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SubjectRe: [RFC PATCH 0/7] Introduce thermal pressure
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Hi Thara,

I have run it on Exynos5433 mainline.
When it is enabled with step_wise thermal governor,
some of my tests are showing ~30-50% regression (i.e. hackbench),
dhrystone ~10%.

Could you tell me which thermal governor was used in your case?
Please also share the name of that benchmark, i will give it a try.
Is it single threaded compute-intensive?

Regards,
Lukasz

On 10/09/2018 06:24 PM, Thara Gopinath wrote:
> Thermal governors can respond to an overheat event for a cpu by
> capping the cpu's maximum possible frequency. This in turn
> means that the maximum available compute capacity of the
> cpu is restricted. But today in linux kernel, in event of maximum
> frequency capping of a cpu, the maximum available compute
> capacity of the cpu is not adjusted at all. In other words, scheduler
> is unware maximum cpu capacity restrictions placed due to thermal
> activity. This patch series attempts to address this issue.
> The benefits identified are better task placement among available
> cpus in event of overheating which in turn leads to better
> performance numbers.
>
> The delta between the maximum possible capacity of a cpu and
> maximum available capacity of a cpu due to thermal event can
> be considered as thermal pressure. Instantaneous thermal pressure
> is hard to record and can sometime be erroneous as there can be mismatch
> between the actual capping of capacity and scheduler recording it.
> Thus solution is to have a weighted average per cpu value for thermal
> pressure over time. The weight reflects the amount of time the cpu has
> spent at a capped maximum frequency. To accumulate, average and
> appropriately decay thermal pressure, this patch series uses pelt
> signals and reuses the available framework that does a similar
> bookkeeping of rt/dl task utilization.
>
> Regarding testing, basic build, boot and sanity testing have been
> performed on hikey960 mainline kernel with debian file system.
> Further aobench (An occlusion renderer for benchmarking realworld
> floating point performance) showed the following results on hikey960
> with debain.
>
> Result Standard Standard
> (Time secs) Error Deviation
> Hikey 960 - no thermal pressure applied 138.67 6.52 11.52%
> Hikey 960 - thermal pressure applied 122.37 5.78 11.57%
>
> Thara Gopinath (7):
> sched/pelt: Add option to make load and util calculations frequency
> invariant
> sched/pelt.c: Add support to track thermal pressure
> sched: Add infrastructure to store and update instantaneous thermal
> pressure
> sched: Initialize per cpu thermal pressure structure
> sched/fair: Enable CFS periodic tick to update thermal pressure
> sched/fair: update cpu_capcity to reflect thermal pressure
> thermal/cpu-cooling: Update thermal pressure in case of a maximum
> frequency capping
>
> drivers/base/arch_topology.c | 1 +
> drivers/thermal/cpu_cooling.c | 20 ++++++++++++-
> include/linux/sched.h | 14 +++++++++
> kernel/sched/Makefile | 2 +-
> kernel/sched/core.c | 2 ++
> kernel/sched/fair.c | 4 +++
> kernel/sched/pelt.c | 40 ++++++++++++++++++--------
> kernel/sched/pelt.h | 7 +++++
> kernel/sched/sched.h | 1 +
> kernel/sched/thermal.c | 66 +++++++++++++++++++++++++++++++++++++++++++
> kernel/sched/thermal.h | 13 +++++++++
> 11 files changed, 157 insertions(+), 13 deletions(-)
> create mode 100644 kernel/sched/thermal.c
> create mode 100644 kernel/sched/thermal.h
>

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