Commit 8589018a authored Dec 16, 2022 by Hao Jia Committed by Peter Zijlstra Dec 27, 2022

sched/core: Adjusting the order of scanning CPU



When select_idle_capacity() starts scanning for an idle CPU, it starts
with target CPU that has already been checked in select_idle_sibling().
So we start checking from the next CPU and try the target CPU at the end.
Similarly for task_numa_assign(), we have just checked numa_migrate_on
of dst_cpu, so start from the next CPU. This also works for
steal_cookie_task(), the first scan must fail and start directly
from the next one.

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20221216062406.7812-3-jiahao.os@bytedance.com

parent feaed763

kernel/sched/core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -6209,7 +6209,7 @@ static bool steal_cookie_task(int cpu, struct sched_domain *sd)
		{
		int i;

		for_each_cpu_wrap(i, sched_domain_span(sd), cpu) {
		for_each_cpu_wrap(i, sched_domain_span(sd), cpu + 1) {
		if (i == cpu)
		continue;

kernel/sched/fair.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1836,7 +1836,7 @@ static void task_numa_assign(struct task_numa_env *env,
		int start = env->dst_cpu;

		/* Find alternative idle CPU. */
		for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
		for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) {
		if (cpu == env->best_cpu \|\| !idle_cpu(cpu) \|\|
		!cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
		continue;
		@@ -6935,7 +6935,7 @@ select_idle_capacity(struct task_struct p, struct sched_domain sd, int target)
		util_min = uclamp_eff_value(p, UCLAMP_MIN);
		util_max = uclamp_eff_value(p, UCLAMP_MAX);

		for_each_cpu_wrap(cpu, cpus, target) {
		for_each_cpu_wrap(cpu, cpus, target + 1) {
		unsigned long cpu_cap = capacity_of(cpu);

		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))