sched/fair: Skip idle cfs_rq

Don't waste time checking whether an idle cfs_rq could be the busiest queue. Furthermore, this can end up selecting a cfs_rq with a high load but being idle in case of migrate_load. Signed-off-by: Vincent Guittot <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Valentin Schneider <[email protected]> Acked-by: Mel Gorman <[email protected]> Link: https://lkml.kernel.org/r/[email protected]
josf · Jan 14, 2021 · fc488ff · fc488ff
1 parent 8c1f560
commit fc488ff
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -9402,8 +9402,11 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		if (rt > env->fbq_type)
 			continue;
 
-		capacity = capacity_of(i);
 		nr_running = rq->cfs.h_nr_running;
+		if (!nr_running)
+			continue;
+
+		capacity = capacity_of(i);
 
 		/*
 		 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could