Version 15 of schedstats dropped counters for some sched_yield:
  yld_exp_empty, yld_act_empty and yld_both_empty. Otherwise, it is
  identical to version 14.
  
  Version 14 of schedstats includes support for sched_domains, which hit the
  mainline kernel in 2.6.20 although it is identical to the stats from version
  12 which was in the kernel from 2.6.13-2.6.19 (version 13 never saw a kernel
  release).  Some counters make more sense to be per-runqueue; other to be
  per-domain.  Note that domains (and their associated information) will only
  be pertinent and available on machines utilizing CONFIG_SMP.
  
  In version 14 of schedstat, there is at least one level of domain
  statistics for each cpu listed, and there may well be more than one
  domain.  Domains have no particular names in this implementation, but
  the highest numbered one typically arbitrates balancing across all the
  cpus on the machine, while domain0 is the most tightly focused domain,
  sometimes balancing only between pairs of cpus.  At this time, there
  are no architectures which need more than three domain levels. The first
  field in the domain stats is a bit map indicating which cpus are affected
  by that domain.
  
  These fields are counters, and only increment.  Programs which make use
  of these will need to start with a baseline observation and then calculate
  the change in the counters at each subsequent observation.  A perl script
  which does this for many of the fields is available at
  
      http://eaglet.rain.com/rick/linux/schedstat/
  
  Note that any such script will necessarily be version-specific, as the main
  reason to change versions is changes in the output format.  For those wishing
  to write their own scripts, the fields are described here.
  
  CPU statistics
  --------------
  cpu<N> 1 2 3 4 5 6 7 8 9
  
  First field is a sched_yield() statistic:
       1) # of times sched_yield() was called
  
  Next three are schedule() statistics:
       2) This field is a legacy array expiration count field used in the O(1)
  	scheduler. We kept it for ABI compatibility, but it is always set to zero.
       3) # of times schedule() was called
       4) # of times schedule() left the processor idle
  
  Next two are try_to_wake_up() statistics:
       5) # of times try_to_wake_up() was called
       6) # of times try_to_wake_up() was called to wake up the local cpu
  
  Next three are statistics describing scheduling latency:
       7) sum of all time spent running by tasks on this processor (in jiffies)
       8) sum of all time spent waiting to run by tasks on this processor (in
          jiffies)
       9) # of timeslices run on this cpu
  
  
  Domain statistics
  -----------------
  One of these is produced per domain for each cpu described. (Note that if
  CONFIG_SMP is not defined, *no* domains are utilized and these lines
  will not appear in the output.)
  
  domain<N> <cpumask> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
  
  The first field is a bit mask indicating what cpus this domain operates over.
  
  The next 24 are a variety of load_balance() statistics in grouped into types
  of idleness (idle, busy, and newly idle):
  
       1) # of times in this domain load_balance() was called when the
          cpu was idle
       2) # of times in this domain load_balance() checked but found
          the load did not require balancing when the cpu was idle
       3) # of times in this domain load_balance() tried to move one or
          more tasks and failed, when the cpu was idle
       4) sum of imbalances discovered (if any) with each call to
          load_balance() in this domain when the cpu was idle
       5) # of times in this domain pull_task() was called when the cpu
          was idle
       6) # of times in this domain pull_task() was called even though
          the target task was cache-hot when idle
       7) # of times in this domain load_balance() was called but did
          not find a busier queue while the cpu was idle
       8) # of times in this domain a busier queue was found while the
          cpu was idle but no busier group was found
  
       9) # of times in this domain load_balance() was called when the
          cpu was busy
      10) # of times in this domain load_balance() checked but found the
          load did not require balancing when busy
      11) # of times in this domain load_balance() tried to move one or
          more tasks and failed, when the cpu was busy
      12) sum of imbalances discovered (if any) with each call to
          load_balance() in this domain when the cpu was busy
      13) # of times in this domain pull_task() was called when busy
      14) # of times in this domain pull_task() was called even though the
          target task was cache-hot when busy
      15) # of times in this domain load_balance() was called but did not
          find a busier queue while the cpu was busy
      16) # of times in this domain a busier queue was found while the cpu
          was busy but no busier group was found
  
      17) # of times in this domain load_balance() was called when the
          cpu was just becoming idle
      18) # of times in this domain load_balance() checked but found the
          load did not require balancing when the cpu was just becoming idle
      19) # of times in this domain load_balance() tried to move one or more
          tasks and failed, when the cpu was just becoming idle
      20) sum of imbalances discovered (if any) with each call to
          load_balance() in this domain when the cpu was just becoming idle
      21) # of times in this domain pull_task() was called when newly idle
      22) # of times in this domain pull_task() was called even though the
          target task was cache-hot when just becoming idle
      23) # of times in this domain load_balance() was called but did not
          find a busier queue while the cpu was just becoming idle
      24) # of times in this domain a busier queue was found while the cpu
          was just becoming idle but no busier group was found
  
     Next three are active_load_balance() statistics:
      25) # of times active_load_balance() was called
      26) # of times active_load_balance() tried to move a task and failed
      27) # of times active_load_balance() successfully moved a task
  
     Next three are sched_balance_exec() statistics:
      28) sbe_cnt is not used
      29) sbe_balanced is not used
      30) sbe_pushed is not used
  
     Next three are sched_balance_fork() statistics:
      31) sbf_cnt is not used
      32) sbf_balanced is not used
      33) sbf_pushed is not used
  
     Next three are try_to_wake_up() statistics:
      34) # of times in this domain try_to_wake_up() awoke a task that
          last ran on a different cpu in this domain
      35) # of times in this domain try_to_wake_up() moved a task to the
          waking cpu because it was cache-cold on its own cpu anyway
      36) # of times in this domain try_to_wake_up() started passive balancing
  
  /proc/<pid>/schedstat
  ----------------
  schedstats also adds a new /proc/<pid>/schedstat file to include some of
  the same information on a per-process level.  There are three fields in
  this file correlating for that process to:
       1) time spent on the cpu
       2) time spent waiting on a runqueue
       3) # of timeslices run on this cpu
  
  A program could be easily written to make use of these extra fields to
  report on how well a particular process or set of processes is faring
  under the scheduler's policies.  A simple version of such a program is
  available at
      http://eaglet.rain.com/rick/linux/schedstat/v12/latency.c