CAVEATS

Performance of 3D applications
--------------------------------------------------------------------------------

The port applies a hack to prevent gpu hangs with 3D applications:

http://github.com/gsutre/netbsd-drmgem/commit/3a32fa0b567af67c03853bc6a271362631

Without the hack, on an laptop with i915GM, glxgears is choppy and the gears
stop moving after 30s.  The kernel log indicates that the gpu hung.

However, this hack induces a performance penalty.  And it seems that the hack is
not always necessary.  On a laptop with Ironlake, there seems to be no gpu hang
without the hack, and the frame rate increases by 50% in tuxracer (even 100% in
glxgears).

To use the port without the hack, simply restore the original intel DRI modules,
from the xserver set (i.e., the files /usr/X11R7/lib/modules/dri/i9*_dri.*).

To directly build the port without the hack,

- either revert the above commit before patching the NetBSD source,
- or, with the automated build, do not pass the option `-m' (but this only works
  if you did not already install the port before).


The hack would probably be obsolete with a recent version of Mesa:

http://cgit.freedesktop.org/~krh/mesa/commit/?id=e67c338b415c983bee570e6644b9684

An attempt to apply this commit instead of the hack failed.  This commit depends
on too many other post-7.8.2 Mesa commits.  Hopefully, the problem with resolve
itself when Mesa is updated in NetBSD.