Re: [Qemu-devel] Lock contention in QEMU

[Weiwei Jia]

I will try it later on. Thank you.

Best,
Weiwei Jia

On Thu, Dec 15, 2016 at 7:13 AM, Paolo Bonzini <address@hidden> wrote:
>
>
> On 15/12/2016 09:04, Stefan Hajnoczi wrote:
>>> Does this feature only work for VirtIO? Does it work for SCSI or IDE?
>> This only works for virtio-blk and virtio-scsi.  The virtio-scsi
>> dataplane support is more recent and I don't remember if it is complete.
>> I've CCed Fam and Paolo who worked on virtio-scsi dataplane.
>>
>> Now that you have mentioned that you aren't using virtio devices, there
>> is another source of lock contention that you will encounter.  I/O
>> request submission takes place in the vcpu thread when ioeventfd is not
>> used.  Only virtio uses ioeventfd so your current QEMU configuration is
>> unable to let the vcpu continue execution during I/O request submission.
>>
>> If you care about performance then using virtio devices is probably the
>> best choice.  Try comparing against virtio-scsi dataplane - you should
>> see a lot less jitter.
>
> Yes, virtio-scsi dataplane is complete.
>
> Paolo
>