dist/ntp/util/hist.c

   1 /*      $NetBSD: hist.c,v 1.2 2003/12/04 16:23:38 drochner Exp $        */
   2
   3 /*
   4  * This program can be used to calibrate the clock reading jitter of a
   5  * particular CPU and operating system. It first tickles every element
   6  * of an array, in order to force pages into memory, then repeatedly calls
   7  * gettimeofday() and, finally, writes out the time values for later
   8  * analysis. From this you can determine the jitter and if the clock ever
   9  * runs backwards.
  10  */
  11
  12 #ifdef HAVE_CONFIG_H
  13 # include <config.h>
  14 #endif
  15
  16 #include "ntp_types.h"
  17
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20
  21 #define NBUF 100001             /* size of basic histogram */
  22 #define NSRT 20000              /* size of overflow histogram */
  23 #define NCNT (600 * 1000000)    /* sample interval (us) */
  24
  25 int col P((long *, long *));
  26
  27 int
  28 main(
  29         int argc,
  30         char *argv[]
  31         )
  32 {
  33         struct timeval ts, tr, tp;
  34         struct timezone tzp;
  35         int i, j, n;
  36         long t, u, v, w, gtod[NBUF], ovfl[NSRT];
  37
  38         /*
  39          * Force pages into memory
  40          */
  41         for (i = 0; i < NBUF; i++)
  42             gtod[i] = 0;
  43         for (i = 0; i < NSRT; i++)
  44             ovfl[i] = 0;
  45
  46         /*
  47          * Construct histogram
  48          */
  49         n = 0;
  50         gettimeofday(&ts, &tzp);
  51         t = ts.tv_sec * 1000000 + ts.tv_usec;
  52         v = t;
  53         while (1) {
  54                 gettimeofday(&tr, &tzp);
  55                 u = tr.tv_sec * 1000000 + tr.tv_usec;
  56                 if (u - v > NCNT)
  57                     break;
  58                 w = u - t;
  59                 if (w <= 0) {
  60 /*
  61                         printf("error <= 0 %ld %d %d, %d %d\n", w, ts.tv_sec,
  62                                ts.tv_usec, tr.tv_sec, tr.tv_usec);
  63 */
  64                 } else if (w > NBUF - 1) {
  65                         ovfl[n] = w;
  66                         if (n < NSRT - 1)
  67                             n++;
  68                 } else {
  69                         gtod[w]++;
  70                 }
  71                 ts = tr;
  72                 t = u;
  73         }
  74
  75         /*
  76          * Write out histogram
  77          */
  78         for (i = 0; i < NBUF - 1; i++) {
  79                 if (gtod[i] > 0)
  80                     printf("%ld %ld\n", i, gtod[i]);
  81         }
  82         if (n == 0)
  83             return;
  84         qsort(
  85 #ifdef QSORT_USES_VOID_P
  86             (void *)
  87 #else
  88             (char *)
  89 #endif
  90             ovfl, (size_t)n, sizeof(long), col);
  91         w = 0;
  92         j = 0;
  93         for (i = 0; i < n; i++) {
  94                 if (ovfl[i] != w) {
  95                         if (j > 0)
  96                             printf("%ld %ld\n", w, j);
  97                         w = ovfl[i];
  98                         j = 1;
  99                 } else
 100                     j++;
 101         }
 102         if (j > 0)
 103             printf("%ld %ld\n", w, j);
 104
 105         exit(0);
 106 }
 107
 108 int
 109 col(
 110         long *x,
 111         long *y
 112         )
 113 {
 114         return (*x - *y);
 115 }