Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy load.

[Anthony Liguori <anthony@codemonkey.ws>]

Gleb Natapov wrote:
> On Mon, Nov 10, 2008 at 09:46:12AM -0600, Anthony Liguori wrote:
>   
>> Gleb Natapov wrote:
>>     
>>> On Mon, Nov 10, 2008 at 09:24:55AM -0600, Anthony Liguori wrote:
>>>   
>>>       
>>>> Gleb Natapov wrote:
>>>>     
>>>>         
>>>>> On Sun, Nov 09, 2008 at 10:36:59AM -0600, Anthony Liguori wrote:
>>>>>   
>>>>>
>>>>>       
>>>>>           
>>>>>> Otherwise, I'm curious if you have any insight into where we're  
>>>>>> pausing  for 10ms that's causing the missed interrupt?
>>>>>>
>>>>>>             
>>>>>>             
>>>>> Don't know yet.
>>>>>         
>>>>>           
>>>> What's your full command line?
>>>>
>>>>     
>>>>         
>>> /home/gleb/install/qemu/org/bin/qemu-system-x86_64 -hda Windows2003.raw -m 1024 -net
>>> nic,model=rtl8139 -net user -vnc 172.17.10.111:1 -usbdevice tablet
>>>   
>>>       
>> -usbdevice tablet may be the culprit.  Is the guest doing an significant IO?
>>
>>     
> -usbdevice tablet has nothing to do with it. Qemu misses interrupt even
> without this option and with SDL screen it misses them in bunches when
> SDL redraws a screen. In case of vnc qemu misses interrupt because of
> fsync() call in raw_flush(), or so my instrumentation shows.
>   

eek, fsync is actually wrong here because there may be pending requests 
in flight that fsync won't take into account.  We should be doing an 
aio_fsync().  You're using IDE right?

Regards,

Anthony Liguori

> --
> 			Gleb.
>