[Mesa-dev] i965 DOTA2 perf issue: faulting and unsynchronized maps

[Eric Anholt]

Those of you at the office yesterday may remember me getting very
excited about perf events suggesting gtt thrashing on DOTA2.

On further testing, i915:i915_gem_evict says that we aren't evicting
things from the GTT after the first run.  We still get the
i915:i915_gem_request_wait_begin stalls on the subdatas, which I believe
are because the BOs are new, and we're doing the first faulting, which
in the kernel assumes synced behavior.

Swapping our unsynced maps to CPU maps (I think this is safe, and
doesn't have the same faulting leading to stalling on the GPU problem)
didn't improve performance, so I'm fairly sure that we can move on from
this issue at this point.
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