From df6a42053513846475ae1fbd224dfbdbcd0c7010 Mon Sep 17 00:00:00 2001 From: Tvrtko Ursulin Date: Tue, 17 Dec 2019 14:20:57 +0000 Subject: [PATCH] drm/i915/pmu: Ensure monotonic rc6 Avoid rc6 counter going backward in close to 0% RC6 scenarios like: 15.005477996 114,246,613 ns i915/rc6-residency/ 16.005876662 667,657 ns i915/rc6-residency/ 17.006131417 7,286 ns i915/rc6-residency/ 18.006615031 18,446,744,073,708,914,688 ns i915/rc6-residency/ 19.007158361 18,446,744,073,709,447,168 ns i915/rc6-residency/ 20.007806498 0 ns i915/rc6-residency/ 21.008227495 1,440,403 ns i915/rc6-residency/ There are two aspects to this fix. First is not assuming rc6 value zero means GT is asleep since that can also mean GPU is fully busy and we do not want to enter the estimation path in that case. Second is ensuring monotonicity on the estimation path itself. I suspect what is happening is with extremely rapid park/unpark cycles we get no updates on the real rc6 and therefore have to careful not to unconditionally trust use last known real rc6 when creating a new estimation. v2: * Simplify logic by not tracking the estimate but last reported value. Signed-off-by: Tvrtko Ursulin Fixes: 16ffe73c186b ("drm/i915/pmu: Use GT parked for estimating RC6 while asleep") Cc: Chris Wilson Reviewed-by: Chris Wilson # v1 Reviewed-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20191217142057.1000-1-tvrtko.ursulin@linux.intel.com --- drivers/gpu/drm/i915/i915_pmu.c | 73 +++++++++++------------------------------ drivers/gpu/drm/i915/i915_pmu.h | 2 +- 2 files changed, 21 insertions(+), 54 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c index 0032547..f3ef670 100644 --- a/drivers/gpu/drm/i915/i915_pmu.c +++ b/drivers/gpu/drm/i915/i915_pmu.c @@ -144,61 +144,40 @@ static inline s64 ktime_since(const ktime_t kt) return ktime_to_ns(ktime_sub(ktime_get(), kt)); } -static u64 __pmu_estimate_rc6(struct i915_pmu *pmu) -{ - u64 val; - - /* - * We think we are runtime suspended. - * - * Report the delta from when the device was suspended to now, - * on top of the last known real value, as the approximated RC6 - * counter value. - */ - val = ktime_since(pmu->sleep_last); - val += pmu->sample[__I915_SAMPLE_RC6].cur; - - pmu->sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val; - - return val; -} - -static u64 __pmu_update_rc6(struct i915_pmu *pmu, u64 val) -{ - /* - * If we are coming back from being runtime suspended we must - * be careful not to report a larger value than returned - * previously. - */ - if (val >= pmu->sample[__I915_SAMPLE_RC6_ESTIMATED].cur) { - pmu->sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0; - pmu->sample[__I915_SAMPLE_RC6].cur = val; - } else { - val = pmu->sample[__I915_SAMPLE_RC6_ESTIMATED].cur; - } - - return val; -} - static u64 get_rc6(struct intel_gt *gt) { struct drm_i915_private *i915 = gt->i915; struct i915_pmu *pmu = &i915->pmu; unsigned long flags; + bool awake = false; u64 val; - val = 0; if (intel_gt_pm_get_if_awake(gt)) { val = __get_rc6(gt); intel_gt_pm_put_async(gt); + awake = true; } spin_lock_irqsave(&pmu->lock, flags); - if (val) - val = __pmu_update_rc6(pmu, val); + if (awake) { + pmu->sample[__I915_SAMPLE_RC6].cur = val; + } else { + /* + * We think we are runtime suspended. + * + * Report the delta from when the device was suspended to now, + * on top of the last known real value, as the approximated RC6 + * counter value. + */ + val = ktime_since(pmu->sleep_last); + val += pmu->sample[__I915_SAMPLE_RC6].cur; + } + + if (val < pmu->sample[__I915_SAMPLE_RC6_LAST_REPORTED].cur) + val = pmu->sample[__I915_SAMPLE_RC6_LAST_REPORTED].cur; else - val = __pmu_estimate_rc6(pmu); + pmu->sample[__I915_SAMPLE_RC6_LAST_REPORTED].cur = val; spin_unlock_irqrestore(&pmu->lock, flags); @@ -210,20 +189,11 @@ static void park_rc6(struct drm_i915_private *i915) struct i915_pmu *pmu = &i915->pmu; if (pmu->enable & config_enabled_mask(I915_PMU_RC6_RESIDENCY)) - __pmu_update_rc6(pmu, __get_rc6(&i915->gt)); + pmu->sample[__I915_SAMPLE_RC6].cur = __get_rc6(&i915->gt); pmu->sleep_last = ktime_get(); } -static void unpark_rc6(struct drm_i915_private *i915) -{ - struct i915_pmu *pmu = &i915->pmu; - - /* Estimate how long we slept and accumulate that into rc6 counters */ - if (pmu->enable & config_enabled_mask(I915_PMU_RC6_RESIDENCY)) - __pmu_estimate_rc6(pmu); -} - #else static u64 get_rc6(struct intel_gt *gt) @@ -232,7 +202,6 @@ static u64 get_rc6(struct intel_gt *gt) } static void park_rc6(struct drm_i915_private *i915) {} -static void unpark_rc6(struct drm_i915_private *i915) {} #endif @@ -281,8 +250,6 @@ void i915_pmu_gt_unparked(struct drm_i915_private *i915) */ __i915_pmu_maybe_start_timer(pmu); - unpark_rc6(i915); - spin_unlock_irq(&pmu->lock); } diff --git a/drivers/gpu/drm/i915/i915_pmu.h b/drivers/gpu/drm/i915/i915_pmu.h index bf52e39..6c1647c 100644 --- a/drivers/gpu/drm/i915/i915_pmu.h +++ b/drivers/gpu/drm/i915/i915_pmu.h @@ -18,7 +18,7 @@ enum { __I915_SAMPLE_FREQ_ACT = 0, __I915_SAMPLE_FREQ_REQ, __I915_SAMPLE_RC6, - __I915_SAMPLE_RC6_ESTIMATED, + __I915_SAMPLE_RC6_LAST_REPORTED, __I915_NUM_PMU_SAMPLERS }; -- 2.7.4