[Bug 81682] [snb] Frequent framerate drops

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81682

--- Comment #23 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to comment #21)
> Interesting, when it recovered, for a short time it went up to 1100MHz
> gpufreq, and the fps suddenly became smooth as silk, 50fps at least. Whilst
> it may not be the proper solution, is there a re to force the gpu up to a
> high freq while I'm gaming? I'm happy to continue debugging with you, but at
> least I could choose when I'm going to get the fps drops :)

You can force the requested frequency to max with "cat
/sys/class/drm/card0/gt_RP0_freq_mhz > /sys/class/drm/card0/gt_max_freq_mhz".
It should not be any better than the autotuning (and likely to be worse).
However, that will not stop the hardware from throttling down to meet thermal
limits.

Looking at the perf output, the unknown symbols are just from a lack of debug
packages, but I think we have enough to suggest that cpufreq is a major factor
in the error. During the stall, it is going mad. Disabling cpufreq (echo
performance > /sys/.../scaling_governor) would be a good test.

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