2001-04-23 Harlan Stenn <stenn@whimsy.udel.edu>
+ * configure.in: 4.0.99k29
+
+ * html/miscopt.htm: Document the "allan" tinker variable.
+ * ntpd/ntp_proto.c (clock_filter): Update comments. Lose etemp;
+ we now use allan_xpt for this.
+ * ntpd/ntp_loopfilter.c: Added allan_xpt as a tinker variable.
+ Reorganize variables and improve comments.
+ (local_clock): Improve comments, use (new) allan_xpt instead of
+ CLOCK_ALLAN. Fix test in S_SYNC state. Update debug info.
+ (rstclock): No longer force allan_xpt to CVLOCK_ALLAN in S_FREQ,
+ S_SYNC, or default case.
+ (loop_config): Document dangerous tinker variables, and add
+ LOOP_ALLAN to the list.
+ * include/ntp_config.h (CONF_CLOCK_ALLAN): Added.
+ * include/ntp.h (LOOP_ALLAN): Added.
+ Allan intercept fixes from Dave Mills.
+
* scripts/mkver.in: Use the C locale so the dates come out in a
consistent format.
From: ASANO Naoyuki <n_asano@imjp.co.jp>
#define PPS_MAXAGE 120 /* kernel pps signal timeout (s) */
/*
- * Program variables
+ * Program variables that can be tinkered.
*/
-static double clock_offset; /* clock offset adjustment (s) */
-double drift_comp; /* clock frequency (s/s) */
-double clock_stability; /* clock stability (s/s) */
double clock_max = CLOCK_MAX; /* max offset before step (s) */
double clock_panic = CLOCK_PANIC; /* max offset before panic (s) */
double clock_phi = CLOCK_PHI; /* dispersion rate (s/s) */
double clock_minstep = CLOCK_MINSTEP; /* step timeout (s) */
+double allan_xpt = CLOCK_ALLAN; /* minimum Allan intercept (s) */
+
+/*
+ * Program variables
+ */
+static double clock_offset; /* clock offset adjustment (s) */
+double drift_comp; /* clock frequency (s/s) */
+double clock_stability; /* clock stability (s/s) */
u_long pps_control; /* last pps sample time */
static void rstclock P((int)); /* state transition function */
int tc_counter; /* poll-adjust counter */
u_long last_time; /* time of last clock update (s) */
double last_offset; /* last clock offset (s) */
-double allan_xpt; /* Allan intercept (s) */
double sys_jitter; /* system RMS jitter (s) */
#if defined(KERNEL_PLL)
* Compute the FLL and PLL frequency adjustments
* conditioned on intricate weighting factors.
* For the FLL, the averaging interval is
- * clamped not to decrease below the Allan
- * intercept and the gain is decreased from
- * unity for mu above CLOCK_MINSEC (1024 s) to
- * zero below CLOCK_MINSEC (256 s). For the PLL,
- * the averaging interval is clamped not to
- * exceed the sustem poll interval. These
- * measures insure stability of the clock
- * discipline even when the rules of fair
- * engagement are broken.
+ * clamped to a minimum of 1024 s and the gain
+ * is decreased from unity for mu above 1024 s
+ * to zero below 256 s. For the PLL, the
+ * averaging interval is clamped not to exceed
+ * the sustem poll interval. No gain factor is
+ * necessary, since the frequency steering above
+ * 1024 s is negligible. Particularly for the
+ * PLL, these measures allow oversampling, but
+ * not undersampling and insure stability even
+ * when the rules of fair engagement are broken.
*/
dtemp = max(mu, allan_xpt);
etemp = min(max(0, mu - CLOCK_MINSEC) /
- CLOCK_ALLAN, 1.);
+ allan_xpt, 1.);
flladj = fp_offset * etemp / (dtemp *
CLOCK_AVG);
dtemp = ULOGTOD(SHIFT_PLL + 2 + sys_poll);
dtemp = SQUARE(clock_stability);
etemp = SQUARE(etemp) - dtemp;
clock_stability = SQRT(dtemp + etemp / CLOCK_AVG);
- allan_xpt = max(CLOCK_ALLAN, clock_stability * CLOCK_ADF);
/*
- * In SYNC state, adjust the poll interval.
+ * In SYNC state, adjust the poll interval. The trick here is to
+ * compare the apparent frequency change induced by the system
+ * jitter over the poll interval, or fritter, to the frequency
+ * stability. If the fritter is greater than the stability,
+ * phase noise predominates and the averaging interval is
+ * increased; otherwise, it is decreased. A bit of hysteresis
+ * helps calm the dance. Works best using burst mode.
