root/tools/testing/selftests/timers/mqueue-lat.c

DEFINITIONS

1. timespec_sub
2. timespec_add
3. mqueue_lat_test
4. main

   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 
  40 long 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 
  48 struct 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 
  58 int 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 
 100 int 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                 return ksft_exit_fail();
 111         }
 112         printf("[OK]\n");
 113         return ksft_exit_pass();
 114 }