From: Dor Laor <dlaor@redhat.com>
To: Gordan Bobic <gordan@bobich.net>
Cc: kvm@vger.kernel.org
Subject: Re: virtio disk slower than IDE?
Date: Sun, 15 Nov 2009 15:15:57 +0200 [thread overview]
Message-ID: <4AFFFF0D.3090608@redhat.com> (raw)
In-Reply-To: <4AFFED49.9010305@bobich.net>
On 11/15/2009 02:00 PM, Gordan Bobic wrote:
> Dor Laor wrote:
>> On 11/14/2009 04:23 PM, Gordan Bobic wrote:
>>> I just tried paravirtualized virtio block devices, and my tests show
>>> that they are approximately 30% slower than emulated IDE devices. I'm
>>> guessing this isn't normal. Is this a known issue or am I likely to have
>>> mosconfigured something? I'm using 64-bit RHEL/CentOS 5 (both host and
>>> guest).
>>
>> Please try to change the io scheduler on the host to io scheduler, it
>> should boost your performance back.
>
> I presume you mean the deadline io scheduler. I tried that (kernel
> parameter elevator=deadline) and it made no measurable difference
> compared to the cfq scheduler.
What version of kvm do you use? Is it rhel5.4?
Can you post the qemu cmdline and the perf test in the guest?
Lastly, do you use cache=wb on qemu? it's just a fun mode, we use
cache=off only.
>
> Gordan
> --
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next prev parent reply other threads:[~2009-11-15 13:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-14 14:23 virtio disk slower than IDE? Gordan Bobic
2009-11-15 9:51 ` Dor Laor
2009-11-15 12:00 ` Gordan Bobic
2009-11-15 13:15 ` Dor Laor [this message]
2009-11-15 22:47 ` Gordan Bobic
2009-11-16 16:40 ` john cooper
2009-11-16 18:11 ` Charles Duffy
2009-11-16 21:09 ` Dor Laor
-- strict thread matches above, loose matches on Subject: below --
2009-11-16 16:53 john cooper
2009-11-17 1:14 ` Gordan Bobic
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