biostacks.bt

#!/usr/bin/env bpftrace
/*
 * biostacks - Show disk I/O latency with initialization stacks.
 *
 * See BPF Performance Tools, Chapter 9, 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.
 */

BEGIN
{
	printf("Tracing block I/O with init stacks. Hit Ctrl-C to end.\n");
}

tracepoint:block:block_io_start
{
	$key = (args.dev, args.sector);
	@reqstack[$key] = kstack;
	@reqts[$key] = nsecs;
}

tracepoint:block:block_rq_issue
/@reqts[args.dev, args.sector]/
{
	$key = (args.dev, args.sector);
	@usecs[@reqstack[$key]] = hist(nsecs - @reqts[$key]);
	delete(@reqstack, $key);
	delete(@reqts, $key);
}

END
{
	clear(@reqstack); clear(@reqts);
}