emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

ntpd: disable frequency estimation code

Browse Source 
function                                             old     new   delta
reset_peer_stats                                     164     168      +4
ntp_init                                             371     368      -3
recv_and_process_peer_pkt                            869     852     -17
update_local_clock                                   823     759     -64
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 4/-84)             Total: -80 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2010-01-17 01:05:58 +01:00
parent e208279722
commit 5b9a910749
1 changed files with 45 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
networking/ntpd.c
View File

@ -57,6 +57,10 @@
* seconds. After WATCH_THRESHOLD seconds we look at accumulated
* offset and estimate frequency drift.
*
* (frequency measurement step seems to not be strictly needed,
* it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION
* define set to 0)
*
* After this, we enter "steady state": we collect a datapoint,
* we select the best peer, if this datapoint is not a new one
* (IOW: if this datapoint isn't for selected peer), sleep
@ -76,21 +80,27 @@
#define INITIAL_SAMLPES 4 /* how many samples do we want for init */
/* Clock discipline parameters and constants */
#define STEP_THRESHOLD 0.128 /* step threshold (s) */
#define WATCH_THRESHOLD 150 /* stepout threshold (s). std ntpd uses 900 (11 mins (!)) */
/* Step threshold (sec). std ntpd uses 0.128.
* 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 (!)) */
/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
//UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (s) */
//UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
#define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
#define BURSTPOLL 0 /* initial poll */
#define MINPOLL 4 /* minimum poll interval (6: 64 s) */
#define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
#define BIGPOLL 10 /* drop to lower poll at any trouble (10: 17 min) */
#define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h) (was 17) */
#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3) /* actively lower poll when we see such big offsets */
#define MINDISP 0.01 /* minimum dispersion (s) */
#define MAXDISP 16 /* maximum dispersion (s) */
#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
* if offset increases over 0.03 sec */
#define POLLDOWN_OFFSET (STEP_THRESHOLD / 4)
#define MINDISP 0.01 /* minimum dispersion (sec) */
#define MAXDISP 16 /* maximum dispersion (sec) */
#define MAXSTRAT 16 /* maximum stratum (infinity metric) */
#define MAXDIST 1 /* distance threshold (s) */
#define MAXDIST 1 /* distance threshold (sec) */
#define MIN_SELECTED 1 /* minimum intersection survivors */
#define MIN_CLUSTERED 3 /* minimum cluster survivors */
@ -109,7 +119,7 @@
* by staying at smaller poll).
*/
#define POLLADJ_GATE 4
/* Compromise Allan intercept (s). doc uses 1500, std ntpd uses 512 */
/* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
#define ALLAN 512
/* PLL loop gain */
#define PLL 65536
@ -214,6 +224,9 @@ typedef struct {
} peer_t;
#define USING_KERNEL_PLL_LOOP 1
#define USING_INITIAL_FREQ_ESTIMATION 0
enum {
OPT_n = (1 << 0),
OPT_q = (1 << 1),
@ -284,6 +297,11 @@ struct globals {
smallint adjtimex_was_done;
smallint initial_poll_complete;
#define STATE_NSET 0 /* initial state, "nothing is set" */
//#define STATE_FSET 1 /* frequency set from file */
#define STATE_SPIK 2 /* spike detected */
//#define STATE_FREQ 3 /* initial frequency */
#define STATE_SYNC 4 /* clock synchronized (normal operation) */
uint8_t discipline_state; // doc calls it c.state
uint8_t poll_exp; // s.poll
