[Mesa-dev] [PATCH] intel: Use a CPU map of the batch on LLC-sharing architectures.

Eric Anholt eric at anholt.net
Fri Jan 25 09:31:48 PST 2013

Kenneth Graunke <kenneth at whitecape.org> writes:

> On 01/20/2013 02:59 PM, Eric Anholt wrote:
>> Before, we were keeping a CPU-only buffer to accumulate the batchbuffer in,
>> which was an improvement over mapping the batch through the GTT directly
>> (since any readback or other failure to stream through write combining
>> correctly would hurt).  However, on LLC-sharing architectures we can do better
>> by mapping the batch directly, which reduces the cache footprint of the
>> application since we no longer have this extra copy of a batchbuffer around.
>> Improves performance of GLBenchmark 2.1 offscreen on IVB by 3.5% +/- 0.4%
>> (n=21).  Improves Lightsmark performance by 1.1 +/- 0.1% (n=76).  Improves
>> cairo-gl performance by 1.9% +/- 1.4% (n=57).
>> No statistically significant difference in GLB2.1 on SNB (n=37).  Improves
>> cairo-gl performance by 2.1% +/- 0.1% (n=278).
> Looks good to me.  Have you tested this on a non-LLC machine?

Not in a long time.  It shouldn't affect performance, since they get the
same behavior as before.
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