Intel845 IGP and XGetImage

Austin Yuan yuanshengquan at
Thu Apr 21 01:18:21 PDT 2005

I found a thread which addressed the same issue I mentioned in xorg
lists. It is "X[Shm]GetImage is slow; what can I do about this? " . 
Now the problem seems on software memory copy from framebuffer to
system memory. I will try shadowfb and compare the result with the
normal case.
Austin Yuan

On 4/21/05, Austin Yuan <yuanshengquan at> wrote:
>   I am working on a project that transfers x window desktop from one
> machine to another machine on intel845 platform. The transfer includes
> 3 operations: get the desktop image, pass it on network, and show the
> image on another side. I use XGetImage/XPutImage to get and show the
> image. Now the problem is that XGetImage takes more time than
> XPutImage and becomes the bottleneck of the whole system(My simple
> demo shows one XGetImage call takes 116498us,but XPutImage only
> 7362us). I trace XGetImage implementation on the server side. It will
> fall into XAAGetImage, and because intel845 IGP driver doesn't
> implement ReadPixmap(I think it is bitblt from framebuffer to system
> memory), It will fall back to software bitblt.
>   My question is whether intel845 IGP supports bitblt from
> framebuffer to system memory. If not, why does XGetImage takes more
> time than XPutImage,and how to optimize it?
> Thanks!
> Austin Yuan.

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