[PATCH] Add debugging feature /proc/timer_stat

Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.

Sample output:

# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
  24,     0 swapper          hrtimer_stop_sched_tick (hrtimer_sched_tick)
  11,     0 swapper          sk_reset_timer (tcp_delack_timer)
   6,     0 swapper          hrtimer_stop_sched_tick (hrtimer_sched_tick)
   2,     1 swapper          queue_delayed_work_on (delayed_work_timer_fn)
  17,     0 swapper          hrtimer_restart_sched_tick (hrtimer_sched_tick)
   2,     1 swapper          queue_delayed_work_on (delayed_work_timer_fn)
   4,  2050 pcscd            do_nanosleep (hrtimer_wakeup)
   5,  4179 sshd             sk_reset_timer (tcp_write_timer)
   4,  2248 yum-updatesd     schedule_timeout (process_timeout)
  18,     0 swapper          hrtimer_restart_sched_tick (hrtimer_sched_tick)
   3,     0 swapper          sk_reset_timer (tcp_delack_timer)
   1,     1 swapper          neigh_table_init_no_netlink (neigh_periodic_timer)
   2,     1 swapper          e1000_up (e1000_watchdog)
   1,     1 init             schedule_timeout (process_timeout)
100 total events, 25.24 events/sec

[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 020d1ff..b6fa5e6 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -218,7 +218,7 @@ int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 }
 EXPORT_SYMBOL_GPL(queue_work);
 
-static void delayed_work_timer_fn(unsigned long __data)
+void delayed_work_timer_fn(unsigned long __data)
 {
 	struct delayed_work *dwork = (struct delayed_work *)__data;
 	struct workqueue_struct *wq = get_wq_data(&dwork->work);
@@ -245,6 +245,7 @@ int fastcall queue_delayed_work(struct workqueue_struct *wq,
 	struct timer_list *timer = &dwork->timer;
 	struct work_struct *work = &dwork->work;
 
+	timer_stats_timer_set_start_info(timer);
 	if (delay == 0)
 		return queue_work(wq, work);
 
@@ -593,8 +594,10 @@ EXPORT_SYMBOL(schedule_work);
  * After waiting for a given time this puts a job in the kernel-global
  * workqueue.
  */
-int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
+int fastcall schedule_delayed_work(struct delayed_work *dwork,
+					unsigned long delay)
 {
+	timer_stats_timer_set_start_info(&dwork->timer);
 	return queue_delayed_work(keventd_wq, dwork, delay);
 }
 EXPORT_SYMBOL(schedule_delayed_work);