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ntp 4.2.6p5

    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 calls
    5:  * gettimeofday() and, finally, writes out the time values for later
    6:  * analysis. From this you can determine the jitter and if the clock ever
    7:  * runs backwards.
    8:  */
    9: 
   10: #ifdef HAVE_CONFIG_H
   11: # include <config.h>
   12: #endif
   13: 
   14: #include "ntp_types.h"
   15: 
   16: #include <stdio.h>
   17: #include <stdlib.h>
   18: 
   19: #define NBUF 100001		/* size of basic histogram */
   20: #define NSRT 20000		/* size of overflow histogram */
   21: #define NCNT (600 * 1000000)	/* sample interval (us) */
   22: 
   23: int col (long *, long *);
   24: 
   25: int
   26: main(
   27: 	int argc,
   28: 	char *argv[]
   29: 	)
   30: {
   31: 	struct timeval ts, tr, tp;
   32: 	struct timezone tzp;
   33: 	int i, j, n;
   34: 	long t, u, v, w, gtod[NBUF], ovfl[NSRT];
   35: 
   36: 	/*
   37: 	 * Force pages into memory
   38: 	 */
   39: 	for (i = 0; i < NBUF; i++)
   40: 	    gtod[i] = 0;
   41: 	for (i = 0; i < NSRT; i++)
   42: 	    ovfl[i] = 0;
   43: 
   44: 	/*
   45: 	 * Construct histogram
   46: 	 */
   47: 	n = 0;
   48: 	gettimeofday(&ts, &tzp);
   49: 	t = ts.tv_sec * 1000000 + ts.tv_usec;
   50: 	v = t;
   51: 	while (1) {
   52: 		gettimeofday(&tr, &tzp);
   53: 		u = tr.tv_sec * 1000000 + tr.tv_usec; 
   54: 		if (u - v > NCNT)
   55: 		    break;
   56: 		w = u - t;
   57: 		if (w <= 0) {
   58: /*
   59: 			printf("error <= 0 %ld %d %d, %d %d\n", w, ts.tv_sec,
   60: 			       ts.tv_usec, tr.tv_sec, tr.tv_usec);
   61: */
   62: 		} else if (w > NBUF - 1) {
   63: 			ovfl[n] = w;
   64: 			if (n < NSRT - 1)
   65: 			    n++;
   66: 		} else {
   67: 			gtod[w]++;
   68: 		}
   69: 		ts = tr;
   70: 		t = u;
   71: 	}
   72: 
   73: 	/*
   74: 	 * Write out histogram
   75: 	 */
   76: 	for (i = 0; i < NBUF - 1; i++) {
   77: 		if (gtod[i] > 0)
   78: 		    printf("%ld %ld\n", i, gtod[i]);
   79: 	}
   80: 	if (n == 0)
   81: 	    return;
   82: 	qsort(
   83: #ifdef QSORT_USES_VOID_P
   84: 	    (void *)
   85: #else
   86: 	    (char *)
   87: #endif
   88: 	    ovfl, (size_t)n, sizeof(long), col);
   89: 	w = 0;
   90: 	j = 0;
   91: 	for (i = 0; i < n; i++) {
   92: 		if (ovfl[i] != w) {
   93: 			if (j > 0)
   94: 			    printf("%ld %ld\n", w, j);
   95: 			w = ovfl[i];
   96: 			j = 1;
   97: 		} else
   98: 		    j++;
   99: 	}
  100: 	if (j > 0)
  101: 	    printf("%ld %ld\n", w, j);
  102:  
  103: 	exit(0);
  104: }
  105: 
  106: int
  107: col(
  108: 	long *x,
  109: 	long *y
  110: 	)
  111: {
  112: 	return (*x - *y);
  113: }