sched/fair: Fix imbalance overflow

When local group is fully busy but its average load is above system load, computing the imbalance will overflow and local group is not the best target for pulling this load. Fixes: 0b0695f ("sched/fair: Rework load_balance()") Reported-by: Tingjia Cao <[email protected]> Signed-off-by: Vincent Guittot <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Tested-by: Tingjia Cao <[email protected]> Link: https://lore.kernel.org/lkml/CABcWv9_DAhVBOq2=W=2ypKE9dKM5s2DvoV8-U0+GDwwuKZ89jQ@mail.gmail.com/T/
niw · Apr 12, 2023 · 91dcf1e · 91dcf1e
1 parent 09a9639
commit 91dcf1e
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -10238,6 +10238,16 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 
 		sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
 				sds->total_capacity;
+
+		/*
+		 * If the local group is more loaded than the average system
+		 * load, don't try to pull any tasks.
+		 */
+		if (local->avg_load >= sds->avg_load) {
+			env->imbalance = 0;
+			return;
+		}
+
 	}
 
 	/*