1/*
2 * This program can be used to calibrate the clock reading jitter of a
3 * particular CPU and operating system. It first tickles every element
4 * of an array, in order to force pages into memory, then repeatedly
5 * reads the system clock and, finally, writes out the time values for
6 * later analysis. From this you can determine the jitter and if the
7 * clock ever runs backwards.
8 */
9
10#ifdef HAVE_CONFIG_H
11# include <config.h>
12#endif
13
14#include <stdio.h>
15#include <sys/time.h>
16#include <stdlib.h>
17#include "ntp_fp.h"
18
19#define NBUF	800002
20#define JAN_1970 2208988800UL		/* Unix base epoch */
21#define CLOCK_GETTIME			/* Solaris hires clock */
22
23char progname[10];
24double sys_residual;
25double average;
26void sys_gettime(l_fp *);
27
28int
29main(
30	int argc,
31	char *argv[]
32	)
33{
34	l_fp tr;
35	int i, j;
36	double dtemp, gtod[NBUF];
37
38	/*
39	 * Force pages into memory
40	 */
41	for (i = 0; i < NBUF; i ++)
42	    gtod[i] = 0;
43
44	/*
45	 * Construct gtod array
46	 */
47	for (i = 0; i < NBUF; i ++) {
48		get_systime(&tr);
49		LFPTOD(&tr, gtod[i]);
50	}
51
52	/*
53	 * Write out gtod array for later processing with Matlab
54	 */
55	average = 0;
56	for (i = 0; i < NBUF - 2; i++) {
57		gtod[i] = gtod[i + 1] - gtod[i];
58		printf("%13.9f\n", gtod[i]);
59		average += gtod[i];
60	}
61
62	/*
63	 * Sort the gtod array and display deciles
64	 */
65	for (i = 0; i < NBUF - 2; i++) {
66		for (j = 0; j <= i; j++) {
67			if (gtod[j] > gtod[i]) {
68				dtemp = gtod[j];
69				gtod[j] = gtod[i];
70				gtod[i] = dtemp;
71			}
72		}
73	}
74	average = average / (NBUF - 2);
75	fprintf(stderr, "Average %13.9f\n", average);
76	fprintf(stderr, "First rank\n");
77	for (i = 0; i < 10; i++)
78		fprintf(stderr, "%2d %13.9f\n", i, gtod[i]);
79	fprintf(stderr, "Last rank\n");
80	for (i = NBUF - 12; i < NBUF - 2; i++)
81		fprintf(stderr, "%2d %13.9f\n", i, gtod[i]);
82	exit(0);
83}
84
85
86/*
87 * get_systime - return system time in NTP timestamp format.
88 */
89void
90get_systime(
91	l_fp *now		/* system time */
92	)
93{
94	double dtemp;
95
96#if defined(HAVE_CLOCK_GETTIME) || defined(HAVE_GETCLOCK)
97	struct timespec ts;	/* seconds and nanoseconds */
98
99	/*
100	 * Convert Unix clock from seconds and nanoseconds to seconds.
101	 */
102# ifdef HAVE_CLOCK_GETTIME
103	clock_gettime(CLOCK_REALTIME, &ts);
104# else
105	getclock(TIMEOFDAY, &ts);
106# endif
107	now->l_i = ts.tv_sec + JAN_1970;
108	dtemp = ts.tv_nsec / 1e9;
109
110#else /* HAVE_CLOCK_GETTIME || HAVE_GETCLOCK */
111	struct timeval tv;	/* seconds and microseconds */
112
113	/*
114	 * Convert Unix clock from seconds and microseconds to seconds.
115	 */
116	gettimeofday(&tv, NULL);
117	now->l_i = tv.tv_sec + JAN_1970;
118	dtemp = tv.tv_usec / 1e6;
119
120#endif /* HAVE_CLOCK_GETTIME || HAVE_GETCLOCK */
121
122	/*
123	 * Renormalize to seconds past 1900 and fraction.
124	 */
125	dtemp += sys_residual;
126	if (dtemp >= 1) {
127		dtemp -= 1;
128		now->l_i++;
129	} else if (dtemp < -1) {
130		dtemp += 1;
131		now->l_i--;
132	}
133	dtemp *= FRAC;
134	now->l_uf = (u_int32)dtemp;
135}
136