Ubuntu Manpage: /proc/timer_stats

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.

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DESCRIPTION

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