proc_timer_stats(5) - Linux manual page (original) (raw)
proctimerstats(5) File Formats Manual proctimerstats(5)
NAME top
/proc/timer_stats - timer statisticsDESCRIPTION top
_/proc/timerstats_ (from Linux 2.6.21 until Linux 4.10)
This is a debugging facility to make timer (ab)use in a
Linux system visible to kernel and user-space developers.
It can be used by kernel and user-space developers to
verify that their code does not make undue use of timers.
The goal is to avoid unnecessary wakeups, thereby
optimizing power consumption.
If enabled in the kernel (**CONFIG_TIMER_STATS**), but not
used, it has almost zero run-time overhead and a relatively
small data-structure overhead. Even if collection is
enabled at run time, overhead is low: all the locking is
per-CPU and lookup is hashed.
The _/proc/timerstats_ file is used both to control sampling
facility and to read out the sampled information.
The _timerstats_ functionality is inactive on bootup. A
sampling period can be started using the following command:
# echo 1 > /proc/timer_stats
The following command stops a sampling period:
# echo 0 > /proc/timer_stats
The statistics can be retrieved by:
$ cat /proc/timer_stats
While sampling is enabled, each readout from
_/proc/timerstats_ will see newly updated statistics. Once
sampling is disabled, the sampled information is kept until
a new sample period is started. This allows multiple
readouts.
Sample output from _/proc/timerstats_:
$ **cat /proc/timer_stats**
Timer Stats Version: v0.3
Sample period: 1.764 s
Collection: active
255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer)
71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer)
58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer)
4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn)
17, 7 rcu_sched rcu_gp_kthread (process_timeout)
...
1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn)
1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn)
1029 total events, 583.333 events/sec
The output columns are:
[1] a count of the number of events, optionally (since
Linux 2.6.23) followed by the letter 'D' if this is a
deferrable timer;
[2] the PID of the process that initialized the timer;
[3] the name of the process that initialized the timer;
[4] the function where the timer was initialized; and (in
parentheses) the callback function that is associated
with the timer.
During the Linux 4.11 development cycle, this file was
removed because of security concerns, as it exposes
information across namespaces. Furthermore, it is possible
to obtain the same information via in-kernel tracing
facilities such as ftrace.SEE ALSO top
[proc(5)](../man5/proc.5.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-05-02 proctimerstats(5)