linux-kernel - Re: [RFC PATCH 2/5] sched/events: Introduce cfs

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Date:   Tue, 28 Mar 2017 10:46:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@....com>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [RFC PATCH 2/5] sched/events: Introduce cfs_rq load tracking
 trace event

On Tue, 28 Mar 2017 07:35:38 +0100
Dietmar Eggemann <dietmar.eggemann@....com> wrote:

>  /* This part must be outside protection */
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 03adf9fb48b1..ac19ab6ced8f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2950,6 +2950,9 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
>  		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
>  	}
>  
> +	if (cfs_rq)
> +		trace_sched_load_cfs_rq(cfs_rq);
> +

Please use TRACE_EVENT_CONDITION(), and test for cfs_rq not NULL.

That way it moves the if (cfs_rq) out of the scheduler code and into
the jump label protected location. That is, the if is only tested when
tracing is enabled.

-- Steve


>  	return decayed;
>  }
>  
> @@ -3170,6 +3173,8 @@ static inline int propagate_entity_load_avg(struct sched_entity *se)
>  	update_tg_cfs_util(cfs_rq, se);
>  	update_tg_cfs_load(cfs_rq, se);
>  
> +	trace_sched_load_cfs_rq(cfs_rq);
> +
>  	return 1;
>  }
>  
> @@ -3359,6 +3364,8 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>  	set_tg_cfs_propagate(cfs_rq);
>  
>  	cfs_rq_util_change(cfs_rq);
> +
> +	trace_sched_load_cfs_rq(cfs_rq);
>  }
>  
>  /**
> @@ -3379,6 +3386,8 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>  	set_tg_cfs_propagate(cfs_rq);
>  
>  	cfs_rq_util_change(cfs_rq);
> +
> +	trace_sched_load_cfs_rq(cfs_rq);
>  }
>  
>  /* Add the load generated by se into cfs_rq's load average */