1/*-
2 * Copyright (c) 2014, Neville-Neil Consulting
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD$
27 *
28 * Author: George V. Neville-Neil
29 *
30 */
31
32/*
33 * Calculate the time overhead of starting, stopping, and recording
34 * pmc counters.
35 *
36 * The only argument is a counter name, such as "instruction-retired"
37 * which is CPU dependent and can be found with pmmcontrol(8) using
38 * pmccontrol -L.
39 *
40 * The start, stop, read and write operations are timed using the
41 * rdtsc() macro which reads the Time Stamp Counter on the CPU.
42 */
43
44#include <stdio.h>
45#include <err.h>
46#include <sysexits.h>
47#include <sys/types.h>
48#include <machine/cpufunc.h>
49#include <pmc.h>
50
51int
52main(int argc, char **argv)
53{
54	pmc_id_t pmcid;
55	pmc_value_t read_value;
56	pmc_value_t read_clear_value;
57	uint64_t tsc1, write_cyc, start_cyc, read_cyc, stop_cyc;
58	char *counter_name;
59
60	if (argc != 2)
61		err(EX_USAGE, "counter-name required");
62
63	counter_name = argv[1];
64
65	if (pmc_init() != 0)
66		err(EX_OSERR, "hwpmc(4) not loaded, kldload or update your kernel");
67
68	if (pmc_allocate(counter_name, PMC_MODE_SC, 0, 0, &pmcid, 64*1024) < 0)
69		err(EX_OSERR, "failed to allocate %s as a system counter in counting mode",
70		    counter_name);
71
72	tsc1 = rdtsc();
73	if (pmc_write(pmcid, 0) < 0)
74		err(EX_OSERR, "failed to zero counter %s", counter_name);
75	write_cyc = rdtsc() - tsc1;
76
77	tsc1 = rdtsc();
78	if (pmc_start(pmcid) < 0)
79		err(EX_OSERR, "failed to start counter %s", counter_name);
80	start_cyc = rdtsc() - tsc1;
81
82	tsc1 = rdtsc();
83	if (pmc_read(pmcid, &read_value) < 0)
84		err(EX_OSERR, "failed to read counter %s", counter_name);
85	read_cyc = rdtsc() - tsc1;
86
87	tsc1 = rdtsc();
88	if (pmc_stop(pmcid) < 0)
89		err(EX_OSERR, "failed to stop counter %s", counter_name);
90	stop_cyc = rdtsc() - tsc1;
91
92	if (pmc_rw(pmcid, 0, &read_clear_value))
93		err(EX_OSERR, "failed to read and zero %s", counter_name);
94
95	if (pmc_release(pmcid) < 0)
96		err(EX_OSERR, "failed to release %s as a system counter in counting mode",
97		    counter_name);
98
99	printf("Counter %s, read value %ld, read/clear value %ld\n",
100	    counter_name, read_value, read_clear_value);
101	printf("Cycles to start: %ld\tstop: %ld\tread: %ld\twrite: %ld\n",
102	    start_cyc, stop_cyc, read_cyc, stop_cyc);
103
104	return(0);
105}
106
107