From 72bffbf57c5247ac6146d1103ef42e9f8d094bc8 Mon Sep 17 00:00:00 2001 From: Dawei Li Date: Thu, 14 Mar 2024 18:59:16 -0700 Subject: sched/fair: Fix initial util_avg calculation Change se->load.weight to se_weight(se) in the calculation for the initial util_avg to avoid unnecessarily inflating the util_avg by 1024 times. The reason is that se->load.weight has the unit/scale as the scaled-up load, while cfs_rg->avg.load_avg has the unit/scale as the true task weight (as mapped directly from the task's nice/priority value). With CONFIG_32BIT, the scaled-up load is equal to the true task weight. With CONFIG_64BIT, the scaled-up load is 1024 times the true task weight. Thus, the current code may inflate the util_avg by 1024 times. The follow-up capping will not allow the util_avg value to go wild. But the calculation should have the correct logic. Signed-off-by: Dawei Li Signed-off-by: Ingo Molnar Reviewed-by: Vincent Guittot Reviewed-by: Vishal Chourasia Link: https://lore.kernel.org/r/20240315015916.21545-1-daweilics@gmail.com --- kernel/sched/fair.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 146ecf9cc3af..900978741a81 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1031,7 +1031,8 @@ void init_entity_runnable_average(struct sched_entity *se) * With new tasks being created, their initial util_avgs are extrapolated * based on the cfs_rq's current util_avg: * - * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight + * util_avg = cfs_rq->avg.util_avg / (cfs_rq->avg.load_avg + 1) + * * se_weight(se) * * However, in many cases, the above util_avg does not give a desired * value. Moreover, the sum of the util_avgs may be divergent, such @@ -1078,7 +1079,7 @@ void post_init_entity_util_avg(struct task_struct *p) if (cap > 0) { if (cfs_rq->avg.util_avg != 0) { - sa->util_avg = cfs_rq->avg.util_avg * se->load.weight; + sa->util_avg = cfs_rq->avg.util_avg * se_weight(se); sa->util_avg /= (cfs_rq->avg.load_avg + 1); if (sa->util_avg > cap) -- cgit v1.2.3