linux-kernel - Re: [RFC PATCH v3 06/10] sched: Add over-utilization/tipping point indicator

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Message-ID: <20180619070103.GB9208@codeaurora.org>
Date:   Tue, 19 Jun 2018 12:31:03 +0530
From:   Pavan Kondeti <pkondeti@...eaurora.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     peterz@...radead.org, rjw@...ysocki.net,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, mingo@...hat.com,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        chris.redpath@....com, patrick.bellasi@....com,
        valentin.schneider@....com, vincent.guittot@...aro.org,
        thara.gopinath@...aro.org, viresh.kumar@...aro.org,
        tkjos@...gle.com, joelaf@...gle.com, smuckle@...gle.com,
        adharmap@...cinc.com, skannan@...cinc.com, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [RFC PATCH v3 06/10] sched: Add over-utilization/tipping point
 indicator

On Mon, May 21, 2018 at 03:25:01PM +0100, Quentin Perret wrote:

<snip>

>  	util_est_enqueue(&rq->cfs, p);
>  	hrtick_update(rq);
> @@ -8121,11 +8144,12 @@ static bool update_nohz_stats(struct rq *rq, bool force)
>   * @local_group: Does group contain this_cpu.
>   * @sgs: variable to hold the statistics for this group.
>   * @overload: Indicate more than one runnable task for any CPU.
> + * @overutilized: Indicate overutilization for any CPU.
>   */
>  static inline void update_sg_lb_stats(struct lb_env *env,
>  			struct sched_group *group, int load_idx,
>  			int local_group, struct sg_lb_stats *sgs,
> -			bool *overload)
> +			bool *overload, int *overutilized)
>  {
>  	unsigned long load;
>  	int i, nr_running;
> @@ -8152,6 +8176,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>  		if (nr_running > 1)
>  			*overload = true;
>  
> +		if (cpu_overutilized(i))
> +			*overutilized = 1;
> +

There is no need to check if every CPU is overutilized or not once
*overutilized is marked as true, right? 

<snip>

>  
> @@ -8586,6 +8621,10 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
>  	 * this level.
>  	 */
>  	update_sd_lb_stats(env, &sds);
> +
> +	if (sched_energy_enabled() && !READ_ONCE(env->dst_rq->rd->overutilized))
> +		goto out_balanced;
> +

Is there any reason for sending no-hz idle kicks but bailing out here when
system is not overutilized?

-- 
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