Re: [ANNOUNCE] kvm-14 release

Laurent Vivier
2007-02-21T14:55:10Z

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Avi Kivity wrote:
> Aurelien Jarno wrote:
>>
>>> What is your disk image file format, or are you using a partition?
>>>
>> I am using a raw image file on an ext3 partition.
>>
>>
>>> Do the results change (on kvm-14) if you pin the guest to a core with
>>> 'taskset 1 qemu ...'
>>>
>> Bingo. It now works even faster than kvm-13!
>>
>> real 0m22.307s
>> user 0m13.935s
>> sys 0m4.720
>>
>>
>
> I'm guessing this is due to the glibc aio implementation, which uses
> threads instead of true aio. The threads may cause the vcpu to migrate
> frequently from one code to another.
>
> There are two possible solutions:
>
> - use native aio from http://www.bullopensource.org/posix/. I think
> the aio signal patches are not yet in, so this may not work.
> - teach the scheduler about the cost of migrating vcpus
> The first approach will solve itself eventually, though slowly if the
> current slow rate of aio merging continues. We'll have to do the second.
>

if you prefer the first one, Sébastien will release very soon aio patches for
2.6.20 with an up-to-date libposix-aio.

[advertising] Keep an eye on the bullopensource website. [/advertising]
:-P

Regards,
Laurent
--
------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org --------------
"Any sufficiently advanced technology is
indistinguishable from magic." - Arthur C. Clarke

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