hwclock: improve filtering of readings
Estimate the 1st and 2nd 10-quantile of the reading delay and accept only readings between them unless the error of the offset predicted from previous samples is larger than the minimum reading error. With the 25 PHC readings per ioctl it should combine about 2-3 readings. This should improve hwclock tracking and synchronization stability when a PHC reading delay occasionally falls below the normal expected minimum, or all readings in the batch are delayed significantly (e.g. due to high PCIe load).
This commit is contained in:
Miroslav Lichvar
parent
b428f901c7
commit
9c64fbb9c4
3 changed files with 94 additions and 19 deletions
4
configure
vendored
4
configure
vendored
|
|
@ -737,7 +737,7 @@ if [ $feat_timestamping = "1" ] && [ $try_timestamping = "1" ] &&
|
|||
&val, sizeof (val));'
|
||||
then
|
||||
add_def HAVE_LINUX_TIMESTAMPING
|
||||
EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o ntp_io_linux.o"
|
||||
EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o ntp_io_linux.o quantiles.o"
|
||||
|
||||
if test_code 'other timestamping options' \
|
||||
'sys/types.h sys/socket.h linux/net_tstamp.h' '' '' '
|
||||
|
|
@ -830,7 +830,7 @@ if [ $feat_refclock = "1" ] && [ $feat_phc = "1" ] && [ $try_phc = "1" ] && \
|
|||
'ioctl(1, PTP_CLOCK_GETCAPS + PTP_SYS_OFFSET, 0);'
|
||||
then
|
||||
grep 'HAVE_LINUX_TIMESTAMPING' config.h > /dev/null ||
|
||||
EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o"
|
||||
EXTRA_OBJECTS="$EXTRA_OBJECTS hwclock.o quantiles.o"
|
||||
add_def FEAT_PHC
|
||||
fi
|
||||
|
||||
|
|
|
|||
82
hwclock.c
82
hwclock.c
|
|
@ -33,6 +33,7 @@
|
|||
#include "local.h"
|
||||
#include "logging.h"
|
||||
#include "memory.h"
|
||||
#include "quantiles.h"
|
||||
#include "regress.h"
|
||||
#include "util.h"
|
||||
|
||||
|
|
@ -43,6 +44,13 @@
|
|||
/* Maximum acceptable frequency offset of the clock */
|
||||
#define MAX_FREQ_OFFSET (2.0 / 3.0)
|
||||
|
||||
/* Quantiles for filtering readings by delay */
|
||||
#define DELAY_QUANT_MIN_K 1
|
||||
#define DELAY_QUANT_MAX_K 2
|
||||
#define DELAY_QUANT_Q 10
|
||||
#define DELAY_QUANT_REPEAT 7
|
||||
#define DELAY_QUANT_MIN_STEP 1.0e-9
|
||||
|
||||
struct HCL_Instance_Record {
|
||||
/* HW and local reference timestamp */
|
||||
struct timespec hw_ref;
|
||||
|
|
@ -73,6 +81,9 @@ struct HCL_Instance_Record {
|
|||
/* Estimated offset and frequency of HW clock relative to local clock */
|
||||
double offset;
|
||||
double frequency;
|
||||
|
||||
/* Estimated quantiles of reading delay */
|
||||
QNT_Instance delay_quants;
|
||||
};
|
||||
|
||||
/* ================================================== */
|
||||
|
|
@ -114,6 +125,9 @@ HCL_CreateInstance(int min_samples, int max_samples, double min_separation, doub
|
|||
clock->valid_coefs = 0;
|
||||
clock->min_separation = min_separation;
|
||||
clock->precision = precision;
|
||||
clock->delay_quants = QNT_CreateInstance(DELAY_QUANT_MIN_K, DELAY_QUANT_MAX_K,
|
||||
DELAY_QUANT_Q, DELAY_QUANT_REPEAT,
|
||||
DELAY_QUANT_MIN_STEP);
|
||||
|
||||
LCL_AddParameterChangeHandler(handle_slew, clock);
|
||||
|
||||
|
|
@ -125,6 +139,7 @@ HCL_CreateInstance(int min_samples, int max_samples, double min_separation, doub
|
|||
void HCL_DestroyInstance(HCL_Instance clock)
