Re: [PATCH] drm/i915: boost GPU and CPU freq when leaving idle

[Chris Wilson <chris@chris-wilson.co.uk>]

On Fri, Jun 28, 2013 at 11:40:27AM -0700, Jesse Barnes wrote:
> On Fri, 28 Jun 2013 19:37:01 +0100
> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > On Fri, Jun 28, 2013 at 09:54:32AM -0700, Jesse Barnes wrote:
> > > Coming out of idle is usually due to some sort of user input (swiping a
> > > screen, clicking a button) and often results in some sort of graphical
> > > animation.  To prevent stutter for a CPU or GPU intensive animation,
> > > boost the GPU and CPU freq to the maximum to get the first frame out as
> > > quickly as possible.  The normal CPU and GPU frequency management code
> > > will take over from there and (hopefully) clock down to save power as
> > > needed if the max frequencies aren't required.
> > > 
> > > This could probably be done more cleanly, and possibly without another
> > > uncached read in the execbuf path if we tracked idleness elsewhere.  I'm
> > > also unsure about the cpufreq calls; I don't really know if this will do
> > > what I want...
> > 
> > Would seem like a good idea to make intel_mark_busy() dtrt and use them.
> 
> That'll give us a slightly delayed idle indicator, but it should work
> ok...
> 
> Owen, if this patch looks like it'll work for you, I'll update it to use
> our mark busy/idle stuff and see if we can merge it upstream.

I'm in favour of a bit of hystersis, probably because I think this is
ultimately a firmware tuning issue. Something that userspace can only
provide hints for, and only the hardware can respond fast enough.

Nevertheless will try out this pair to see if makes my systems sweat.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre