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 * preempt_timing.c
21 *
22 * DESCRIPTION
23 * This program indicated the preemption delays that may be encountered
24 * by realtime apps. The program runs with the scheduling policy of
25 * SCHED_FIFO at a maximum SCHED_FIFO priority. It is bound to a single
26 * processor and its address space is locked as well. It makes successive
27 * calls to the gettimeofday() function(via inlined assembly to read the
28 * TSC).The value returned between two such consecutive calls is reported
29 * as the latency.
30 * The maximum, minimum and average delays are reported for x pairs of such
31 * calls.
32 *
33 * USAGE:
34 * Use run_auto.sh script in current directory to build and run test.
35 *
36 * AUTHOR
37 *
38 *
39 * HISTORY
40 *
41 *
42 *****************************************************************************/
43
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <unistd.h>
47 #include <sys/time.h>
48 #include <sys/types.h>
49 #include <sched.h>
50 #include <string.h>
51 #include <errno.h>
52 #include <sys/mman.h>
53 #include <stdint.h>
54 #include <librttest.h>
55
56 #include "tst_tsc.h"
57
58 #define ITERATIONS 1000000ULL
59 #define INTERVALS 10
60
usage(void)61 void usage(void)
62 {
63 rt_help();
64 printf("preempt_timing specific options:\n");
65 }
66
parse_args(int c,char * v)67 int parse_args(int c, char *v)
68 {
69
70 int handled = 1;
71 switch (c) {
72 case 'h':
73 usage();
74 exit(0);
75 default:
76 handled = 0;
77 break;
78 }
79 return handled;
80 }
81
82 unsigned long long sample_list[ITERATIONS];
main(int argc,char * argv[])83 int main(int argc, char *argv[])
84 {
85 unsigned long long i, j, delta, min, max, avg;
86 struct sched_param param;
87 cpu_set_t mask;
88 int err;
89
90 #ifdef TSC_UNSUPPORTED
91 printf("Error: test cannot be executed on an arch wihout TSC.\n");
92 return ENOTSUP;
93 #endif
94
95 max = avg = 0;
96 min = -1;
97 setup();
98
99 rt_init("h", parse_args, argc, argv);
100
101 /* switch to SCHED_FIFO 99 */
102 param.sched_priority = sched_get_priority_max(SCHED_FIFO);
103 err = sched_setscheduler(0, SCHED_FIFO, ¶m);
104
105 /* Check that the user has the appropriate privileges */
106 if (err) {
107 if (errno == EPERM) {
108 fprintf(stderr,
109 "This program runs with a scheduling policy of SCHED_FIFO at priority %d\n",
110 param.sched_priority);
111 fprintf(stderr,
112 "You don't have the necessary privileges to create such a real-time process.\n");
113 } else {
114 fprintf(stderr, "Failed to set scheduler, errno %d\n",
115 errno);
116 }
117 exit(1);
118 }
119
120 /* BIND TO A SINGLE CPU */
121 CPU_ZERO(&mask);
122 CPU_SET(0, &mask);
123 err = sched_setaffinity(0, sizeof(mask), &mask);
124 if (err < 0) {
125 printf("Can't set affinity: %d %s\n", err, strerror(err));
126 exit(-1);
127 }
128
129 for (j = 0; j < INTERVALS; j++) {
130 /* Collect samples */
131 for (i = 0; i < ITERATIONS; i++)
132 rdtscll(sample_list[i]);
133
134 /* Process samples */
135 for (i = 0; i < (ITERATIONS - 1); i++) {
136 delta = sample_list[i + 1] - sample_list[i];
137 if (delta < min)
138 min = delta;
139 if (delta > max)
140 max = delta;
141 if (delta > 100000)
142 printf("maxd(%llu:%llu): %llu %llu = %llu\n", j,
143 i, sample_list[i], sample_list[i + 1],
144 delta);
145 avg += delta;
146 }
147 usleep(100); /*let necessary things happen */
148 }
149 avg /= (ITERATIONS * INTERVALS);
150
151 printf("%lld pairs of gettimeofday() calls completed\n",
152 ITERATIONS * INTERVALS);
153 printf("Time between calls:\n");
154 printf("Minimum: %llu \n", min);
155 printf("Maximum: %llu \n", max);
156 printf("Average: %llu \n", avg);
157
158 return 0;
159 }
160