From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v5 09/14] sched: Add over-utilization/tipping point
 indicator
Date: Thu, 2 Aug 2018 14:26:29 +0200
Message-ID: <20180802122629.GU2476@hirez.programming.kicks-ass.net>
References: <20180724122521.22109-1-quentin.perret@arm.com>
 <20180724122521.22109-10-quentin.perret@arm.com>
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To: Quentin Perret <quentin.perret@arm.com>
Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org
List-Id: linux-pm@vger.kernel.org

On Tue, Jul 24, 2018 at 01:25:16PM +0100, Quentin Perret wrote:
> @@ -5100,8 +5118,17 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  		update_cfs_group(se);
>  	}
>  
> -	if (!se)
> +	if (!se) {
>  		add_nr_running(rq, 1);
> +		/*
> +		 * The utilization of a new task is 'wrong' so wait for it
> +		 * to build some utilization history before trying to detect
> +		 * the overutilized flag.
> +		 */
> +		if (flags & ENQUEUE_WAKEUP)
> +			update_overutilized_status(rq);
> +
> +	}
>  
>  	hrtick_update(rq);
>  }

That is a somewhat dodgy hack. There is no guarantee what so ever that
when the task wakes next its history is any better. The comment doesn't
reflect this I feel.