[tip: sched/core] sched/core: Adjusting the order of scanning CPU

[tip-bot2 for Hao Jia]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     8589018acc65e5ddfd111f0a7ee85f9afde3a830
Gitweb:        https://git.kernel.org/tip/8589018acc65e5ddfd111f0a7ee85f9afde3a830
Author:        Hao Jia <jiahao.os@xxxxxxxxxxxxx>
AuthorDate:    Fri, 16 Dec 2022 14:24:06 +08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 27 Dec 2022 12:52:17 +01:00

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@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221216062406.7812-3-jiahao.os@xxxxxxxxxxxxx
---
 kernel/sched/core.c | 2 +-
 kernel/sched/fair.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1f3259c..048ec24 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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;
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index aaff209..e9d906a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -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))