1/*	$NetBSD: select.c,v 1.2 2008/03/21 16:03:33 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 * THIS IS NOT A GOOD TEST OF REALTIME DISPATCH LATENCY AND SHOULD NOT
31 * BE USED AS ONE.
32 *
33 * Two threads are involved in the test.  Every 100ms the first thread
34 * writes a byte down a pipe.  The second thread waits to read it.  The
35 * time taken for the byte to move between threads is measured.  With
36 * no arguments, it uses timeshared threads.  When given any argument
37 * (junk will do) it uses realtime threads.  Ctrl-C ends the test.
38 */
39
40#include <sys/mman.h>
41#include <sys/resource.h>
42
43#include <pthread.h>
44#include <stdio.h>
45#include <stdlib.h>
46#include <unistd.h>
47#include <sched.h>
48#include <limits.h>
49#include <signal.h>
50#include <err.h>
51
52pthread_barrier_t	barrier;
53struct timespec		start;
54int			fds[2];
55int 			done;
56long			max = 0;
57long			min = LONG_MAX;
58
59static void
60sigint(int junk)
61{
62
63	done = 1;
64}
65
66static void *
67reader(void *cookie)
68{
69	struct timespec end;
70	char buf[1];
71	long val;
72
73	for (;;) {
74		(void)pthread_barrier_wait(&barrier);
75		if (read(fds[0], buf, sizeof(buf)) == -1) {
76			err(1, "read");
77		}
78		clock_gettime(CLOCK_MONOTONIC, &end);
79		timespecsub(&end, &start, &end);
80		val = (long)end.tv_sec * 1000000000 + (long)end.tv_nsec;
81		printf("%ld\n", val);
82		if (val > max)
83			max = val;
84		if (val < min)
85			min = val;
86	}
87}
88
89int
90main(int argc, char *argv[])
91{
92	static struct timespec delay = { 0, 100000000 };	/* 100ms */
93	struct sched_param sp;
94	pthread_t pt;
95	char buf[1];
96
97	if (geteuid() != 0) {
98		errx(1, "run me as root");
99	}
100	if (pipe(fds)) {
101		err(1, "pipe");
102	}
103	pthread_barrier_init(&barrier, NULL, 2);
104	if (pthread_create(&pt, NULL, reader, NULL)) {
105		errx(1, "pthread_create failed");
106	}
107	if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
108		err(1, "mlockall");
109	}
110	if (signal(SIGINT, sigint)) {
111		err(1, "siginal");
112	}
113	if (argc != 1) {
114		/* Have an argument, use realtime priorities. */
115		sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 2;
116		if (pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp)) {
117			errx(1, "pthread_setschedparam");
118		}
119		sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 1;
120		if (pthread_setschedparam(pt, SCHED_FIFO, &sp)) {
121			errx(1, "pthread_setschedparam");
122		}
123	} else {
124		/* Not realtime, set the maximum timeshared priority. */
125		if (setpriority(PRIO_PROCESS, 0, -20)) {
126			err(1, "setpriority");
127		}
128	}
129
130	do {
131		(void)pthread_barrier_wait(&barrier);
132		while (nanosleep(&delay, NULL) != 0) {
133			/* nothing */
134		}
135		clock_gettime(CLOCK_MONOTONIC, &start);
136		if (write(fds[1], buf, sizeof(buf)) == -1) {
137			err(1, "write");
138		}
139	} while (!done);
140
141	printf("\nmin %ldns, max=%ldns\n", min, max);
142	return 0;
143}
144