offcputime.bt

#!/usr/local/bin/bpftrace
/*
 * offcputime - Summarize off-CPU time by stack trace (bpftrace version).
 *
 * See BPF Performance Tools, Chapter 6, for an explanation of this tool.
 *
 * Copyright (c) 2019 Brendan Gregg.
 * Licensed under the Apache License, Version 2.0 (the "License").
 * This was originally created for the BPF Performance Tools book
 * published by Addison Wesley. ISBN-13: 9780136554820
 * When copying or porting, include this comment.
 *
 * 16-Feb-2019  Brendan Gregg   Created this.
 */

#include <linux/sched.h>

BEGIN
{
	printf("Tracing nanosecond time in off-CPU stacks. Ctrl-C to end.\n");
}

kprobe:finish_task_switch
{
	// record previous thread sleep time
	$prev = (struct task_struct *)arg0;
	if ($1 == 0 || $prev->tgid == $1) {
		@start[$prev->pid] = nsecs;
	}

	// get the current thread start time
	$last = @start[tid];
	if ($last != 0) {
		@[kstack, ustack, comm] = sum(nsecs - $last);
		delete(@start[tid]);
	}
}

END
{
	clear(@start);
}