[cairo] XShm, again

Vladimir Vukicevic vladimir at pobox.com
Sat Aug 16 17:21:53 PDT 2008

On Aug 15, 2008, at 11:51 PM, Chris Wilson wrote:

> Hi all,
> I've been playing around with the basic xshm patch again and I'm still
> seeing disappointing results. In short, it appears to consistently  
> slow
> down text. This is just the basic patch to enable _get_image_surface()
> and _draw_image_surface() to use XShm, and it is highly likely that  
> the
> thresholds could be tweaked etc. However, I expect better results if  
> we
> can reduce the frequency of GetImage/PutImage altogether - I think
> Behdad has been thinking along similar lines.
> Please take a look at the patch and see if any obvious stupidity leaps
> out.

One of our interns spent a while looking at XShm for cairo in mozilla;  
he documented some of his findings here -- http://www.ericbutler.net/blog/2008/07/adventures-in-x-programming/ 
  . He was just trying to use it for fast image upload and was getting  
consistently disappointing results.  Given that your own results don't  
really show any big speedups (and the ones that are shown are strange  
-- why is tessellate-256-100 affected by xshm or no xshm?  why is  
paint-solid-rgb-source showing speedups?), is it worth pursuing this?

     - Vlad

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