Re: [PATCH v5 1/4] sched/fair: add util_est on top of PELT

From: Peter Zijlstra
Date: Tue Mar 06 2018 - 13:56:38 EST


On Thu, Feb 22, 2018 at 05:01:50PM +0000, Patrick Bellasi wrote:
> +/**
> + * Estimation Utilization for FAIR tasks.
> + *
> + * Support data structure to track an Exponential Weighted Moving Average
> + * (EWMA) of a FAIR task's utilization. New samples are added to the moving
> + * average each time a task completes an activation. Sample's weight is
> + * chosen so that the EWMA will be relatively insensitive to transient changes
> + * to the task's workload.
> + *
> + * @enqueued: instantaneous estimated utilization of a task/cpu
> + * task: the task's util_avg at last task dequeue time
> + * cfs_rq: the sum of util_est.enqueued for each RUNNABLE task on that CPU
> + *
> + * Thus, the util_est.enqueued of a task represents the contribution on the
> + * estimated utilization of the CPU where that task is currently enqueued.
> + *
> + * @ewma: the Exponential Weighted Moving Average (EWMA) utilization of a task
> + * Only for tasks we track a moving average of the past instantaneous
> + * estimated utilization. This allows to absorb sporadic drops in
> + * utilization of an otherwise almost periodic task.
> + *
> + */

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