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167 lines
4.3 KiB
167 lines
4.3 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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* rdtsc-latency.c
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*
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* DESCRIPTION
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* Simple program to measure the time between several pairs of calls to
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* rdtsc(). Based off of gtod-latency.c
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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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* Use "-j" to enable jvm simulator.
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*
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* AUTHOR
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* Darren Hart <dvhltc@us.ibm.com>
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*
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* HISTORY
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* 2006-Nov-15: Initial version by Darren Hart <dvhltc@us.ibm.com>
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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 <errno.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 1000000
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void usage(void)
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{
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rt_help();
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printf("rdtsc-latency specific options:\n");
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printf(" This testcase don't expect any commandline 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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/* return difference in nanoseconds */
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unsigned long long tv_minus(struct timeval *tv_start, struct timeval *tv_end)
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{
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unsigned long long nsecs;
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nsecs = (tv_end->tv_sec - tv_start->tv_sec) * 1000000000ULL;
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nsecs += (tv_end->tv_usec - tv_start->tv_usec) * 1000;
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return nsecs;
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}
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/* calculate the tsc period */
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unsigned long long tsc_period_ps(void)
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{
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struct timeval tv_start;
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struct timeval tv_end;
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unsigned long long tsc_start, tsc_end;
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rdtscll(tsc_start);
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gettimeofday(&tv_start, NULL);
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sleep(1);
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rdtscll(tsc_end);
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gettimeofday(&tv_end, NULL);
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return (1000 * tv_minus(&tv_start, &tv_end)) / tsc_minus(tsc_start,
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tsc_end);
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}
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int main(int argc, char *argv[])
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{
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int i, err;
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unsigned long long deltas[ITERATIONS];
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unsigned long long max, min, avg, tsc_a, tsc_b, tsc_period;
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struct sched_param param;
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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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setup();
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rt_init("h", parse_args, argc, argv);
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/* no arguments */
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if (argc > 1) {
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fprintf(stderr, "%s accepts no arguments\n", argv[0]);
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exit(1);
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}
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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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/* calculate the tsc period in picoseconds */
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tsc_period = tsc_period_ps();
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/* collect ITERATIONS pairs of gtod calls */
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max = min = avg = 0;
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for (i = 0; i < ITERATIONS; i++) {
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rdtscll(tsc_a);
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rdtscll(tsc_b);
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deltas[i] = (tsc_minus(tsc_a, tsc_b) * tsc_period) / 1000; /* tsc period is in ps */
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if (i == 0 || deltas[i] < min)
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min = deltas[i];
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if (deltas[i] > max)
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max = deltas[i];
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avg += deltas[i];
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}
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avg /= ITERATIONS;
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/* report on deltas */
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printf("Calculated tsc period = %llu ps\n", tsc_period);
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printf("%d pairs of rdtsc() calls completed\n", ITERATIONS);
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printf("Time between calls:\n");
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printf(" Max: %llu ns\n", max);
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printf(" Min: %llu ns\n", min);
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printf(" Avg: %llu ns\n", avg);
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return 0;
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}
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