diff options
author | Ingo Molnar <mingo@elte.hu> | 2007-02-16 01:28:13 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-16 08:13:59 -0800 |
commit | 82f67cd9fca8c8762c15ba7ed0d5747588c1e221 (patch) | |
tree | 1ff7e5cc496580b85bb42fb1d7b19dcbef7b7776 /Documentation/hrtimer/timer_stats.txt | |
parent | 8bfd9a7a229b5f3d3eda5d7d45c2eebec5b4ba16 (diff) | |
download | kernel_samsung_smdk4412-82f67cd9fca8c8762c15ba7ed0d5747588c1e221.zip kernel_samsung_smdk4412-82f67cd9fca8c8762c15ba7ed0d5747588c1e221.tar.gz kernel_samsung_smdk4412-82f67cd9fca8c8762c15ba7ed0d5747588c1e221.tar.bz2 |
[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>
Diffstat (limited to 'Documentation/hrtimer/timer_stats.txt')
-rw-r--r-- | Documentation/hrtimer/timer_stats.txt | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/Documentation/hrtimer/timer_stats.txt b/Documentation/hrtimer/timer_stats.txt new file mode 100644 index 0000000..27f782e --- /dev/null +++ b/Documentation/hrtimer/timer_stats.txt @@ -0,0 +1,68 @@ +timer_stats - timer usage statistics +------------------------------------ + +timer_stats is a debugging facility to make the timer (ab)usage in a Linux +system visible to kernel and userspace developers. It is not intended for +production usage as it adds significant overhead to the (hr)timer code and the +(hr)timer data structures. + +timer_stats should be used by kernel and userspace developers to verify that +their code does not make unduly use of timers. This helps to avoid unnecessary +wakeups, which should be avoided to optimize power consumption. + +It can be enabled by CONFIG_TIMER_STATS in the "Kernel hacking" configuration +section. + +timer_stats collects information about the timer events which are fired in a +Linux system over a sample period: + +- the pid of the task(process) which initialized the timer +- the name of the process which initialized the timer +- the function where the timer was intialized +- the callback function which is associated to the timer +- the number of events (callbacks) + +timer_stats adds an entry to /proc: /proc/timer_stats + +This entry is used to control the statistics functionality and to read out the +sampled information. + +The timer_stats functionality is inactive on bootup. + +To activate a sample period issue: +# echo 1 >/proc/timer_stats + +To stop a sample period issue: +# echo 0 >/proc/timer_stats + +The statistics can be retrieved by: +# cat /proc/timer_stats + +The readout of /proc/timer_stats automatically disables sampling. The sampled +information is kept until a new sample period is started. This allows multiple +readouts. + +Sample output of /proc/timer_stats: + +Timerstats sample period: 3.888770 s + 12, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick) + 15, 1 swapper hcd_submit_urb (rh_timer_func) + 4, 959 kedac schedule_timeout (process_timeout) + 1, 0 swapper page_writeback_init (wb_timer_fn) + 28, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick) + 22, 2948 IRQ 4 tty_flip_buffer_push (delayed_work_timer_fn) + 3, 3100 bash schedule_timeout (process_timeout) + 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn) + 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn) + 1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer) + 1, 2292 ip __netdev_watchdog_up (dev_watchdog) + 1, 23 events/1 do_cache_clean (delayed_work_timer_fn) +90 total events, 30.0 events/sec + +The first column is the number of events, the second column the pid, the third +column is the name of the process. The forth column shows the function which +initialized the timer and in parantheses the callback function which was +executed on expiry. + + Thomas, Ingo + |