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hwclock: improve filtering of readings

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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
2022-06-09 12:21:38 +02:00
parent b428f901c7
commit 9c64fbb9c4
3 changed files with 94 additions and 19 deletions
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27
test/unit/hwclock.c
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@@ -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