A DTrace script to print the average, min, and max run queue count by CPU

runq.d

#!/usr/sbin/dtrace -s
/*
 * runq.d - run queue sizes by CPU.
 *
 * This prints the average, min, and max run queue count by CPU each second.  A
 * consistently large run queue count is a sign of CPU saturation.
 *
 * USAGE:	runq.d
 *
 * FIELDS:
 *		CPU		    cpu ID
 *		avg-rq    average run queue count over the last 1 second (sorry, no floats in D)
 *		min-rq    minimum run queue count over the last 1 second
 *		max-rq    maximum run queue count over the last 1 second
 *		%idle     percent of the time the CPU state was idle
 *
 * 03-Nov-2015  Colin Jones
 */

#pragma D option quiet

profile-1000hz
/curthread->last_processor->state == 4/ /* idle */
{
  @idle[cpu] = count();
}

profile-1000hz
{
  this->runq_count = curthread->last_processor->processor_set->pset_runq.count;
  @min_rq[cpu] = min(this->runq_count);
  @max_rq[cpu] = max(this->runq_count);
  @avg_rq[cpu] = avg(this->runq_count);
}

profile:::tick-1sec
{
  /* turn it into a percentage: we take 1000 samples/second, so dividing the idle sample count by 10 makes sense */
  normalize(@idle, 10);
  printf("\n%8s %8s %8s %8s %8s\n", "CPU", "avg-rq", "min-rq", "max-rq", "%idle");
  printa("%8d %@8d %@8d %@8d %@8d\n", @avg_rq, @min_rq, @max_rq, @idle);
  clear(@idle);
  clear(@min_rq);
  clear(@max_rq);
  clear(@avg_rq);
}