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ntpd: step when |offset| > 1 sec, not 0.125 sec

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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>
This commit is contained in:
Denys Vlasenko 2016-02-10 06:55:07 +01:00
parent f2c043acfc
commit fc47fcefb6
1 changed files with 36 additions and 18 deletions
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52
networking/ntpd.c
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@ -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:
@ -131,9 +131,12 @@
#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
/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
@ -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,