[Intel-gfx] [PATCH 7/9] drm/i915/gt: Switch to manual evaluation of RPS

[Andi Shyti]

Hi Chris,

On Mon, Apr 27, 2020 at 09:54:06AM +0100, Chris Wilson wrote:
> As with the realisation for soft-rc6, we respond to idling the engines
> within microseconds, far faster than the response times for HW RC6 and
> RPS. Furthermore, our fast parking upon idle, prevents HW RPS from
> running for many desktop workloads, as the RPS evaluation intervals are
> on the order of tens of milliseconds, but the typical workload is just a
> couple of milliseconds, but yet we still need to determine the best
> frequency for user latency versus power.
> 
> Recognising that the HW evaluation intervals are a poor fit, and that
> they were deprecated [in bspec at least] from gen10, start to wean
> ourselves off them and replace the EI with a timer and our accurate
> busy-stats. The principle benefit of manually evaluating RPS intervals
> is that we can be more responsive for better performance and powersaving
> for both spiky workloads and steady-state.
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1698
> Fixes: 98479ada421a ("drm/i915/gt: Treat idling as a RPS downclock event")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Andi Shyti <andi.shyti at intel.com>

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

Thanks,
Andi