diff options
| -rw-r--r-- | networking/ntpd.c | 52 |
1 files changed, 29 insertions, 23 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c index ba666b513..b0bfe440f 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -138,6 +138,7 @@ * by staying at smaller poll). */ #define POLLADJ_GATE 4 +#define TIMECONST_HACK_GATE 2 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */ #define ALLAN 512 /* PLL loop gain */ @@ -339,6 +340,7 @@ struct globals { double last_update_offset; // c.last double last_update_recv_time; // s.t double discipline_jitter; // c.jitter + double offset_to_jitter_ratio; //double cluster_offset; // s.offset //double cluster_jitter; // s.jitter #if !USING_KERNEL_PLL_LOOP @@ -1337,7 +1339,8 @@ update_local_clock(peer_t *p) return 1; /* "ok to increase poll interval" */ } #endif - set_new_values(STATE_SYNC, /*offset:*/ 0, recv_time); + offset = 0; + set_new_values(STATE_SYNC, offset, recv_time); } else { /* abs_offset <= STEP_THRESHOLD */ @@ -1355,6 +1358,7 @@ update_local_clock(peer_t *p) G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG); if (G.discipline_jitter < G_precision_sec) G.discipline_jitter = G_precision_sec; + G.offset_to_jitter_ratio = fabs(offset) / G.discipline_jitter; VERB3 bb_error_msg("discipline jitter=%f", G.discipline_jitter); switch (G.discipline_state) { @@ -1443,7 +1447,7 @@ update_local_clock(peer_t *p) /* We are in STATE_SYNC now, but did not do adjtimex yet. * (Any other state does not reach this, they all return earlier) - * By this time, freq_drift and G.last_update_offset are set + * By this time, freq_drift and offset are set * to values suitable for adjtimex. */ #if !USING_KERNEL_PLL_LOOP @@ -1482,40 +1486,42 @@ update_local_clock(peer_t *p) tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET; /* 65536 is one ppm */ tmx.freq = G.discipline_freq_drift * 65536e6; - tmx.offset = G.last_update_offset * 1000000; /* usec */ #endif tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR; - tmx.offset = (G.last_update_offset * 1000000); /* usec */ - /* + (G.last_update_offset < 0 ? -0.5 : 0.5) - too small to bother */ + tmx.offset = (offset * 1000000); /* usec */ tmx.status = STA_PLL; if (G.ntp_status & LI_PLUSSEC) tmx.status |= STA_INS; if (G.ntp_status & LI_MINUSSEC) tmx.status |= STA_DEL; + tmx.constant = G.poll_exp - 4; - //tmx.esterror = (u_int32)(clock_jitter * 1e6); - //tmx.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); + /* EXPERIMENTAL. + * The below if statement should be unnecessary, but... + * It looks like Linux kernel's PLL is far too gentle in changing + * tmx.freq in response to clock offset. Offset keeps growing + * and eventually we fall back to smaller poll intervals. + * We can make correction more agressive (about x2) by supplying + * PLL time constant which is one less than the real one. + * To be on a safe side, let's do it only if offset is significantly + * larger than jitter. + */ + if (tmx.constant > 0 && G.offset_to_jitter_ratio > TIMECONST_HACK_GATE) + tmx.constant--; + + //tmx.esterror = (uint32_t)(clock_jitter * 1e6); + //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); rc = adjtimex(&tmx); if (rc < 0) bb_perror_msg_and_die("adjtimex"); /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4. * Not sure why. Perhaps it is normal. */ - VERB3 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld constant:%ld status:0x%x", - rc, tmx.freq, tmx.offset, tmx.constant, tmx.status); -#if 0 - VERB3 { - /* always gives the same output as above msg */ - memset(&tmx, 0, sizeof(tmx)); - if (adjtimex(&tmx) < 0) - bb_perror_msg_and_die("adjtimex"); - VERB3 bb_error_msg("c adjtimex freq:%ld offset:%+ld constant:%ld status:0x%x", - tmx.freq, tmx.offset, tmx.constant, tmx.status); - } -#endif + VERB3 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x", + rc, tmx.freq, tmx.offset, tmx.status); G.kernel_freq_drift = tmx.freq / 65536; - VERB2 bb_error_msg("update peer:%s, offset:%+f, jitter:%f, clock drift:%+.3f ppm", - p->p_dotted, G.last_update_offset, G.discipline_jitter, (double)tmx.freq / 65536); + VERB2 bb_error_msg("update peer:%s, offset:%+f, jitter:%f, clock drift:%+.3f ppm, tc:%d", + p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant); return 1; /* "ok to increase poll interval" */ } @@ -1651,7 +1657,7 @@ recv_and_process_peer_pkt(peer_t *p) if (!p->reachable_bits) { /* 1st datapoint ever - replicate offset in every element */ int i; - for (i = 1; i < NUM_DATAPOINTS; i++) { + for (i = 0; i < NUM_DATAPOINTS; i++) { p->filter_datapoint[i].d_offset = datapoint->d_offset; } } @@ -1706,7 +1712,7 @@ recv_and_process_peer_pkt(peer_t *p) ? "grows" : "falls" ); } - if (rc > 0 && fabs(q->filter_offset) < POLLADJ_GATE * G.discipline_jitter) { + if (rc > 0 && G.offset_to_jitter_ratio < POLLADJ_GATE) { /* was += G.poll_exp but it is a bit * too optimistic for my taste at high poll_exp's */ G.polladj_count += MINPOLL; |