linux-kernel - Re: [PATCH v7 19/23] sched: Consolidate pick_*_task to task_is

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Date: Fri, 22 Dec 2023 10:23:43 +0000
From: Metin Kaya <metin.kaya@....com>
To: John Stultz <jstultz@...gle.com>, LKML <linux-kernel@...r.kernel.org>
Cc: Joel Fernandes <joelaf@...gle.com>, Qais Yousef <qyousef@...gle.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Valentin Schneider <vschneid@...hat.com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Zimuzo Ezeozue <zezeozue@...gle.com>, Youssef Esmat
 <youssefesmat@...gle.com>, Mel Gorman <mgorman@...e.de>,
 Daniel Bristot de Oliveira <bristot@...hat.com>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Boqun Feng <boqun.feng@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>,
 Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak
 <kprateek.nayak@....com>, Thomas Gleixner <tglx@...utronix.de>,
 kernel-team@...roid.com
Subject: Re: [PATCH v7 19/23] sched: Consolidate pick_*_task to
 task_is_pushable helper

On 20/12/2023 12:18 am, John Stultz wrote:
> From: Connor O'Brien <connoro@...gle.com>
> 
> This patch consolidates rt and deadline pick_*_task functions to
> a task_is_pushable() helper
> 
> This patch was broken out from a larger chain migration
> patch originally by Connor O'Brien.
> 
> Cc: Joel Fernandes <joelaf@...gle.com>
> Cc: Qais Yousef <qyousef@...gle.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
> Cc: Youssef Esmat <youssefesmat@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Cc: Metin Kaya <Metin.Kaya@....com>
> Cc: Xuewen Yan <xuewen.yan94@...il.com>
> Cc: K Prateek Nayak <kprateek.nayak@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: kernel-team@...roid.com
> Signed-off-by: Connor O'Brien <connoro@...gle.com>
> [jstultz: split out from larger chain migration patch,
>   renamed helper function]
> Signed-off-by: John Stultz <jstultz@...gle.com>
> ---
> v7:
> * Split from chain migration patch
> * Renamed function
> ---
>   kernel/sched/deadline.c | 10 +---------
>   kernel/sched/rt.c       | 11 +----------
>   kernel/sched/sched.h    | 10 ++++++++++
>   3 files changed, 12 insertions(+), 19 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index def1eb23318b..1f3bc50de678 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2049,14 +2049,6 @@ static void task_fork_dl(struct task_struct *p)
>   /* Only try algorithms three times */
>   #define DL_MAX_TRIES 3
>   
> -static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
> -{
> -	if (!task_on_cpu(rq, p) &&
> -	    cpumask_test_cpu(cpu, &p->cpus_mask))
> -		return 1;
> -	return 0;
> -}
> -
>   /*
>    * Return the earliest pushable rq's task, which is suitable to be executed
>    * on the CPU, NULL otherwise:
> @@ -2075,7 +2067,7 @@ static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu
>   	if (next_node) {
>   		p = __node_2_pdl(next_node);
>   
> -		if (pick_dl_task(rq, p, cpu))
> +		if (task_is_pushable(rq, p, cpu) == 1)

Nit: ` == 1` part is redundant, IMHO.

>   			return p;
>   
>   		next_node = rb_next(next_node);
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index cf0eb4aac613..15161de88753 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1812,15 +1812,6 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
>   /* Only try algorithms three times */
>   #define RT_MAX_TRIES 3
>   
> -static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
> -{
> -	if (!task_on_cpu(rq, p) &&
> -	    cpumask_test_cpu(cpu, &p->cpus_mask))
> -		return 1;
> -
> -	return 0;
> -}
> -
>   /*
>    * Return the highest pushable rq's task, which is suitable to be executed
>    * on the CPU, NULL otherwise
> @@ -1834,7 +1825,7 @@ static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
>   		return NULL;
>   
>   	plist_for_each_entry(p, head, pushable_tasks) {
> -		if (pick_rt_task(rq, p, cpu))
> +		if (task_is_pushable(rq, p, cpu) == 1)

Ditto.

>   			return p;
>   	}
>   
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 19afe532771f..ef3d327e267c 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -3554,6 +3554,16 @@ void push_task_chain(struct rq *rq, struct rq *dst_rq, struct task_struct *task)
>   	set_task_cpu(task, dst_rq->cpu);
>   	activate_task(dst_rq, task, 0);
>   }
> +
> +static inline
> +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu)

Nit: I know the function is just renamed in this patch, but should we 
change the return type to bool while we are at it?

> +{
> +	if (!task_on_cpu(rq, p) &&
> +	    cpumask_test_cpu(cpu, &p->cpus_mask))
> +		return 1;
> +
> +	return 0;
> +}
>   #endif
>   
>   #endif /* _KERNEL_SCHED_SCHED_H */