LXR linux/tools/testing/selftests/timers/mqueue-lat.c

   1/* Measure mqueue timeout latency
   2 *              by: john stultz (john.stultz@linaro.org)
   3 *              (C) Copyright Linaro 2013
   4 *
   5 *              Inspired with permission from example test by:
   6 *                      Romain Francoise <romain@orebokech.com>
   7 *              Licensed under the GPLv2
   8 *
   9 *  To build:
  10 *      $ gcc mqueue-lat.c -o mqueue-lat -lrt
  11 *
  12 *   This program is free software: you can redistribute it and/or modify
  13 *   it under the terms of the GNU General Public License as published by
  14 *   the Free Software Foundation, either version 2 of the License, or
  15 *   (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 of
  19 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 *   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#ifdef KTEST
  33#include "../kselftest.h"
  34#else
  35static inline int ksft_exit_pass(void)
  36{
  37        exit(0);
  38}
  39static inline int ksft_exit_fail(void)
  40{
  41        exit(1);
  42}
  43#endif
  44
  45#define NSEC_PER_SEC 1000000000ULL
  46
  47#define TARGET_TIMEOUT          100000000       /* 100ms in nanoseconds */
  48#define UNRESONABLE_LATENCY     40000000        /* 40ms in nanosecs */
  49
  50
  51long long timespec_sub(struct timespec a, struct timespec b)
  52{
  53        long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
  54
  55        ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
  56        return ret;
  57}
  58
  59struct timespec timespec_add(struct timespec ts, unsigned long long ns)
  60{
  61        ts.tv_nsec += ns;
  62        while (ts.tv_nsec >= NSEC_PER_SEC) {
  63                ts.tv_nsec -= NSEC_PER_SEC;
  64                ts.tv_sec++;
  65        }
  66        return ts;
  67}
  68
  69int mqueue_lat_test(void)
  70{
  71
  72        mqd_t q;
  73        struct mq_attr attr;
  74        struct timespec start, end, now, target;
  75        int i, count, ret;
  76
  77        q = mq_open("/foo", O_CREAT | O_RDONLY, 0666, NULL);
  78        if (q < 0) {
  79                perror("mq_open");
  80                return -1;
  81        }
  82        mq_getattr(q, &attr);
  83
  84
  85        count = 100;
  86        clock_gettime(CLOCK_MONOTONIC, &start);
  87
  88        for (i = 0; i < count; i++) {
  89                char buf[attr.mq_msgsize];
  90
  91                clock_gettime(CLOCK_REALTIME, &now);
  92                target = now;
  93                target = timespec_add(now, TARGET_TIMEOUT); /* 100ms */
  94
  95                ret = mq_timedreceive(q, buf, sizeof(buf), NULL, &target);
  96                if (ret < 0 && errno != ETIMEDOUT) {
  97                        perror("mq_timedreceive");
  98                        return -1;
  99                }
 100        }
 101        clock_gettime(CLOCK_MONOTONIC, &end);
 102
 103        mq_close(q);
 104
 105        if ((timespec_sub(start, end)/count) > TARGET_TIMEOUT + UNRESONABLE_LATENCY)
 106                return -1;
 107
 108        return 0;
 109}
 110
 111int main(int argc, char **argv)
 112{
 113        int ret;
 114
 115        printf("Mqueue latency :                          ");
 116
 117        ret = mqueue_lat_test();
 118        if (ret < 0) {
 119                printf("[FAILED]\n");
 120                return ksft_exit_fail();
 121        }
 122        printf("[OK]\n");
 123        return ksft_exit_pass();
 124}
 125