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 35 static inline int ksft_exit_pass(void) 36 { 37 exit(0); 38 } 39 static 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 51 long 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 59 struct 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 69 int 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 } 110 111 int 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