[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, 54 insertions, 0 deletions

diff --git a/include/linux/timer.h b/include/linux/timer.h
index 44d41e9..719113b 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -2,6 +2,7 @@
 #define _LINUX_TIMER_H
 
 #include <linux/list.h>
+#include <linux/ktime.h>
 #include <linux/spinlock.h>
 #include <linux/stddef.h>
 
@@ -15,6 +16,11 @@ struct timer_list {
 	unsigned long data;
 
 	struct tvec_t_base_s *base;
+#ifdef CONFIG_TIMER_STATS
+	void *start_site;
+	char start_comm[16];
+	int start_pid;
+#endif
 };
 
 extern struct tvec_t_base_s boot_tvec_bases;
@@ -73,6 +79,54 @@ extern unsigned long next_timer_interrupt(void);
  */
 extern unsigned long get_next_timer_interrupt(unsigned long now);
 
+/*
+ * Timer-statistics info:
+ */
+#ifdef CONFIG_TIMER_STATS
+
+extern void init_timer_stats(void);
+
+extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
+				     void *timerf, char * comm);
+
+static inline void timer_stats_account_timer(struct timer_list *timer)
+{
+	timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
+				 timer->function, timer->start_comm);
+}
+
+extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
+					       void *addr);
+
+static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
+{
+	__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
+}
+
+static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
+{
+	timer->start_site = NULL;
+}
+#else
+static inline void init_timer_stats(void)
+{
+}
+
+static inline void timer_stats_account_timer(struct timer_list *timer)
+{
+}
+
+static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
+{
+}
+
+static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
+{
+}
+#endif
+
+extern void delayed_work_timer_fn(unsigned long __data);
+
 /**
  * add_timer - start a timer
  * @timer: the timer to be added