| From 60cc5c0272b1384b996f8a0bdeb1b6f77d0467da Mon Sep 17 00:00:00 2001 |
| From: Vincent Guittot <vincent.guittot@linaro.org> |
| Date: Mon, 24 Feb 2020 09:52:14 +0000 |
| Subject: [PATCH] sched/fair: Reorder enqueue/dequeue_task_fair path |
| |
| commit 6d4d22468dae3d8757af9f8b81b848a76ef4409d upstream. |
| |
| 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: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c |
| index a49fddb29d07..5558256609db 100644 |
| --- a/kernel/sched/fair.c |
| +++ b/kernel/sched/fair.c |
| @@ -5219,32 +5219,31 @@ 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); |
| /* |
| @@ -5304,17 +5303,13 @@ 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: */ |
| @@ -5332,16 +5327,19 @@ 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); |
| |
| -- |
| 2.7.4 |
| |