[PATCH 4/6] sched/fair: Skip prefer sibling move between SMT group and non-SMT group

[Tim Chen]

From: Tim C Chen <tim.c.chen@xxxxxxxxxxxxxxx>

Do not try to move tasks between non SMT sched group and SMT sched
group for "prefer sibling" load balance.
Let asym_active_balance_busiest() handle that case properly.
Otherwise we could get task bouncing back and forth between
the SMT sched group and non SMT sched group.

Reviewed-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a325db34b02..58ef7d529731 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10411,8 +10411,12 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	/*
 	 * Try to move all excess tasks to a sibling domain of the busiest
 	 * group's child domain.
+	 *
+	 * Do not try to move between non smt sched group and smt sched
+	 * group. Let asym active balance properly handle that case.
 	 */
 	if (sds.prefer_sibling && local->group_type == group_has_spare &&
+	    !asymmetric_groups(sds.busiest, sds.local) &&
 	    busiest->sum_nr_running > local->sum_nr_running + 1)
 		goto force_balance;
 
-- 
2.32.0