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SubjectRe: [RFC PATCH v3 07/10] sched/fair: Introduce an energy estimation helper function
On Mon, May 21, 2018 at 03:25:02PM +0100, Quentin Perret wrote:

<snip>

>
> +/*
> + * Returns the util of "cpu" if "p" wakes up on "dst_cpu".
> + */
> +static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
> +{
> + unsigned long util, util_est;
> + struct cfs_rq *cfs_rq;
> +
> + /* Task is where it should be, or has no impact on cpu */
> + if ((task_cpu(p) == dst_cpu) || (cpu != task_cpu(p) && cpu != dst_cpu))
> + return cpu_util(cpu);
> +
> + cfs_rq = &cpu_rq(cpu)->cfs;
> + util = READ_ONCE(cfs_rq->avg.util_avg);
> +
> + if (dst_cpu == cpu)
> + util += task_util(p);
> + else
> + util = max_t(long, util - task_util(p), 0);
> +
> + if (sched_feat(UTIL_EST)) {
> + util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
> + if (dst_cpu == cpu)
> + util_est += _task_util_est(p);
> + else
> + util_est = max_t(long, util_est - _task_util_est(p), 0);

For UTIL_EST case, the waking task will not have any contribution in the
previous CPU's util_est. So we can just use the previous CPU util_est as is.

> + util = max(util, util_est);
> + }
> +
> + return min_t(unsigned long, util, capacity_orig_of(cpu));
> +}
> +

--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

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