int polladj_count; // c.count
@ -292,7 +310,6 @@ struct globals {
double last_update_recv_time; // s.t
double discipline_jitter; // c.jitter
//TODO: add s.jitter - grep for it here and see clock_combine() in doc
#define USING_KERNEL_PLL_LOOP 1
#if !USING_KERNEL_PLL_LOOP
double discipline_freq_drift; // c.freq
//TODO: conditionally calculate wander? it's used only for logging
@ -581,8 +598,10 @@ static void
reset_peer_stats(peer_t *p, double offset)
{
int i;
bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
for (i = 0; i < NUM_DATAPOINTS; i++) {
if (offset < 16 * STEP_THRESHOLD) {
if (small_ofs) {
p->filter_datapoint[i].d_recv_time -= offset;
if (p->filter_datapoint[i].d_offset != 0) {
p->filter_datapoint[i].d_offset -= offset;
@ -593,7 +612,7 @@ reset_peer_stats(peer_t *p, double offset)
p->filter_datapoint[i].d_dispersion = MAXDISP;
}
}
if (offset < 16 * STEP_THRESHOLD) {
if (small_ofs) {
p->lastpkt_recv_time -= offset;
} else {
p->reachable_bits = 0;
@ -1105,12 +1124,6 @@ set_new_values(int disc_state, double offset, double recv_time)
G.last_update_offset = offset;
G.last_update_recv_time = recv_time;
}
/* Clock state definitions */
#define STATE_NSET 0 /* initial state, "nothing is set" */
#define STATE_FSET 1 /* frequency set from file */
#define STATE_SPIK 2 /* spike detected */
#define STATE_FREQ 3 /* initial frequency */
#define STATE_SYNC 4 /* clock synchronized (normal operation) */
/* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
static NOINLINE int
update_local_clock(peer_t *p)
@ -1156,6 +1169,7 @@ update_local_clock(peer_t *p)
#if !USING_KERNEL_PLL_LOOP
freq_drift = 0;
#endif
#if USING_INITIAL_FREQ_ESTIMATION
if (G.discipline_state == STATE_FREQ) {
/* Ignore updates until the stepout threshold */
if (since_last_update < WATCH_THRESHOLD) {
@ -1163,10 +1177,11 @@ update_local_clock(peer_t *p)
WATCH_THRESHOLD - since_last_update);
return 0; /* "leave poll interval as is" */
}
#if !USING_KERNEL_PLL_LOOP
# if !USING_KERNEL_PLL_LOOP
freq_drift = (offset - G.last_update_offset) / since_last_update;
#endif
# endif
}
#endif
/* There are two main regimes: when the
* offset exceeds the step threshold and when it does not.
@ -1225,10 +1240,12 @@ update_local_clock(peer_t *p)
run_script("step", offset);
#if USING_INITIAL_FREQ_ESTIMATION
if (G.discipline_state == STATE_NSET) {
set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
return 1; /* "ok to increase poll interval" */
}
#endif
set_new_values(STATE_SYNC, /*offset:*/ 0, recv_time);
} else { /* abs_offset <= STEP_THRESHOLD */
@ -1255,11 +1272,15 @@ update_local_clock(peer_t *p)
*/
exit(0);
}
#if USING_INITIAL_FREQ_ESTIMATION
/* This is the first update received and the frequency
* has not been initialized. The first thing to do
* is directly measure the oscillator frequency.
*/
set_new_values(STATE_FREQ, offset, recv_time);
#else
set_new_values(STATE_SYNC, offset, recv_time);
#endif
VERB3 bb_error_msg("transitioning to FREQ, datapoint ignored");
return 0; /* "leave poll interval as is" */
@ -1274,6 +1295,7 @@ update_local_clock(peer_t *p)
break;
#endif
#if USING_INITIAL_FREQ_ESTIMATION
case STATE_FREQ:
/* since_last_update >= WATCH_THRESHOLD, we waited enough.
* Correct the phase and frequency and switch to SYNC state.
@ -1281,6 +1303,7 @@ update_local_clock(peer_t *p)
*/
set_new_values(STATE_SYNC, offset, recv_time);
break;
#endif
default:
#if !USING_KERNEL_PLL_LOOP
@ -1579,9 +1602,7 @@ recv_and_process_peer_pkt(peer_t *p)
/* If drift is dangerously large, immediately
* drop poll interval one step down.
*/
if (q->filter_offset < -POLLDOWN_OFFSET
|| q->filter_offset > POLLDOWN_OFFSET
) {
if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
VERB3 bb_error_msg("offset:%f > POLLDOWN_OFFSET", q->filter_offset);
goto poll_down;
}