Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755333AbZFXJ3T (ORCPT ); Wed, 24 Jun 2009 05:29:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753206AbZFXJ3G (ORCPT ); Wed, 24 Jun 2009 05:29:06 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:42451 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752999AbZFXJ3F (ORCPT ); Wed, 24 Jun 2009 05:29:05 -0400 Date: Wed, 24 Jun 2009 10:29:15 +0100 From: Alan Cox To: john stultz Cc: Ingo Molnar , Miroslav Lichvar , Thomas Gleixner , Linus Torvalds , Andrew Morton , LKML , Martin Schwidefsky Subject: Re: [GIT pull] ntp updates for 2.6.31 Message-ID: <20090624102915.4df3fa85@lxorguk.ukuu.org.uk> In-Reply-To: <1245793316.3305.5.camel@localhost> References: <1f1b08da0906151316s7d25f8ceraa1bc967a8abe172@mail.gmail.com> <1f1b08da0906151641u4cd964e6vf1a61afe50cc1d90@mail.gmail.com> <20090616090647.GD13771@elte.hu> <20090616125248.GA23541@localhost> <1245253102.6067.94.camel@jstultz-laptop> <20090617172325.GA32332@localhost> <20090617172601.GA3493@elte.hu> <20090618121320.GA13025@localhost> <20090623095745.GC30634@elte.hu> <20090623131628.GA11827@localhost> <20090623133625.GA3026@elte.hu> <1245793316.3305.5.camel@localhost> X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1085 Lines: 25 > On Tue, 2009-06-23 at 15:36 +0200, Ingo Molnar wrote: > > The PPS patches i've seen just export IRQ timestamps to user-space. Correct. They improve the sampling information quality and help cut down on jitter between the IRQ sampling and using the timestamp. The jitter is what matters most here and NTP can figure out constant latencies rather well. > At some point that stops being NTP. NTP has quite a bit of userland > policy for filtering and managing a number of different network clocks > (other ntp servers, PPS sources, etc). > > >From what you're describing (direct offset from a hardware time device > used to steer the clock directly in kernel), you might want to look at > the STP code in s390 (stp_sync_clock). And also hardware distributed timing systems like those that distribute a clock with ethernet signals. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/