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Date: Mon, 29 Apr 2024 15:33:04 +0100 From: Luis Machado <luis.machado@....com> To: Peter Zijlstra <peterz@...radead.org> Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com, linux-kernel@...r.kernel.org, kprateek.nayak@....com, wuyun.abel@...edance.com, tglx@...utronix.de, efault@....de, nd <nd@....com>, John Stultz <jstultz@...gle.com>, Hongyan.Xia2@....com Subject: Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue Hi Peter, On 4/26/24 10:32, Peter Zijlstra wrote: > On Thu, Apr 25, 2024 at 01:49:49PM +0200, Peter Zijlstra wrote: >> On Thu, Apr 25, 2024 at 12:42:20PM +0200, Peter Zijlstra wrote: >> >>>> I wonder if the delayed dequeue logic is having an unwanted effect on the calculation of >>>> utilization/load of the runqueue and, as a consequence, we're scheduling things to run on >>>> higher OPP's in the big cores, leading to poor decisions for energy efficiency. >>> >>> Notably util_est_update() gets delayed. Given we don't actually do an >>> enqueue when a delayed task gets woken, it didn't seem to make sense to >>> update that sooner. >> >> The PELT runnable values will be inflated because of delayed dequeue. >> cpu_util() uses those in the @boost case, and as such this can indeed >> affect things. >> >> This can also slightly affect the cgroup case, but since the delay goes >> away as contention goes away, and the cgroup case must already assume >> worst case overlap, this seems limited. >> >> /me goes ponder things moar. > > First order approximation of a fix would be something like the totally > untested below I suppose... I gave this a try on the Pixel 6, and I noticed some improvement (see below), but not enough to bring it back to the original levels. (1) m6.6-stock - Basic EEVDF with wakeup preemption fix (baseline) (2) m6.6-eevdf-complete: m6.6-stock plus this series. (3) m6.6-eevdf-complete-no-delay-dequeue: (2) + NO_DELAY_DEQUEUE (4) m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero: (2) + NO_DELAY_DEQUEUE + NO_DELAY_ZERO (5) m6.6-eevdf-complete-no-delay-zero: (2) + NO_DELAY_ZERO (6) m6.6-eevdf-complete-pelt-fix: (2) + the proposed load_avg update patch. I included (3), (4) and (5) to exercise the impact of disabling the individual scheduler features. Energy use. +------------+------------------------------------------------------+-----------+ | cluster | tag | perc_diff | +------------+------------------------------------------------------+-----------+ | CPU | m6.6-stock | 0.0% | | CPU-Big | m6.6-stock | 0.0% | | CPU-Little | m6.6-stock | 0.0% | | CPU-Mid | m6.6-stock | 0.0% | | GPU | m6.6-stock | 0.0% | | Total | m6.6-stock | 0.0% | | CPU | m6.6-eevdf-complete | 114.51% | | CPU-Big | m6.6-eevdf-complete | 90.75% | | CPU-Little | m6.6-eevdf-complete | 98.74% | | CPU-Mid | m6.6-eevdf-complete | 213.9% | | GPU | m6.6-eevdf-complete | -7.04% | | Total | m6.6-eevdf-complete | 100.92% | | CPU | m6.6-eevdf-complete-no-delay-dequeue | 117.77% | | CPU-Big | m6.6-eevdf-complete-no-delay-dequeue | 113.79% | | CPU-Little | m6.6-eevdf-complete-no-delay-dequeue | 97.47% | | CPU-Mid | m6.6-eevdf-complete-no-delay-dequeue | 189.0% | | GPU | m6.6-eevdf-complete-no-delay-dequeue | -6.74% | | Total | m6.6-eevdf-complete-no-delay-dequeue | 103.84% | | CPU | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | 120.45% | | CPU-Big | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | 113.65% | | CPU-Little | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | 99.04% | | CPU-Mid | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | 201.14% | | GPU | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | -5.37% | | Total | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | 106.38% | | CPU | m6.6-eevdf-complete-no-delay-zero | 119.05% | | CPU-Big | m6.6-eevdf-complete-no-delay-zero | 107.55% | | CPU-Little | m6.6-eevdf-complete-no-delay-zero | 98.66% | | CPU-Mid | m6.6-eevdf-complete-no-delay-zero | 206.58% | | GPU | m6.6-eevdf-complete-no-delay-zero | -5.25% | | Total | m6.6-eevdf-complete-no-delay-zero | 105.14% | | CPU | m6.6-eevdf-complete-pelt-fix | 105.56% | | CPU-Big | m6.6-eevdf-complete-pelt-fix | 100.45% | | CPU-Little | m6.6-eevdf-complete-pelt-fix | 94.4% | | CPU-Mid | m6.6-eevdf-complete-pelt-fix | 150.94% | | GPU | m6.6-eevdf-complete-pelt-fix | -3.96% | | Total | m6.6-eevdf-complete-pelt-fix | 93.31% | +------------+------------------------------------------------------+-----------+ Utilization and load levels. +---------+------------------------------------------------------+----------+-----------+ | cluster | tag | variable | perc_diff | +---------+------------------------------------------------------+----------+-----------+ | little | m6.6-stock | load | 0.0% | | little | m6.6-stock | util | 0.0% | | little | m6.6-eevdf-complete | load | 29.56% | | little | m6.6-eevdf-complete | util | 55.4% | | little | m6.6-eevdf-complete-no-delay-dequeue | load | 42.89% | | little | m6.6-eevdf-complete-no-delay-dequeue | util | 69.47% | | little | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | load | 51.05% | | little | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | util | 76.55% | | little | m6.6-eevdf-complete-no-delay-zero | load | 34.51% | | little | m6.6-eevdf-complete-no-delay-zero | util | 72.53% | | little | m6.6-eevdf-complete-pelt-fix | load | 29.96% | | little | m6.6-eevdf-complete-pelt-fix | util | 59.82% | | mid | m6.6-stock | load | 0.0% | | mid | m6.6-stock | util | 0.0% | | mid | m6.6-eevdf-complete | load | 29.37% | | mid | m6.6-eevdf-complete | util | 75.22% | | mid | m6.6-eevdf-complete-no-delay-dequeue | load | 36.4% | | mid | m6.6-eevdf-complete-no-delay-dequeue | util | 80.28% | | mid | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | load | 30.35% | | mid | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | util | 90.2% | | mid | m6.6-eevdf-complete-no-delay-zero | load | 37.83% | | mid | m6.6-eevdf-complete-no-delay-zero | util | 93.79% | | mid | m6.6-eevdf-complete-pelt-fix | load | 33.57% | | mid | m6.6-eevdf-complete-pelt-fix | util | 67.83% | | big | m6.6-stock | load | 0.0% | | big | m6.6-stock | util | 0.0% | | big | m6.6-eevdf-complete | load | 97.39% | | big | m6.6-eevdf-complete | util | 12.63% | | big | m6.6-eevdf-complete-no-delay-dequeue | load | 139.69% | | big | m6.6-eevdf-complete-no-delay-dequeue | util | 22.58% | | big | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | load | 125.36% | | big | m6.6-eevdf-complete-no-delay-dequeue-no-delay-zero | util | 23.15% | | big | m6.6-eevdf-complete-no-delay-zero | load | 128.56% | | big | m6.6-eevdf-complete-no-delay-zero | util | 25.03% | | big | m6.6-eevdf-complete-pelt-fix | load | 130.73% | | big | m6.6-eevdf-complete-pelt-fix | util | 17.52% | +---------+------------------------------------------------------+----------+-----------+
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