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Date: Wed, 12 Jun 2024 16:08:08 +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, John Stultz <jstultz@...gle.com>, Hongyan.Xia2@....com Subject: Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue On 6/5/24 10:42, Peter Zijlstra wrote: > On Wed, Jun 05, 2024 at 10:14:47AM +0100, Luis Machado wrote: >> ... thanks for the patch! The above seems to do it for me. I can see >> more reasonable energy use with the eevdf-complete series. Still a >> bit higher. Might be noise, we'll see. > > W00t!!! > > Let me write a decent Changelog and stuff it in the git tree along with > all the other bits. > > Thanks for all the testing. I've been doing some more testing of the eevdf-complete series with the Pixel6/EAS platform. Hopefully these numbers will prove useful. The energy regression from the original delayed-dequeue patch seems to have been mostly fixed (with your proposed patch). Energy readings for the big and mid cores are mostly stable and comparable with stock eevdf (without eevdf-complete). The only difference I can spot now is in the energy use of the little cores. Compared to stock eevdf, the delayed-dequeue code seems to make the energy use of the little cores a bit spiky, meaning sometimes we get the expected level of energy use, but other times we get 40%, 60% or even 90% more. For instance... (1) m6.6-eevdf-stock*: stock eevdf runs (2) m6.6-eevdf-complete-ndd-dz*: eevdf-complete + NO_DELAY_DEQUEUE + DELAY_ZERO (3) m6.6-eevdf-complete-dd-dz*: eevdf-complete + DELAY_DEQUEUE + DELAY_ZERO +------------+---------------------------------+-----------+ | channel | tag | perc_diff | +------------+---------------------------------+-----------+ | CPU-Little | m6.6-eevdf-stock-1 | 0.0% | | CPU-Little | m6.6-eevdf-stock-2 | -4.21% | | CPU-Little | m6.6-eevdf-stock-3 | -7.86% | | CPU-Little | m6.6-eevdf-stock-4 | -5.67% | | CPU-Little | m6.6-eevdf-stock-5 | -6.61% | | CPU-Little | m6.6-eevdf-complete-ndd-dz-1 | -2.21% | | CPU-Little | m6.6-eevdf-complete-ndd-dz-2 | -9.99% | | CPU-Little | m6.6-eevdf-complete-ndd-dz-3 | -6.1% | | CPU-Little | m6.6-eevdf-complete-ndd-dz-4 | -5.66% | | CPU-Little | m6.6-eevdf-complete-ndd-dz-5 | -7.12% | | CPU-Little | m6.6-eevdf-complete-dd-dz-1 | 96.69% | | CPU-Little | m6.6-eevdf-complete-dd-dz-2 | 22.1% | | CPU-Little | m6.6-eevdf-complete-dd-dz-3 | 44.82% | | CPU-Little | m6.6-eevdf-complete-dd-dz-4 | -0.23% | | CPU-Little | m6.6-eevdf-complete-dd-dz-5 | 8.28% | +------------+---------------------------------+-----------+ Looking at what might explain the spiky behavior with DELAY_DEQUEUE, I noticed the idle residency data (we have 2 idle states) also shows some spikyness and potential clues. Looks like (1) and (2) manage to switch to idle states in a consistent manner, whereas (3) seems a bit erratic and more prone to take a shallower idle state (idle 0) as opposed to a deeper idle state (idle 1). (1) and (2) seem to make better use of the deeper idle state. +-------------------------------+---------+------------+-------+ | tag | cluster | idle_state | time | +-------------------------------+---------+------------+-------+ | m6.6-eevdf-stock-1 | little | not idle | 63.49 | | m6.6-eevdf-stock-1 | little | idle 0 | 30.66 | | m6.6-eevdf-stock-1 | little | idle 1 | 12.15 | | m6.6-eevdf-stock-2 | little | not idle | 62.6 | | m6.6-eevdf-stock-2 | little | idle 0 | 31.13 | | m6.6-eevdf-stock-2 | little | idle 1 | 14.56 | | m6.6-eevdf-stock-3 | little | not idle | 63.98 | | m6.6-eevdf-stock-3 | little | idle 0 | 31.54 | | m6.6-eevdf-stock-3 | little | idle 1 | 15.91 | | m6.6-eevdf-stock-4 | little | not idle | 64.18 | | m6.6-eevdf-stock-4 | little | idle 0 | 31.32 | | m6.6-eevdf-stock-4 | little | idle 1 | 15.83 | | m6.6-eevdf-stock-5 | little | not idle | 63.32 | | m6.6-eevdf-stock-5 | little | idle 0 | 30.4 | | m6.6-eevdf-stock-5 | little | idle 1 | 14.33 | | m6.6-eevdf-complete-ndd-dz-1 | little | not idle | 62.62 | | m6.6-eevdf-complete-ndd-dz-1 | little | idle 0 | 29.48 | | m6.6-eevdf-complete-ndd-dz-1 | little | idle 1 | 13.19 | | m6.6-eevdf-complete-ndd-dz-2 | little | not idle | 64.12 | | m6.6-eevdf-complete-ndd-dz-2 | little | idle 0 | 27.62 | | m6.6-eevdf-complete-ndd-dz-2 | little | idle 1 | 14.73 | | m6.6-eevdf-complete-ndd-dz-3 | little | not idle | 62.86 | | m6.6-eevdf-complete-ndd-dz-3 | little | idle 0 | 27.87 | | m6.6-eevdf-complete-ndd-dz-3 | little | idle 1 | 14.97 | | m6.6-eevdf-complete-ndd-dz-4 | little | not idle | 63.01 | | m6.6-eevdf-complete-ndd-dz-4 | little | idle 0 | 28.2 | | m6.6-eevdf-complete-ndd-dz-4 | little | idle 1 | 14.11 | | m6.6-eevdf-complete-ndd-dz-5 | little | not idle | 62.1 | | m6.6-eevdf-complete-ndd-dz-5 | little | idle 0 | 29.06 | | m6.6-eevdf-complete-ndd-dz-5 | little | idle 1 | 14.73 | | m6.6-eevdf-complete-dd-dz-1 | little | not idle | 46.18 | | m6.6-eevdf-complete-dd-dz-1 | little | idle 0 | 53.78 | | m6.6-eevdf-complete-dd-dz-1 | little | idle 1 | 3.75 | | m6.6-eevdf-complete-dd-dz-2 | little | not idle | 57.64 | | m6.6-eevdf-complete-dd-dz-2 | little | idle 0 | 40.47 | | m6.6-eevdf-complete-dd-dz-2 | little | idle 1 | 7.39 | | m6.6-eevdf-complete-dd-dz-3 | little | not idle | 43.14 | | m6.6-eevdf-complete-dd-dz-3 | little | idle 0 | 57.73 | | m6.6-eevdf-complete-dd-dz-3 | little | idle 1 | 3.65 | | m6.6-eevdf-complete-dd-dz-4 | little | not idle | 58.97 | | m6.6-eevdf-complete-dd-dz-4 | little | idle 0 | 36.4 | | m6.6-eevdf-complete-dd-dz-4 | little | idle 1 | 9.42 | | m6.6-eevdf-complete-dd-dz-5 | little | not idle | 55.85 | | m6.6-eevdf-complete-dd-dz-5 | little | idle 0 | 36.75 | | m6.6-eevdf-complete-dd-dz-5 | little | idle 1 | 13.14 | +-------------------------------+---------+------------+-------+ I can't draw a precise conclusion, but it might be down to delayed util_est updates or even the additional time the delayed-dequeue tasks spend on the runqueue. But delayed-dequeue does change the overall behavior a bit on these heterogeneous platforms, energy-wise.
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