From fc47fcefb6401605b142c30025c597dc4d110087 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Wed, 10 Feb 2016 06:55:07 +0100
Subject: ntpd: step when |offset| > 1 sec, not 0.125 sec
update_local_clock 769 820 +51
recv_and_process_peer_pkt 838 862 +24
reset_peer_stats 137 133 -4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 75/-4) Total: 71 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
networking/ntpd.c | 54 ++++++++++++++++++++++++++++++++++++------------------
1 file changed, 36 insertions(+), 18 deletions(-)
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 9732c9b1a..32590a185 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -112,7 +112,7 @@
*
* 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
+ * - if largish offset (>= STEP_THRESHOLD == 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:
@@ -131,11 +131,14 @@
#define RESPONSE_INTERVAL 16 /* wait for reply up to N secs */
/* Step threshold (sec). std ntpd uses 0.128.
+ */
+#define STEP_THRESHOLD 1
+/* Slew threshold (sec): adjtimex() won't accept offsets larger than this.
* Using exact power of 2 (1/8) results in smaller code
*/
-#define STEP_THRESHOLD 0.125
+#define SLEW_THRESHOLD 0.125
/* Stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
-#define WATCH_THRESHOLD 128
+#define WATCH_THRESHOLD 128
/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
//UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
@@ -143,7 +146,7 @@
* 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 STEP_THRESHOLD
#define BIGOFF_INTERVAL (1 << 7) /* 128 s */
#define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
@@ -157,10 +160,10 @@
#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.
- * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
+ * With SLEW_THRESHOLD = 0.125, it means we try to sync more aggressively
* if offset increases over ~0.04 sec
*/
-//#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
+//#define POLLDOWN_OFFSET (SLEW_THRESHOLD / 3)
#define MINDISP 0.01 /* minimum dispersion (sec) */
#define MAXDISP 16 /* maximum dispersion (sec) */
#define MAXSTRAT 16 /* maximum stratum (infinity metric) */
@@ -720,7 +723,7 @@ static void
reset_peer_stats(peer_t *p, double offset)
{
int i;
- bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
+ bool small_ofs = fabs(offset) < STEP_THRESHOLD;
/* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP
* and clear reachable bits, but this proved to be too agressive:
@@ -771,7 +774,7 @@ add_peers(const char *s)
p->p_fd = -1;
p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
p->next_action_time = G.cur_time; /* = set_next(p, 0); */
- reset_peer_stats(p, 16 * STEP_THRESHOLD);
+ reset_peer_stats(p, STEP_THRESHOLD);
llist_add_to(&G.ntp_peers, p);
G.peer_cnt++;
@@ -1638,14 +1641,7 @@ update_local_clock(peer_t *p)
tmx.freq = G.discipline_freq_drift * 65536e6;
#endif
tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
- 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 = (int)G.poll_exp - 4 > 0 ? (int)G.poll_exp - 4 : 0;
+ tmx.constant = (int)G.poll_exp - 4;
/* EXPERIMENTAL.
* The below if statement should be unnecessary, but...
* It looks like Linux kernel's PLL is far too gentle in changing
@@ -1656,8 +1652,27 @@ update_local_clock(peer_t *p)
* 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)
+ if (G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
tmx.constant--;
+ tmx.offset = (long)(offset * 1000000); /* usec */
+ if (SLEW_THRESHOLD < STEP_THRESHOLD) {
+ if (tmx.offset > (long)(SLEW_THRESHOLD * 1000000)) {
+ tmx.offset = (long)(SLEW_THRESHOLD * 1000000);
+ tmx.constant--;
+ }
+ if (tmx.offset < -(long)(SLEW_THRESHOLD * 1000000)) {
+ tmx.offset = -(long)(SLEW_THRESHOLD * 1000000);
+ tmx.constant--;
+ }
+ }
+ if (tmx.constant < 0)
+ tmx.constant = 0;
+
+ 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.esterror = (uint32_t)(clock_jitter * 1e6);
//tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
@@ -1931,6 +1946,9 @@ recv_and_process_peer_pkt(peer_t *p)
increase_interval:
adjust_poll(MINPOLL);
} else {
+ VERB3 if (rc > 0)
+ bb_error_msg("want smaller poll interval: offset/jitter ratio > %u",
+ POLLADJ_GATE);
adjust_poll(-G.poll_exp * 2);
}
}
@@ -1939,7 +1957,7 @@ recv_and_process_peer_pkt(peer_t *p)
pick_normal_interval:
interval = poll_interval(INT_MAX);
if (fabs(offset) >= BIGOFF && interval > BIGOFF_INTERVAL) {
- /* If we are synced, offsets are less than STEP_THRESHOLD,
+ /* If we are synced, offsets are less than SLEW_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,
--
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