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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