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

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Message-ID: <2929CFC1-9B83-4268-988E-4BD17454DB88@oracle.com>
Date: Wed, 14 May 2025 23:01:01 +0000
From: Prakash Sangappa <prakash.sangappa@...cle.com>
To: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
CC: "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org"
	<rostedt@...dmis.org>,
        "mathieu.desnoyers@...icios.com"
	<mathieu.desnoyers@...icios.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "kprateek.nayak@....com"
	<kprateek.nayak@....com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 4/6] Sched: Add scheduler stat for cpu time slice
 extension



> On May 14, 2025, at 5:37 AM, Madadi Vineeth Reddy <vineethr@...ux.ibm.com> wrote:
> 
> 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.


Will update documentation. 

-Prakash

> 
> 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)
>