sched/fair: Use utilization to select misfit task

Utilization is used to detect a misfit task but the load is then used to
select the task on the CPU which can lead to select a small task with
high weight instead of the task that triggered the misfit migration.

Check that task can't fit the CPU's capacity when selecting the misfit
task instead of using the load.

Signed-off-by: Vincent Guittot <[email protected]>
Acked-by: Valentin Schneider <[email protected]>
Cc: Ben Segall <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: [email protected]
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 3 insertions, 8 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f489f603f317..1fd6f3917fe7 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7408,13 +7408,8 @@ static int detach_tasks(struct lb_env *env)
 			break;
 
 		case migrate_misfit:
-			load = task_h_load(p);
-
-			/*
-			 * Load of misfit task might decrease a bit since it has
-			 * been recorded. Be conservative in the condition.
-			 */
-			if (load/2 < env->imbalance)
+			/* This is not a misfit task */
+			if (task_fits_capacity(p, capacity_of(env->src_cpu)))
 				goto next;
 
 			env->imbalance = 0;
@@ -8358,7 +8353,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 	if (busiest->group_type == group_misfit_task) {
 		/* Set imbalance to allow misfit tasks to be balanced. */
 		env->migration_type = migrate_misfit;
-		env->imbalance = busiest->group_misfit_task_load;
+		env->imbalance = 1;
 		return;
 	}