7f45eb7957
Time smoothing determines an offset that needs to be applied to the cooked time to make it smooth for external observers. Observed offset and frequency change slowly and there are no discontinuities. This can be used on an NTP server to make it easier for the clients to track the time and keep their clocks close together even when large offset or frequency corrections are applied to the server's clock (e.g. after being offline for longer time). Accumulated offset and frequency are smoothed out in three stages. In the first stage, the frequency is changed at a constant rate (wander) up to a maximum, in the second stage the frequency stays at the maximum for as long as needed and in the third stage the frequency is brought back to zero. Time smoothing is configured by the smoothtime directive. It takes two arguments, maximum frequency offset and maximum wander. It's disabled by default.
40 lines
1.3 KiB
C
40 lines
1.3 KiB
C
/*
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chronyd/chronyc - Programs for keeping computer clocks accurate.
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**********************************************************************
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* Copyright (C) Miroslav Lichvar 2015
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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**********************************************************************
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=======================================================================
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This module implements time smoothing.
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*/
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#ifndef GOT_SMOOTH_H
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#define GOT_SMOOTH_H
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extern void SMT_Initialise(void);
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extern void SMT_Finalise(void);
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extern int SMT_IsEnabled(void);
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extern double SMT_GetOffset(struct timeval *now);
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extern void SMT_Reset(struct timeval *now);
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#endif
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