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 }
115