From aff76ab795364569b1cac58c1d0bc7df956e3899 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 24 Nov 2020 18:35:21 +0000 Subject: drm/i915/gt: Limit frequency drop to RPe on parking 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 Tested-by: Edward Baker Fixes: 043cd2d14ede ("drm/i915/gt: Leave rps->cur_freq on unpark") Signed-off-by: Chris Wilson Cc: Edward Baker Cc: Andi Shyti Cc: Lyude Paul Cc: # v5.8+ Reviewed-by: Rodrigo Vivi Reviewed-by: Andi Shyti Link: https://patchwork.freedesktop.org/patch/msgid/20201124183521.28623-1-chris@chris-wilson.co.uk (cherry picked from commit f7ed83cc1925f0b8ce2515044d674354035c3af9) Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/gt/intel_rps.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c index e6a00eea0631..c1c9cc0ad3b9 100644 --- a/drivers/gpu/drm/i915/gt/intel_rps.c +++ b/drivers/gpu/drm/i915/gt/intel_rps.c @@ -883,6 +883,10 @@ 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; + } GT_TRACE(rps_to_gt(rps), "park:%x\n", rps->cur_freq); } -- cgit v1.2.3-58-ga151