From: Vincent Guittot vincent.guittot@linaro.org
[ Upstream commit 6d4d22468dae3d8757af9f8b81b848a76ef4409d ]
The walk through the cgroup hierarchy during the enqueue/dequeue of a task is split in 2 distinct parts for throttled cfs_rq without any added value but making code less readable.
Change the code ordering such that everything related to a cfs_rq (throttled or not) will be done in the same loop.
In addition, the same steps ordering is used when updating a cfs_rq:
- update_load_avg - update_cfs_group - update *h_nr_running
This reordering enables the use of h_nr_running in PELT algorithm.
No functional and performance changes are expected and have been noticed during tests.
Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Mel Gorman mgorman@techsingularity.net Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: "Dietmar Eggemann dietmar.eggemann@arm.com" Acked-by: Peter Zijlstra a.p.zijlstra@chello.nl Cc: Juri Lelli juri.lelli@redhat.com Cc: Valentin Schneider valentin.schneider@arm.com Cc: Phil Auld pauld@redhat.com Cc: Hillf Danton hdanton@sina.com Link: https://lore.kernel.org/r/20200224095223.13361-5-mgorman@techsingularity.net Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/fair.c | 42 ++++++++++++++++++++---------------------- 1 file changed, 20 insertions(+), 22 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index eeaf34d65742..0e042e847ed3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5232,32 +5232,31 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) cfs_rq = cfs_rq_of(se); enqueue_entity(cfs_rq, se, flags);
- /* - * end evaluation on encountering a throttled cfs_rq - * - * note: in the case of encountering a throttled cfs_rq we will - * post the final h_nr_running increment below. - */ - if (cfs_rq_throttled(cfs_rq)) - break; cfs_rq->h_nr_running++; cfs_rq->idle_h_nr_running += idle_h_nr_running;
+ /* end evaluation on encountering a throttled cfs_rq */ + if (cfs_rq_throttled(cfs_rq)) + goto enqueue_throttle; + flags = ENQUEUE_WAKEUP; }
for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); - cfs_rq->h_nr_running++; - cfs_rq->idle_h_nr_running += idle_h_nr_running;
+ /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) - break; + goto enqueue_throttle;
update_load_avg(cfs_rq, se, UPDATE_TG); update_cfs_group(se); + + cfs_rq->h_nr_running++; + cfs_rq->idle_h_nr_running += idle_h_nr_running; }
+enqueue_throttle: if (!se) { add_nr_running(rq, 1); /* @@ -5317,17 +5316,13 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) cfs_rq = cfs_rq_of(se); dequeue_entity(cfs_rq, se, flags);
- /* - * end evaluation on encountering a throttled cfs_rq - * - * note: in the case of encountering a throttled cfs_rq we will - * post the final h_nr_running decrement below. - */ - if (cfs_rq_throttled(cfs_rq)) - break; cfs_rq->h_nr_running--; cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+ /* end evaluation on encountering a throttled cfs_rq */ + if (cfs_rq_throttled(cfs_rq)) + goto dequeue_throttle; + /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { /* Avoid re-evaluating load for this entity: */ @@ -5345,16 +5340,19 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); - cfs_rq->h_nr_running--; - cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+ /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) - break; + goto dequeue_throttle;
update_load_avg(cfs_rq, se, UPDATE_TG); update_cfs_group(se); + + cfs_rq->h_nr_running--; + cfs_rq->idle_h_nr_running -= idle_h_nr_running; }
+dequeue_throttle: if (!se) sub_nr_running(rq, 1);