"With all of this invasive work going on, regressions
are currently prevalent from stability problems to graphical
corruption to slower 2D performance. While these are problems users
will face with the new distribution updates in H1'09, some have
been trying out different driver configurations in order to
circumvent the situation. Canonical, for example, had been toying
with the idea of enabling greedy migration heuristics by default.
"The migration heuristics deal with how pixmaps move to video
memory, but when operating under the greedy mode, some acceleration
routines are avoided, where some of the current performance
problems seem to be taking place. This problem should ultimately be
corrected in EXA and UXA, but for now, Canonical's Bryce Harrington
has been considering setting the migration heuristics to greedy in
order to increase the xf86-video-intel 2D performance. The
MigrationHeuristics option can be set to greedy in the xorg.conf
file.
"To see how much of a difference the greedy migration heuristics
make, we decided to test out the different driver options. Using X
Server 1.6 with the latest xf86-video-intel 2.6.3 driver from
Ubuntu 9.04, we ran a set of benchmarks when the driver was using
its default EXA acceleration method, EXA with the greedy migration
heuristics, UXA acceleration, and then when reverting to the older
xf86-video-intel 2.4.1 driver and using EXA acceleration.
Previously we have found that UXA to offer faster performance,
which is based upon the EXA API but uses the Graphics Execution
Manager for managing its pixmaps."
