[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 #17 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to Ray Strode [halfline] from comment #16)
> (In reply to Chris Wilson from comment #15)
> > > can the driver just boost whenever an input device fires off an event ? keep
> > > interactive performance up when the user is interacting...
> > 
> > How to determine which request corresponds to the interactive stream?
> why do you need to ?  at the end of the day the question is whether the gpu
> is 500mhz or 1300mhz right?  just make it 1300mhz if there's input and let
> it downscale on its own when it stops animating and the user stops typing
> and swiping.

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. 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.

> > As a
> > gfx driver we have no knowledge of input devices. The system as a whole
> > struggles to identify interactive processes! The easiest way for us to
> > identify user tasks is by looking at what affects the output.
> But why do we need to know what processes are interactive ?

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.

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