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
              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/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 6.9.1             2024-05-02               proc_timer_stats(5)