Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756629AbZFWTtj (ORCPT ); Tue, 23 Jun 2009 15:49:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754393AbZFWTtc (ORCPT ); Tue, 23 Jun 2009 15:49:32 -0400 Received: from mx2.redhat.com ([66.187.237.31]:49427 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752126AbZFWTtc (ORCPT ); Tue, 23 Jun 2009 15:49:32 -0400 Date: Tue, 23 Jun 2009 21:49:16 +0200 From: Miroslav Lichvar To: Ingo Molnar Cc: John Stultz , Thomas Gleixner , Linus Torvalds , Andrew Morton , LKML Subject: Re: [GIT pull] ntp updates for 2.6.31 Message-ID: <20090623194916.GA18657@localhost> References: <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> <20090623143323.GA13932@localhost> <20090623191838.GB14852@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090623191838.GB14852@elte.hu> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1150 Lines: 31 On Tue, Jun 23, 2009 at 09:18:38PM +0200, Ingo Molnar wrote: > > * Miroslav Lichvar wrote: > > > > > I'm not very familiar with the PPS API, is there something > > > > wrong with it? > > > > > > The PPS patches i've seen just export IRQ timestamps to > > > user-space. > > > > > > That is not very robust in my opinion when it comes to do time > > > approximations - to get quick, low-latency action and precise > > > measurements it's best to keep the critical path as short as > > > possible, and within a single source code repository: i.e. > > > within the kernel. > > > > That's what kernel PPS discipline does, it will be probably > > included later. Its performance is an order or two better than the > > PLL/FLL discipline. > > Is there some kernel patch i can look at? It's in the old PPSkit patches for 2.4 kernels, function hardpps(). -- Miroslav Lichvar -- 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/