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1/* Measure mqueue timeout latency2 * by: john stultz (john.stultz@linaro.org)3 * (C) Copyright Linaro 20134 *5 * Inspired with permission from example test by:6 * Romain Francoise <romain@orebokech.com>7 * Licensed under the GPLv28 *9 * To build:10 * $ gcc mqueue-lat.c -o mqueue-lat -lrt11 *12 * This program is free software: you can redistribute it and/or modify13 * it under the terms of the GNU General Public License as published by14 * the Free Software Foundation, either version 2 of the License, or15 * (at your option) any later version.16 *17 * This program is distributed in the hope that it will be useful,18 * but WITHOUT ANY WARRANTY; without even the implied warranty of19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the20 * GNU General Public License for more details.21 */22 23#include <stdio.h>24#include <stdlib.h>25#include <time.h>26#include <sys/time.h>27#include <sys/timex.h>28#include <string.h>29#include <signal.h>30#include <errno.h>31#include <mqueue.h>32#include "../kselftest.h"33 34#define NSEC_PER_SEC 1000000000ULL35 36#define TARGET_TIMEOUT 100000000 /* 100ms in nanoseconds */37#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */38 39 40long long timespec_sub(struct timespec a, struct timespec b)41{42 long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;43 44 ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;45 return ret;46}47 48struct timespec timespec_add(struct timespec ts, unsigned long long ns)49{50 ts.tv_nsec += ns;51 while (ts.tv_nsec >= NSEC_PER_SEC) {52 ts.tv_nsec -= NSEC_PER_SEC;53 ts.tv_sec++;54 }55 return ts;56}57 58int mqueue_lat_test(void)59{60 61 mqd_t q;62 struct mq_attr attr;63 struct timespec start, end, now, target;64 int i, count, ret;65 66 q = mq_open("/foo", O_CREAT | O_RDONLY, 0666, NULL);67 if (q < 0) {68 perror("mq_open");69 return -1;70 }71 mq_getattr(q, &attr);72 73 74 count = 100;75 clock_gettime(CLOCK_MONOTONIC, &start);76 77 for (i = 0; i < count; i++) {78 char buf[attr.mq_msgsize];79 80 clock_gettime(CLOCK_REALTIME, &now);81 target = now;82 target = timespec_add(now, TARGET_TIMEOUT); /* 100ms */83 84 ret = mq_timedreceive(q, buf, sizeof(buf), NULL, &target);85 if (ret < 0 && errno != ETIMEDOUT) {86 perror("mq_timedreceive");87 return -1;88 }89 }90 clock_gettime(CLOCK_MONOTONIC, &end);91 92 mq_close(q);93 94 if ((timespec_sub(start, end)/count) > TARGET_TIMEOUT + UNRESONABLE_LATENCY)95 return -1;96 97 return 0;98}99 100int main(int argc, char **argv)101{102 int ret;103 104 printf("Mqueue latency : ");105 fflush(stdout);106 107 ret = mqueue_lat_test();108 if (ret < 0) {109 printf("[FAILED]\n");110 ksft_exit_fail();111 }112 printf("[OK]\n");113 ksft_exit_pass();114}115