linux-kernel - [PATCH V2 3/3] Sched: Add scheduler stat for cpu time slice extension

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Message-ID: <20250418193410.2010058-4-prakash.sangappa@oracle.com>
Date: Fri, 18 Apr 2025 19:34:10 +0000
From: Prakash Sangappa <prakash.sangappa@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: peterz@...radead.org, rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        tglx@...utronix.de, bigeasy@...utronix.de
Subject: [PATCH V2 3/3] Sched: Add scheduler stat for cpu time slice extension

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 c91856f908d6..2c5c928f1128 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -327,6 +327,7 @@ 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);
 
 /**
  * struct prev_cputime - snapshot of system and user cputime
@@ -541,6 +542,7 @@ 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 7022729d02ee..d8e3bf126248 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -453,6 +453,7 @@ bool rseq_delay_resched(void)
 		return false;
 
 	t->rseq_sched_delay = 1;
+	update_stat_preempt_delayed(t);
 
 	return true;
 }
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 59b381cef472..6a08e6ece98d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -931,6 +931,11 @@ 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);
+}
+
 static void hrtick_rq_init(struct rq *rq)
 {
 #ifdef CONFIG_SMP
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index ef047add7f9e..e160e14b348f 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1213,6 +1213,7 @@ 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)
-- 
2.43.5