[Mesa-dev] [Bug 87886] constant fps drops with Intel and Radeon

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=87886

--- Comment #27 from Stéphane Travostino <stephane.travostino at gmail.com> ---
(In reply to Eero Tamminen from comment #26)
> as root, mount debugfs and monitor CAGF (actual GPU frequency) value from
> "/sys/kernel/debug/dri/0/i915_frequency_info", or if you have older kernel
> from "/sys/kernel/debug/dri/0/i915_cur_delayinfo"  Does it keep up, or go
> down when you get FPS drop?
> 
> (If it goes down, this seems like kernel power management issue.)

Good call! Watching i915_frequency_info while running glxgears on Intel, I see
it starts at 1100 MHz and after a few seconds it starts to drop to 650 MHz and
up again, repeatedly.
Frequency changes collerate with FPS changes in glxgears, so yeah, it seems it
is a kernel pm issue.

I tried booting up with i915.powersave=0 i915.enable_rc6=0, also tried
disabling Runtime PM on the Intel card via powertop but I can't find a way to
force the frequency to max values to be 100% sure it's frequency switching
related.

Any idea where to go from there?

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