diff options
| -rw-r--r-- | networking/ntpd.c | 83 |
1 files changed, 60 insertions, 23 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c index 9c16b2b6b..2bd53f884 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -212,8 +212,8 @@ typedef struct { } msg_t; typedef struct { - double d_recv_time; double d_offset; + double d_recv_time; double d_dispersion; } datapoint_t; @@ -517,23 +517,34 @@ static void filter_datapoints(peer_t *p) { int i, idx; + double sum, wavg; + datapoint_t *fdp; + +#if 0 +/* Simulations have shown that use of *averaged* offset for p->filter_offset + * is in fact worse than simply using last received one: with large poll intervals + * (>= 2048) averaging code uses offset values which are outdated by hours, + * and time/frequency correction goes totally wrong when fed essentially bogus offsets. + */ int got_newest; - double minoff, maxoff, wavg, sum, w; + double minoff, maxoff, w; double x = x; /* for compiler */ double oldest_off = oldest_off; double oldest_age = oldest_age; double newest_off = newest_off; double newest_age = newest_age; - minoff = maxoff = p->filter_datapoint[0].d_offset; + fdp = p->filter_datapoint; + + minoff = maxoff = fdp[0].d_offset; for (i = 1; i < NUM_DATAPOINTS; i++) { - if (minoff > p->filter_datapoint[i].d_offset) - minoff = p->filter_datapoint[i].d_offset; - if (maxoff < p->filter_datapoint[i].d_offset) - maxoff = p->filter_datapoint[i].d_offset; + if (minoff > fdp[i].d_offset) + minoff = fdp[i].d_offset; + if (maxoff < fdp[i].d_offset) + maxoff = fdp[i].d_offset; } - idx = p->datapoint_idx; /* most recent datapoint */ + idx = p->datapoint_idx; /* most recent datapoint's index */ /* Average offset: * Drop two outliers and take weighted average of the rest: * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32 @@ -555,24 +566,24 @@ filter_datapoints(peer_t *p) VERB4 { bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s", i, - p->filter_datapoint[idx].d_offset, - p->filter_datapoint[idx].d_dispersion, dispersion(&p->filter_datapoint[idx]), - G.cur_time - p->filter_datapoint[idx].d_recv_time, - (minoff == p->filter_datapoint[idx].d_offset || maxoff == p->filter_datapoint[idx].d_offset) + fdp[idx].d_offset, + fdp[idx].d_dispersion, dispersion(&fdp[idx]), + G.cur_time - fdp[idx].d_recv_time, + (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset) ? " (outlier by offset)" : "" ); } - sum += dispersion(&p->filter_datapoint[idx]) / (2 << i); + sum += dispersion(&fdp[idx]) / (2 << i); - if (minoff == p->filter_datapoint[idx].d_offset) { + if (minoff == fdp[idx].d_offset) { minoff -= 1; /* so that we don't match it ever again */ } else - if (maxoff == p->filter_datapoint[idx].d_offset) { + if (maxoff == fdp[idx].d_offset) { maxoff += 1; } else { - oldest_off = p->filter_datapoint[idx].d_offset; - oldest_age = G.cur_time - p->filter_datapoint[idx].d_recv_time; + oldest_off = fdp[idx].d_offset; + oldest_age = G.cur_time - fdp[idx].d_recv_time; if (!got_newest) { got_newest = 1; newest_off = oldest_off; @@ -605,6 +616,32 @@ filter_datapoints(peer_t *p) } p->filter_offset = wavg; +#else + + fdp = p->filter_datapoint; + idx = p->datapoint_idx; /* most recent datapoint's index */ + + /* filter_offset: simply use the most recent value */ + p->filter_offset = fdp[idx].d_offset; + + /* n-1 + * --- dispersion(i) + * filter_dispersion = \ ------------- + * / (i+1) + * --- 2 + * i=0 + */ + wavg = 0; + sum = 0; + for (i = 0; i < NUM_DATAPOINTS; i++) { + sum += dispersion(&fdp[idx]) / (2 << i); + wavg += fdp[idx].d_offset; + idx = (idx - 1) & (NUM_DATAPOINTS - 1); + } + wavg /= NUM_DATAPOINTS; + p->filter_dispersion = sum; +#endif + /* +----- -----+ ^ 1/2 * | n-1 | * | --- | @@ -618,13 +655,13 @@ filter_datapoints(peer_t *p) */ sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { - sum += SQUARE(wavg - p->filter_datapoint[i].d_offset); + sum += SQUARE(wavg - fdp[i].d_offset); } sum = SQRT(sum / NUM_DATAPOINTS); p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec; - VERB3 bb_error_msg("filter offset:%+f(corr:%e) disp:%f jitter:%f", - p->filter_offset, x, + VERB3 bb_error_msg("filter offset:%+f disp:%f jitter:%f", + p->filter_offset, p->filter_dispersion, p->filter_jitter); } @@ -1667,15 +1704,15 @@ recv_and_process_peer_pkt(peer_t *p) p->reachable_bits |= 1; if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) { - bb_error_msg("reply from:%s reach:0x%02x offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f", + bb_error_msg("reply from:%s offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x", p->p_dotted, - p->reachable_bits, datapoint->d_offset, p->lastpkt_delay, p->lastpkt_status, p->lastpkt_stratum, p->lastpkt_refid, - p->lastpkt_rootdelay + p->lastpkt_rootdelay, + p->reachable_bits /* not shown: m_ppoll, m_precision_exp, m_rootdisp, * m_reftime, m_orgtime, m_rectime, m_xmttime */ |