linux-kernel - Re: Slow file transfer speeds with CFQ IO scheduler in some cases

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Message-ID: <20081110104423.GA26778@kernel.dk>
Date:	Mon, 10 Nov 2008 11:44:24 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	"Vitaly V. Bursov" <vitalyb@...enet.dn.ua>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Slow file transfer speeds with CFQ IO scheduler in some cases

On Sun, Nov 09 2008, Vitaly V. Bursov wrote:
> Hello,
> 
> I'm building small server system with openvz kernel and have ran into
> some IO performance problems. Reading a single file via NFS delivers
> around 9 MB/s over gigabit network, but while reading, say, 2 different
> or same file 2 times at the same time I get >60MB/s.
> 
> Changing IO scheduler to deadline or anticipatory fixes problem.
> 
> Tested kernels:
>   OpenVZ RHEL5 028stab059.3 (9 MB/s with HZ=100, 20MB/s with HZ=1000
>                  fast local reads)
>   Vanilla 2.6.27.5 (40 MB/s with HZ=100, slow local reads)
> 
> Vanilla performs better in worst case but I believe 40 is still low
> concerning test results below.

Can you check with this patch applied?

http://bugzilla.kernel.org/attachment.cgi?id=18473&action=view

-- 
Jens Axboe

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