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Message-ID: <49B7DC25.6010500@codemonkey.ws>
Date: Wed, 11 Mar 2009 10:43:33 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH] vnc: shared buffer: skip some optimizations.
References: <49B7CE21.4030104@redhat.com>
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To: qemu-devel@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>

Gerd Hoffmann wrote:
>   Hi,
>
> When using a shared display surface buffer some of the optimizations
> done by the vnc server code don't work.  In shared buffer mode the guest
> may update the screen while the vnc server looks at the framebuffer.
> That in turn makes some code racy, the dirty bitmap walk through for
> example, leading to screen corruption.  Right now this is visible with
> xenfb only.  I expect simliar issues will show up for vga too once we
> run the vcpus in threads.
>   

:-/  I'd rather disable the shared buffers.

The minimization optimization is extremely important for VNC 
performance.  It's a much bigger win than the memory copy that you lose 
when using shared buffers.

Regards,

Anthony Liguori

> please apply
>   Gerd
>