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 ksft_exit_fail(); 111 } 112 printf("[OK]\n"); 113 ksft_exit_pass(); 114 } 115