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authorLukasz Luba <lukasz.luba@arm.com>2021-06-14 20:12:38 +0100
committerPeter Zijlstra <peterz@infradead.org>2021-06-17 14:11:43 +0200
commit8f1b971b4750e83e8fbd2f91a9efd4a38ad0ae51 (patch)
tree2f38807a61ee20b3ec4b46970f68f59d4d8b67c9 /arch/arm/boot/dts
parent489f16459e0008c7a5c4c5af34bd80898aa82c2d (diff)
downloadlinux-8f1b971b4750e83e8fbd2f91a9efd4a38ad0ae51.tar.bz2
sched/cpufreq: Consider reduced CPU capacity in energy calculation
Energy Aware Scheduling (EAS) needs to predict the decisions made by SchedUtil. The map_util_freq() exists to do that. There are corner cases where the max allowed frequency might be reduced (due to thermal). SchedUtil as a CPUFreq governor, is aware of that but EAS is not. This patch aims to address it. SchedUtil stores the maximum allowed frequency in 'sugov_policy::next_freq' field. EAS has to predict that value, which is the real used frequency. That value is made after a call to cpufreq_driver_resolve_freq() which clamps to the CPUFreq policy limits. In the existing code EAS is not able to predict that real frequency. This leads to energy estimation errors. To avoid wrong energy estimation in EAS (due to frequency miss prediction) make sure that the step which calculates Performance Domain frequency, is also aware of the allowed CPU capacity. Furthermore, modify map_util_freq() to not extend the frequency value. Instead, use map_util_perf() to extend the util value in both places: SchedUtil and EAS, but for EAS clamp it to max allowed CPU capacity. In the end, we achieve the same desirable behavior for both subsystems and alignment in regards to the real CPU frequency. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> (For the schedutil part) Link: https://lore.kernel.org/r/20210614191238.23224-1-lukasz.luba@arm.com
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