Re: [Qemu-devel] [PATCH 00/16] aio_context_acquire/release pushdown, part 2

[Paolo Bonzini]

On 19/01/2017 18:01, Stefan Hajnoczi wrote:
>>> This is a big and somewhat risky change.  Have you run any performance
>>> benchmarks?
>>
>> Not recently; I ran them a year ago and there was no measurable difference.
> 
> Good, please re-run for the final version.

Done, went better than expected. :)

base
4k-1 null   READ: io=6646.8MB, aggrb=226852KB/s, minb=226852KB/s, 
maxb=226852KB/s, mint=30000msec, maxt=30000msec
4k-1 nvme   READ: io=3086.4MB, aggrb=105342KB/s, minb=105342KB/s, 
maxb=105342KB/s, mint=30001msec, maxt=30001msec
4k-32 nvme  READ: io=14246MB, aggrb=486241KB/s, minb=486241KB/s, 
maxb=486241KB/s, mint=30001msec, maxt=30001msec

patched:
4k-1 null   READ: io=7044.5MB, aggrb=240436KB/s, minb=240436KB/s, 
maxb=240436KB/s, mint=30000msec, maxt=30000msec
4k-1 nvme   READ: io=3463.3MB, aggrb=118208KB/s, minb=118208KB/s, 
maxb=118208KB/s, mint=30001msec, maxt=30001msec
4k-32 nvme  READ: io=15217MB, aggrb=519378KB/s, minb=519378KB/s, 
maxb=519378KB/s, mint=30001msec, maxt=30001msec

null is null-co://, nvme is a fast (180kIOPS on bare-metal) NVMe SSD.

So it seems to be some 5-10% faster.  No idea why so I would not give too
much importance on the numbers, but at least it's not worse.

Paolo