linux-kernel - Re: [PATCH v2 3/3] sched/tp: Add new tracepoint to track compute energy computation

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Date:   Mon, 20 Feb 2023 11:22:45 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Qais Yousef <qyousef@...alina.io>
Cc:     linux-kernel@...r.kernel.org, Wei Wang <wvw@...gle.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Xuewen Yan <xuewen.yan94@...il.com>,
        Hank <han.lin@...iatek.com>,
        Jonathan JMChen <Jonathan.JMChen@...iatek.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v2 3/3] sched/tp: Add new tracepoint to track compute
 energy computation

Hi Qais,

On 2/5/23 22:43, Qais Yousef wrote:
> It was useful to track feec() placement decision and debug the spare
> capacity and optimization issues vs uclamp_max.
> 
> Signed-off-by: Qais Yousef <qyousef@...alina.io>
> ---
>   include/trace/events/sched.h | 4 ++++
>   kernel/sched/core.c          | 1 +
>   kernel/sched/fair.c          | 7 ++++++-
>   3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index fbb99a61f714..20cc884f72ff 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -735,6 +735,10 @@ DECLARE_TRACE(sched_update_nr_running_tp,
>   	TP_PROTO(struct rq *rq, int change),
>   	TP_ARGS(rq, change));
>   
> +DECLARE_TRACE(sched_compute_energy_tp,
> +	TP_PROTO(struct task_struct *p, int dst_cpu, unsigned long energy),
> +	TP_ARGS(p, dst_cpu, energy));
> +
>   #endif /* _TRACE_SCHED_H */
>   
>   /* This part must be outside protection */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 4580fe3e1d0c..5f6dde9b892b 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -110,6 +110,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
> +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
>   
>   DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
>   
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a8c3d92ff3f6..801e903c4307 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7295,11 +7295,16 @@ compute_energy(struct energy_env *eenv, struct perf_domain *pd,
>   {
>   	unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu);
>   	unsigned long busy_time = eenv->pd_busy_time;
> +	unsigned long energy;
>   
>   	if (dst_cpu >= 0)
>   		busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time);
>   
> -	return em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
> +	energy = em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
> +
> +	trace_sched_compute_energy_tp(p, dst_cpu, energy);

Could we also dump the max_util and busy_time?

> +
> +	return energy;
>   }
>   
>   /*


IMO this one is really helpful. I hope it won't be an issue if we can
have it in this code path.

Regards,
Lukasz