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159 lines
4.1 KiB
159 lines
4.1 KiB
/******************************************************************************
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*
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* Copyright © International Business Machines Corp., 2006, 2008
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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
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* the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* NAME
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* preempt_timing.c
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*
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* DESCRIPTION
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* This program indicated the preemption delays that may be encountered
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* by realtime apps. The program runs with the scheduling policy of
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* SCHED_FIFO at a maximum SCHED_FIFO priority. It is bound to a single
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* processor and its address space is locked as well. It makes successive
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* calls to the gettimeofday() function(via inlined assembly to read the
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* TSC).The value returned between two such consecutive calls is reported
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* as the latency.
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* The maximum, minimum and average delays are reported for x pairs of such
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* calls.
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*
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* USAGE:
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* Use run_auto.sh script in current directory to build and run test.
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*
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* AUTHOR
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*
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*
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* HISTORY
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*
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*
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*****************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <sched.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/mman.h>
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#include <stdint.h>
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#include <librttest.h>
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#include <libtsc.h>
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#define ITERATIONS 1000000ULL
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#define INTERVALS 10
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void usage(void)
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{
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rt_help();
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printf("preempt_timing specific options:\n");
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}
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int parse_args(int c, char *v)
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{
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int handled = 1;
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switch (c) {
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case 'h':
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usage();
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exit(0);
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default:
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handled = 0;
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break;
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}
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return handled;
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}
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unsigned long long sample_list[ITERATIONS];
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int main(int argc, char *argv[])
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{
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unsigned long long i, j, delta, min, max, avg;
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struct sched_param param;
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cpu_set_t mask;
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int err;
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#ifdef TSC_UNSUPPORTED
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printf("Error: test cannot be executed on an arch wihout TSC.\n");
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return ENOTSUP;
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#endif
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max = avg = 0;
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min = -1;
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setup();
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rt_init("h", parse_args, argc, argv);
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/* switch to SCHED_FIFO 99 */
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param.sched_priority = sched_get_priority_max(SCHED_FIFO);
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err = sched_setscheduler(0, SCHED_FIFO, ¶m);
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/* Check that the user has the appropriate privileges */
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if (err) {
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if (errno == EPERM) {
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fprintf(stderr,
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"This program runs with a scheduling policy of SCHED_FIFO at priority %d\n",
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param.sched_priority);
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fprintf(stderr,
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"You don't have the necessary privileges to create such a real-time process.\n");
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} else {
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fprintf(stderr, "Failed to set scheduler, errno %d\n",
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errno);
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}
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exit(1);
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}
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/* BIND TO A SINGLE CPU */
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CPU_ZERO(&mask);
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CPU_SET(0, &mask);
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err = sched_setaffinity(0, sizeof(mask), &mask);
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if (err < 0) {
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printf("Can't set affinity: %d %s\n", err, strerror(err));
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exit(-1);
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}
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for (j = 0; j < INTERVALS; j++) {
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/* Collect samples */
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for (i = 0; i < ITERATIONS; i++)
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rdtscll(sample_list[i]);
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/* Process samples */
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for (i = 0; i < (ITERATIONS - 1); i++) {
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delta = sample_list[i + 1] - sample_list[i];
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if (delta < min)
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min = delta;
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if (delta > max)
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max = delta;
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if (delta > 100000)
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printf("maxd(%llu:%llu): %llu %llu = %llu\n", j,
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i, sample_list[i], sample_list[i + 1],
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delta);
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avg += delta;
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}
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usleep(100); /*let necessary things happen */
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}
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avg /= (ITERATIONS * INTERVALS);
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printf("%lld pairs of gettimeofday() calls completed\n",
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ITERATIONS * INTERVALS);
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printf("Time between calls:\n");
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printf("Minimum: %llu \n", min);
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printf("Maximum: %llu \n", max);
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printf("Average: %llu \n", avg);
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return 0;
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}
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