linux-kernel - [PATCH V5 4/6] Sched: Add scheduler stat for cpu time slice extension

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Message-ID: <20250603233654.1838967-5-prakash.sangappa@oracle.com>
Date: Tue,  3 Jun 2025 23:36:52 +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, kprateek.nayak@....com,
        vineethr@...ux.ibm.com
Subject: [PATCH V5 4/6] 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>
---
v5:
- Added #ifdef CONFIG_RSEQ
---
 include/linux/sched.h | 7 +++++++
 kernel/rseq.c         | 1 +
 kernel/sched/core.c   | 7 +++++++
 kernel/sched/debug.c  | 4 ++++
 4 files changed, 19 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 14069ebe26e2..6c2e9d30c2fc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -340,6 +340,9 @@ 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);
+#ifdef CONFIG_RSEQ
+extern void update_stat_preempt_delayed(struct task_struct *t);
+#endif
 
 /* wrapper function to trace from this header file */
 DECLARE_TRACEPOINT(sched_set_state_tp);
@@ -566,6 +569,10 @@ struct sched_statistics {
 	u64				nr_wakeups_passive;
 	u64				nr_wakeups_idle;
 
+#ifdef CONFIG_RSEQ
+	u64				nr_preempt_delay_granted;
+#endif
+
 #ifdef CONFIG_SCHED_CORE
 	u64				core_forceidle_sum;
 #endif
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 e5307389b30a..95fce557a294 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -940,6 +940,13 @@ void hrtick_local_start(u64 delay)
 	rq_unlock(rq, &rf);
 }
 
+#ifdef CONFIG_RSEQ
+void update_stat_preempt_delayed(struct task_struct *t)
+{
+	schedstat_inc(t->stats.nr_preempt_delay_granted);
+}
+#endif
+
 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..b178cb0e2904 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1217,6 +1217,10 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
 		P_SCHEDSTAT(nr_wakeups_passive);
 		P_SCHEDSTAT(nr_wakeups_idle);
 
+#ifdef CONFIG_RSEQ
+		P_SCHEDSTAT(nr_preempt_delay_granted);
+#endif
+
 		avg_atom = p->se.sum_exec_runtime;
 		if (nr_switches)
 			avg_atom = div64_ul(avg_atom, nr_switches);
-- 
2.43.5