#! /usr/bin/env stap
# Copyright (C) 2010 Red Hat, Inc.
# Write by William Cohen <wcohen@redhat.com>
#
# cycle_theif provide the following information for a specified pid:
#   Number of times the task is migrated to another cpu
#   How long the task is scheduled on and off a processor.
#   task pid that run with the task is scheduled off the processor
#
#
# Run the script with:
#   stap cycle_thief.stp -x pid
#
# control-c to exit data collection

global last_cpu = -1
global pid_on, pid_off, migrated
global time_on, time_off
global cycle_thief

probe kernel.trace("sched_switch") {
  t = gettimeofday_us(); c = cpu();
  if ($prev->pid == target() && $next->pid != target()) {
    /* being switched out */
    pid_off = t; last_cpu = c;
    if (pid_on) time_on <<< pid_off - pid_on;
  } else if ($prev->pid != target() && $next->pid == target()) {
    /* being switched in */
    pid_on = t;
    if (pid_off) time_off <<< pid_on - pid_off;
    if (c != last_cpu) ++migrated;
  }
  /* watch what other processes scheduled while pid off */
  if (pid_off > pid_on && c == last_cpu) {
    cycle_thief[$next->pid] <<< 1;
  }
}

probe end {
  printf("\n")
  printf("task %d migrated: %d\n", target(), migrated)
  if (@count(time_on)) {
    printf("\n")
    printf("task %d on processor (us):\n", target())
    print(@hist_log(time_on));
  }
  if (@count(time_off)) {
    printf("\n")
    printf("task %d off processor (us)\n", target())
      print(@hist_log(time_off));
  }

  printf("other pids taking processor from task %d\n", target())
  foreach (p in cycle_thief-)
    printf("%6d %10d\n", p, @count(cycle_thief[p]))
}