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
ksft_exit_pass(void)35 static inline int ksft_exit_pass(void)
36 {
37 exit(0);
38 }
ksft_exit_fail(void)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
timespec_sub(struct timespec a,struct timespec b)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
timespec_add(struct timespec ts,unsigned long long ns)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
mqueue_lat_test(void)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
main(int argc,char ** argv)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