Re: [Qemu-devel] [PATCH] Fix and simplify gui timer logic.

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/08/2010 08:18 AM, Gerd Hoffmann wrote:
> On 06/08/10 13:50, Paul Brook wrote:
>>>>> Kill nographic timer.  Have a global gui_timer instead.  Have the gui
>>>>> timer enabled unconditionally.  We need a timer running anyway for 
>>>>> mmio
>>>>> flush, so the whole have-gui-timer-only-when-needed logic is pretty
>>>>> pointless.  It also simplifies displaylisteners coming and going at
>>>>> runtime, we don't need to care about the timer then as it runs 
>>>>> anyway.
>>>>
>>>> Linking mmio flushes to the gui is completely bogus.  The fact that 
>>>> we're
>>>> doing arbitrary periodic mmio flushes suggests something else is 
>>>> horribly
>>>> broken.
>>>
>>> Was added by commit
>>>
>>> http://git.qemu.org/qemu.git/commit/?id=62a2744ca09a0b44b8406ea0c430c4c67a2 
>>>
>>> c3231
>>>
>>> Patch description makes sense to me.  Of course we could have a 
>>> separate
>>> timer for the mmio flushes instead of re-using the gui timer.  But we
>>> would have more wakeups then ...
>>
>> This suggests we are incorrectly coalescing writes, and we should 
>> actually be
>> notifying qemu when (at least) he first write occurs. If we aren't 
>> outputting
>> anything we don't want to be waking up periodically just to flush an 
>> empty
>> MMIO buffer.
>
> That is completely unrelated to this patch though.  The patch doesn't 
> change mmio flush behaviour at all.  And the periodic wakeup was there 
> even before the mmio flush patch was added.  Even without gui, 
> although I can't see a obvious reason for it ...

Agreed.  Regardless of the periodic mmio flush, having a separate 
nographic timer isn't terribly helpful IMHO.

Regards,

Anthony Liguori

> cheers,
>   Gerd
>
>
>