[LinuxPPS] cross posting [time-nuts] NTP API on Linux 2.6.26

[Udo van den Heuvel]

Michael Meier wrote:
>>> In the redhat rpm for ntp I find:
>>> # clock_gettime needs -lrt
>>> sed -i.gettime 's|^LIBS = @LIBS@|& -lrt|' ntp{d,q,dc,date}/Makefile.in
> 
> I'm impressed. Would be interesting to know when they put that in - 
> because it should have been rather useless and a waste of cpu before 
> kernel 2.6.26...
> 
>>> Dec 26 11:02:31 epia ntpd[13820]: precision = 1.000 usec
>>> Dec 26 11:29:41 epia ntpd[13969]: precision = 1.541 usec
> 
> The second one does look good, was the first one with a non-nano kernel?

Dunno for sure, could be.
It was an ntp I had been running on 2.6.26.2 or so since a while.
I needed to rebuild ntp to nmake stuff work again.

> available today. It should be a bit faster with 64 bit kernel and 
> userland, but still expensive. 1.5 us on an EPIA is actually better than 
> I expected, I'm getting 0.7 us on a Pentium 3 and 1.3 us on a Pentium 4 
> (yes, they were actually a lot slower than the pentium 3 in that, and 
> that is not the only thing they sucked at - luckily intel fixed it with 
> the core2).
> This should however not have a bad effect on timekeeping, as that 
> overhead is pretty constant, so it will give you an constant offset.

OK, thanks for explaining.
As I understand I am fine and can wait for the kernel and glibc to catch 
up to the changes we do by hand.

Udo