Limit deboosting and boosting to keep ourselves at the extremes when in the respective power modes (i.e. slowly decrease frequencies while in the HIGH_POWER zone and slowly increase frequencies while in the LOW_POWER zone). On idle, we will hit the timeout and drop to the next level quickly, and conversely if busy we expect to hit a waitboost and rapidly switch into max power. This should improve the UX experience by keeping the GPU clocks higher than they ostensibly should be (based on simple busyness) by switching into the INTERACTIVE mode (due to waiting for pageflips) and increasing clocks via waitboosting. This will incur some additional power, our saving grace should be rc6 and powergating to keep the extra current draw in check. Food for future thought would be deadline scheduling? If we know certain contexts (high priority compositors) absolutely must hit the next vblank then we can raise the frequencies ahead of time. Part of this is covered by per-context frequencies, where userspace is given control over the frequency range they want the GPU to execute at (for largely the same problem as this, where the workload is very latency sensitive but at the EI level appears mostly idle). Indeed, the per-context series does extend the modeset boosting to include a frequency range tweak which seems applicable to solving this jittery UX behaviour. Reported-by: Lyude Paul <lyude@xxxxxxxxxx> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109408 References: 0d55babc8392 ("drm/i915: Drop stray clearing of rps->last_adj") References: 60548c554be2 ("drm/i915: Interactive RPS mode") Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Lyude Paul <lyude@xxxxxxxxxx> Cc: Eero Tamminen <eero.t.tamminen@xxxxxxxxx> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Cc: Michel Thierry <michel.thierry@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_irq.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 441d2674b272..d26e3d19c993 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1288,6 +1288,18 @@ static void gen6_pm_rps_work(struct work_struct *work) rps->last_adj = adj; + /* + * Limit deboosting and boosting to keep ourselves at the extremes + * when in the respective power modes (i.e. slowly decrease frequencies + * while in the HIGH_POWER zone and slowly increase frequencies while + * in the LOW_POWER zone). On idle, we will hit the timeout and drop + * to the next level quickly, and conversely if busy we expect to + * hit a waitboost and rapidly switch into max power. + */ + if ((adj < 0 && rps->power.mode == HIGH_POWER) || + (adj > 0 && rps->power.mode == LOW_POWER)) + rps->last_adj = 0; + /* sysfs frequency interfaces may have snuck in while servicing the * interrupt */ -- 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
