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reference: rework makestep

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Rework makestep to cancel accumulated offset and step with the new
offset instead of accumulating new offset first, canceling all
accumulated offset and making the step.

This avoids two large frequency changes to initiate and cancel a slew
before making the step.
This commit is contained in:
Miroslav Lichvar
2014-06-05 14:46:22 +02:00
parent 64ba5a5b65
commit 20d2363fb7
4 changed files with 28 additions and 19 deletions
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34
reference.c
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@@ -553,15 +553,15 @@ maybe_log_offset(double offset, time_t now)
/* ================================================== */
static void
maybe_make_step()
static int
is_step_limit_reached(double offset, double offset_correction)
{
if (make_step_limit == 0) {
return;
return 0;
} else if (make_step_limit > 0) {
make_step_limit--;
}
LCL_MakeStep(make_step_threshold);
return fabs(offset - offset_correction) > make_step_threshold;
}
/* ================================================== */
@@ -790,7 +790,7 @@ REF_SetReference(int stratum,
double update_interval;
double elapsed;
double correction_rate;
double uncorrected_offset;
double uncorrected_offset, accumulate_offset, step_offset;
struct timeval now, raw_now;
assert(initialised);
@@ -868,6 +868,16 @@ REF_SetReference(int stratum,
correction_rate = correction_time_ratio * 0.5 * offset_sd * update_interval;
/* Check if the clock should be stepped */
if (is_step_limit_reached(our_offset, uncorrected_offset)) {
/* Cancel the uncorrected offset and correct the total offset by step */
accumulate_offset = uncorrected_offset;
step_offset = our_offset - uncorrected_offset;
} else {
accumulate_offset = our_offset;
step_offset = 0.0;
}
/* Eliminate updates that are based on totally unreliable frequency
information. Ignore this limit with manual reference. */
@@ -902,21 +912,23 @@ REF_SetReference(int stratum,
our_residual_freq = new_freq - our_frequency;
LCL_AccumulateFrequencyAndOffset(our_frequency, our_offset, correction_rate);
LCL_AccumulateFrequencyAndOffset(our_frequency, accumulate_offset, correction_rate);
} else {
DEBUG_LOG(LOGF_Reference, "Skew %f too large to track, offset=%f", skew, accumulate_offset);
#if 0
LOG(LOGS_INFO, LOGF_Reference, "Skew %f too large to track, offset=%f", skew, our_offset);
#endif
LCL_AccumulateOffset(our_offset, correction_rate);
LCL_AccumulateOffset(accumulate_offset, correction_rate);
our_residual_freq = frequency;
}
update_leap_status(leap, raw_now.tv_sec);
maybe_log_offset(our_offset, raw_now.tv_sec);
maybe_make_step();
if (step_offset != 0.0) {
LCL_ApplyStepOffset(step_offset);
LOG(LOGS_WARN, LOGF_Reference, "System clock was stepped by %.6f seconds", -step_offset);
}
abs_freq_ppm = LCL_ReadAbsoluteFrequency();