Re: [PATCH v5 4/4] sched/fair: update util_est only on util_avg updates

[Peter Zijlstra]

On Thu, Feb 22, 2018 at 05:01:53PM +0000, Patrick Bellasi wrote:
> +#define UTIL_EST_NEED_UPDATE_FLAG 0x1

> @@ -5321,12 +5345,19 @@ static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
>  	if (!task_sleep)
>  		return;
>  
> +	/*
> +	 * Skip update of task's estimated utilization if the PELT signal has
> +	 * never been updated (at least once) since last enqueue time.
> +	 */
> +	ue = READ_ONCE(p->se.avg.util_est);
> +	if (ue.enqueued & UTIL_EST_NEED_UPDATE_FLAG)
> +		return;

The name and function seem inverted, if the flag is set, we do _NOT_
update util_est.

How about something like UTIL_EST_UNCHANGED ? That would give:

	/*
	 * If the PELT values haven't changed since enqueue time,
	 * skip the util_est update.
	 */
	if (enqueue & UTIL_EST_UNCHANGED)
		return;