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authorDenys Vlasenko <vda.linux@googlemail.com>2014-09-27 20:56:09 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2014-09-27 20:56:09 (GMT)
commitd3fe9602714e01b228fa0c625901e748912a7775 (patch)
treeda2169608d86f751ab4bc1b48263d9a832cffa06
parent186b98a86f069bb65bf4110e324d75fef98857c0 (diff)
downloadbusybox-master.tar.gz
busybox-master.tar.bz2
ntpd: be less eager to use shorter poll intervalsHEADmaster
* on step, poll interval drops to 8.5 mins instead of 32 seconds * on total loss of all replies (no replies from any peer for last 8 requests), also drop poll interval to 8.5 mins instead of 32 seconds * on send abd recv errors, RETRY_INTERVAL is now 32 seconds, not 5 seconds * on timing out listening to reply, instead of unconditional shortening poll interval by x4, clamp it to NOREPLY_INTERVAL (512 seconds) * if a largish offset is seen, clamp nexp poll interval to 128 seconds, not 64 seconds function old new delta clamp_pollexp_and_set_MAXSTRAT - 37 +37 recv_and_process_peer_pkt 861 869 +8 poll_interval 52 48 -4 update_local_clock 762 752 -10 ntpd_main 1063 1050 -13 ------------------------------------------------------------------------------ (add/remove: 1/0 grow/shrink: 1/3 up/down: 45/-27) Total: 18 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--networking/ntpd.c80
1 files changed, 41 insertions, 39 deletions
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 2d1ad69..b2b2791 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -109,35 +109,43 @@
* datapoints after the step.
*/
-#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 */
-/* Clock discipline parameters and constants */
+#define RETRY_INTERVAL 32 /* on send/recv error, retry in N secs (need to be power of 2) */
+#define NOREPLY_INTERVAL 512 /* sent, but got no reply: cap next query by this many seconds */
+#define RESPONSE_INTERVAL 16 /* wait for reply up to N secs */
/* Step threshold (sec). std ntpd uses 0.128.
- * Using exact power of 2 (1/8) results in smaller code */
+ * Using exact power of 2 (1/8) results in smaller code
+ */
#define STEP_THRESHOLD 0.125
-#define WATCH_THRESHOLD 128 /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
+/* Stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
+#define WATCH_THRESHOLD 128
/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
//UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
+/*
+ * If we got |offset| > BIGOFF from a peer, cap next query interval
+ * for this peer by this many seconds:
+ */
+#define BIGOFF (STEP_THRESHOLD * 8)
+#define BIGOFF_INTERVAL (1 << 7) /* 128 s */
+
#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,
+/*
+ * 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_).
*/
#define BIGPOLL 10 /* 2^10 sec ~= 17 min */
#define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
-/* Actively lower poll when we see such big offsets.
+/*
+ * Actively lower poll when we see such big offsets.
* With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
- * if offset increases over ~0.04 sec */
+ * if offset increases over ~0.04 sec
+ */
#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
#define MINDISP 0.01 /* minimum dispersion (sec) */
#define MAXDISP 16 /* maximum dispersion (sec) */
@@ -972,6 +980,16 @@ step_time(double offset)
}
}
+static void clamp_pollexp_and_set_MAXSTRAT(void)
+{
+ if (G.poll_exp < MINPOLL)
+ G.poll_exp = MINPOLL;
+ if (G.poll_exp >= BIGPOLL)
+ G.poll_exp = BIGPOLL - 1;
+ G.polladj_count = 0;
+ G.stratum = MAXSTRAT;
+}
+
/*
* Selection and clustering, and their helpers
@@ -1453,9 +1471,7 @@ update_local_clock(peer_t *p)
exit(0);
}
- G.polladj_count = 0;
- G.poll_exp = MINPOLL;
- G.stratum = MAXSTRAT;
+ clamp_pollexp_and_set_MAXSTRAT();
run_script("step", offset);
@@ -1654,28 +1670,16 @@ update_local_clock(peer_t *p)
* (helpers first)
*/
static unsigned
-retry_interval(void)
-{
- /* Local problem, want to retry soon */
- unsigned interval, r;
- interval = RETRY_INTERVAL;
- r = rand();
- interval += r % (unsigned)(RETRY_INTERVAL / 4);
- VERB4 bb_error_msg("chose retry interval:%u", interval);
- return interval;
-}
-static unsigned
-poll_interval(int exponent)
+poll_interval(int upper_bound)
{
unsigned interval, r, mask;
- exponent = G.poll_exp + exponent;
- if (exponent < 0)
- exponent = 0;
- interval = 1 << exponent;
+ interval = 1 << G.poll_exp;
+ if (interval > upper_bound)
+ interval = upper_bound;
mask = ((interval-1) >> 4) | 1;
r = rand();
interval += r & mask; /* ~ random(0..1) * interval/16 */
- VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
+ VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d)", interval, G.poll_exp);
return interval;
}
static NOINLINE void
@@ -1741,7 +1745,7 @@ recv_and_process_peer_pkt(peer_t *p)
|| errno == EAGAIN
) {
//TODO: always do this?
- interval = retry_interval();
+ interval = poll_interval(RETRY_INTERVAL);
goto set_next_and_ret;
}
xfunc_die();
@@ -1897,8 +1901,8 @@ 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) {
+ interval = poll_interval(INT_MAX);
+ if (fabs(offset) >= BIGOFF && 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.
@@ -2248,7 +2252,7 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv)
/* Timed out waiting for reply */
close(p->p_fd);
p->p_fd = -1;
- timeout = poll_interval(-2); /* -2: try a bit sooner */
+ timeout = poll_interval(NOREPLY_INTERVAL);
bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
p->p_dotted, p->reachable_bits, timeout);
set_next(p, timeout);
@@ -2339,9 +2343,7 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv)
goto have_reachable_peer;
}
/* No peer responded for last 8 packets, panic */
- G.polladj_count = 0;
- G.poll_exp = MINPOLL;
- G.stratum = MAXSTRAT;
+ clamp_pollexp_and_set_MAXSTRAT();
run_script("unsync", 0.0);
have_reachable_peer: ;
}