Messages in this thread | | | Date | Mon, 20 Mar 2023 12:39:10 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/core: Minor optimize pick_next_task() when core-sched enable |
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On Wed, Mar 08, 2023 at 06:04:13PM +0800, Hao Jia wrote:
> core max: task2 (cookie 0) > > rq0 rq1 > task0(cookie non-zero) task2(cookie 0) > task1(cookie 0) > task3(cookie 0) > ... > > pick-task: idle pick-task: task2 > > CPU0 and CPU1 are two CPUs on the same core, task0 and task2 are the > highest priority tasks on rq0 and rq1 respectively, task2 is @max > on the entire core.
I'm assuming this all starts by rq0 doing a pick and getting task0. Because any other selection would go down the whole !need_sync route.
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index af017e038b48..765cd14c52e1 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -236,8 +236,8 @@ void sched_core_enqueue(struct rq *rq, struct task_struct *p) > { > rq->core->core_task_seq++; > > - if (!p->core_cookie) > - return; > + if (p->core_cookie) > + rq->cookied_count++; > > rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less); > }
> @@ -2061,14 +2066,12 @@ static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) > uclamp_rq_inc(rq, p); > p->sched_class->enqueue_task(rq, p, flags); > > - if (sched_core_enabled(rq)) > - sched_core_enqueue(rq, p); > + sched_core_enqueue(rq, p); > } > > static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) > { > - if (sched_core_enabled(rq)) > - sched_core_dequeue(rq, p, flags); > + sched_core_dequeue(rq, p, flags); > > if (!(flags & DEQUEUE_NOCLOCK)) > update_rq_clock(rq);
Yeah, this is an absolute no-no, it makes the overhead of the second rb tree unconditional.
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