[Intel-gfx] Performance regression, please revert commit 441ef916ae6569c88b3d6abaf7fea4d69be49d76

[Knut Petersen]

There is a massive performance regression on i915GM hardware,
opening/closing/redrawing looks as if it is done in slow motion.

I bisected the problem to:

commit 441ef916ae6569c88b3d6abaf7fea4d69be49d76
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Jan 10 19:14:21 2013 +0000

     intel: Throttle harder

     Filling the rings is a very unpleasant user experience, so cap the
     number of batches we allow to be inflight at any one time.

     Interestingly, as also found with SNA, throttling can improve
     performance by reducing RSS. However, typically throughput is improved
     (at the expense of latency) by oversubscribing work to the GPU and a
     10-20% slowdown is commonplace for cairo-traces. Notably, x11perf is
     less affected and in particular application level benchmarks show no
     change.

     Note that this exposes another bug in libdrm-intel 2.4.40 on gen2/3.

     Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Please revert 441ef (or limit the new code to hardware that benefits from it)

cu,
  Knut