[Intel-gfx] [PATCH 1/6] RFCish: write only mappings (aka non-blocking)

[Ben Widawsky]

I'm going to keep this short...
Patch 5 is my test case.
On Gen6 I see slightly better performance. On Gen5 I see really really
improvements (like 3x) for non GTT write only maps over regular mmaps.
GTT mappings don't really show any improvements as a whole.

Better tests would be nice, but without more significant Mesa changes,
or better benchmarks, I'm not sure how to get those.  While I think
these patches are mostly complete, ideas for better testing are very
welcome. Also of course, general optimizations or pointing out my errors
would be nice.