linux-kernel - Re: [Patch v5 1/6] sched/pelt.c: Add support to track thermal pressure

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Message-ID: <20191107163942.74bfnsabh4dyvlo5@e107158-lin.cambridge.arm.com>
Date:   Thu, 7 Nov 2019 16:39:44 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, ionela.voinescu@....com,
        vincent.guittot@...aro.org, rui.zhang@...el.com,
        edubezval@...il.com, qperret@...gle.com,
        linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, daniel.lezcano@...aro.org
Subject: Re: [Patch v5 1/6] sched/pelt.c: Add support to track thermal
 pressure

Hi Thara

On 11/05/19 13:49, Thara Gopinath 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@...aro.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;
> +}

Care to add a tracepoint to this new signal like we now have for the other
ones?

Thanks

--
Qais Yousef

> +
>  #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
>