proc_timer_stats(5) — Linux manual page

NAME | DESCRIPTION | SEE ALSO | COLOPHON

proc_timer_stats(5)        File Formats Manual       proc_timer_stats(5)

NAME         top

       /proc/timer_stats - timer statistics

DESCRIPTION         top

       /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         top

       proc(5)

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02            proc_timer_stats(5)