[PATCH V3 3/4] Sched: Add scheduler stat for cpu time slice extension

[Prakash Sangappa <prakash.sangappa@oracle.com>]

Add scheduler stat to record number of times the thread was granted
cpu time slice extension.

Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.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 cce3a0496703..1367171b4a9e 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 0cfdaf5b6c8e..4c1586977f1b 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 05a952ec15ae..cb5bc0d41b01 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -936,6 +936,11 @@ 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 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)
-- 
2.43.5