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 * sched_jitter.c
21 *
22 * DESCRIPTION
23 * This test measures scheduling jitter w/ realtime processes.
24 *
25 * It spawns a realtime thread that repeatedly times how long it takes to
26 * do a fixed amount of work. It then prints out the maximum jitter seen
27 * (longest execution time - the shortest execution time).
28 * It also spawns off a realtime thread of higher priority that simply
29 * wakes up and goes back to sleep. This tries to measure how much overhead
30 * the scheduler adds in switching quickly to another task and back.
31 *
32 * USAGE:
33 * Use run_auto.sh script in current directory to build and run test.
34 *
35 * AUTHOR
36 * John Stultz <johnstul@us.ibm.com>
37 *
38 * HISTORY
39 * 2006-May-05: Initial version by John Stultz <johnstul@us.ibm.com>
40 * 2007-July-18: Support to gather stats by Ankita Garg <ankita@in.ibm.com>
41 *
42 * This line has to be added to avoid a stupid CVS problem
43 *****************************************************************************/
44
45 #include <stdio.h>
46 #include <time.h>
47 #include <pthread.h>
48 #include <sched.h>
49 #include <unistd.h>
50 #include <libstats.h>
51 #include <librttest.h>
52
53 #define NUMRUNS 1000
54 #define NUMLOOPS 1000000
55 #define NSEC_PER_SEC 1000000000
56 #define WORKLEN 64
57 #define ISLEEP 50000
58
59 int array[WORKLEN];
60
61 volatile int flag; /*let interrupter know we're done */
62
usage(void)63 void usage(void)
64 {
65 rt_help();
66 printf("sched_jitter specific options:\n");
67 }
68
parse_args(int c,char * v)69 int parse_args(int c, char *v)
70 {
71
72 int handled = 1;
73 switch (c) {
74 case 'h':
75 usage();
76 exit(0);
77 default:
78 handled = 0;
79 break;
80 }
81 return handled;
82 }
83
ts_sub(struct timespec a,struct timespec b)84 unsigned long long ts_sub(struct timespec a, struct timespec b)
85 {
86 unsigned long long first, second;
87
88 first = (unsigned long long)a.tv_sec * NSEC_PER_SEC + a.tv_nsec;
89 second = (unsigned long long)b.tv_sec * NSEC_PER_SEC + b.tv_nsec;
90 return first - second;
91 }
92
print_unit(unsigned long long val)93 void print_unit(unsigned long long val)
94 {
95 if (val > 1000000)
96 printf("%f ms\n", (float)(val) / 1000000);
97 else if (val > 1000)
98 printf("%f us\n", (float)(val) / 1000);
99 else
100 printf("%f ns\n", (float)val);
101
102 }
103
do_work(int runs)104 void do_work(int runs)
105 {
106 int i, j;
107 for (i = 0; i < runs; i++) {
108 for (j = 0; j < WORKLEN - 1; j++)
109 array[j] = array[j] + array[j + 1];
110 for (j = 0; j < WORKLEN - 1; j++)
111 array[j] = array[j] - array[j + 1];
112 }
113 }
114
thread_worker(void * arg)115 void *thread_worker(void *arg)
116 {
117 struct timespec start, stop;
118 int i;
119 unsigned long long delta;
120 unsigned long long min = -1, max = 0;
121
122 stats_container_t dat;
123 stats_record_t rec;
124
125 stats_container_init(&dat, NUMRUNS);
126
127 for (i = 0; i < NUMRUNS; i++) {
128
129 do_work(1); /* warm cache */
130
131 /* do test */
132 clock_gettime(CLOCK_MONOTONIC, &start);
133 do_work(NUMLOOPS);
134 clock_gettime(CLOCK_MONOTONIC, &stop);
135
136 /* calc delta, min and max */
137 delta = ts_sub(stop, start);
138 if (delta < min)
139 min = delta;
140 if (delta > max)
141 max = delta;
142 rec.x = i;
143 rec.y = delta;
144 stats_container_append(&dat, rec);
145
146 printf("delta: %llu ns\n", delta);
147 usleep(1); /* let other things happen */
148 }
149
150 printf("max jitter: ");
151 print_unit(max - min);
152 stats_container_save("samples", "Scheduling Jitter Scatter Plot",
153 "Iteration", "Delay (ns)", &dat, "points");
154 return NULL;
155 }
156
thread_interrupter(void * arg)157 void *thread_interrupter(void *arg)
158 {
159 while (!flag)
160 usleep(ISLEEP);
161 return NULL;
162 }
163
main(int argc,char * argv[])164 int main(int argc, char *argv[])
165 {
166 int worker, interrupter;
167
168 setup();
169
170 rt_init("h", parse_args, argc, argv);
171
172 interrupter = create_fifo_thread(thread_interrupter, NULL, 80);
173 sleep(1);
174 worker = create_fifo_thread(thread_worker, NULL, 10);
175
176 join_thread(worker);
177 flag = 1;
178 join_thread(interrupter);
179
180 return 0;
181 }
182