[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 #18 from Ray Strode [halfline] <rstrode at redhat.com> ---
(In reply to Chris Wilson from comment #17)
> The gfx driver doesn't have that information. I'm not sure if the kernel
> knows what is an active hid, and certainly there's no link to it to either
> the cpu scheduler or to us. 
I don't understand, the kernel sends input events from
keyboard/mice/touchscreens to userspace via /dev/input/eventN interface, so why
couldn't the clock speed get boosted any time an event got posted to one of
those devices?

git grep seems to suggest there's a function called input_register_handler()
that lets various parts of the kernel hook into the event stream for all
devices (granted this was just 60 seconds of searching, so I may be missing
something).

> From our perspective the only way we can
> identify such streams is by looking at what ends up on the display, and
> backtracking from there. The piece that pulls all of this together is the
> compositor.
But wouldn't it better if we could ramp up the clockspeed before firefox
started rerendering a page getting drag scrolled, not after the compositor is
responding to damage requests?

> Because we are looking for anything that interacts with the user to
> preferentially give those low latency. We identify these by contexts which
> are tied to files and processes. On the other hand, we can remove that
> guesswork if userspace is able to tell us what is high priority and what is
> not.
Okay, so it's not just video card in turbo mode or power save mode, but also
certain GL contexts getting preferential access to the card.  Seems like a
worthwhile thing to have, I guess, but giving gnome-shell preferential access
doesn't help firefox rerender faster, right ?

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