man > proc_timer_stats(5)

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 ver‐
              ify  that their code does not make undue use of timers.  The goal is to avoid unneces‐
              sary 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 facility 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 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
       proc(5)

Linux man-pages 6.7                          2023-08-15                          proc_timer_stats(5)