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82f67cd9fc
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>
69 lines
2.7 KiB
Plaintext
69 lines
2.7 KiB
Plaintext
timer_stats - timer usage statistics
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timer_stats is a debugging facility to make the timer (ab)usage in a Linux
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system visible to kernel and userspace developers. It is not intended for
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production usage as it adds significant overhead to the (hr)timer code and the
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(hr)timer data structures.
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timer_stats should be used by kernel and userspace developers to verify that
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their code does not make unduly use of timers. This helps to avoid unnecessary
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wakeups, which should be avoided to optimize power consumption.
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It can be enabled by CONFIG_TIMER_STATS in the "Kernel hacking" configuration
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section.
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timer_stats collects information about the timer events which are fired in a
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Linux system over a sample period:
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- the pid of the task(process) which initialized the timer
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- the name of the process which initialized the timer
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- the function where the timer was intialized
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- the callback function which is associated to the timer
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- the number of events (callbacks)
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timer_stats adds an entry to /proc: /proc/timer_stats
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This entry is used to control the statistics functionality and to read out the
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sampled information.
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The timer_stats functionality is inactive on bootup.
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To activate a sample period issue:
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# echo 1 >/proc/timer_stats
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To stop a sample period issue:
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# echo 0 >/proc/timer_stats
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The statistics can be retrieved by:
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# cat /proc/timer_stats
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The readout of /proc/timer_stats automatically disables sampling. The sampled
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information is kept until a new sample period is started. This allows multiple
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readouts.
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Sample output of /proc/timer_stats:
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Timerstats sample period: 3.888770 s
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12, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
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15, 1 swapper hcd_submit_urb (rh_timer_func)
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4, 959 kedac schedule_timeout (process_timeout)
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1, 0 swapper page_writeback_init (wb_timer_fn)
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28, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
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22, 2948 IRQ 4 tty_flip_buffer_push (delayed_work_timer_fn)
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3, 3100 bash schedule_timeout (process_timeout)
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1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
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1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
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1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
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1, 2292 ip __netdev_watchdog_up (dev_watchdog)
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1, 23 events/1 do_cache_clean (delayed_work_timer_fn)
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90 total events, 30.0 events/sec
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The first column is the number of events, the second column the pid, the third
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column is the name of the process. The forth column shows the function which
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initialized the timer and in parantheses the callback function which was
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executed on expiry.
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Thomas, Ingo
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