From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932212Ab0CIDZR (ORCPT ); Mon, 8 Mar 2010 22:25:17 -0500 Received: from mail-pz0-f200.google.com ([209.85.222.200]:35851 "EHLO mail-pz0-f200.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932183Ab0CIDZM (ORCPT ); Mon, 8 Mar 2010 22:25:12 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=ACFpeDJ6WDwqE3Kr/biVV7ArDsXNLH7Hw+vQfFND0+Os2JFmvIs/oN5VAMFRLU3S10 j6oWKGraGfoHSik+bUtmEaO5UuIYtDBXMTpIO0ZPRBd0Q22+xU47YXCjCaJxR+j/HPGH zTXwN6cobp9WyDm9YRaHMeDaSFGkyGT+obhfs= MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 8 Mar 2010 19:25:07 -0800 X-Google-Sender-Auth: fea9b19159c097f9 Message-ID: <1f1b08da1003081925p61a810e4v96be56640287d61@mail.gmail.com> Subject: Re: [PATCHv2 0/6] pps: time synchronization over LPT From: john stultz To: Alexander Gordeev Cc: linux-kernel@vger.kernel.org, linuxpps@ml.enneenne.com, "Nikita V. Youshchenko" , stas@lvk.cs.msu.su, Rodolfo Giometti Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 24, 2010 at 4:28 AM, Alexander Gordeev wrote: > This patchset is tested against the vanilla 2.6.32.9 kernel. But we are > actually using it on 2.6.31.12-rt20 rt-preempt kernel most of the time. > Also there is a version which should be applied on top of LinuxPPS out > of tree patches (i.e. all clients and low-level irq timestamps stuff). > Those who are interested in other versions of the patchset can find > them in my git repository: > http://lvk.cs.msu.su/~lasaine/timesync/linux-2.6-timesync.git > > There is one problem however: hardpps() works bad when used on top > of 2.6.33-rc* with CONFIG_NO_HZ enabled. The reason for this is commit > a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601. Without it hardpps() is able > to sync to 1us precision in about 10 seconds. With it Uh. Not sure I see right off why the logarithmic time accumulation would give you troubles. Its actually there to try to fix a couple of NTP issues that cropped up when the accumulation interval was pushed out to 2HZ with CONFIG_NO_HZ. Do you have any extra insight here as to whats going on with your code? The only thing I could guess would be second_overflow() is happening closer to the actual overflow, but maybe less regularly? But again, I'm not sure how this would be drastically different then before with the 2HZ accumulation period. thanks -john