[tip: sched/core] sched/fair: Do not compute NUMA Balancing stats unnecessarily during lb

[tip-bot2 for K Prateek Nayak]

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

Commit-ID:     0ac1ee9ebfb7fa2af4a267fe0e8fa275ba8ec6fc
Gitweb:        https://git.kernel.org/tip/0ac1ee9ebfb7fa2af4a267fe0e8fa275ba8ec6fc
Author:        K Prateek Nayak <kprateek.nayak@xxxxxxx>
AuthorDate:    Mon, 23 Dec 2024 04:34:05 
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 13 Jan 2025 14:10:25 +01:00

sched/fair: Do not compute NUMA Balancing stats unnecessarily during lb

Aggregate nr_numa_running and nr_preferred_running when load balancing
at NUMA domains only. While at it, also move the aggregation below the
idle_cpu() check since an idle CPU cannot have any preferred tasks.

Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241223043407.1611-7-kprateek.nayak@xxxxxxx
---
 kernel/sched/fair.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 52f7278..650d698 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10409,7 +10409,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 				      bool *sg_overloaded,
 				      bool *sg_overutilized)
 {
-	int i, nr_running, local_group;
+	int i, nr_running, local_group, sd_flags = env->sd->flags;
 
 	memset(sgs, 0, sizeof(*sgs));
 
@@ -10433,10 +10433,6 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 		if (cpu_overutilized(i))
 			*sg_overutilized = 1;
 
-#ifdef CONFIG_NUMA_BALANCING
-		sgs->nr_numa_running += rq->nr_numa_running;
-		sgs->nr_preferred_running += rq->nr_preferred_running;
-#endif
 		/*
 		 * No need to call idle_cpu() if nr_running is not 0
 		 */
@@ -10446,10 +10442,17 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 			continue;
 		}
 
+#ifdef CONFIG_NUMA_BALANCING
+		/* Only fbq_classify_group() uses this to classify NUMA groups */
+		if (sd_flags & SD_NUMA) {
+			sgs->nr_numa_running += rq->nr_numa_running;
+			sgs->nr_preferred_running += rq->nr_preferred_running;
+		}
+#endif
 		if (local_group)
 			continue;
 
-		if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
+		if (sd_flags & SD_ASYM_CPUCAPACITY) {
 			/* Check for a misfit task on the cpu */
 			if (sgs->group_misfit_task_load < rq->misfit_task_load) {
 				sgs->group_misfit_task_load = rq->misfit_task_load;