|
||||
{
|
||||
LCL_RemoveParameterChangeHandler(handle_slew, clock);
|
||||
QNT_DestroyInstance(clock->delay_quants);
|
||||
Free(clock->y_data);
|
||||
Free(clock->x_data);
|
||||
Free(clock);
|
||||
|
|
@ -148,14 +163,25 @@ int
|
|||
HCL_ProcessReadings(HCL_Instance clock, int n_readings, struct timespec tss[][3],
|
||||
struct timespec *hw_ts, struct timespec *local_ts, double *err)
|
||||
{
|
||||
double delay, min_delay = 0.0, hw_sum, local_sum, local_prec;
|
||||
int i, combined;
|
||||
double delay, raw_delay, min_delay, low_delay, high_delay, e, pred_err;
|
||||
double delay_sum, hw_sum, local_sum, local_prec, freq;
|
||||
int i, min_reading, combined;
|
||||
struct timespec ts1, ts2;
|
||||
|
||||
if (n_readings < 1)
|
||||
return 0;
|
||||
|
||||
/* Work out the current correction multiplier needed to get cooked delays */
|
||||
LCL_CookTime(&tss[0][0], &ts1, NULL);
|
||||
LCL_CookTime(&tss[n_readings - 1][2], &ts2, NULL);
|
||||
if (UTI_CompareTimespecs(&tss[0][0], &tss[n_readings - 1][2]) < 0)
|
||||
freq = UTI_DiffTimespecsToDouble(&ts1, &ts2) /
|
||||
UTI_DiffTimespecsToDouble(&tss[0][0], &tss[n_readings - 1][2]);
|
||||
else
|
||||
freq = 1.0;
|
||||
|
||||
for (i = 0; i < n_readings; i++) {
|
||||
delay = UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
|
||||
delay = freq * UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
|
||||
|
||||
if (delay < 0.0) {
|
||||
/* Step in the middle of a reading? */
|
||||
|
|
@ -163,30 +189,60 @@ HCL_ProcessReadings(HCL_Instance clock, int n_readings, struct timespec tss[][3]
|
|||
return 0;
|
||||
}
|
||||
|
||||
if (i == 0 || min_delay > delay)
|
||||
if (i == 0 || min_delay > delay) {
|
||||
min_delay = delay;
|
||||
min_reading = i;
|
||||
}
|
||||
|
||||
QNT_Accumulate(clock->delay_quants, delay);
|
||||
}
|
||||
|
||||
local_prec = LCL_GetSysPrecisionAsQuantum();
|
||||
|
||||
/* Combine best readings */
|
||||
for (i = combined = 0, hw_sum = local_sum = 0.0; i < n_readings; i++) {
|
||||
delay = UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
|
||||
if (delay > min_delay + MAX(local_prec, clock->precision))
|
||||
low_delay = QNT_GetQuantile(clock->delay_quants, DELAY_QUANT_MIN_K);
|
||||
high_delay = QNT_GetQuantile(clock->delay_quants, DELAY_QUANT_MAX_K);
|
||||
low_delay = MIN(low_delay, high_delay);
|
||||
high_delay = MAX(high_delay, low_delay + local_prec);
|
||||
|
||||
/* Combine readings with delay in the expected interval */
|
||||
for (i = combined = 0, delay_sum = hw_sum = local_sum = 0.0; i < n_readings; i++) {
|
||||
raw_delay = UTI_DiffTimespecsToDouble(&tss[i][2], &tss[i][0]);
|
||||
delay = freq * raw_delay;
|
||||
|
||||
if (delay < low_delay || delay > high_delay)
|
||||
continue;
|
||||
|
||||
delay_sum += delay;
|
||||
hw_sum += UTI_DiffTimespecsToDouble(&tss[i][1], &tss[0][1]);
|
||||
local_sum += UTI_DiffTimespecsToDouble(&tss[i][0], &tss[0][0]) + delay / 2.0;
|
||||
local_sum += UTI_DiffTimespecsToDouble(&tss[i][0], &tss[0][0]) + raw_delay / 2.0;
|
||||
combined++;
|
||||
}
|
||||
|
||||
assert(combined);
|
||||
DEBUG_LOG("Combined %d readings lo=%e hi=%e", combined, low_delay, high_delay);
|
||||
|
||||
UTI_AddDoubleToTimespec(&tss[0][1], hw_sum / combined, hw_ts);
|
||||
UTI_AddDoubleToTimespec(&tss[0][0], local_sum / combined, local_ts);
