[Intel-gfx] [PATCH 1/2] drm/i915/gt: Try to smooth RPS spikes

[Andi Shyti]

Hi Chris,

On Tue, Apr 14, 2020 at 05:14:22PM +0100, Chris Wilson wrote:
> By the time we respond to the RPS interrupt [inside a worker], the GPU
> may be running a different workload. As we look to make the evalution
> intervals shorter, these spikes are more likely to okay. Let's try to
> smooth over the spikes in the workload by comparing the EI interrupt
> [up/down events] with the most recently completed EI; if both say up,
> then increase the clocks, if they disagree stay the same. In principle,
> this means we now take 2 up EI to go increase into the next bin, and
> similary 2 down EI to decrease. However, if the worker runs fast enough,
> the previous EI in the registers will be the same as triggered the
> interrupt, so responsiveness remains unaffect. [Under the current scheme
> where EI are on the order of 10ms, it is likely that this is true and we
> compare the interrupt with the EI that caused it.]

looks reasonable to me. Wouldn't it make also sense to evaluate
the difference between the current and the previous pm_iir?

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

Andi