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authorDenys Vlasenko <vda.linux@googlemail.com>2013-12-08 15:11:04 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2013-12-08 15:11:04 (GMT)
commit0b3a38b9f573634faa4f2bc8b0ffb6f55c0958f5 (patch)
treefc8a21a57df124a3bafce78f144ef5e160e926b0
parent777be10ebebb4afdaf057a5abe094c86eb6d8a2c (diff)
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ntpd: speed up resyncing if our clock is seriously off
function old new delta recv_and_process_peer_pkt 892 922 +30 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--networking/ntpd.c46
1 files changed, 39 insertions, 7 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c
index fd2f24a..ed83415 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -90,12 +90,24 @@
* was hibernated, someone set totally wrong date, etc),
* then the time is stepped, all datapoints are discarded,
* and we go back to steady state.
+ *
+ * Made some changes to speed up re-syncing after our clock goes bad
+ * (tested with suspending my laptop):
+ * - if largish offset (>= STEP_THRESHOLD * 8 == 1 sec) is seen
+ * from a peer, schedule next query for this peer soon
+ * without drastically lowering poll interval for everybody.
+ * This makes us collect enough data for step much faster:
+ * e.g. at poll = 10 (1024 secs), step was done within 5 minutes
+ * after first reply which indicated that our clock is 14 seconds off.
+ * - on step, do not discard d_dispersion data of the existing datapoints,
+ * do not clear reachable_bits. This prevents discarding first ~8
+ * datapoints after the step.
*/
-#define RETRY_INTERVAL 5 /* on error, retry in N secs */
+#define RETRY_INTERVAL 5 /* on error, retry in N secs */
#define RESPONSE_INTERVAL 15 /* wait for reply up to N secs */
-#define INITIAL_SAMPLES 4 /* how many samples do we want for init */
-#define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
+#define INITIAL_SAMPLES 4 /* how many samples do we want for init */
+#define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
/* Clock discipline parameters and constants */
@@ -109,6 +121,10 @@
#define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
#define BURSTPOLL 0 /* initial poll */
#define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
+/* If we got largish offset from a peer, cap next query interval
+ * for this peer by this many seconds:
+ */
+#define BIGOFF_INTERVAL (1 << 6)
/* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
* then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
*/
@@ -1658,11 +1674,13 @@ recv_and_process_peer_pkt(peer_t *p)
ssize_t size;
msg_t msg;
double T1, T2, T3, T4;
- double dv;
+ double dv, offset;
unsigned interval;
datapoint_t *datapoint;
peer_t *q;
+ offset = 0;
+
/* We can recvfrom here and check from.IP, but some multihomed
* ntp servers reply from their *other IP*.
* TODO: maybe we should check at least what we can: from.port == 123?
@@ -1766,13 +1784,13 @@ recv_and_process_peer_pkt(peer_t *p)
p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
datapoint = &p->filter_datapoint[p->datapoint_idx];
datapoint->d_recv_time = T4;
- datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
+ datapoint->d_offset = offset = ((T2 - T1) + (T3 - T4)) / 2;
datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
if (!p->reachable_bits) {
/* 1st datapoint ever - replicate offset in every element */
int i;
for (i = 0; i < NUM_DATAPOINTS; i++) {
- p->filter_datapoint[i].d_offset = datapoint->d_offset;
+ p->filter_datapoint[i].d_offset = offset;
}
}
@@ -1780,7 +1798,7 @@ recv_and_process_peer_pkt(peer_t *p)
if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
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,
- datapoint->d_offset,
+ offset,
p->lastpkt_delay,
p->lastpkt_status,
p->lastpkt_stratum,
@@ -1865,6 +1883,20 @@ recv_and_process_peer_pkt(peer_t *p)
/* Decide when to send new query for this peer */
pick_normal_interval:
interval = poll_interval(0);
+ if (fabs(offset) >= STEP_THRESHOLD * 8 && interval > BIGOFF_INTERVAL) {
+ /* If we are synced, offsets are less than STEP_THRESHOLD,
+ * or at the very least not much larger than it.
+ * Now we see a largish one.
+ * Either this peer is feeling bad, or packet got corrupted,
+ * or _our_ clock is wrong now and _all_ peers will show similar
+ * largish offsets too.
+ * I observed this with laptop suspend stopping clock.
+ * In any case, it makes sense to make next request soonish:
+ * cases 1 and 2: get a better datapoint,
+ * case 3: allows to resync faster.
+ */
+ interval = BIGOFF_INTERVAL;
+ }
set_next_and_ret:
set_next(p, interval);