Re: [Xen-devel] vram_dirty vs. shadow paging dirty tracking

[Anthony Liguori <aliguori@xxxxxxxxxx>]

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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> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> >     
>   

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