proc_timer_stats(5) File Formats Manual proc_timer_stats(5)
NAME
/proc/timer_stats - timer statistics
DESCRIPTION
/proc/timer_stats (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 un-
necessary 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/timer_stats file is used both to control sampling fa-
cility and to read out the sampled information.
The timer_stats 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/timer_stats
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/timer_stats:
$ 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 paren-
theses) 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 in-
formation via in-kernel tracing facilities such as ftrace.
SEE ALSO
proc(5)
Linux man-pages 6.9.1 2024-05-02 proc_timer_stats(5)
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