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authorVincent Guittot <vincent.guittot@linaro.org>2019-02-06 17:14:21 +0100
committerIngo Molnar <mingo@kernel.org>2019-02-11 08:02:12 +0100
commit31bc6aeaab1d1de8959b67edbed5c7a4b3cdbe7c (patch)
tree9c08168669f6c166c773fb4a776ab1616832a220
parentc9ba7560c550fe6c1f4a8f0666bea41d2a349d1d (diff)
sched/fair: Optimize update_blocked_averages()
Removing a cfs_rq from rq->leaf_cfs_rq_list can break the parent/child ordering of the list when it will be added back. In order to remove an empty and fully decayed cfs_rq, we must remove its children too, so they will be added back in the right order next time. With a normal decay of PELT, a parent will be empty and fully decayed if all children are empty and fully decayed too. In such a case, we just have to ensure that the whole branch will be added when a new task is enqueued. This is default behavior since : commit f6783319737f ("sched/fair: Fix insertion in rq->leaf_cfs_rq_list") In case of throttling, the PELT of throttled cfs_rq will not be updated whereas the parent will. This breaks the assumption made above unless we remove the children of a cfs_rq that is throttled. Then, they will be added back when unthrottled and a sched_entity will be enqueued. As throttled cfs_rq are now removed from the list, we can remove the associated test in update_blocked_averages(). Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: sargun@sargun.me Cc: tj@kernel.org Cc: xiexiuqi@huawei.com Cc: xiezhipeng1@huawei.com Link: https://lkml.kernel.org/r/1549469662-13614-2-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/fair.c26
1 files changed, 21 insertions, 5 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 38d4669aa2ef..027f8e1b5b66 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -346,6 +346,18 @@ static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
if (cfs_rq->on_list) {
+ struct rq *rq = rq_of(cfs_rq);
+
+ /*
+ * With cfs_rq being unthrottled/throttled during an enqueue,
+ * it can happen the tmp_alone_branch points the a leaf that
+ * we finally want to del. In this case, tmp_alone_branch moves
+ * to the prev element but it will point to rq->leaf_cfs_rq_list
+ * at the end of the enqueue.
+ */
+ if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
+ rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
+
list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
cfs_rq->on_list = 0;
}
@@ -4438,6 +4450,10 @@ static int tg_unthrottle_up(struct task_group *tg, void *data)
/* adjust cfs_rq_clock_task() */
cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
cfs_rq->throttled_clock_task;
+
+ /* Add cfs_rq with already running entity in the list */
+ if (cfs_rq->nr_running >= 1)
+ list_add_leaf_cfs_rq(cfs_rq);
}
return 0;
@@ -4449,8 +4465,10 @@ static int tg_throttle_down(struct task_group *tg, void *data)
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
/* group is entering throttled state, stop time */
- if (!cfs_rq->throttle_count)
+ if (!cfs_rq->throttle_count) {
cfs_rq->throttled_clock_task = rq_clock_task(rq);
+ list_del_leaf_cfs_rq(cfs_rq);
+ }
cfs_rq->throttle_count++;
return 0;
@@ -4553,6 +4571,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
break;
}
+ assert_list_leaf_cfs_rq(rq);
+
if (!se)
add_nr_running(rq, task_delta);
@@ -7700,10 +7720,6 @@ static void update_blocked_averages(int cpu)
for_each_leaf_cfs_rq(rq, cfs_rq) {
struct sched_entity *se;
- /* throttled entities do not contribute to load */
- if (throttled_hierarchy(cfs_rq))
- continue;
-
if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq))
update_tg_load_avg(cfs_rq, 0);