Hi Chris,
On Tue, Nov 24, 2020 at 06:35:21PM +0000, Chris Wilson wrote:
We treat idling the GT (intel_rps_park) as a downclock event, and reduce the frequency we intend to restart the GT with. Since the two workloads are likely related (e.g. a compositor rendering every 16ms), we want to carry the frequency and load information from across the idling. However, we do also need to update the frequencies so that workloads that run for less than 1ms are autotuned by RPS (otherwise we leave compositors running at max clocks, draining excess power). Conversely, if we try to run too slowly, the next workload has to run longer. Since there is a hysteresis in the power graph, below a certain frequency running a short workload for longer consumes more energy than running it slightly higher for less time. The exact balance point is unknown beforehand, but measurements with 30fps media playback indicate that RPe is a better choice.
Reported-by: Edward Baker edward.baker@intel.com Fixes: 043cd2d14ede ("drm/i915/gt: Leave rps->cur_freq on unpark") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Edward Baker edward.baker@intel.com Cc: Andi Shyti andi.shyti@intel.com Cc: Lyude Paul lyude@redhat.com Cc: stable@vger.kernel.org # v5.8+
drivers/gpu/drm/i915/gt/intel_rps.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c index b13e7845d483..f74d5e09e176 100644 --- a/drivers/gpu/drm/i915/gt/intel_rps.c +++ b/drivers/gpu/drm/i915/gt/intel_rps.c @@ -907,6 +907,10 @@ void intel_rps_park(struct intel_rps *rps) adj = -2; rps->last_adj = adj; rps->cur_freq = max_t(int, rps->cur_freq + adj, rps->min_freq);
- if (rps->cur_freq < rps->efficient_freq) {
rps->cur_freq = rps->efficient_freq;rps->last_adj = 0;- }
looks OK to me, makes sense:
Reviewed-by: Andi Shyti andi.shyti@intel.com
Thanks, Andi