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Filename : cycle_thief.stp
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#!/usr/bin/stap
# Copyright (C) 2010-2016 Red Hat, Inc.
# Write by William Cohen <wcohen@redhat.com>
#
# cycle_thief provide the following information for the specified pid:
#   Number of times the task is migrated to another cpu
#   How long the task is scheduled on and off a processor
#   Tasks that run when the task is scheduled off the processor
#   IRQs that run when the task is scheduled on 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, irq_entry
global cycle_thief, irq_thief, cycle_thief_name


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;
    cycle_thief_name[$next->pid] = kernel_string($next->comm)
  }
}

/* what interrupts occur while process is running */
probe kernel.{trace("irq_handler_entry")!, trace("irq_entry")}
{
  t = gettimeofday_us(); c = cpu();
  i = @defined($irq) ? $irq : $id;
  /* watch what irq run while pid is running */
  if (pid_on > pid_off && c == last_cpu) {
    irq_entry[i] = t;
  }
}


probe kernel.{trace("irq_handler_exit")!, trace("irq_exit")}
{
  i = @defined($irq) ? $irq : $id;
  t = gettimeofday_us(); c = cpu(); irqt=irq_entry[i]
  /* watch what irq run while pid is running */
  if (pid_on > pid_off && c == last_cpu &&  irqt) {
     irq_thief[i] <<< t - irqt;
     delete irq_entry[i];
  }
}


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

  printf("\n")
  printf("irq taking processor from task %d\n", target())

  printf("%6s %10s %10s %10s %10s %10s\n", "irq", "count",
      "min(us)", "avg(us)", "max(us)", "variance(us^2)")
  foreach (p in irq_thief-)
    printf("%6d %10d %10d %10d %10d %10d\n", p, @count(irq_thief[p]),
      @min(irq_thief[p]), @avg(irq_thief[p]), @max(irq_thief[p]),
      @variance(irq_thief[p]))

}