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
40long 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
48struct 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
58int 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
100int 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