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