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Annotation of embedaddon/ntp/util/jitter.c, revision 1.1

1.1     ! misho       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 "jitter.h"
        !            18: 
        !            19: #define NBUF   800002
        !            20: #define FRAC   4294967296.             /* a bbbbillion */
        !            21: #define JAN_1970 2208988800UL          /* Unix base epoch */
        !            22: #define CLOCK_GETTIME                  /* Solaris hires clock */
        !            23: 
        !            24: int debug;
        !            25: char progname[10];
        !            26: double sys_residual;
        !            27: double average;
        !            28: void sys_gettime(l_fp *);
        !            29: 
        !            30: int
        !            31: main(
        !            32:        int argc,
        !            33:        char *argv[]
        !            34:        )
        !            35: {
        !            36:        l_fp tr;
        !            37:        int i, j;
        !            38:        double dtemp, gtod[NBUF];
        !            39: 
        !            40:        /*
        !            41:         * Force pages into memory
        !            42:         */
        !            43:        for (i = 0; i < NBUF; i ++)
        !            44:            gtod[i] = 0;
        !            45: 
        !            46:        /*
        !            47:         * Construct gtod array
        !            48:         */
        !            49:        for (i = 0; i < NBUF; i ++) {
        !            50:                get_systime(&tr);
        !            51:                LFPTOD(&tr, gtod[i]);
        !            52:        }
        !            53: 
        !            54:        /*
        !            55:         * Write out gtod array for later processing with Matlab
        !            56:         */
        !            57:        average = 0;
        !            58:        for (i = 0; i < NBUF - 2; i++) {
        !            59:                gtod[i] = gtod[i + 1] - gtod[i];
        !            60:                printf("%13.9f\n", gtod[i]);
        !            61:                average += gtod[i];
        !            62:        }
        !            63: 
        !            64:        /*
        !            65:         * Sort the gtod array and display deciles
        !            66:         */
        !            67:        for (i = 0; i < NBUF - 2; i++) {
        !            68:                for (j = 0; j <= i; j++) {
        !            69:                        if (gtod[j] > gtod[i]) {
        !            70:                                dtemp = gtod[j];
        !            71:                                gtod[j] = gtod[i];
        !            72:                                gtod[i] = dtemp;
        !            73:                        }
        !            74:                }
        !            75:        }
        !            76:        average = average / (NBUF - 2);
        !            77:        fprintf(stderr, "Average %13.9f\n", average);
        !            78:        fprintf(stderr, "First rank\n");
        !            79:        for (i = 0; i < 10; i++)
        !            80:                fprintf(stderr, "%2d %13.9f\n", i, gtod[i]);
        !            81:        fprintf(stderr, "Last rank\n");
        !            82:        for (i = NBUF - 12; i < NBUF - 2; i++)
        !            83:                fprintf(stderr, "%2d %13.9f\n", i, gtod[i]);
        !            84:        exit(0);
        !            85: }
        !            86: 
        !            87: 
        !            88: /*
        !            89:  * get_systime - return system time in NTP timestamp format.
        !            90:  */
        !            91: void
        !            92: get_systime(
        !            93:        l_fp *now               /* system time */
        !            94:        )
        !            95: {
        !            96:        double dtemp;
        !            97: 
        !            98: #if defined(HAVE_CLOCK_GETTIME) || defined(HAVE_GETCLOCK)
        !            99:        struct timespec ts;     /* seconds and nanoseconds */
        !           100: 
        !           101:        /*
        !           102:         * Convert Unix clock from seconds and nanoseconds to seconds.
        !           103:         */
        !           104: # ifdef HAVE_CLOCK_GETTIME
        !           105:        clock_gettime(CLOCK_REALTIME, &ts);
        !           106: # else
        !           107:        getclock(TIMEOFDAY, &ts);
        !           108: # endif
        !           109:        now->l_i = ts.tv_sec + JAN_1970;
        !           110:        dtemp = ts.tv_nsec / 1e9;
        !           111: 
        !           112: #else /* HAVE_CLOCK_GETTIME || HAVE_GETCLOCK */
        !           113:        struct timeval tv;      /* seconds and microseconds */
        !           114: 
        !           115:        /*
        !           116:         * Convert Unix clock from seconds and microseconds to seconds.
        !           117:         */
        !           118:        gettimeofday(&tv, NULL);
        !           119:        now->l_i = tv.tv_sec + JAN_1970;
        !           120:        dtemp = tv.tv_usec / 1e6;
        !           121: 
        !           122: #endif /* HAVE_CLOCK_GETTIME || HAVE_GETCLOCK */
        !           123: 
        !           124:        /*
        !           125:         * Renormalize to seconds past 1900 and fraction.
        !           126:         */
        !           127:        dtemp += sys_residual;
        !           128:        if (dtemp >= 1) {
        !           129:                dtemp -= 1;
        !           130:                now->l_i++;
        !           131:        } else if (dtemp < -1) {
        !           132:                dtemp += 1;
        !           133:                now->l_i--;
        !           134:        }
        !           135:        dtemp *= FRAC;
        !           136:        now->l_uf = (u_int32)dtemp;
        !           137: }