Hello All , On Mon, 1 Jun 2009, Ray Lee wrote:
A site with three or four differant system types , ie: sparc running sloaris , pc running openbsd , Dec(hp) running VMS , Dec(hp) Alpha running Linux , ... This moving the Hardware Arch & OS differencews is sometimes done to limit hacks & software glicthes by NOT using the same hardware arch or OS .On Mon, Jun 1, 2009 at 4:58 PM, John Stultz <johnstul@xxxxxxxxxx> wrote:On Tue, 2009-06-02 at 01:22 +0200, Ingo Molnar wrote:* John Stultz <johnstul@xxxxxxxxxx> wrote:On Wed, 2009-05-06 at 09:46 +0000, tip-bot for john stultz wrote:ntp: adjust SHIFT_PLL to improve NTP convergence The conversion to the ntpv4 reference model f19923937321244e7dc334767eb4b67e0e3d5c74 ("ntp: convert to the NTP4 reference model") in 2.6.19 added nanosecond resolution the adjtimex interface, but also changed the "stiffness" of the frequency adjustments, causing NTP convergence time to greatly increase. SHIFT_PLL, which reduces the stiffness of the freq adjustments, was designed to be inversely linked to HZ, and the reference value of 4 was designed for Unix systems using HZ=100. However Linux's clock steering code mostly independent of HZ. So this patch reduces the SHIFT_PLL value from 4 to 2, which causes NTPd behavior to match kernels prior to 2.6.19, greatly reducing convergence times, and improving close synchronization through environmental thermal changes. [ Impact: tweak NTP algorithm for faster convergence ]So I've been speaking with Miroslav (cc'ed) who maintains the RH ntpd packages, and he's concerned that this patch takes us out of NTP's expected behavior, which may cause problems when dealing with non-linux systems using NTP.I might be missing something here - but Linux converging faster seems like a genuinely good thing. What non-Linux problem could there be? Linux's convergence is really Linux's private issue.Yea. It does seem that way. Miroslav can likely expand on the issue to help clarify, but as I understand it, the example is if you have a number of systems that are peers in an NTP network. All of them are using the same userland NTP daemon. However, if the rate of change that corrections are applied is different in half of them, you will have problems getting all the systems to converge together.Your point is clear, however -- reasonably speaking -- how many instances will there be out there of networks of peers partially upgraded versus lone systems slowly or never converging off of masters?
By my naive understanding, the latter would strongly outnumber the former.
You'd be VERY unhappily suprised . Hth , JimL -- +------------------------------------------------------------------+ | James W. Laferriere | System Techniques | Give me VMS | | Network&System Engineer | 2133 McCullam Ave | Give me Linux | | babydr@xxxxxxxxxxxxxxxx | Fairbanks, AK. 99701 | only on AXP | +------------------------------------------------------------------+
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