[Mesa-dev] [RFC] ARB_shader_clock, hardware counters and i965

[Emil Velikov]

Hi all,

I am looking at ARB_shader_clock with i965 in mind.

So far I've got the most of the infra/plumbing, and a fancy a new intrinsic :)

On the hardware side, I was thinking about using the Observability
Architecture (OA) counters. The fun part is that those tend to vary
quite a bit based on the hardware generation. So far I'm leaning
towards:
 - "Count of XXX threads dispatched to EUs" for BRW and later.
 - "XXX Shader Active Time" for earlier (SNB-HSW/VLV) hardware.

Do there sound appropriate, or should we opt for the various knobs in
'Flexible EU event counters' ? Is there some alternative piece of
hardware in i965, which I can use ?


Going for OA has a small catch. Reading through the PRM, it is not
obvious if one can track the same source twice (the
GL_AMD_performance_monitor implementation comes to mind). I'm about to
take a closer look into brw_performance_monitor.[ch] shortly, but if
any gotchas/fancy interactions come to mind let me know.

Thanks
Emil

P.S. Does anyone recall the consensus wrt adding the 2015 extensions
to GL3.txt ?