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Date: Mon, 17 Aug 2015 16:45:50 +0900
From: byungchul.park@....com
To: mingo@...nel.org, peterz@...radead.org
Cc: linux-kernel@...r.kernel.org, yuyang.du@...el.com,
Byungchul Park <byungchul.park@....com>
Subject: [PATCH v2 1/3] sched: sync a se with its cfs_rq when attaching and dettaching
From: Byungchul Park <byungchul.park@....com>
current code is wrong with cfs_rq's avg loads when changing a task's
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 avg loads
with both *prev* cfs_rq and next cfs_rq when changing its group.
not only for changing cgroup, but also for changing sched class, we
also need to sync a se with its cfs_rq, that is, when leaving from
fair class and returning back to fair class.
in addition, i introduced two functions for attaching/detaching a se
from/to its cfs_rq, and let them use those functions. and i place
that function call to where a se is attached/detached to/from cfs_rq.
Signed-off-by: Byungchul Park <byungchul.park@....com>
---
kernel/sched/fair.c | 82 ++++++++++++++++++++++++++++++---------------------
1 file changed, 48 insertions(+), 34 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4d5f97b..fc6b39c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2709,6 +2709,31 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
update_tg_load_avg(cfs_rq, 0);
}
+static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ se->avg.last_update_time = cfs_rq->avg.last_update_time;
+ cfs_rq->avg.load_avg += se->avg.load_avg;
+ cfs_rq->avg.load_sum += se->avg.load_sum;
+ cfs_rq->avg.util_avg += se->avg.util_avg;
+ cfs_rq->avg.util_sum += se->avg.util_sum;
+}
+
+static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ __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);
+
+ 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);
+}
+
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
@@ -2717,27 +2742,20 @@ enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
u64 now = cfs_rq_clock_task(cfs_rq);
int migrated = 0, decayed;
- if (sa->last_update_time == 0) {
- sa->last_update_time = now;
+ if (sa->last_update_time == 0)
migrated = 1;
- }
- else {
+ else
__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
- se->on_rq * scale_load_down(se->load.weight),
- cfs_rq->curr == se, NULL);
- }
+ se->on_rq * scale_load_down(se->load.weight),
+ cfs_rq->curr == se, NULL);
decayed = update_cfs_rq_load_avg(now, cfs_rq);
cfs_rq->runnable_load_avg += sa->load_avg;
cfs_rq->runnable_load_sum += sa->load_sum;
- if (migrated) {
- cfs_rq->avg.load_avg += sa->load_avg;
- cfs_rq->avg.load_sum += sa->load_sum;
- cfs_rq->avg.util_avg += sa->util_avg;
- cfs_rq->avg.util_sum += sa->util_sum;
- }
+ if (migrated)
+ attach_entity_load_avg(cfs_rq, se);
if (decayed || migrated)
update_tg_load_avg(cfs_rq, 0);
@@ -7911,17 +7929,7 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
#ifdef CONFIG_SMP
/* Catch up with the cfs_rq and remove our load when we leave */
- __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq), &se->avg,
- se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se, NULL);
-
- 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);
+ detach_entity_load_avg(cfs_rq, se);
#endif
}
@@ -7940,6 +7948,11 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
+#ifdef CONFIG_SMP
+ /* synchronize task with its cfs_rq */
+ attach_entity_load_avg(cfs_rq_of(&p->se), &p->se);
+#endif
+
if (!task_on_rq_queued(p)) {
/*
@@ -8032,23 +8045,24 @@ 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 */
+ detach_entity_load_avg(cfs_rq, se);
+#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 */
+ attach_entity_load_avg(cfs_rq, se);
#endif
- }
}
void free_fair_sched_group(struct task_group *tg)
--
1.7.9.5
--
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