Re: [PATCH] sched/core: Optimize the process of picking the max prio task for the core
From: cruzzhao
Date: Sun Oct 02 2022 - 03:29:39 EST
在 2022/9/29 下午3:18, Cruz Zhao 写道:
> When we pick the max prio task for the core in the case of
> sched_core_enabled(), if there's a task with a higher prio sched
> class in the runqueue of a SMT, it's not necessary for other SMTs
> to traverse lower prio sched classes. So we can change the traversal
> order: for each sched class, if there exists a max prio task among
> the core, pick it and break the loop.
>
> To compare the prio of the tasks with the same sched class, we
> introduce sched_class::prio_less().
>
> Signed-off-by: Cruz Zhao <CruzZhao@xxxxxxxxxxxxxxxxx>
> ---
> kernel/sched/core.c | 33 ++++++++++++++++++++++-----------
> kernel/sched/deadline.c | 11 +++++++++++
> kernel/sched/fair.c | 5 ++++-
> kernel/sched/idle.c | 10 ++++++++++
> kernel/sched/rt.c | 10 ++++++++++
> kernel/sched/sched.h | 5 +++--
> kernel/sched/stop_task.c | 10 ++++++++++
> 7 files changed, 70 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index a2d8a1f..50e28c8 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -189,7 +189,7 @@ static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool
> return !dl_time_before(a->dl.deadline, b->dl.deadline);
>
> if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
> - return cfs_prio_less(a, b, in_fi);
> + return fair_sched_class.prio_less(a, b, in_fi);
>
> return false;
> }
> @@ -5886,6 +5886,7 @@ static inline struct task_struct *pick_task(struct rq *rq)
> int i, cpu, occ = 0;
> struct rq *rq_i;
> bool need_sync;
> + struct sched_class *class;
>
> if (!sched_core_enabled(rq))
> return __pick_next_task(rq, prev, rf);
> @@ -5978,12 +5979,6 @@ static inline struct task_struct *pick_task(struct rq *rq)
> }
> }
>
> - /*
> - * For each thread: do the regular task pick and find the max prio task
> - * amongst them.
> - *
> - * Tie-break prio towards the current CPU
> - */
> for_each_cpu_wrap(i, smt_mask, cpu) {
> rq_i = cpu_rq(i);
>
> @@ -5994,12 +5989,28 @@ static inline struct task_struct *pick_task(struct rq *rq)
> */
> if (i != cpu && (rq_i != rq->core || !core_clock_updated))
> update_rq_clock(rq_i);
> + }
>
> - p = rq_i->core_pick = pick_task(rq_i);
> - if (!max || prio_less(max, p, fi_before))
> - max = p;
> + /*
> + * For each thread: do the regular task pick and find the max prio task
> + * amongst them.
> + *
> + * Tie-break prio towards the current CPU
> + */
> + for_each_class(class) {
> + for_each_cpu_wrap(i, smt_mask, cpu) {
> + rq_i = cpu_rq(i);
> + p = rq_i->core_pick = class->pick_task(rq_i);
> + if (!max || (p && class->prio_less(max, p, fi_before)))
> + max = p;
> + }
> + if (max)
> + break;
> }
>
> + if (!max)
> + BUG();
> +
> cookie = rq->core->core_cookie = max->core_cookie;
>
> /*
> @@ -6010,7 +6021,7 @@ static inline struct task_struct *pick_task(struct rq *rq)
> rq_i = cpu_rq(i);
> p = rq_i->core_pick;
>
> - if (!cookie_equals(p, cookie)) {
> + if (!p || !cookie_equals(p, cookie)) {
> p = NULL;
> if (cookie)
> p = sched_core_find(rq_i, cookie);
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 86dea6a..8e7aa7d 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1942,6 +1942,7 @@ static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
>
> return sched_stop_runnable(rq) || sched_dl_runnable(rq);
> }
> +
> #endif /* CONFIG_SMP */
>
> /*
> @@ -2054,6 +2055,13 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
> enqueue_pushable_dl_task(rq, p);
> }
>
> +#ifdef CONFIG_SCHED_CORE
> +static bool prio_less_dl(struct task_struct *a, struct task_struct *b, bool in_fi)
> +{
> + return !dl_time_before(a->dl.deadline, b->dl.deadline);
> +}
> +#endif
> +
> /*
> * scheduler tick hitting a task of our scheduling class.
