From be15f3edcc4074aec8aea493ba0749599c6c3791 Mon Sep 17 00:00:00 2001
From: Hao Jia <jiahao.os@bytedance.com>
Date: Fri, 16 Dec 2022 14:24:05 +0800
Subject: [PATCH] sched/numa: Stop an exhastive search if an idle core is found

References: bsc#1189999 (Scheduler functional and performance backports)
Patch-mainline: v6.3-rc1
Git-commit: feaed76376fd612b9450ad1251aec20a63ccfe92

In update_numa_stats() we try to find an idle cpu on the NUMA node,
preferably an idle core. we can stop looking for the next idle core
or idle cpu after finding an idle core. But we can't stop the
whole loop of scanning the CPU, because we need to calculate
approximate NUMA stats at a point in time. For example,
the src and dst nr_running is needed by task_numa_find_cpu().

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20221216062406.7812-2-jiahao.os@bytedance.com
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 96aa86b1aaa6..f7229595793b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1665,7 +1665,7 @@ static void update_numa_stats(struct task_numa_env *env,
 		ns->nr_running += rq->cfs.h_nr_running;
 		ns->compute_capacity += capacity_of(cpu);
 
-		if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
+		if (find_idle && idle_core < 0 && !rq->nr_running && idle_cpu(cpu)) {
 			if (READ_ONCE(rq->numa_migrate_on) ||
 			    !cpumask_test_cpu(cpu, env->p->cpus_ptr))
 				continue;