[PATCH v4] sched: sync with the prev cfs when changing cgroup within a cpu

[byungchul . park]

From: Byungchul Park <byungchul.p...@lge.com>

change from v3 to v4
* adjust cfs load in "queued" case, too

change from v2 to v3
* rebase to tip git

change from v1 to v2
* use #ifdef CONFIG_SMP to load tracking code
* make commit message compact which made confused

----->8-----
>From 1d5bcc21cece51eca250986846ed9b01a174bd54 Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul.p...@lge.com>
Date: Thu, 13 Aug 2015 09:18:07 +0900
Subject: [PATCH v4] sched: sync with the prev cfs when changing cgroup within
 a cpu

current code seems to be wrong with cfs_rq's avg loads when changing
a task's cgroup(=cfs_rq) to another. i tested with "echo pid > cgroup" and
found that e.g. cfs_rq->avg.load_avg became larger and larger whenever i
changed a cgroup to another again and again.

we have to sync se's average load with both *prev* cfs_rq and next cfs_rq
when changing its group.

Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
---
 kernel/sched/fair.c |   34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2a33d7b..979ca2c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8017,23 +8017,37 @@ static void task_move_group_fair(struct task_struct *p, 
int queued)
        if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
                queued = 1;
 
+       cfs_rq = cfs_rq_of(se);
        if (!queued)
-               se->vruntime -= cfs_rq_of(se)->min_vruntime;
+               se->vruntime -= cfs_rq->min_vruntime;
+
+#ifdef CONFIG_SMP
+       /* synchronize task with its prev cfs_rq */
+       if (!queued)
+               __update_load_avg(cfs_rq->avg.last_update_time, 
cpu_of(rq_of(cfs_rq)),
+                               &se->avg, se->on_rq * 
scale_load_down(se->load.weight),
+                               cfs_rq->curr == se, NULL);
+
+       /* remove our load when we leave */
+       cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - 
se->avg.load_avg, 0);
+       cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - 
se->avg.load_sum, 0);
+       cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - 
se->avg.util_avg, 0);
+       cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - 
se->avg.util_sum, 0);
+#endif
        set_task_rq(p, task_cpu(p));
        se->depth = se->parent ? se->parent->depth + 1 : 0;
-       if (!queued) {
-               cfs_rq = cfs_rq_of(se);
+       cfs_rq = cfs_rq_of(se);
+       if (!queued)
                se->vruntime += cfs_rq->min_vruntime;
 
 #ifdef CONFIG_SMP
-               /* Virtually synchronize task with its new cfs_rq */
-               p->se.avg.last_update_time = cfs_rq->avg.last_update_time;
-               cfs_rq->avg.load_avg += p->se.avg.load_avg;
-               cfs_rq->avg.load_sum += p->se.avg.load_sum;
-               cfs_rq->avg.util_avg += p->se.avg.util_avg;
-               cfs_rq->avg.util_sum += p->se.avg.util_sum;
+       /* Virtually synchronize task with its new cfs_rq */
+       p->se.avg.last_update_time = cfs_rq->avg.last_update_time;
+       cfs_rq->avg.load_avg += p->se.avg.load_avg;
+       cfs_rq->avg.load_sum += p->se.avg.load_sum;
+       cfs_rq->avg.util_avg += p->se.avg.util_avg;
+       cfs_rq->avg.util_sum += p->se.avg.util_sum;
 #endif
-       }
 }
 
 void free_fair_sched_group(struct task_group *tg)
-- 
1.7.9.5

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