On Thu, Jun 29, 2017 at 12:47 PM, Paolo Bonzini <pbonz...@redhat.com> wrote:
>> On Thu, Jun 29, 2017 at 5:34 AM, Paolo Bonzini <pbonz...@redhat.com> wrote:
>> > On 28/06/2017 01:57, Alistair Francis wrote:
>> > I'm not sure I agree with this change, which is effectively delaying the
>> > processing of events. The question to me is which handles are
>> > triggering so fast that QEMU effectively busy waits.
>>
>> Yeah, that is what I was trying to figure out, but didn't make much headway.
>>
>> I kept seeing zero timeouts, which means that the thread never blocks
>> and this patch helps a lot.
>
> Perhaps you can use tracepoints? There shouldn't be many handles registered,
> since on Windows even the GUI actions all go through messages.
>
>> > Maybe your QEMUs can get some breath with commit 12f8def0e0 ("win32:
>> > replace custom mutex and condition variable with native primitives",
>> > 2017-03-27), since the native primitives are more efficient and TCG 2.8
>> > used condvars a lot for qemu_io_proceeded_cond.
>>
>> Ok, I will try that.
No luck, I tried applying that and it didn't make any difference.
>>
>> Does this mean you don't see the same slowness on QEMU 2.9?
>
> I have not tried, but the patch is only working around the real issue,
> as Fam pointed out.
Agreed. I'll keep digging and see what I can find.
Thanks,
Alistair
>
> Paolo
>
