[Mesa-dev] [PATCH] i965: Prefer Meta over the BLT for BlitFramebuffer.

[Kenneth Graunke]

On Thursday, January 15, 2015 08:56:23 AM Ben Widawsky wrote:
> On Thu, Jan 15, 2015 at 01:41:14AM -0800, Kenneth Graunke wrote:
> > There's some debate about whether we should use Meta or BLORP,
> > but either should run circles around the BLT engine.
> > 
> > Improves performance in "copypixrate -blit -back" (from Mesa demos)
> > by 232.037% +/- 3.15795% (n=10) on Broadwell GT3e.
> > 
> > Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> > ---
> >  src/mesa/drivers/dri/i965/intel_fbo.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > Ben: this might be a good candidate for your braswell branch.
> > 
> 
> I'll give it a run through the benchmarks assuming I can get a working machine.
> I am always concerned about this kind of switch because it seems very benchmark
> dependent to me. If we happen to have benchmarks which are extremely GPU/RCS
> limited, I could only imagine this would hurt, for example.
> 
> Anyway, I'll let the data speak for itself when I have it. Thanks for giving me
> new things to try.

I doubt that it's very benchmark dependent.  In every case that we've looked
at, the BLT has proven to be slightly slower to massively slower.  I've never
seen it be faster.

--Ken
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