drm/i915/gt: Switch to manual evaluation of RPS
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: 98479ada ("drm/i915/gt: Treat idling as a RPS downclock event") Signed-off-by:Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Andi Shyti <andi.shyti@intel.com> Reviewed-by:
Andi Shyti <andi.shyti@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200429205446.3259-4-chris@chris-wilson.co.uk
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