Re: Please ignore patch [chrony-dev] [PATCH] MacOS X dynamic drift removal interval

[Bryan Christianson <bryan@xxxxxxxxxxxxx>]

Stupid error - please ignore this patch. Should have learned by now to not make changes at 1:00 am.

> On 18/08/2015, at 7:59 am, Bryan Christianson <bryan@xxxxxxxxxxxxx> wrote:
> 
> Adjust the drift removal interval based on the observed offset_sd.
> A newly calculated interval goes into effect after the current drift removal has completed.
> When offset_sd is high, the interval is increased resulting in fewer wakeups to adjust the drift offset.
> At lower values of offset_sd the drift removal adjustment interval is pinned to 0.5 seconds.
> The predicted error applied at the start of an adjustment is based on the remaining time of the drift removal that is currently in effect.
> Default drift removal adjustment interval is 4.0 seconds (was 1.0)
> If not synchronised set interval to  maximum of default interval and current interval
> ---
> sys_macosx.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 61 insertions(+), 7 deletions(-)
> 
> diff --git a/sys_macosx.c b/sys_macosx.c
> index 5d7c1d5..4b5279c 100644
> --- a/sys_macosx.c
> +++ b/sys_macosx.c
> @@ -70,6 +70,21 @@ static double current_freq;
> 
> static double adjustment_requested;
> 
> +/* Interval in seconds between adjustments to cancel systematic drift */
> +
> +#define DRIFT_REMOVAL_INTERVAL (4.0)
> +#define DRIFT_REMOVAL_INTERVAL_MIN (0.5)
> +
> +static double drift_removal_interval;
> +static double current_drift_removal_interval;
> +static struct timeval Tdrift;
> +
> +/* weighting applied to error in calculating drift_removal_interval */
> +#define ERROR_WEIGHT (0.5)
> +
> +/* minimum resolution of current_frequency */
> +#define FREQUENCY_RES (1.0e-9)
> +
> /* ================================================== */
> 
> static void
> @@ -80,10 +95,13 @@ clock_initialise(void)
>   offset_register = 0.0;
>   adjustment_requested = 0.0;
>   current_freq = 0.0;
> +  drift_removal_interval = DRIFT_REMOVAL_INTERVAL;
> +  current_drift_removal_interval = DRIFT_REMOVAL_INTERVAL;
> 
>   if (gettimeofday(&T0, NULL) < 0) {
>     LOG_FATAL(LOGF_SysMacOSX, "gettimeofday() failed");
>   }
> +  Tdrift = T0;
> 
>   newadj.tv_sec = 0;
>   newadj.tv_usec = 0;
> @@ -108,7 +126,7 @@ start_adjust(void)
> {
>   struct timeval newadj, oldadj;
>   struct timeval T1;
> -  double elapsed, accrued_error, predicted_error;
> +  double elapsed, accrued_error, predicted_error, drift_removal_elapsed;
>   double adjust_required;
>   double rounding_error;
>   double old_adjust_remaining;
> @@ -120,7 +138,14 @@ start_adjust(void)
> 
>   UTI_DiffTimevalsToDouble(&elapsed, &T1, &T0);
>   accrued_error = elapsed * current_freq;
> -  predicted_error = DRIFT_REMOVAL_INTERVAL / 2.0 * current_freq;
> +
> +  UTI_DiffTimevalsToDouble(&drift_removal_elapsed, &T1, &Tdrift);
> +  predicted_error = MIN(0.0, (current_drift_removal_interval -  drift_removal_elapsed) / 2.0 * current_freq);

should be MAX not MIN


Sorry about that.
-- 
Bryan Christianson


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