Re: [Qemu-devel] virtio-blk performance regression and qemu-kvm

[Stefan Hajnoczi]

On Wed, Feb 22, 2012 at 4:48 PM, Dongsu Park
<address@hidden> wrote:
>> Try turning ioeventfd off for the virtio-blk device:
>>
>> -device virtio-blk-pci,ioeventfd=off,...
>>
>> You might see better performance since ramdisk I/O should be very
>> low-latency.  The overhead of using ioeventfd might not make it
>> worthwhile.  The ioeventfd feature was added post-0.14 IIRC.  Normally
>> it helps avoid stealing vcpu time and also causing lock contention
>> inside the guest - but if host I/O latency is extremely low it might
>> be faster to issue I/O from the vcpu thread.
>
> Thanks for the tip. I tried that too, but no success.

My guesses have all been wrong.  Maybe it's time to git bisect this instead :).

Stefan