From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751566AbWHJUbU (ORCPT ); Thu, 10 Aug 2006 16:31:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750781AbWHJUbR (ORCPT ); Thu, 10 Aug 2006 16:31:17 -0400 Received: from science.horizon.com ([192.35.100.1]:22836 "HELO science.horizon.com") by vger.kernel.org with SMTP id S1751206AbWHJUbI (ORCPT ); Thu, 10 Aug 2006 16:31:08 -0400 Date: 10 Aug 2006 16:31:06 -0400 Message-ID: <20060810203106.1476.qmail@science.horizon.com> From: linux@horizon.com To: akpm@osdl.org Subject: Re: [NTP 8/9] convert to the NTP4 reference model Cc: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >>> For the ntp ignorami amongst us... what is a "nanokernel reference >>> implementation" and why do we want one? > > It's the behaviour the current ntp daemon expects, the ntp documentation > has more information and a link to the package (e.g. under Debian at > /usr/share/doc/ntp-doc/html/kern.html). > > So... the current kernel is behaving in a manner other than that which the > NTP daemon expects? Does this cause any problems? To explain more clearly... The original NTP kernel interface was defined in units of microseconds. That's what Linux implements. As computers have gotten faster and can now split microseconds easily, a new kernel interface using nanosecond units was defined ("the nanokernel", confusing as that name is to OS hackers), and there's an STA_NANO bit in the adjtimex() status field to tell the application which units it's using. The current ntpd supports both, but Linux loses some possible timing resolution because of quantization effects, and the ntpd hackers would really like to be able to drop the backwards compatibility code. Ulrich Windl has been maintaining a patch set to do the conversion for years, but it's hard to keep in sync.