linux-kernel - Re: [PATCH V4 4/6] Sched: Add scheduler stat for cpu time slice extension

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Message-ID: <d3bb8ecd-3ac2-4025-bd81-4d612bb26995@linux.ibm.com>
Date: Wed, 14 May 2025 18:07:56 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: peterz@...radead.org, rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        tglx@...utronix.de, bigeasy@...utronix.de, kprateek.nayak@....com,
        linux-kernel@...r.kernel.org,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH V4 4/6] Sched: Add scheduler stat for cpu time slice
 extension

On 14/05/25 03:15, Prakash Sangappa wrote:
> Add scheduler stat to record number of times the thread was granted
> cpu time slice extension.
> 
> Signed-off-by: Prakash Sangappa <prakash.sangappa@...cle.com>
> ---
>  include/linux/sched.h | 2 ++
>  kernel/rseq.c         | 1 +
>  kernel/sched/core.c   | 5 +++++
>  kernel/sched/debug.c  | 1 +
>  4 files changed, 9 insertions(+)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index c279232ca6a2..8cf756e80ae9 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -340,6 +340,7 @@ extern void io_schedule_finish(int token);
>  extern long io_schedule_timeout(long timeout);
>  extern void io_schedule(void);
>  extern void hrtick_local_start(u64 delay);
> +extern void update_stat_preempt_delayed(struct task_struct *t);
>  
>  /* wrapper function to trace from this header file */
>  DECLARE_TRACEPOINT(sched_set_state_tp);
> @@ -563,6 +564,7 @@ struct sched_statistics {
>  	u64				nr_wakeups_affine_attempts;
>  	u64				nr_wakeups_passive;
>  	u64				nr_wakeups_idle;
> +	u64				nr_preempt_delay_granted;
>  
>  #ifdef CONFIG_SCHED_CORE
>  	u64				core_forceidle_sum;
> diff --git a/kernel/rseq.c b/kernel/rseq.c
> index 44d0f3ae0cd3..c4bc52f8ba9c 100644
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -475,6 +475,7 @@ bool rseq_delay_resched(void)
>  		return false;
>  
>  	t->sched_time_delay = 1;
> +	update_stat_preempt_delayed(t);
>  
>  	return true;
>  }
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 31928cbcd907..880368756b48 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -938,6 +938,11 @@ void hrtick_local_start(u64 delay)
>  	rq_unlock(rq, &rf);
>  }
>  
> +void update_stat_preempt_delayed(struct task_struct *t)
> +{
> +	schedstat_inc(t->stats.nr_preempt_delay_granted);

I think schedstat documentation also needs to be updated
and may be bump the version number.

Thanks,
Madadi Vineeth Reddy

> +}
> +
>  static void hrtick_rq_init(struct rq *rq)
>  {
>  #ifdef CONFIG_SMP
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index 4cba21f5d24d..6b753f56c312 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -1216,6 +1216,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
>  		P_SCHEDSTAT(nr_wakeups_affine_attempts);
>  		P_SCHEDSTAT(nr_wakeups_passive);
>  		P_SCHEDSTAT(nr_wakeups_idle);
> +		P_SCHEDSTAT(nr_preempt_delay_granted);
>  
>  		avg_atom = p->se.sum_exec_runtime;
>  		if (nr_switches)