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Date: Tue, 4 Jun 2024 14:18:56 +0100
From: Qais Yousef <qyousef@layalina.io>
To: John Stultz <jstultz@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Connor O'Brien <connoro@google.com>,
	Joel Fernandes <joelaf@google.com>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>,
	Zimuzo Ezeozue <zezeozue@google.com>,
	Youssef Esmat <youssefesmat@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Metin Kaya <Metin.Kaya@arm.com>,
	Xuewen Yan <xuewen.yan94@gmail.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>, kernel-team@android.com
Subject: Re: [PATCH v10 5/7] sched: Consolidate pick_*_task to
 task_is_pushable helper
Message-ID: <20240604131856.xo6jxe2geetq6jlg@airbuntu>
References: <20240507045450.895430-1-jstultz@google.com>
 <20240507045450.895430-6-jstultz@google.com>
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In-Reply-To: <20240507045450.895430-6-jstultz@google.com>

On 05/06/24 21:54, John Stultz wrote:
> From: Connor O'Brien <connoro@google.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@google.com>
> Cc: Qais Yousef <qyousef@layalina.io>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Zimuzo Ezeozue <zezeozue@google.com>
> Cc: Youssef Esmat <youssefesmat@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Metin Kaya <Metin.Kaya@arm.com>
> Cc: Xuewen Yan <xuewen.yan94@gmail.com>
> Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: kernel-team@android.com
> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
> Tested-by: Metin Kaya <metin.kaya@arm.com>
> Reviewed-by: Metin Kaya <metin.kaya@arm.com>
> Reviewed-by: Valentin Schneider <vschneid@redhat.com>
> Signed-off-by: Connor O'Brien <connoro@google.com>
> [jstultz: split out from larger chain migration patch,
>  renamed helper function]
> Signed-off-by: John Stultz <jstultz@google.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 eaedc69c5e30..ae583a427539 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2179,14 +2179,6 @@ 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:
> @@ -2205,7 +2197,7 @@ 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)

Any reason we're checking specifically for == 1? Could the function later
return something other than 0 or 1?

It's explaining if 1 could end up meaning something else in the commit message
and in function docs. Otherwise let's make it a bool and not do explicit check
for return value.

With this

Reviewed-by: Qais Yousef <qyousef@layalina.io>

>  			return p;
>  
>  		next_node = rb_next(next_node);
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 975cb49a64dc..8b6fb77e095b 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1791,15 +1791,6 @@ 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
> @@ -1813,7 +1804,7 @@ 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)
>  			return p;
>  	}
>  
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 2d41ebe200c7..e46f69ba9ba2 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -3490,6 +3490,16 @@ void move_queued_task_locked(struct rq *rq, struct rq *dst_rq, struct task_struc
>  	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)
> +{
> +	if (!task_on_cpu(rq, p) &&
> +	    cpumask_test_cpu(cpu, &p->cpus_mask))
> +		return 1;
> +
> +	return 0;
> +}
>  #endif
>  
>  #endif /* _KERNEL_SCHED_SCHED_H */
> -- 
> 2.45.0.rc1.225.g2a3ae87e7f-goog
>