> *
> @@ -2704,6 +2712,9 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
> .pick_next_task = pick_next_task_dl,
> .put_prev_task = put_prev_task_dl,
> .set_next_task = set_next_task_dl,
> +#ifdef CONFIG_SCHED_CORE
> + .prio_less = prio_less_dl,
> +#endif
>
> #ifdef CONFIG_SMP
> .balance = balance_dl,
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e4a0b8b..eca2636 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -11516,7 +11516,7 @@ void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
> se_fi_update(se, rq->core->core_forceidle_seq, in_fi);
> }
>
> -bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
> +static bool prio_less_fair(struct task_struct *a, struct task_struct *b, bool in_fi)
> {
> struct rq *rq = task_rq(a);
> struct sched_entity *sea = &a->se;
> @@ -12159,6 +12159,9 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task
> .pick_next_task = __pick_next_task_fair,
> .put_prev_task = put_prev_task_fair,
> .set_next_task = set_next_task_fair,
> +#ifdef CONFIG_SCHED_CORE
> + .prio_less = prio_less_fair,
> +#endif
>
> #ifdef CONFIG_SMP
> .balance = balance_fair,
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index f26ab26..a3c3e37 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -436,6 +436,13 @@ static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool fir
> schedstat_inc(rq->sched_goidle);
> }
>
> +#ifdef CONFIG_SCHED_CORE
> +static bool prio_less_idle(struct task_struct *a, struct task_struct *b, bool in_fi)
> +{
> + return false;
> +}
> +#endif
> +
> #ifdef CONFIG_SMP
> static struct task_struct *pick_task_idle(struct rq *rq)
> {
> @@ -507,6 +514,9 @@ static void update_curr_idle(struct rq *rq)
> .pick_next_task = pick_next_task_idle,
> .put_prev_task = put_prev_task_idle,
> .set_next_task = set_next_task_idle,
> +#ifdef CONFIG_SCHED_CORE
> + .prio_less = prio_less_idle,
> +#endif
>
> #ifdef CONFIG_SMP
> .balance = balance_idle,
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index d869bcf..4459a90 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1838,6 +1838,13 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
> enqueue_pushable_task(rq, p);
> }
>
> +static bool prio_less_rt(struct task_struct *a, struct task_struct *b, bool in_fi)
> +{
> + int pa = rt_prio(a->prio), pb = rt_prio(b->prio);
> +
> + return -pa < -pb;
> +}
> +
> #ifdef CONFIG_SMP
>
> /* Only try algorithms three times */
> @@ -2685,6 +2692,9 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
> .pick_next_task = pick_next_task_rt,
> .put_prev_task = put_prev_task_rt,
> .set_next_task = set_next_task_rt,
> +#ifdef CONFIG_SCHED_CORE
> + .prio_less = prio_less_rt,
> +#endif
>
> #ifdef CONFIG_SMP
> .balance = balance_rt,
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 1644242..6d8055c 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1218,8 +1218,6 @@ static inline raw_spinlock_t *__rq_lockp(struct rq *rq)
> return &rq->__lock;
> }
>
> -bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool fi);
> -
> /*
> * Helpers to check if the CPU's core cookie matches with the task's cookie
> * when core scheduling is enabled.
> @@ -2155,6 +2153,9 @@ struct sched_class {
>
> void (*put_prev_task)(struct rq *rq, struct task_struct *p);
> void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first);
> +#ifdef CONFIG_SCHED_CORE
> + bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi);
It should be:
+ bool (*prio_less)(struct task_struct *a, struct task_struct *b, bool
in_fi);
> +#endif
>
> #ifdef CONFIG_SMP
> int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf);
> diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
> index 8559059..c9ddaaa 100644
> --- a/kernel/sched/stop_task.c
> +++ b/kernel/sched/stop_task.c
> @@ -84,6 +84,13 @@ static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
> update_current_exec_runtime(curr, now, delta_exec);
> }
>
> +#ifdef CONFIG_SCHED_CORE
> +static bool prio_less_stop(struct task_struct *a, struct task_struct *b, bool in_fi)
> +{
> + return false;
> +}
> +#endif
> +
> /*
> * scheduler tick hitting a task of our scheduling class.
> *
> @@ -125,6 +132,9 @@ static void update_curr_stop(struct rq *rq)
> .pick_next_task = pick_next_task_stop,
> .put_prev_task = put_prev_task_stop,
> .set_next_task = set_next_task_stop,
> +#ifdef CONFIG_SCHED_CORE
> + .prio_less = prio_less_stop,
> +#endif
>
> #ifdef CONFIG_SMP
> .balance = balance_stop,