gethostlatency.bt

#!/usr/bin/env bpftrace
/*
 * gethostlatency	Trace getaddrinfo/gethostbyname[2] calls.
 *			For Linux, uses bpftrace and eBPF.
 *
 * This can be useful for identifying DNS latency, by identifying which
 * remote host name lookups were slow, and by how much.
 *
 * This uses dynamic tracing of user-level functions and registers, and may
 # need modifications to match your software and processor architecture.
 *
 * USAGE: gethostlatency.bt
 *
 * This is a bpftrace version of the bcc tool of the same name.
 *
 * Copyright 2018 Netflix, Inc.
 * Licensed under the Apache License, Version 2.0 (the "License")
 *
 * 08-Sep-2018	Brendan Gregg	Created this.
 */

config = { missing_probes = "ignore" }

BEGIN
{
	printf("Tracing getaddr/gethost calls... Hit Ctrl-C to end.\n");
	printf("%-9s %-6s %-16s %6s %s\n", "TIME", "PID", "COMM", "LATms",
	    "HOST");
}

uprobe:libc:getaddrinfo,
uprobe:libc:gethostbyname,
uprobe:libc:gethostbyname2
{
	@start[tid] = nsecs;
	@name[tid] = arg0;
}

uretprobe:libc:getaddrinfo,
uretprobe:libc:gethostbyname,
uretprobe:libc:gethostbyname2
/@start[tid]/
{
	$latms = (nsecs - @start[tid]) / 1e6;
	time("%H:%M:%S  ");
	printf("%-6d %-16s %6d %s\n", pid, comm, $latms, str(@name[tid]));
	delete(@start, tid);
	delete(@name, tid);
}