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| author | Peter Zijlstra <peterz@infradead.org> | 2019-05-29 23:36:44 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2019-08-08 10:09:31 +0300 |
| commit | 67692435c411e5c53a1c588ecca2037aebd81f2e (patch) | |
| tree | 53d9c44e6e80654a60c652493d4b0cc948ce5818 /kernel/sched/core.c | |
| parent | 5f2a45fc9e89e022233085e6f0f352eb6ff770bb (diff) | |
| download | linux-67692435c411e5c53a1c588ecca2037aebd81f2e.tar.xz | |
sched: Rework pick_next_task() slow-path
Avoid the RETRY_TASK case in the pick_next_task() slow path.
By doing the put_prev_task() early, we get the rt/deadline pull done,
and by testing rq->nr_running we know if we need newidle_balance().
This then gives a stable state to pick a task from.
Since the fast-path is fair only; it means the other classes will
always have pick_next_task(.prev=NULL, .rf=NULL) and we can simplify.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aaron Lu <aaron.lwe@gmail.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: mingo@kernel.org
Cc: Phil Auld <pauld@redhat.com>
Cc: Julien Desfossez <jdesfossez@digitalocean.com>
Cc: Nishanth Aravamudan <naravamudan@digitalocean.com>
Link: https://lkml.kernel.org/r/aa34d24b36547139248f32a30138791ac6c02bd6.1559129225.git.vpillai@digitalocean.com
Diffstat (limited to 'kernel/sched/core.c')
| -rw-r--r-- | kernel/sched/core.c | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7bbe78a31ba5..a6661852907b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3791,7 +3791,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) p = fair_sched_class.pick_next_task(rq, prev, rf); if (unlikely(p == RETRY_TASK)) - goto again; + goto restart; /* Assumes fair_sched_class->next == idle_sched_class */ if (unlikely(!p)) @@ -3800,14 +3800,19 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) return p; } -again: +restart: + /* + * Ensure that we put DL/RT tasks before the pick loop, such that they + * can PULL higher prio tasks when we lower the RQ 'priority'. + */ + prev->sched_class->put_prev_task(rq, prev, rf); + if (!rq->nr_running) + newidle_balance(rq, rf); + for_each_class(class) { - p = class->pick_next_task(rq, prev, rf); - if (p) { - if (unlikely(p == RETRY_TASK)) - goto again; + p = class->pick_next_task(rq, NULL, NULL); + if (p) return p; - } } /* The idle class should always have a runnable task: */ |