Messages in this thread | | | Date | Tue, 24 Oct 2023 17:03:25 +0200 | Subject | Re: [RFC PATCH v2 1/2] sched/fair: Introduce UTIL_FITS_CAPACITY feature (v2) | From | Dietmar Eggemann <> |
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On 24/10/2023 08:10, Chen Yu wrote: > On 2023-10-23 at 11:04:49 -0400, Mathieu Desnoyers wrote: >> On 2023-10-23 10:11, Dietmar Eggemann wrote: >>> On 19/10/2023 18:05, Mathieu Desnoyers wrote:
[...]
>>> Or like find_energy_efficient_cpu() (feec(), used in >>> Energy-Aware-Scheduling (EAS)) which uses cpu_util(cpu, p, cpu, 0) to get: >>> >>> max(util_avg(CPU + p), util_est(CPU + p)) >> >> I've tried using cpu_util(), but unfortunately anything that considers >> blocked/sleeping tasks in its utilization total does not work for my >> use-case. >> >> From cpu_util(): >> >> * CPU utilization is the sum of running time of runnable tasks plus the >> * recent utilization of currently non-runnable tasks on that CPU. >> > > I thought cpu_util() indicates the utilization decay sum of task that was once > "running" on this CPU, but will not sum up the "util/load" of the blocked/sleeping > task?
cpu_util() here refers to:
cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost)
which when called with (cpu, p, cpu, 0) and task_cpu(p) != cpu returns:
max(util_avg(CPU + p), util_est(CPU + p))
The term `CPU utilization` in cpu_util()'s header stands for cfs_rq->avg.util_avg.
It does not sum up the utilization of blocked tasks but it can contain it. They have to be a blocked tasks and not tasks which were running in cfs_rq since we subtract utilization of tasks which are migrating away from the cfs_rq (cfs_rq->removed.util_avg in remove_entity_load_avg() and update_cfs_rq_load_avg()). > accumulate_sum() > /* only the running task's util will be sum up */ > if (running) > sa->util_sum += contrib << SCHED_CAPACITY_SHIFT; > > WRITE_ONCE(sa->util_avg, sa->util_sum / divider);
__update_load_avg_cfs_rq()
___update_load_sum(..., cfs_rq->curr != NULL ^^^^^^^^^^^^^^^^^^^^ running accumulate_sum()
if (periods) /* decay _sum */ sa->util_sum = decay_load(sa->util_sum, ...)
if (load) /* decay and accrue _sum */ contrib = __accumulate_pelt_segments(...)
When crossing periods we decay the old _sum and when additionally load != 0 we decay and accrue the new _sum as well.
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