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authorDawei Li <daweilics@gmail.com>2024-03-15 04:59:16 +0300
committerIngo Molnar <mingo@kernel.org>2024-05-17 10:49:44 +0300
commit72bffbf57c5247ac6146d1103ef42e9f8d094bc8 (patch)
tree2eaf427114098793768a7a252c9a49690e76799f
parent0f1c74befa656305ecc85c954dc31f84c1cc26e1 (diff)
downloadlinux-72bffbf57c5247ac6146d1103ef42e9f8d094bc8.tar.xz
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 <daweilics@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Vishal Chourasia <vishalc@linux.ibm.com> Link: https://lore.kernel.org/r/20240315015916.21545-1-daweilics@gmail.com
-rw-r--r--kernel/sched/fair.c5
1 files 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)