timer_stats - timer usage statistics------------------------------------ timer_stats is a debugging facility to make the timer (ab)usage in a Linuxsystem visible to kernel and userspace developers. It is not intended forproduction 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 thattheir code does not make unduly use of timers. This helps to avoid unnecessarywakeups, which should be avoided to optimize power consumption. It can be enabled by CONFIG_TIMER_STATS in the "Kernel hacking" configurationsection. timer_stats collects information about the timer events which are fired in aLinux 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 thesampled 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 sampledinformation is kept until a new sample period is started. This allows multiplereadouts. 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 thirdcolumn is the name of the process. The forth column shows the function whichinitialized the timer and in parantheses the callback function which wasexecuted on expiry.     Thomas, Ingo