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ntpd: log jitter on update too; increase assumed clock precision x2 - to 2ms
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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03a99e3d5c
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74584b8665
@ -276,11 +276,12 @@ struct globals {
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unsigned verbose;
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unsigned peer_cnt;
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/* refid: 32-bit code identifying the particular server or reference clock
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* in stratum 0 packets this is a four-character ASCII string,
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* called the kiss code, used for debugging and monitoring
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* in stratum 1 packets this is a four-character ASCII string
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* assigned to the reference clock by IANA. Example: "GPS "
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* in stratum 2+ packets, it's IPv4 address or 4 first bytes of MD5 hash of IPv6
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* in stratum 0 packets this is a four-character ASCII string,
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* called the kiss code, used for debugging and monitoring
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* in stratum 1 packets this is a four-character ASCII string
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* assigned to the reference clock by IANA. Example: "GPS "
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* in stratum 2+ packets, it's IPv4 address or 4 first bytes
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* of MD5 hash of IPv6
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*/
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uint32_t refid;
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uint8_t ntp_status;
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@ -289,27 +290,35 @@ struct globals {
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* mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
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* system clock hardware representation is to the nanosecond.
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*
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* Delays, jitters of various kinds are clamper down to precision.
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* Delays, jitters of various kinds are clamped down to precision.
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*
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* If precision_sec is too large, discipline_jitter gets clamped to it
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* and if offset is much smaller than discipline_jitter, poll interval
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* grows even though we really can benefit from staying at smaller one,
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* collecting non-lagged datapoits and correcting the offset.
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* and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
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* interval grows even though we really can benefit from staying at
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* smaller one, collecting non-lagged datapoits and correcting offset.
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* (Lagged datapoits exist when poll_exp is large but we still have
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* systematic offset error - the time distance between datapoints
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* is significat and older datapoints have smaller offsets.
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* is significant and older datapoints have smaller offsets.
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* This makes our offset estimation a bit smaller than reality)
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* Due to this effect, setting G_precision_sec close to
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* STEP_THRESHOLD isn't such a good idea - offsets may grow
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* too big and we will step. I observed it with -6.
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*
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* OTOH, setting precision too small would result in futile attempts
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* to syncronize to the unachievable precision.
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* OTOH, setting precision_sec far too small would result in futile
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* attempts to syncronize to an unachievable precision.
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*
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* -6 is 1/64 sec, -7 is 1/128 sec and so on.
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* -8 is 1/256 ~= 0.003906 (worked well for me --vda)
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* -9 is 1/512 ~= 0.001953 (let's try this for some time)
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*/
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#define G_precision_exp -8
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#define G_precision_sec (1.0 / (1 << (- G_precision_exp)))
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#define G_precision_exp -9
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/*
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* G_precision_exp is used only for construction outgoing packets.
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* It's ok to set G_precision_sec to a slightly different value
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* (One which is "nicer looking" in logs).
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* Exact value would be (1.0 / (1 << (- G_precision_exp))):
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*/
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#define G_precision_sec 0.002
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uint8_t stratum;
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/* Bool. After set to 1, never goes back to 0: */
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smallint initial_poll_complete;
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@ -1334,8 +1343,10 @@ update_local_clock(peer_t *p)
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* weighted offset differences. Used by the poll adjust code.
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*/
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etemp = SQUARE(G.discipline_jitter);
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dtemp = SQUARE(MAXD(fabs(offset - G.last_update_offset), G_precision_sec));
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dtemp = SQUARE(offset - G.last_update_offset);
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G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
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if (G.discipline_jitter < G_precision_sec)
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G.discipline_jitter = G_precision_sec;
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VERB3 bb_error_msg("discipline jitter=%f", G.discipline_jitter);
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switch (G.discipline_state) {
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@ -1495,8 +1506,8 @@ update_local_clock(peer_t *p)
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}
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#endif
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G.kernel_freq_drift = tmx.freq / 65536;
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VERB2 bb_error_msg("update peer:%s, offset:%+f, clock drift:%+ld ppm",
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p->p_dotted, G.last_update_offset, G.kernel_freq_drift);
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VERB2 bb_error_msg("update peer:%s, offset:%+f, jitter:%f, clock drift:%+ld ppm",
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p->p_dotted, G.last_update_offset, G.discipline_jitter, G.kernel_freq_drift);
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return 1; /* "ok to increase poll interval" */
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}
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