[Intel-gfx] [PATCH 9/9] drm/i915/gt: Restore aggressive post-boost downclocking

[Andi Shyti]

Hi Chris,

On Mon, Apr 27, 2020 at 06:06:40PM +0100, Chris Wilson wrote:
> Quoting Chris Wilson (2020-04-27 13:40:46)
> > Quoting Chris Wilson (2020-04-27 09:54:08)
> > > We reduced the clocks slowly after a boost event based on the
> > > observation that the smoothness of animations suffered. However, since
> > > reducing the evalution intervals, we should be able to respond to the
> > > rapidly fluctuating workload of a simple desktop animation and so
> > > restore the more aggressive downclocking.
> > > 
> > > References: 2a8862d2f3da ("drm/i915: Reduce the RPS shock")
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > *** ANECDOTAL ***
> 
> > I spot checked a few games during scenes where the GPU was not capped
> > out, and it was drawing about ~100MHz less for ~1W less.
> 
> For example, vsync'ed Talos,
> 
> hw: 59.7
> 2553.86,Joules,power/energy-pkg/,192545269820,100.00,,
> 1355.92,Joules,power/energy-cores/,192545266374,100.00,,
> 556.36,Joules,power/energy-gpu/,192545263536,100.00,,
> 86989,M,i915/actual-frequency/,192545247535,100.00,,
> 12736813129,ns,i915/rc6-residency/,192545239813,100.00,,
> 118321566117,ns,i915/rcs0-busy/,192545235095,100.00,,
> 0,ns,i915/bcs0-busy/,192545229596,100.00,,
> 0,ns,i915/vcs0-busy/,192545222782,100.00,,
> 
> manual: 59.7
> 2490.58,Joules,power/energy-pkg/,190751537693,100.00,,
> 1447.89,Joules,power/energy-cores/,190751542360,100.00,,
> 394.93,Joules,power/energy-gpu/,190751543518,100.00,,
> 67956,M,i915/actual-frequency/,190751526709,100.00,,
> 40240837120,ns,i915/rc6-residency/,190751523820,100.00,,
> 147090761985,ns,i915/rcs0-busy/,190751525291,100.00,,
> 0,ns,i915/bcs0-busy/,190751523611,100.00,,
> 0,ns,i915/vcs0-busy/,190751520733,100.00,,
> 
> > *** ANECDOTAL ***

Thanks anecdotes and the measurements!

Reviewed-by: Andi Shyti <andi.shyti at intel.com>

Andi