[OpenJDK 2D-Dev] Disabling offscreen pixmaps by default?

Clemens Eisserer linuxhippy at gmail.com
Wed Nov 26 19:16:50 UTC 2008


Would it be possible to disable offscreen pixmaps by default when
running the X11 pipeline and when the xserver is running locally and
does not support SHMPIxmaps?
EXA based drivers (radeon/intel/nouveau) in general place pixmaps in
VRAM which kills performance and don't support SHMPixmaps.

Yes, pmoffscreen is sometimes slower, but it avoids really horrible
worst-case scenarious which happen on EXA based drivers.
And because even antialiased text causes fallbacks, worst case is quite common.
I ran some swing benchmarks, and results are horrible when running on
top of EXA based drivers, a 5x slowdown is not uncommon here.

All major distributions now enable EXA by default, at least when using
the intel-driver.
I am not sure about radeon, but their EXA implementation is quite
solid too - so sooner or later they will also use Exa by default if
they do not already default to it.
Finally the latest NVidia-Beta driver disables SHMPixmaps by default -
however it has smarter migration heuristics which keep the pixmap in
sysmem - only causing a ~2x slowdown.

- Clemens

More information about the 2d-dev mailing list