[PATCH 1/2] sched/numa: Stop an exhastive search if an idle core is found

From: Hao Jia
Date: Fri Oct 21 2022 - 02:16:29 EST


In update_numa_stats() we try to find an idle cpu on the NUMA node,
preferably an idle core. When we find an idle core,
we can stop searching.

Signed-off-by: Hao Jia <jiahao.os@xxxxxxxxxxxxx>
---
kernel/sched/fair.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e4a0b8bd941c..b7cbec539c77 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1792,7 +1792,7 @@ 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;
@@ -1801,6 +1801,9 @@ static void update_numa_stats(struct task_numa_env *env,
ns->idle_cpu = cpu;

idle_core = numa_idle_core(idle_core, cpu);
+ /* If we find an idle core, stop searching. */
+ if (idle_core >= 0)
+ ns->idle_cpu = idle_core;
}
}
rcu_read_unlock();
@@ -1808,9 +1811,6 @@ static void update_numa_stats(struct task_numa_env *env,
ns->weight = cpumask_weight(cpumask_of_node(nid));

ns->node_type = numa_classify(env->imbalance_pct, ns);
-
- if (idle_core >= 0)
- ns->idle_cpu = idle_core;
}

static void task_numa_assign(struct task_numa_env *env,
--
2.37.0