[PATCH] vulkan: Add VK_EXT_calibrated_timestamps extension (radv and anv) [v4]

[Keith Packard]

Jason Ekstrand <jason at jlekstrand.net> writes:


> You've got me almost convinced as well.  Thanks for the diagrams!  I think
> instead of adding 1 perhaps what we want is
>
> max2(sample_interval_ns, gpu_tick_ns + monotonic_tick_ns)
>
> Where monotonic_tick_ns is maybe as low as 1.  Am I following you correctly?

Not quite; I was thinking that because the sample_interval_ns is
measured by sampling the monotonic clock twice, the actual interval can
be up to 1 tick longer, so

max2(sample_interval_ns + monotonic_tick_ns, gpu_tick_ns)

The gpu_tick_ns is computed, not measured, and so accurately reflects
the maximum deviation in the measurements.

-- 
-keith
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