1 /******************************************************************************
2 *
3 * Copyright © International Business Machines Corp., 2006, 2008
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
13 * the GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * NAME
20 * rdtsc-latency.c
21 *
22 * DESCRIPTION
23 * Simple program to measure the time between several pairs of calls to
24 * rdtsc(). Based off of gtod-latency.c
25 *
26 * USAGE:
27 * Use run_auto.sh script in current directory to build and run test.
28 * Use "-j" to enable jvm simulator.
29 *
30 * AUTHOR
31 * Darren Hart <dvhltc@us.ibm.com>
32 *
33 * HISTORY
34 * 2006-Nov-15: Initial version by Darren Hart <dvhltc@us.ibm.com>
35 *
36 *****************************************************************************/
37
38 #include <stdio.h>
39 #include <stdlib.h>
40 #include <unistd.h>
41 #include <sys/time.h>
42 #include <sys/types.h>
43 #include <sched.h>
44 #include <errno.h>
45 #include <stdint.h>
46 #include <librttest.h>
47
48 #include "tst_tsc.h"
49
50 #define ITERATIONS 1000000
51
usage(void)52 void usage(void)
53 {
54 rt_help();
55 printf("rdtsc-latency specific options:\n");
56 printf(" This testcase don't expect any commandline options\n");
57 }
58
parse_args(int c,char * v)59 int parse_args(int c, char *v)
60 {
61
62 int handled = 1;
63 switch (c) {
64 case 'h':
65 usage();
66 exit(0);
67 default:
68 handled = 0;
69 break;
70 }
71 return handled;
72 }
73
74 /* return difference in nanoseconds */
tv_minus(struct timeval * tv_start,struct timeval * tv_end)75 unsigned long long tv_minus(struct timeval *tv_start, struct timeval *tv_end)
76 {
77 unsigned long long nsecs;
78 nsecs = (tv_end->tv_sec - tv_start->tv_sec) * 1000000000ULL;
79 nsecs += (tv_end->tv_usec - tv_start->tv_usec) * 1000;
80 return nsecs;
81 }
82
83 /* calculate the tsc period */
tsc_period_ps(void)84 unsigned long long tsc_period_ps(void)
85 {
86 struct timeval tv_start;
87 struct timeval tv_end;
88 unsigned long long tsc_start, tsc_end;
89
90 rdtscll(tsc_start);
91 gettimeofday(&tv_start, NULL);
92 sleep(1);
93 rdtscll(tsc_end);
94 gettimeofday(&tv_end, NULL);
95
96 return (1000 * tv_minus(&tv_start, &tv_end)) / tsc_minus(tsc_start,
97 tsc_end);
98 }
99
main(int argc,char * argv[])100 int main(int argc, char *argv[])
101 {
102 int i, err;
103 unsigned long long deltas[ITERATIONS];
104 unsigned long long max, min, avg, tsc_a, tsc_b, tsc_period;
105 struct sched_param param;
106
107 #ifdef TSC_UNSUPPORTED
108 printf("Error: test cannot be executed on an arch wihout TSC.\n");
109 return ENOTSUP;
110 #endif
111
112 setup();
113
114 rt_init("h", parse_args, argc, argv);
115
116 /* no arguments */
117 if (argc > 1) {
118 fprintf(stderr, "%s accepts no arguments\n", argv[0]);
119 exit(1);
120 }
121
122 /* switch to SCHED_FIFO 99 */
123 param.sched_priority = sched_get_priority_max(SCHED_FIFO);
124 err = sched_setscheduler(0, SCHED_FIFO, ¶m);
125
126 /* Check that the user has the appropriate privileges */
127 if (err) {
128 if (errno == EPERM) {
129 fprintf(stderr,
130 "This program runs with a scheduling policy of SCHED_FIFO at priority %d\n",
131 param.sched_priority);
132 fprintf(stderr,
133 "You don't have the necessary privileges to create such a real-time process.\n");
134 } else {
135 fprintf(stderr, "Failed to set scheduler, errno %d\n",
136 errno);
137 }
138 exit(1);
139 }
140
141 /* calculate the tsc period in picoseconds */
142 tsc_period = tsc_period_ps();
143
144 /* collect ITERATIONS pairs of gtod calls */
145 max = min = avg = 0;
146 for (i = 0; i < ITERATIONS; i++) {
147 rdtscll(tsc_a);
148 rdtscll(tsc_b);
149 deltas[i] = (tsc_minus(tsc_a, tsc_b) * tsc_period) / 1000; /* tsc period is in ps */
150 if (i == 0 || deltas[i] < min)
151 min = deltas[i];
152 if (deltas[i] > max)
153 max = deltas[i];
154 avg += deltas[i];
155 }
156 avg /= ITERATIONS;
157
158 /* report on deltas */
159 printf("Calculated tsc period = %llu ps\n", tsc_period);
160 printf("%d pairs of rdtsc() calls completed\n", ITERATIONS);
161 printf("Time between calls:\n");
162 printf(" Max: %llu ns\n", max);
163 printf(" Min: %llu ns\n", min);
164 printf(" Avg: %llu ns\n", avg);
165
166 return 0;
167 }
168