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12#define NR_LOOPS 10000000
13
14#include <string.h>
15#include <stdio.h>
16#include <stdlib.h>
17#include <unistd.h>
18#include <time.h>
19#include <sys/types.h>
20#include <sys/time.h>
21#include <signal.h>
22
23static volatile int soak_done;
24unsigned long long clock_frequency;
25unsigned long long timebase_frequency;
26double timebase_multiplier;
27
28static inline unsigned long long mftb(void)
29{
30 unsigned long low;
31
32 asm volatile("mftb %0" : "=r" (low));
33
34 return low;
35}
36
37static void sigalrm_handler(int unused)
38{
39 soak_done = 1;
40}
41
42
43
44
45
46static void cpu_soak_usecs(unsigned long usecs)
47{
48 struct itimerval val;
49
50 memset(&val, 0, sizeof(val));
51 val.it_value.tv_usec = usecs;
52
53 signal(SIGALRM, sigalrm_handler);
54 setitimer(ITIMER_REAL, &val, NULL);
55
56 while (1) {
57 if (soak_done)
58 break;
59 }
60
61 signal(SIGALRM, SIG_DFL);
62}
63
64
65
66
67
68static void get_proc_frequency(void)
69{
70 FILE *f;
71 char line[128];
72 char *p, *end;
73 unsigned long v;
74 double d;
75 char *override;
76
77
78 cpu_soak_usecs(0.25 * 1000000);
79
80 f = fopen("/proc/cpuinfo", "r");
81 if (f == NULL)
82 return;
83
84 timebase_frequency = 0;
85
86 while (fgets(line, sizeof(line), f) != NULL) {
87 if (strncmp(line, "timebase", 8) == 0) {
88 p = strchr(line, ':');
89 if (p != NULL) {
90 v = strtoull(p + 1, &end, 0);
91 if (end != p + 1)
92 timebase_frequency = v;
93 }
94 }
95
96 if (((strncmp(line, "clock", 5) == 0) ||
97 (strncmp(line, "cpu MHz", 7) == 0))) {
98 p = strchr(line, ':');
99 if (p != NULL) {
100 d = strtod(p + 1, &end);
101 if (end != p + 1) {
102
103 if ((d * 1000000ULL) > clock_frequency)
104 clock_frequency = d * 1000000ULL;
105 }
106 }
107 }
108 }
109
110 fclose(f);
111
112 override = getenv("FREQUENCY");
113 if (override)
114 clock_frequency = strtoull(override, NULL, 10);
115
116 if (timebase_frequency)
117 timebase_multiplier = (double)clock_frequency
118 / timebase_frequency;
119 else
120 timebase_multiplier = 1;
121}
122
123static void do_null_syscall(unsigned long nr)
124{
125 unsigned long i;
126
127 for (i = 0; i < nr; i++)
128 getppid();
129}
130
131#define TIME(A, STR) \
132
133int main(void)
134{
135 unsigned long tb_start, tb_now;
136 struct timespec tv_start, tv_now;
137 unsigned long long elapsed_ns, elapsed_tb;
138
139 get_proc_frequency();
140
141 clock_gettime(CLOCK_MONOTONIC, &tv_start);
142 tb_start = mftb();
143
144 do_null_syscall(NR_LOOPS);
145
146 clock_gettime(CLOCK_MONOTONIC, &tv_now);
147 tb_now = mftb();
148
149 elapsed_ns = (tv_now.tv_sec - tv_start.tv_sec) * 1000000000ULL +
150 (tv_now.tv_nsec - tv_start.tv_nsec);
151 elapsed_tb = tb_now - tb_start;
152
153 printf("%10.2f ns %10.2f cycles\n", (float)elapsed_ns / NR_LOOPS,
154 (float)elapsed_tb * timebase_multiplier / NR_LOOPS);
155
156 return 0;
157}
158