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conf: change default corrtimeratio to 3.0

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This improves the overall frequency accuracy of the clock at a slight
cost in the time accuracy.
This commit is contained in:
Miroslav Lichvar 2014-05-21 12:08:10 +02:00
parent cf3c7b3bd6
commit 3e1dc801b0
2 changed files with 9 additions and 10 deletions
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17
chrony.texi.in
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@ -1513,9 +1513,9 @@ the password command automatically.
@subsection corrtimeratio @subsection corrtimeratio
When @code{chronyd} makes a time correction, it controls how quickly When @code{chronyd} makes a time correction, it controls how quickly
the system clock is slewed (so far only on Linux). This rate the system clock is slewed (so far only on Linux). This rate
temporarily affects the frequency error of the system clock. affects the frequency error of the system clock.
The @code{corrtimeratio} directive controls the ratio between the The @code{corrtimeratio} directive sets the ratio between the
duration in which the clock is slewed for an average correction duration in which the clock is slewed for an average correction
according to the source history and the interval in which the according to the source history and the interval in which the
corrections are done (usually the NTP polling interval). Corrections corrections are done (usually the NTP polling interval). Corrections
@ -1523,22 +1523,21 @@ larger than the average take less time and smaller corrections take
more time, the amount of the correction and the correction time are more time, the amount of the correction and the correction time are
inversely proportional. inversely proportional.
Increasing @code{corrtimeratio} makes the overall frequency error of Increasing @code{corrtimeratio} improves the overall frequency error
the system clock smaller, but increases the overall time error as of the system clock, but increases the overall time error as the
the corrections will take longer. corrections take longer.
By default, the ratio is 1, which means the duration of an average By default, the ratio is set to 3, the time accuracy of the clock is
correction will be close to the update interval. preferred over its frequency accuracy.
The syntax is The syntax is
@example @example
corrtimeratio 10 corrtimeratio 100
@end example @end example
The current remaining correction is shown in the @code{tracking} report The current remaining correction is shown in the @code{tracking} report
(@pxref{tracking command}) as the @code{System time} value. (@pxref{tracking command}) as the @code{System time} value.
@c }}} @c }}}
@c {{{ deny @c {{{ deny
@node deny directive @node deny directive

2
conf.c
View file

@ -86,7 +86,7 @@ static char *drift_file = NULL;
static char *rtc_file = NULL; static char *rtc_file = NULL;
static unsigned long command_key_id; static unsigned long command_key_id;
static double max_update_skew = 1000.0; static double max_update_skew = 1000.0;
static double correction_time_ratio = 1.0; static double correction_time_ratio = 3.0;
static double max_clock_error = 1.0; /* in ppm */ static double max_clock_error = 1.0; /* in ppm */
static double reselect_distance = 1e-4; static double reselect_distance = 1e-4;