[Bug 102199] Kabylake has poor performance, doesn't upclock during activity quickly with single display configurations

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102199

--- Comment #4 from Lyude Paul <lyude at redhat.com> ---
(In reply to Jani Nikula from comment #2)
> Semi-clueless shot in the dark: Does loading vs. not loading the DMC
> firmware make a difference?

No unfortunately. In fact the performance almost seems to be worse, and it
doesn't look like it chooses to boost very often.

Regarding i915_rps_boost_info, I see some very interesting patterns when
gnome-shell is animating. The GPU almost never boosts up even when continuously
replaying the activity overlay animations, and stays at 300 MHz. Very, very
rarely it will decide to boost at which point I can see mutter reporting the
FPS doubling. The boost doesn't last very long though, and shortly after goes
away. Even more interestingly, when the GPU is rendering the animations it is
marked as busy in i915_rps_boost_info despite never actually boosting.

Now, I didn't notice this until just now but something else that's rather
interesting happens when I stop replaying the animations. The second I stop,
the GPU immediately boosts for a split second, then stops. This happens
consistently as well.

If I monitor i915_rps_boost_info while running two displays + gnome-shell
though, the GPU boosts almost immediately when the animations start, and mutter
reports FPS counts much closer to what I would expect. Additionally, the boost
count for gnome-shell's process (marked as system-logind) actually starts going
up during animations and labeling itself as actively boosting. Unplugging the
display again makes the GPU stop boosting like before.

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