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Date:   Mon, 13 May 2019 14:08:30 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Qais Yousef <qais.yousef@arm.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org,
        Pavankumar Kondeti <pkondeti@codeaurora.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Uwe Kleine-Konig <u.kleine-koenig@pengutronix.de>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Quentin Perret <quentin.perret@arm.com>
Subject: Re: [PATCH v2 6/7] sched: Add sched_overutilized tracepoint
Message-ID: <20190513120830.GS2623@hirez.programming.kicks-ass.net>
References: <20190510113013.1193-1-qais.yousef@arm.com>
 <20190510113013.1193-7-qais.yousef@arm.com>
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On Fri, May 10, 2019 at 12:30:12PM +0100, Qais Yousef wrote:

> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index cbcb47972232..0cf42d13d6c4 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -600,6 +600,10 @@ DECLARE_TRACE(pelt_se,
>  	TP_PROTO(int cpu, const char *path, struct sched_entity *se),
>  	TP_ARGS(cpu, path, se));
>  
> +DECLARE_TRACE(sched_overutilized,
> +	TP_PROTO(int overutilized),
> +	TP_ARGS(overutilized));
> +
>  #endif /* _TRACE_SCHED_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 81036c34fd29..494032220fe7 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4965,8 +4965,10 @@ static inline bool cpu_overutilized(int cpu)
>  
>  static inline void update_overutilized_status(struct rq *rq)
>  {
> -	if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
> +	if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
>  		WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
> +		trace_sched_overutilized(1);
> +	}
>  }
>  #else
>  static inline void update_overutilized_status(struct rq *rq) { }
> @@ -8330,8 +8332,11 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
>  
>  		/* Update over-utilization (tipping point, U >= 0) indicator */
>  		WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
> +
> +		trace_sched_overutilized(!!(sg_status & SG_OVERUTILIZED));
>  	} else if (sg_status & SG_OVERUTILIZED) {
>  		WRITE_ONCE(env->dst_rq->rd->overutilized, SG_OVERUTILIZED);
> +		trace_sched_overutilized(1);
>  	}
>  }

Note how the state is per root domain and the tracepoint doesn't
communicate that.