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SubjectRe: [PATCH AUTOSEL 5.12 62/80] sched/fair: Take thermal pressure into account while estimating energy
On Mon, Jul 05, 2021 at 09:13:59AM +0100, Lukasz Luba wrote:
>Hi Sasha,
>+CC Greg
>On 7/5/21 12:05 AM, Sasha Levin wrote:
>>From: Lukasz Luba <>
>>[ 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
>>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 <>
>>Signed-off-by: Peter Zijlstra (Intel) <>
>>Reviewed-by: Vincent Guittot <>
>>Reviewed-by: Dietmar Eggemann <>
>>Signed-off-by: Sasha Levin <>
>> 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:
>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

I took that patch for 5.13-5.10, thanks!


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