[Qemu-devel] Re: [PATCH v5 0/4] virtio: Use ioeventfd for virtqueue notify

[Stefan Hajnoczi]

On Thu, Jan 6, 2011 at 6:00 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Thu, Jan 06, 2011 at 04:41:50PM +0000, Stefan Hajnoczi wrote:
>> Here are 4k sequential read results (cache=none) to check whether we
>> see an ioeventfd performance regression with virtio-blk.
>>
>> The idea is to use a small blocksize with an I/O pattern (sequential
>> reads) that is cheap and executes quickly.  Therefore we're doing many
>> iops and the cost virtqueue kick/notify is especially important.
>> We're not trying to stress the disk, we're trying to make the
>> difference in ioeventfd=on/off apparent.
>>
>> I did 2 runs for both ioeventfd=off and ioeventfd=on.  The results are
>> similar: 1% and 2% degradation in MB/s or iops.  We'd have to do more
>> runs to see if the degradation is statistically significant, but the
>> percentage value is so low that I'm satisfied.
>>
>> Are you happy to merge virtio-ioeventfd v6 + your fixups?
>
> BTW if you could do some migration stress-testing too,
> would be nice. autotest has support for it now.

Okay, I'll let you know the results.

Stefan