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Date: Tue, 11 Aug 2015 09:42:43 +0900
From: byungchul.park@....com
To: mingo@...nel.org, peterz@...radead.org
Cc: linux-kernel@...r.kernel.org,
Byungchul Park <byungchul.park@....com>
Subject: [PATCH v2] sched: sync with the prev cfs when changing cgroup within a cpu
From: Byungchul Park <byungchul.park@....com>
change from v1 to v2
* use #ifdef CONFIG_SMP to load tracking code
* make commit message compact which made confused
----->8-----
>From 02edcf69369bed72916304b449b82a74029ea908 Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul.park@....com>
Date: Tue, 11 Aug 2015 09:30:17 +0900
Subject: [PATCH v2] sched: sync with the prev cfs when changing cgroup within
a cpu
current code seems to be wrong with cfs_rq->blocked_load_avg when changing
a task's cgroup(=cfs_rq) to another. i tested with "echo pid > cgroup" and
found that cfs_rq->blocked_load_avg became larger and larger whenever i
changed a cgroup to another again and again.
it is possible to move between groups within *a* cpu, and each cfs_rq is
tracking its own blocked load. so we have to sync se's average load with
both *prev* cfs_rq and next cfs_rq when changing its group. i also removed
some comments mentioning migration_task_rq_fair().
Signed-off-by: Byungchul Park <byungchul.park@....com>
---
kernel/sched/fair.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ffa70dc..759a394 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8229,8 +8229,18 @@ static void task_move_group_fair(struct task_struct *p, int queued)
if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
queued = 1;
- if (!queued)
- se->vruntime -= cfs_rq_of(se)->min_vruntime;
+ if (!queued) {
+ cfs_rq = cfs_rq_of(se);
+ se->vruntime -= cfs_rq->min_vruntime;
+
+#ifdef CONFIG_SMP
+ /*
+ * we must synchronize with the prev cfs.
+ */
+ __synchronize_entity_decay(se);
+ subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
+#endif
+ }
set_task_rq(p, task_cpu(p));
se->depth = se->parent ? se->parent->depth + 1 : 0;
if (!queued) {
@@ -8238,9 +8248,7 @@ static void task_move_group_fair(struct task_struct *p, int queued)
se->vruntime += cfs_rq->min_vruntime;
#ifdef CONFIG_SMP
/*
- * migrate_task_rq_fair() will have removed our previous
- * contribution, but we must synchronize for ongoing future
- * decay.
+ * we must synchronize with the next cfs for ongoing future decay.
*/
se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
--
1.7.9.5
--
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