Re: vram_dirty vs. shadow paging dirty tracking

[Anthony Liguori <aliguori@us.ibm.com>]

Zhai, Edwin wrote:
> On Tue, Mar 13, 2007 at 02:32:56PM -0500, Anthony Liguori wrote:
>   
>> When thinking about multithreading the device model, it occurred to me 
>> that it's a little odd that we're doing a memcmp to determine which 
>> portions of the VRAM has changed.  Couldn't we just use dirty page 
>>     
>
> we made this code to improve the user vnc responsiveness long before.
> now QEMU has new vnc implementation to resolve this issue and this code 
> introduce perf drop for guest of linux with X or windows.
>   

Compared to what, just updating the full screen 30 times a second?  I 
suspect that's not as bad as it sounds since SDL will be using a XShmImage.

The VNC minimization is done based on a timer however so sticking the 
timer stuff into a thread is still useful.  Of course, we should be able 
to quickly determine how useful this is by just changing SDL to update 
the whole image...

Regards,

Anthony Liguori

> so i'd like to send a patch to revert it and make a proper solution in future.
>
> thanks,
>
>   
>> tracking in the shadow paging code?  That should significantly lower the 
>> overhead of this plus I believe the infrastructure is already mostly 
>> there in the shadow2 code.
>>
>> Is this a sane idea?
>>
>> Regards,
>>
>> Anthony Liguori
>>
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>>     
>
>