diff options
| -rw-r--r-- | networking/ntpd.c | 45 |
1 files changed, 28 insertions, 17 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c index a8738951f..e7e992205 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -276,11 +276,12 @@ struct globals { unsigned verbose; unsigned peer_cnt; /* refid: 32-bit code identifying the particular server or reference clock - * in stratum 0 packets this is a four-character ASCII string, - * called the kiss code, used for debugging and monitoring - * in stratum 1 packets this is a four-character ASCII string - * assigned to the reference clock by IANA. Example: "GPS " - * in stratum 2+ packets, it's IPv4 address or 4 first bytes of MD5 hash of IPv6 + * in stratum 0 packets this is a four-character ASCII string, + * called the kiss code, used for debugging and monitoring + * in stratum 1 packets this is a four-character ASCII string + * assigned to the reference clock by IANA. Example: "GPS " + * in stratum 2+ packets, it's IPv4 address or 4 first bytes + * of MD5 hash of IPv6 */ uint32_t refid; uint8_t ntp_status; @@ -289,27 +290,35 @@ struct globals { * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the * system clock hardware representation is to the nanosecond. * - * Delays, jitters of various kinds are clamper down to precision. + * Delays, jitters of various kinds are clamped down to precision. * * If precision_sec is too large, discipline_jitter gets clamped to it - * and if offset is much smaller than discipline_jitter, poll interval - * grows even though we really can benefit from staying at smaller one, - * collecting non-lagged datapoits and correcting the offset. + * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll + * interval grows even though we really can benefit from staying at + * smaller one, collecting non-lagged datapoits and correcting offset. * (Lagged datapoits exist when poll_exp is large but we still have * systematic offset error - the time distance between datapoints - * is significat and older datapoints have smaller offsets. + * is significant and older datapoints have smaller offsets. * This makes our offset estimation a bit smaller than reality) * Due to this effect, setting G_precision_sec close to * STEP_THRESHOLD isn't such a good idea - offsets may grow * too big and we will step. I observed it with -6. * - * OTOH, setting precision too small would result in futile attempts - * to syncronize to the unachievable precision. + * OTOH, setting precision_sec far too small would result in futile + * attempts to syncronize to an unachievable precision. * * -6 is 1/64 sec, -7 is 1/128 sec and so on. + * -8 is 1/256 ~= 0.003906 (worked well for me --vda) + * -9 is 1/512 ~= 0.001953 (let's try this for some time) */ -#define G_precision_exp -8 -#define G_precision_sec (1.0 / (1 << (- G_precision_exp))) +#define G_precision_exp -9 + /* + * G_precision_exp is used only for construction outgoing packets. + * It's ok to set G_precision_sec to a slightly different value + * (One which is "nicer looking" in logs). + * Exact value would be (1.0 / (1 << (- G_precision_exp))): + */ +#define G_precision_sec 0.002 uint8_t stratum; /* Bool. After set to 1, never goes back to 0: */ smallint initial_poll_complete; @@ -1334,8 +1343,10 @@ update_local_clock(peer_t *p) * weighted offset differences. Used by the poll adjust code. */ etemp = SQUARE(G.discipline_jitter); - dtemp = SQUARE(MAXD(fabs(offset - G.last_update_offset), G_precision_sec)); + dtemp = SQUARE(offset - G.last_update_offset); G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG); + if (G.discipline_jitter < G_precision_sec) + G.discipline_jitter = G_precision_sec; VERB3 bb_error_msg("discipline jitter=%f", G.discipline_jitter); switch (G.discipline_state) { @@ -1495,8 +1506,8 @@ update_local_clock(peer_t *p) } #endif G.kernel_freq_drift = tmx.freq / 65536; - VERB2 bb_error_msg("update peer:%s, offset:%+f, clock drift:%+ld ppm", - p->p_dotted, G.last_update_offset, G.kernel_freq_drift); + VERB2 bb_error_msg("update peer:%s, offset:%+f, jitter:%f, clock drift:%+ld ppm", + p->p_dotted, G.last_update_offset, G.discipline_jitter, G.kernel_freq_drift); return 1; /* "ok to increase poll interval" */ } |