Intel Gen11+ Graphics See An Easy Bump On Mesa 20.1-devel

There's been a lot of interesting work hitting Mesa Git this week ahead of the Mesa 20.1 code branching and feature freeze. Merged this afternoon was a rather simple optimization benefiting Gen11 (Icelake) and newer for their open-source Vulkan driver, it's such a simple change it is almost surprising it took so long to benefit.

The change to the Intel "ANV" Vulkan driver is for allowing all clear colors for texturing on Gen11+ hardware.

Due to an architectural improvement with Gen11 with now having two indirect clear colors, one of which will always work for texturing regardless of the format, it can basically be unconditionally used. Intel's Jason Ekstrand explained, "Because it's a simple HW indirect and doesn't involve copying surface states around, we can use it in the sampler without having to worry about surface states having out-of-date clear values. The result is that we can now allow any clear color when texturing."

With this simple change of just adding a conditional statement for Gen11 and newer to allow for any clear color for sampling, the benefits are profound. Jason noted, "This cuts the number of resolves in a RenderDoc trace of Dota2 by 95% on Gen11+ (you read that right) and improves perf by 3.5%. It improves perf in a handful of other workloads < 1%."

So the number of resolves ends up being greatly reduced and helps out Dota 2 as the main beneficiary but potentially other Vulkan games as well, we'll see during our next round of Icelake Core i7-1065G7 benchmarking. Not bad in any case for such a simple patch.

Mesa 20.1-devel should be proceeding to its release candidate phase in the days ahead and ideally going stable before the end of May with this improvement and much more.