[ntp:questions] Linux HZ free ntp

Uwe Klein uwe_klein_habertwedt at t-online.de
Fri Dec 15 13:02:03 UTC 2006


Hmm,
I don't know if this is of interest to anyone here:
( afaiu there is developement for Linux to loose the regular timertick )

uwe

from lwn.net:
http://lwn.net/Articles/213878/

Patch: HZ free ntp

On Wed, 2006-12-06 at 15:33 +0100, Roman Zippel wrote:
 > On Wed, 6 Dec 2006, Ingo Molnar wrote:
 > > i disagree with you and it's pretty low-impact anyway. There's still
 > > quite many HZ/tick assumptions all around the time code (NTP being one
 > > example), we'll deal with those via other patches.
 >
 > Why do you pick on the NTP code? That's actually one of the places where
 > assumptions about HZ are largely gone. NTP state is updated incrementally
 > and this won't change, but the update frequency can now be easily
 > disconnected from HZ.

Hey Roman,
Here's my rough first attempt at doing so. I'd not call it easy, but
maybe you have some suggestions for a simpler way?

Basically INTERVAL_LENGTH_NSEC defines the NTP interval length that the
time code will use to accumulate with. In this patch I've pushed it out
to a full second, but it could be set via config (NSEC_PER_SEC/HZ for
regular systems, something larger for systems using dynticks).

Thoughts?

-john




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