|
||||
if (combined > 0) {
|
||||
UTI_AddDoubleToTimespec(&tss[0][1], hw_sum / combined, hw_ts);
|
||||
UTI_AddDoubleToTimespec(&tss[0][0], local_sum / combined, local_ts);
|
||||
*err = MAX(delay_sum / combined / 2.0, clock->precision);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/* Accept the reading with minimum delay if its interval does not contain
|
||||
the current offset predicted from previous samples */
|
||||
|
||||
*hw_ts = tss[min_reading][1];
|
||||
UTI_AddDoubleToTimespec(&tss[min_reading][0], min_delay / freq / 2.0, local_ts);
|
||||
*err = MAX(min_delay / 2.0, clock->precision);
|
||||
|
||||
return 1;
|
||||
pred_err = 0.0;
|
||||
LCL_CookTime(local_ts, &ts1, NULL);
|
||||
if (!HCL_CookTime(clock, hw_ts, &ts2, &e) ||
|
||||
((pred_err = UTI_DiffTimespecsToDouble(&ts1, &ts2)) > *err)) {
|
||||
DEBUG_LOG("Accepted reading err=%e prerr=%e", *err, pred_err);
|
||||
return 1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* ================================================== */
|
||||
|
|
|
|||
|
|
@ -18,9 +18,13 @@
|
|||
**********************************************************************
|
||||
*/
|
||||
|
||||
#include <hwclock.c>
|
||||
#include <config.h>
|
||||
#include "test.h"
|
||||
|
||||
#if defined(FEAT_PHC) || defined(HAVE_LINUX_TIMESTAMPING)
|
||||
|
||||
#include <hwclock.c>
|
||||
|
||||
#define MAX_READINGS 20
|
||||
|
||||
void
|
||||
|
|
@ -30,9 +34,10 @@ test_unit(void)
|
|||
struct timespec readings[MAX_READINGS][3];
|
||||
HCL_Instance clock;
|
||||
double freq, jitter, interval, dj, err, sum;
|
||||
int i, j, k, l, n_readings, count;
|
||||
int i, j, k, l, new_sample, n_readings, count;
|
||||
|
||||
LCL_Initialise();
|
||||
TST_RegisterDummyDrivers();
|
||||
|
||||
for (i = 1; i <= 8; i++) {
|
||||
clock = HCL_CreateInstance(random() % (1 << i), 1 << i, 1.0, 1e-9);
|
||||
|
|
@ -51,11 +56,14 @@ test_unit(void)
|
|||
|
||||
clock->n_samples = 0;
|
||||
clock->valid_coefs = 0;
|
||||
QNT_Reset(clock->delay_quants);
|
||||
|
||||
new_sample = 0;
|
||||
|
||||
for (k = 0; k < 100; k++) {
|
||||
UTI_AddDoubleToTimespec(&start_hw_ts, k * interval * freq, &hw_ts);
|
||||
UTI_AddDoubleToTimespec(&start_local_ts, k * interval, &local_ts);
|
||||
if (HCL_CookTime(clock, &hw_ts, &ts, NULL)) {
|
||||
if (HCL_CookTime(clock, &hw_ts, &ts, NULL) && new_sample) {
|
||||
dj = fabs(UTI_DiffTimespecsToDouble(&ts, &local_ts) / jitter);
|
||||
DEBUG_LOG("delta/jitter %f", dj);
|
||||
if (clock->n_samples >= clock->max_samples / 2)
|
||||
|
|
@ -76,8 +84,12 @@ test_unit(void)
|
|||
|
||||
UTI_ZeroTimespec(&hw_ts);
|
||||
UTI_ZeroTimespec(&local_ts);
|
||||
if (HCL_ProcessReadings(clock, n_readings, readings, &hw_ts, &local_ts, &err))
|
||||
if (HCL_ProcessReadings(clock, n_readings, readings, &hw_ts, &local_ts, &err)) {
|
||||
HCL_AccumulateSample(clock, &hw_ts, &local_ts, 2.0 * jitter);
|
||||
new_sample = 1;
|
||||
} else {
|
||||
new_sample = 0;
|
||||
}
|
||||
}
|
||||
|
||||
TEST_CHECK(clock->valid_coefs == (clock->n_samples >= 2));
|
||||
|
|
@ -96,3 +108,10 @@ test_unit(void)
|
|||
|
||||
LCL_Finalise();
|
||||
}
|
||||
#else
|
||||
void
|
||||
test_unit(void)
|
||||
{
|
||||
TEST_REQUIRE(0);
|
||||
}
|
||||
#endif
|
||||
|
|
|
|||
Loading…
Reference in a new issue