Messages in this thread |  | | Subject | Re: [PATCH AUTOSEL 5.12 62/80] sched/fair: Take thermal pressure into account while estimating energy | From | Lukasz Luba <> | Date | Mon, 5 Jul 2021 09:13:59 +0100 |
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Hi Sasha,
+CC Greg
On 7/5/21 12:05 AM, Sasha Levin wrote: > From: Lukasz Luba <lukasz.luba@arm.com> > > [ Upstream commit 489f16459e0008c7a5c4c5af34bd80898aa82c2d ] > > Energy Aware Scheduling (EAS) needs to be able to predict the frequency > requests made by the SchedUtil governor to properly estimate energy used > in the future. It has to take into account CPUs utilization and forecast > Performance Domain (PD) frequency. There is a corner case when the max > allowed frequency might be reduced due to thermal. SchedUtil is aware of > that reduced frequency, so it should be taken into account also in EAS > estimations. > > SchedUtil, as a CPUFreq governor, knows the maximum allowed frequency of > a CPU, thanks to cpufreq_driver_resolve_freq() and internal clamping > to 'policy::max'. SchedUtil is responsible to respect that upper limit > while setting the frequency through CPUFreq drivers. This effective > frequency is stored internally in 'sugov_policy::next_freq' and EAS has > to predict that value. > > In the existing code the raw value of arch_scale_cpu_capacity() is used > for clamping the returned CPU utilization from effective_cpu_util(). > This patch fixes issue with too big single CPU utilization, by introducing > clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU > capacity reduced by thermal pressure raw value. > > Thanks to knowledge about allowed CPU capacity, we don't get too big value > for a single CPU utilization, which is then added to the util sum. The > util sum is used as a source of information for estimating whole PD energy. > To avoid wrong energy estimation in EAS (due to capped frequency), make > sure that the calculation of util sum is aware of allowed CPU capacity. > > This thermal pressure might be visible in scenarios where the CPUs are not > heavily loaded, but some other component (like GPU) drastically reduced > available power budget and increased the SoC temperature. Thus, we still > use EAS for task placement and CPUs are not over-utilized. > > Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > Link: https://lore.kernel.org/r/20210614191128.22735-1-lukasz.luba@arm.com > Signed-off-by: Sasha Levin <sashal@kernel.org> > --- > kernel/sched/fair.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-)
It has been picked up automatically right? To make it fully working you need also this patch: https://lore.kernel.org/linux-pm/20210614191030.22241-1-lukasz.luba@arm.com/
It makes sure that the thermal pressure signal gets proper information also for CPUs which were offline and then wake-up. It has a proper fix tagging with commit hash id. That patch can be ported to stable: v5.6+ I can send it to stable list. Please let me know if you need any help.
The same applies to patch which I found for v5.13-stable: [PATCH AUTOSEL 5.13 65/85] sched/fair: Take thermal pressure into account while estimating energy https://lore.kernel.org/stable/20210704230420.1488358-65-sashal@kernel.org/T/#u
Regards, Lukasz
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