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#include "../kselftest.h"
  33
  34#define NSEC_PER_SEC 1000000000ULL
  35
  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
 106        ret = mqueue_lat_test();
 107        if (ret < 0) {
 108                printf("[FAILED]\n");
 109                return ksft_exit_fail();
 110        }
 111        printf("[OK]\n");
 112        return ksft_exit_pass();
 113}
 114