Instead of always selecting the source with minimum stratum, add weighted
stratum to the distance when comparing selectable sources. The weight
can be configured with new stratumweight directive and can be set to
zero to ignore stratum completely, by default 1.0.
Each source has a score against currently selected source which is
updated (multiplied by ratio of their distances) when one of the two
sources has a new sample. When the score reaches a limit, the source
will be selected. This should allow to slowly select the source with
minimum distance without frequent reselecting.
To avoid switching between sources with very variable distances (e.g. on
LAN or when upstream server uses a longer polling interval), sources
that are currently not selected are penalized by a fixed distance. This
can be configured with new reselectdist directive (100 microseconds by
default).
A new tempcomp directive can be used to specify a file for reading
current temperature, update interval and compensation coefficients. The
clock frequency corrections are applied in local module and are invisible
in upper layers. The measurements and corrections can be logged to
tempcomp.log file.
Fallback drifts are long-term averages of the system clock drift
calculated over exponentially increasing intervals. They are used when
the clock is unsynchronised to avoid quickly drifting away from true
time if there was a short-term deviation in drift before the
synchronisation was lost.
The attached patch adds support for mlockall() as well as the SCHED_FIFO
real-time scheduler. It should result in reduced (and more consistent)
latency. Usage is documented in all the documents.
This is a verbatim copy of the files at that stage of the repository that was
built from the CVS import. It allows future development to see a bit of recent
history, but without carrying around the baggage going back to 1997. If that
is really required, git grafts can be used.
