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-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. If enabled in the config
-but not used it has almost zero runtime overhead, and a relatively small
-data structure overhead. Even if collection is enabled runtime all the
-locking is per-CPU and lookup is hashed.
-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
-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 initialized
-- 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
-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 parenthesis the callback function which was
-executed on expiry.
- Thomas, Ingo
-Added flag to indicate 'deferrable timer' in /proc/timer_stats. A deferrable
-timer will appear as follows
- 10D, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)