latency2.c revision 1.1 
1/*	$NetBSD: latency2.c,v 1.1 2008/05/28 11:34:07 ad Exp $	*/
2
3/*-
4 * Copyright (c) 2008 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/*
30 * Two threads are involved in the test.  Every 100ms the first thread
31 * wakes the second.  The time taken for the wakeup to arrive is
32 * measured.  Ctrl-C ends the test.
33 */
34
35#include <sys/mman.h>
36#include <sys/resource.h>
37
38#include <pthread.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <unistd.h>
42#include <sched.h>
43#include <limits.h>
44#include <signal.h>
45#include <err.h>
46#include <lwp.h>
47
48pthread_barrier_t	barrier;
49struct timespec		start;
50int 			done;
51long			max = 0;
52long			min = LONG_MAX;
53lwpid_t			lid;
54long			sum;
55long			samples;
56
57static void
58sigint(int junk)
59{
60
61	done = 1;
62}
63
64static void *
65reader(void *cookie)
66{
67	struct timespec end;
68	long val;
69
70	lid = _lwp_self();
71
72	for (;;) {
73		(void)pthread_barrier_wait(&barrier);
74		while (_lwp_park(NULL, 0, &lid, NULL) != 0) {
75			/* nothing */
76		}
77		clock_gettime(CLOCK_MONOTONIC, &end);
78		timespecsub(&end, &start, &end);
79		val = (long)end.tv_sec * 1000000000 + (long)end.tv_nsec;
80		printf("%ld\n", val);
81		if (val > max)
82			max = val;
83		if (val < min)
84			min = val;
85		sum += val;
86		samples++;
87	}
88}
89
90int
91main(int argc, char *argv[])
92{
93	static struct timespec delay = { 0, 100000000 };	/* 100ms */
94	struct sched_param sp;
95	pthread_t pt;
96	cpuset_t *cs;
97	int cpuid;
98
99	if (geteuid() != 0) {
100		errx(1, "run me as root");
101	}
102	pthread_barrier_init(&barrier, NULL, 2);
103	if (pthread_create(&pt, NULL, reader, NULL)) {
104		errx(1, "pthread_create failed");
105	}
106	if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
107		err(1, "mlockall");
108	}
109	if (signal(SIGINT, sigint)) {
110		err(1, "siginal");
111	}
112
113	cs = calloc(sizeof(cpuset_t), 0);
114	if (cs == NULL) {
115		err(1, "malloc");
116	}
117	cpuid = pthread_curcpu_np();
118	CPU_SET(cpuid, cs);
119	if (_sched_setaffinity(0, 0, sizeof(cpuset_t), cs) < 0) {
120		err(1, "_sched_setaffinity");
121	}
122
123	sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 2;
124	if (pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp)) {
125		errx(1, "pthread_setschedparam");
126	}
127	sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 1;
128	if (pthread_setschedparam(pt, SCHED_FIFO, &sp)) {
129		errx(1, "pthread_setschedparam");
130	}
131
132	do {
133		(void)pthread_barrier_wait(&barrier);
134		while (nanosleep(&delay, NULL) != 0) {
135			/* nothing */
136		}
137		clock_gettime(CLOCK_MONOTONIC, &start);
138		if (_lwp_unpark(lid, &lid) != 0) {
139			err(1, "_lwp_unpark");
140		}
141	} while (!done);
142
143	printf("\nmin=%ldns, max=%ldns, mean=%ldns\n", min, max, sum / samples);
144	return 0;
145}
146