[Intel-gfx] [PATCH] drm/i915: Update MOCS settings for gen 9

[David Weinehall]

On Thu, Apr 27, 2017 at 04:55:20PM +0200, Arkadiusz Hiler wrote:
> On Wed, Apr 26, 2017 at 06:00:41PM +0300, David Weinehall wrote:
> > Add a bunch of MOCS entries for gen 9 that were missing from intel_mocs.
> > Some of these are used by media-sdk; if these entries are missing
> > the default will instead be to do everything uncached.
> > 
> > This patch improves media-sdk performance with up to 60%
> > with the (admittedly synthetic) benchmarks we use in our nightly
> > testing, without regressing any other benchmarks.
> 
> Hey David,
> 
> I am testing some of the extended MOCS with Mesa and the differences I
> see fit in the margins of statistical error.
> 
> Odd, I thought, so to make sure I haven't messed up anything in the
> process of compiling, setting LD_LIBRARY_PATH and benchmarking I turned
> everything to UNCACHED - and I saw severe performance drop.
> 
> So here is the question it induced:
> 
> Have you used the "closest neighbour" from entries available or did you
> defaulted to the UNCACHED ones? That could be the culprit.
> 
> Note: I have tested MOCS for VB and Render Target only, and only in a
> few synthetic cases - it will require much more fine-tuning and
> benchmarking before any final conclusions.

As I mentioned in the commit message, the improvements only manifest
themselves for media-sdk workloads (and presumably other workloads
that uses the same hardware); if you see any performance regressions
with these additional entries I'd be interested to know.


Kind regards, David Weinehall