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Filename : bkl_stats.stp
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#!/usr/bin/stap

/*
 * Copyright (C) 2009 Red Hat Inc.
 * 
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License v.2.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Description: displays statistics for waiting and holding big kernel lock (BKL)
 *
 * Run: stap bkl_stats.stap
 *
 * Author: William Cohen <wcohen@redhat.com> 
 */

global holder_time
global holder_stats, wait_stats
global names

probe begin { printf("biglock_stats running\n"); }

probe end, timer.s(5) {
  print_stats()
}

function print_stats() {
  # print out time waiting and time lock held
  printf("big kernel lock waiting statistics\n");
  printf("%-16s %6s %6s %6s %6s %6s\n",
         "name", "tid", "count", "min", "avg", "max");
  foreach (p+ in names) {
    if (@count(wait_stats[p]))
      printf("%16s %6d %6d %6d %6d %6d\n", names[p], p,
            @count(wait_stats[p]), @min(wait_stats[p]),
            @avg(wait_stats[p]), @max(wait_stats[p]));
  }

  printf("\n\nbig kernel lock holder statistics\n");
  printf("%-16s %6s %6s %6s %6s %6s\n",
         "name", "tid", "count", "min", "avg", "max");
  foreach (p+ in names) {
    if (@count(holder_stats[p]))
      printf("%16s %6d %6d %6d %6d %6d\n", names[p], p,
            @count(holder_stats[p]), @min(holder_stats[p]),
            @avg(holder_stats[p]), @max(holder_stats[p]));
  }
}

probe kernel.function("_lock_kernel").return!,
      kernel.function("lock_kernel").return
{
  t = gettimeofday_us()
  s = @entry(gettimeofday_us())
  holder_time[tid()] = t
  # record the amount of time waiting for the lock
  if (s) {
     wait_stats[tid()] <<< t - s
     names[tid()] = execname()
  }
}

probe kernel.function("_unlock_kernel")!,
      kernel.function("unlock_kernel")
{
  t = gettimeofday_us()
  s = holder_time[tid()]
  holder_time[tid()] = t
  # record the amount of time the process held the lock
  if (s) {
     holder_stats[tid()] <<< t - s
     names[tid()] = execname()
  }
}