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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Wed, 6 Nov 2019 09:24:34 +0100
Message-ID: <CAKfTPtBgp5sb46qD3Uygk-9E1EDMibJkDiA-o3R_6iqYXEdBmg@mail.gmail.com>
Subject: Re: [Patch v5 1/6] sched/pelt.c: Add support to track thermal pressure
To:     Thara Gopinath <thara.gopinath@linaro.org>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ionela Voinescu <ionela.voinescu@arm.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Quentin Perret <qperret@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Amit Kachhap <amit.kachhap@gmail.com>,
        Javi Merino <javi.merino@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>
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On Tue, 5 Nov 2019 at 19:49, Thara Gopinath <thara.gopinath@linaro.org> wrote:
>
> Extrapolating on the exisiting framework to track rt/dl utilization using
> pelt signals, add a similar mechanism to track thermal pressure. The
> difference here from rt/dl utilization tracking is that, instead of
> tracking time spent by a cpu running a rt/dl task through util_avg,
> the average thermal pressure is tracked through load_avg. This is
> because thermal pressure signal is weighted "delta" capacity
> and is not binary(util_avg is binary). "delta capacity" here
> means delta between the actual capacity of a cpu and the decreased
> capacity a cpu due to a thermal event.
> In order to track average thermal pressure, a new sched_avg variable
> avg_thermal is introduced. Function update_thermal_load_avg can be called
> to do the periodic bookeeping (accumulate, decay and average)
> of the thermal pressure.
>
> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
>  kernel/sched/pelt.c  | 13 +++++++++++++
>  kernel/sched/pelt.h  |  7 +++++++
>  kernel/sched/sched.h |  1 +
>  3 files changed, 21 insertions(+)
>
> diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
> index a96db50..3821069 100644
> --- a/kernel/sched/pelt.c
> +++ b/kernel/sched/pelt.c
> @@ -353,6 +353,19 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
>         return 0;
>  }
>
> +int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
> +{
> +       if (___update_load_sum(now, &rq->avg_thermal,
> +                              capacity,
> +                              capacity,
> +                              capacity)) {
> +               ___update_load_avg(&rq->avg_thermal, 1, 1);
> +               return 1;
> +       }
> +
> +       return 0;
> +}
> +
>  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>  /*
>   * irq:
> diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
> index afff644..c74226d 100644
> --- a/kernel/sched/pelt.h
> +++ b/kernel/sched/pelt.h
> @@ -6,6 +6,7 @@ int __update_load_avg_se(u64 now, struct cfs_rq *cfs_rq, struct sched_entity *se
>  int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq);
>  int update_rt_rq_load_avg(u64 now, struct rq *rq, int running);
>  int update_dl_rq_load_avg(u64 now, struct rq *rq, int running);
> +int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity);
>
>  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>  int update_irq_load_avg(struct rq *rq, u64 running);
> @@ -159,6 +160,12 @@ update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
>  }
>
>  static inline int
> +update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
> +{
> +       return 0;
> +}
> +
> +static inline int
>  update_irq_load_avg(struct rq *rq, u64 running)
>  {
>         return 0;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 0db2c1b..d5d82c8 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -944,6 +944,7 @@ struct rq {
>  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>         struct sched_avg        avg_irq;
>  #endif
> +       struct sched_avg        avg_thermal;
>         u64                     idle_stamp;
>         u64                     avg_idle;
>
> --
> 2.1.4
>