[Mesa-dev] [PATCH] mesa: Use a 565 format for GL_RGB and GL_UNSIGNED_SHORT_5_6_5 textures.

[Eero Tamminen]

Hi,

On 05.10.2017 18:15, Eero Tamminen wrote:
> On 05.10.2017 01:16, Eric Anholt wrote:
>> Kenneth Graunke <kenneth at whitecape.org> writes:
>>
>>> Found while trying to optimize an application.
>>>
>>> Not observed to help performance on i965, but should at least reduce
>>> the memory usage of such textures a bit.
> 
> I run benchmarks on it on few platforms and didn't see any performance 
> changes either.
> 
> Tested-by: Eero Tamminen <eero.t.tamminen at intel.com>

After looking at the longer time perf trends, there's actually an impact 
in one test-case, GLB v2.7 Egypt (when using 1/2 HD screen size).  On 
half the platforms, the change is still within variance, but not on all 
platforms, and ezBench bisected this commit.

It has visible:
- Positive impact on SNB GT2
- Negative impact on BYT, BSW, BXT, SKL GT2, KBL GT2

Impact is most visible on (non-TDP limited) SKL GT2, about 4% drop.

Because of the nature of the test (e.g. easily impacted by power 
management because it's partly CPU bound), I don't think this enough of 
a reason to revert the change, results might change again when textures 
get render buffer compression.


>> Reviewed-by: Eric Anholt <eric at anholt.net>


	- Eero