[Qemu-devel] Re: [PATCH 10/10] Maintaing number of dirty pages

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/01/2010 10:52 AM, Avi Kivity wrote:
> On 12/01/2010 06:49 PM, Anthony Liguori wrote:
>>> We need actual measurements instead of speculations.
>>
>>
>> Yes, I agree 100%.  I think the place to start is what I suggested in 
>> a previous note in this thread, we need to measure actual stall time 
>> in the guest.
>
> I'd actually start at the host.  How much time does 
> ioctl(KVM_GET_DIRTY_LOG) take?  What's the percentage of time 
> qemu_mutex is held?

The question is, what really are the symptoms of the problem.  It's not 
necessarily a bad thing if KVM_GET_DIRTY_LOG takes a long while 
qemu_mutex is held.

Is the problem that the monitor responds slowly?  Is the problem that 
the guest isn't consistently getting execution time?  Is the proper 
simply that the guest isn't getting enough total execution time?

I think we need to identify exactly what the problem is before we look 
for sources.

Regards,

Anthony Liguori