[PATCH 1/2] sched/fair: completely remove update_cfs_group() in dequeue path

[Aaron Lu]

---
 kernel/sched/fair.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2adb6a6abbce..a21ab72819ce 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6434,7 +6434,6 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 
 		update_load_avg(cfs_rq, se, UPDATE_TG);
 		se_update_runnable(se);
-		update_cfs_group(se);
 
 		cfs_rq->h_nr_running--;
 		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
-- 
2.40.1

Than P95 latency of the schbench workload I described in patch4's
changelog will increase to > 1ms(base and patch4's P95 < 100us):

Latency percentiles (usec) runtime 300 (s) (18504 total samples)
        50.0th: 20 (9537 samples)
        75.0th: 25 (4869 samples)
        90.0th: 29 (2264 samples)
        95.0th: 2564 (909 samples)
        *99.0th: 20768 (740 samples)
        99.5th: 23520 (93 samples)
        99.9th: 31520 (74 samples)
        min=6, max=40072

If I further remove update_cfs_group() completely in enqueue path on top
of the last change: