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Subject[PATCH v3 3/3] sched/fair: Kill wake_cap()
Date
From: Morten Rasmussen <morten.rasmussen@arm.com>

Capacity-awareness in the wake-up path previously involved disabling
wake_affine in certain scenarios. We have just made select_idle_sibling()
capacity-aware, so this isn't needed anymore.

Remove wake_cap() entirely.

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
[Changelog tweaks]
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/fair.c | 30 +-----------------------------
1 file changed, 1 insertion(+), 29 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index aebc2e0e6c8a1..0df85c32d69cd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6146,33 +6146,6 @@ static unsigned long cpu_util_without(int cpu, struct task_struct *p)
return min_t(unsigned long, util, capacity_orig_of(cpu));
}

-/*
- * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
- * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
- *
- * In that case WAKE_AFFINE doesn't make sense and we'll let
- * BALANCE_WAKE sort things out.
- */
-static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
-{
- long min_cap, max_cap;
-
- if (!static_branch_unlikely(&sched_asym_cpucapacity))
- return 0;
-
- min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
- max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;
-
- /* Minimum capacity is close to max, no need to abort wake_affine */
- if (max_cap - min_cap < max_cap >> 3)
- return 0;
-
- /* Bring task utilization in sync with prev_cpu */
- sync_entity_load_avg(&p->se);
-
- return !task_fits_capacity(p, min_cap);
-}
-
/*
* Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
* to @dst_cpu.
@@ -6437,8 +6410,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
new_cpu = prev_cpu;
}

- want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) &&
- cpumask_test_cpu(cpu, p->cpus_ptr);
+ want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
}

rcu_read_lock();
--
2.24.0
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