*/
if (state == S_SYNC) {
- if (clock_stability < CLOCK_MAXSTAB &&
- fabs(clock_offset) < CLOCK_PGATE * sys_jitter) {
+ if (sys_jitter / mu > clock_stability) {
tc_counter += sys_poll;
if (tc_counter > CLOCK_LIMIT) {
tc_counter = CLOCK_LIMIT;
#ifdef DEBUG
if (debug > 1)
printf(
- "local_clock: mu %.0f allan %.0f fadj %.3f fll %.3f pll %.3f\n",
- mu, allan_xpt, clock_frequency * 1e6, flladj * 1e6,
- plladj * 1e6);
+ "local_clock: mu %.0f fadj %.3f fll %.3f pll %.3f\n",
+ mu, clock_frequency * 1e6, flladj * 1e6, plladj *
+ 1e6);
#endif /* DEBUG */
#ifdef DEBUG
- if (debug > 1)
+ if (debug)
printf(
- "local_clock: jit %.6f freq %.3f stab %.3f poll %d cnt %d\n",
- sys_jitter, drift_comp * 1e6, clock_stability * 1e6,
+ "local_clock: noise %.3f stabil %.3f poll %d count %d\n",
+ sys_jitter * 1e6 / mu, clock_stability * 1e6,
sys_poll, tc_counter);
#endif /* DEBUG */
return (retval);
*/
case S_FREQ:
sys_poll = NTP_MINPOLL;
- allan_xpt = CLOCK_ALLAN;
last_time = current_time;
break;
*/
case S_SYNC:
sys_poll = NTP_MINPOLL;
- allan_xpt = CLOCK_ALLAN;
tc_counter = 0;
break;
*/
default:
sys_poll = NTP_MINPOLL;
- allan_xpt = CLOCK_ALLAN;
last_time = current_time;
last_offset = clock_offset = 0;
break;
#endif /* KERNEL_PLL */
break;
- case LOOP_MAX:
+ /*
+ * Special tinker variables for Ulrich Windl. Very dangerous.
+ */
+ case LOOP_MAX: /* step threshold */
clock_max = freq;
break;
- case LOOP_PANIC:
+ case LOOP_PANIC: /* panic exit threshold */
clock_panic = freq;
break;
- case LOOP_PHI:
+ case LOOP_PHI: /* dispersion rate */
clock_phi = freq;
break;
- case LOOP_MINSTEP:
+ case LOOP_MINSTEP: /* watchdog bark */
clock_minstep = freq;
break;
- case LOOP_MINPOLL:
+ case LOOP_MINPOLL: /* ephemeral association poll */
if (freq < NTP_MINPOLL)
freq = NTP_MINPOLL;
sys_minpoll = (u_char)freq;
+
+ case LOOP_ALLAN: /* minimum Allan intercept */
+ if (freq < CLOCK_ALLAN)
+ freq = CLOCK_ALLAN;
+ allan_xpt = freq;
}
}
* Update dispersions since the last update and at the same
* time initialize the distance and index vectors. The distance
* is a compound metric: If the sample dispersion is less than
- * MAXDISTANCE and younger than the Allan intercept, use delay.
- * Otherwise, use MAXDISTANCE plus conventional distance.
+ * MAXDISTANCE and younger than the minimum Allan intercept, use
+ * delay. Otherwise, use MAXDISTANCE plus conventional distance.
*/
dtemp = clock_phi * (current_time - peer->update);
- etemp = min(allan_xpt, NTP_SHIFT * ULOGTOD(sys_poll));
peer->update = current_time;
for (i = NTP_SHIFT - 1; i >= 0; i--) {
if (i != 0) {
ftemp = peer->filter_delay[j] / 2. +
peer->filter_disp[j];
if (ftemp < MAXDISTANCE && current_time -
- peer->filter_epoch[j] < etemp)
+ peer->filter_epoch[j] < allan_xpt)
dst[i] = peer->filter_delay[j];
else
dst[i] = MAXDISTANCE + ftemp;
}
/*
- * Sort the sampsamples in the register by the compound metric.
+ * Sort the samples in the register by the compound metric.
*/
for (i = 1; i < NTP_SHIFT; i++) {
for (j = 0; j < i; j++) {
projects / thirdparty / ntp.git / commitdiff
