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.

Orabug: 37583007

Signed-off-by: Prakash Sangappa <[email protected]>
Reviewed-by: Chris Hyser <[email protected]>

Author: Prakash Sangappa

include/linux/sched.h

@@ -328,6 +328,7 @@ 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
@@ -533,6 +534,7 @@ 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;

kernel/rseq.c

@@ -364,6 +364,7 @@ bool rseq_delay_resched(void)
 		return false;
 
 	t->rseq_sched_delay = 1;
+	update_stat_preempt_delayed(t);
 
 	return true;
 }

kernel/sched/core.c

@@ -918,6 +918,11 @@ 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

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)