[ntp:questions] strange time behaviour

hvengel at astound.net hvengel at astound.net
Wed May 27 21:48:45 UTC 2009

On May 26, 1:20 am, hal-use... at ip-64-139-1-69.sjc.megapath.net (Hal
Murray) wrote:
> There has been a lot of work on the timekeeping area of the Linux kernel
> recently.  I'd probably update to a recent kernel.

Yes there has been and you have to be careful when using newer kernels
since one of those changes is to move from microsecond to nanosecond
resolution.  The issue there is that glibc was out of sync with these
kernel changes and as a result ntp would build setup for a microsecond
kernel and this would result in the time keeping being somewhat
unstable although this would only be noticed if you were using a
refclock.  So you need to either use a patched version of glibc or
create a patch for ntp that has the missing declarations.  Development
glibc now has been patched to correctly handle a linux nanokernel.

The other "issue" with kernels newer than 2.6.19 is that the time
adjustments were too stiff and to correct this you need to use the
convergence patch that will be part of 2.6.31.  But a properly setup
new kernel with a few tweaks can give very good time keeping

Also you might want to consider using a slower tick rate than 1KHz.
Thats probably too fast for a Geode but it might not have anything to
do with this time keeping problem.

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