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

[Michael S. Tsirkin]

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.

-- 
MST