EXA and MigrationHeuristic

Stephane Marchesin marchesin at icps.u-strasbg.fr
Wed May 28 12:28:31 PDT 2008

On 5/28/08, Juliusz Chroboczek <Juliusz.Chroboczek at pps.jussieu.fr> wrote:
> Dear all,
>  After my recent adventures with Radeon, XAA and EXA, I've come to the
>  conclusion that setting MigrationHeuristic to greedy drastically helps
>  performance of Firefox redraws on both Radeon and i965GM hardware.
>  By drastically, I mean it -- a redraw of a full-screen Firefox goes
>  from 3 to 5 seconds (!) down to a fraction of a second.
>  Now I haven't read the sources of Firefox (let him who has cast me the
>  first stone), but I believe that Firefox performs client-side backing
>  store using absolutely humonguous pixmaps.  While we may argue that
>  what Firefox does is stupid, I think we should try to support this
>  kind of usage.
>  Isn't the default value of MigrationHeuristic incorrect ?  Should we
>  switch to greedy as default ?  (Julien tells me that he believes that
>  Ubuntu have already made the switch.)

It's a bad move. Doing this prevents us from diagnosing issues and
fixing them, and thus globally slows down the advance of EXA and the
point at which it becomes usable for everyone.

My opinion is that you should profile and understand the issue, and
fix EXA (or firefox) to behave better.


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