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
timespec_sub(struct timespec a,struct timespec b)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
timespec_add(struct timespec ts,unsigned long long ns)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
mqueue_lat_test(void)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
main(int argc,char ** argv)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 }
115