EXA and MigrationHeuristic

[Juliusz Chroboczek]

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.)

                                        Juliusz