[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>
diff --git a/kernel/timer.c b/kernel/timer.c
index f058e6c..c3c67f3 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -35,6 +35,7 @@
#include <linux/syscalls.h>
#include <linux/delay.h>
#include <linux/tick.h>
+#include <linux/kallsyms.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -263,6 +264,18 @@
list_add_tail(&timer->entry, vec);
}
+#ifdef CONFIG_TIMER_STATS
+void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
+{
+ if (timer->start_site)
+ return;
+
+ timer->start_site = addr;
+ memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
+ timer->start_pid = current->pid;
+}
+#endif
+
/**
* init_timer - initialize a timer.
* @timer: the timer to be initialized
@@ -274,11 +287,16 @@
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
+#ifdef CONFIG_TIMER_STATS
+ timer->start_site = NULL;
+ timer->start_pid = -1;
+ memset(timer->start_comm, 0, TASK_COMM_LEN);
+#endif
}
EXPORT_SYMBOL(init_timer);
static inline void detach_timer(struct timer_list *timer,
- int clear_pending)
+ int clear_pending)
{
struct list_head *entry = &timer->entry;
@@ -325,6 +343,7 @@
unsigned long flags;
int ret = 0;
+ timer_stats_timer_set_start_info(timer);
BUG_ON(!timer->function);
base = lock_timer_base(timer, &flags);
@@ -375,6 +394,7 @@
tvec_base_t *base = per_cpu(tvec_bases, cpu);
unsigned long flags;
+ timer_stats_timer_set_start_info(timer);
BUG_ON(timer_pending(timer) || !timer->function);
spin_lock_irqsave(&base->lock, flags);
timer->base = base;
@@ -407,6 +427,7 @@
{
BUG_ON(!timer->function);
+ timer_stats_timer_set_start_info(timer);
/*
* This is a common optimization triggered by the
* networking code - if the timer is re-modified
@@ -437,6 +458,7 @@
unsigned long flags;
int ret = 0;
+ timer_stats_timer_clear_start_info(timer);
if (timer_pending(timer)) {
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
@@ -570,6 +592,8 @@
fn = timer->function;
data = timer->data;
+ timer_stats_account_timer(timer);
+
set_running_timer(base, timer);
detach_timer(timer, 1);
spin_unlock_irq(&base->lock);
@@ -1229,7 +1253,8 @@
{
tvec_base_t *base = __get_cpu_var(tvec_bases);
- hrtimer_run_queues();
+ hrtimer_run_queues();
+
if (time_after_eq(jiffies, base->timer_jiffies))
__run_timers(base);
}
@@ -1675,6 +1700,8 @@
int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
+ init_timer_stats();
+
BUG_ON(err == NOTIFY_BAD);
register_cpu_notifier(&timers_nb);
open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);