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/* Measure mqueue timeout latency
* by: john stultz (john.stultz@linaro.org)
* (C) Copyright Linaro 2013
*
* Inspired with permission from example test by:
* Romain Francoise <romain@orebokech.com>
* Licensed under the GPLv2
*
* To build:
* $ gcc mqueue-lat.c -o mqueue-lat -lrt
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>
#include <sys/timex.h>
#include <string.h>
#include <signal.h>
#include <errno.h>
#include <mqueue.h>
#include "../kselftest.h"
#define NSEC_PER_SEC 1000000000ULL
#define TARGET_TIMEOUT 100000000 /* 100ms in nanoseconds */
#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
long long timespec_sub(struct timespec a, struct timespec b)
{
long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
return ret;
}
struct timespec timespec_add(struct timespec ts, unsigned long long ns)
{
ts.tv_nsec += ns;
while (ts.tv_nsec >= NSEC_PER_SEC) {
ts.tv_nsec -= NSEC_PER_SEC;
ts.tv_sec++;
}
return ts;
}
int mqueue_lat_test(void)
{
mqd_t q;
struct mq_attr attr;
struct timespec start, end, now, target;
int i, count, ret;
q = mq_open("/foo", O_CREAT | O_RDONLY, 0666, NULL);
if (q < 0) {
perror("mq_open");
return -1;
}
mq_getattr(q, &attr);
count = 100;
clock_gettime(CLOCK_MONOTONIC, &start);
for (i = 0; i < count; i++) {
char buf[attr.mq_msgsize];
clock_gettime(CLOCK_REALTIME, &now);
target = now;
target = timespec_add(now, TARGET_TIMEOUT); /* 100ms */
ret = mq_timedreceive(q, buf, sizeof(buf), NULL, &target);
if (ret < 0 && errno != ETIMEDOUT) {
perror("mq_timedreceive");
return -1;
}
}
clock_gettime(CLOCK_MONOTONIC, &end);
mq_close(q);
if ((timespec_sub(start, end)/count) > TARGET_TIMEOUT + UNRESONABLE_LATENCY)
return -1;
return 0;
}
int main(int argc, char **argv)
{
int ret;
printf("Mqueue latency : ");
ret = mqueue_lat_test();
if (ret < 0) {
printf("[FAILED]\n");
return ksft_exit_fail();
}
printf("[OK]\n");
return ksft_exit_pass();
}
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