diff options
| -rw-r--r-- | networking/ntpd.c | 64 |
1 files changed, 43 insertions, 21 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c index 5431b7499..5cad738c6 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -390,8 +390,13 @@ static void filter_datapoints(peer_t *p, double t) { int i, idx; + int got_newest; double minoff, maxoff, wavg, sum, w; - double x = x; + 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; for (i = 1; i < NUM_DATAPOINTS; i++) { @@ -416,6 +421,7 @@ filter_datapoints(peer_t *p, double t) // / (i+1) // --- 2 // i=0 + got_newest = 0; sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { VERB4 { @@ -437,23 +443,36 @@ filter_datapoints(peer_t *p, double t) if (maxoff == p->filter_datapoint[idx].d_offset) { maxoff += 1; } else { - x = p->filter_datapoint[idx].d_offset * w; + oldest_off = p->filter_datapoint[idx].d_offset; + oldest_age = t - p->filter_datapoint[idx].d_recv_time; + if (!got_newest) { + got_newest = 1; + newest_off = oldest_off; + newest_age = oldest_age; + } + x = oldest_off * w; wavg += x; w /= 2; } idx = (idx - 1) & (NUM_DATAPOINTS - 1); } + p->filter_dispersion = sum; wavg += x; /* add another older6/64 to form older6/32 */ + /* Fix systematic underestimation with large poll intervals. + * Imagine that we still have a bit of uncorrected drift, + * and poll interval is big (say, 100 sec). Offsets form a progression: + * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent. + * The algorithm above drops 0.0 and 0.7 as outliers, + * and then we have this estimation, ~25% off from 0.7: + * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125 + */ + x = newest_age / (oldest_age - newest_age); /* in above example, 100 / (600 - 100) */ + if (x < 1) { + x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */ + wavg += x; + } p->filter_offset = wavg; - p->filter_dispersion = sum; -//TODO: fix systematic underestimation with large poll intervals. -// Imagine that we still have a bit of uncorrected drift, -// and poll interval is big. Offsets form a progression: -// 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7, 0.7 is most recent. -// The algorithm above drops 0.0 and 0.7 as outliers, -// and then we have this estimation, ~25% off from 0.7: -// 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125 // +----- -----+ ^ 1/2 // | n-1 | @@ -472,8 +491,10 @@ filter_datapoints(peer_t *p, double t) sum = SQRT(sum) / NUM_DATAPOINTS; p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec; - VERB3 bb_error_msg("filter offset:%f disp:%f jitter:%f", - p->filter_offset, p->filter_dispersion, p->filter_jitter); + VERB3 bb_error_msg("filter offset:%f(corr:%e) disp:%f jitter:%f", + p->filter_offset, x, + p->filter_dispersion, + p->filter_jitter); } @@ -948,7 +969,7 @@ set_new_values(int disc_state, double offset, double recv_time) * of the last clock filter sample, which must be earlier than * the current time. */ - VERB3 bb_error_msg("disc_state=%d last_update_offset=%f last_update_recv_time=%f", + VERB3 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f", disc_state, offset, recv_time); G.discipline_state = disc_state; G.last_update_offset = offset; @@ -1227,26 +1248,27 @@ update_local_clock(peer_t *p, double t) tmx.constant = G.poll_exp - 4; //tmx.esterror = (u_int32)(clock_jitter * 1e6); //tmx.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); - VERB3 bb_error_msg("b adjtimex freq:%ld offset:%ld constant:%ld status:0x%x", - tmx.freq, tmx.offset, tmx.constant, tmx.status); rc = adjtimex(&tmx); if (rc < 0) bb_perror_msg_and_die("adjtimex"); - if (G.kernel_freq_drift != tmx.freq / 65536) { - G.kernel_freq_drift = tmx.freq / 65536; - VERB2 bb_error_msg("kernel clock drift: %ld ppm", G.kernel_freq_drift); - } - VERB3 { - bb_error_msg("adjtimex:%d freq:%ld offset:%ld constant:%ld status:0x%x", + /* 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 + if (G.kernel_freq_drift != tmx.freq / 65536) { + G.kernel_freq_drift = tmx.freq / 65536; + VERB2 bb_error_msg("kernel clock drift: %ld ppm", G.kernel_freq_drift); } // #define STA_MODE 0x4000 /* mode (0 = PLL, 1 = FLL) (ro) */ - ? // it appeared after a while: |