[ntp:questions] Re: ntpd PLL and clock overshoot
uwe_klein_habertwedt at t-online.de
Mon Oct 16 18:26:41 UTC 2006
user at domain.invalid wrote:
> In all kernels I have seen over the last several years the adjtime()
> system call is implemented in the kernel/kern_clock.c kernel module.
> There may be a library wrapper for it, but the actual adjustment is done
> in the kernel at each timer interrupt.
Hey user ;-)
Which Linux SemiMajor version (are you | is being) referencing : 2.[0,2,4,6] ?
i don't know shit about ntpd related timehandling with linux (yet).
I've done realtime stuff on linux 2.2, 2.4 ( started with 2.6 ).
up to now i have used one ntpd synced (black)box to do bookkeeping on
timeslip of my embedded and rather undermuscled (SC400/8MB) RT thingies.
fixing slip by adjusting my timeconstants, doing nothing against jitter.
( time corrections do not reach the RT clock anyway.)
Which Linux SemiMajor version are you referencing 2.[0,2,4,6] ?
recent sources of linux 2.6.1n seem to be extensively revamped. the mentioned
files and functions are not present.
"something" seems to have been moved into the high resolution timer stuff.
How current is the ntpd developers picture of recent linux ?
I am in the process of building and deploying distributed sweep receivers
(that replace a single 4 Band receiver at the end of several hundred feet of koax)
that have to run in sync ( <10ms ).
my interest here is do i stay with my current method or can i leverage
ntpd to do housekeeping for my little boxes and adjust hardware clockrate
in some way ( VCXO, or just heating up the builtin Xtal )
More information about the questions