Task group load-contributions are not updated when tasks belonging to
task groups are migrated by active load-balancing. If no other task
belonging to the same task group is already queued at the destination
cpu the group sched_entity will be enqueued with load_avg_contrib=0.
Hence, weighted_cpuload() won't reflect the newly added load.
The load may remain invisible until the next tick, when the sched_entity
load_avg_contrib and task group contributions are reevaluated.
The enqueue loop
for_each_entity(se) {
enqueue_entity(cfs_rq,se)
...
enqueue_entity_load_avg(cfs_rq,se)
...
update_entity_load_avg(se)
...
__update_entity_load_avg_contrib(se)
...
...
update_cfs_rq_blocked_load(cfs_rq)
...
__update_cfs_rq_tg_load_contrib(cfs_rq)
...
}
currently skips __update_entity_load_avg_contrib() and
__update_cfs_rq_tg_load_contrib() for group entities for active
load-balance migrations. The former updates the sched_entity
load_avg_contrib, and the latter updates the task group contribution
which is needed by the former. They must both be called to ensure that
load doesn't temporarily disappear.
cc: Paul Turner <p...@google.com>
cc: Ben Segall <bseg...@google.com>
Signed-off-by: Morten Rasmussen <morten.rasmus...@arm.com>
---
kernel/sched/fair.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index be9e97b..2b6e2eb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2521,7 +2521,8 @@ static inline void update_entity_load_avg(struct
sched_entity *se,
else
now = cfs_rq_clock_task(group_cfs_rq(se));
- if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
+ if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq) &&
+ entity_is_task(se))
return;
contrib_delta = __update_entity_load_avg_contrib(se);
@@ -2609,6 +2610,10 @@ static inline void enqueue_entity_load_avg(struct cfs_rq
*cfs_rq,
cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
/* we force update consideration on load-balancer moves */
update_cfs_rq_blocked_load(cfs_rq, !wakeup);
+
+ /* We force update group contributions on load-balancer moves */
+ if (wakeup && !entity_is_task(se))
+ __update_cfs_rq_tg_load_contrib(cfs_rq, 0);
}
/*
--
1.7.9.5
--
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