page allocation failures
> when the write load gets high, and also quite often the machine would just
> freeze up and had to be rebooted.
>
> With 2.6.38 I was down to 6-10 megabyte/s write speed, whereas 3.0 seem to
> give me 100+ megabyte/s with the exact same workload, I've seen up to 150
> megabyte/s writes at good times. This is on a box with AES-NI, so the
> crypto is not the limiting factor.
That is an amazing improvement. I wish I know what caused it I really have
no idea. You have quite a deep stack there and the change could be anywhere.
Still, it is good to hear such positive reports - thanks!
NeilBrown
>
> I have from time to time sent out an email regarding my page allocation
> failures, but never really got any takers on trying to fault find it, my
> tickets with ubuntu also never got any real attention. I haven't really
> pushed it super hard with 3.0, but I've thrown loads at it that would make
> 2.6.38 lock up.
>
> Just wanted to send in this success report that this finally seem to have
> seen some really nice improvements!
>
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prev parent reply other threads:[~2011-11-09 21:58 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-08 9:28 mdraid write performance in different kernels up to 3.0, 3.0 shows huge improvement Mikael Abrahamsson
2011-11-09 21:58 ` NeilBrown [this message]
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