/* $NetBSD: latency1.c,v 1.1 2008/05/23 22:22:36 ad Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* THIS IS NOT A GOOD TEST OF REALTIME DISPATCH LATENCY AND SHOULD NOT
* BE USED AS ONE.
*
* Two threads are involved in the test. Every 100ms the first thread
* writes a byte down a pipe. The second thread waits to read it. The
* time taken for the byte to move between threads is measured. With
* no arguments, it uses timeshared threads. When given any argument
* (junk will do) it uses realtime threads. Ctrl-C ends the test.
*/
#include <sys/mman.h>
#include <sys/resource.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <limits.h>
#include <signal.h>
#include <err.h>
pthread_barrier_t barrier;
struct timespec start;
int fds[2];
int done;
long max = 0;
long min = LONG_MAX;
static void
sigint(int junk)
{
done = 1;
}
static void *
reader(void *cookie)
{
struct timespec end;
char buf[1];
long val;
for (;;) {
(void)pthread_barrier_wait(&barrier);
if (read(fds[0], buf, sizeof(buf)) == -1) {
err(1, "read");
}
clock_gettime(CLOCK_MONOTONIC, &end);
timespecsub(&end, &start, &end);
val = (long)end.tv_sec * 1000000000 + (long)end.tv_nsec;
printf("%ld\n", val);
if (val > max)
max = val;
if (val < min)
min = val;
}
}
int
main(int argc, char *argv[])
{
static struct timespec delay = { 0, 100000000 }; /* 100ms */
struct sched_param sp;
pthread_t pt;
char buf[1];
if (geteuid() != 0) {
errx(1, "run me as root");
}
if (pipe(fds)) {
err(1, "pipe");
}
pthread_barrier_init(&barrier, NULL, 2);
if (pthread_create(&pt, NULL, reader, NULL)) {
errx(1, "pthread_create failed");
}
if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
err(1, "mlockall");
}
if (signal(SIGINT, sigint)) {
err(1, "siginal");
}
if (argc != 1) {
/* Have an argument, use realtime priorities. */
sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 2;
if (pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp)) {
errx(1, "pthread_setschedparam");
}
sp.sched_priority = sched_get_priority_max(SCHED_FIFO) - 1;
if (pthread_setschedparam(pt, SCHED_FIFO, &sp)) {
errx(1, "pthread_setschedparam");
}
} else {
/* Not realtime, set the maximum timeshared priority. */
if (setpriority(PRIO_PROCESS, 0, -20)) {
err(1, "setpriority");
}
}
do {
(void)pthread_barrier_wait(&barrier);
while (nanosleep(&delay, NULL) != 0) {
/* nothing */
}
clock_gettime(CLOCK_MONOTONIC, &start);
if (write(fds[1], buf, sizeof(buf)) == -1) {
err(1, "write");
}
} while (!done);
printf("\nmin %ldns, max=%ldns\n", min, max);
return 0;
}
