From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422820AbWAMS4S (ORCPT ); Fri, 13 Jan 2006 13:56:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422822AbWAMS4S (ORCPT ); Fri, 13 Jan 2006 13:56:18 -0500 Received: from gateway-1237.mvista.com ([12.44.186.158]:15101 "EHLO hermes.mvista.com") by vger.kernel.org with ESMTP id S1422820AbWAMS4S (ORCPT ); Fri, 13 Jan 2006 13:56:18 -0500 Subject: Re: Dual core Athlons and unsynced TSCs From: Sven-Thorsten Dietrich To: thockin@hockin.org Cc: Lee Revell , linux-kernel In-Reply-To: <20060113185533.GA18301@hockin.org> References: <1137104260.2370.85.camel@mindpipe> <20060113180620.GA14382@hockin.org> <1137175117.15108.18.camel@mindpipe> <20060113181631.GA15366@hockin.org> <1137175792.15108.26.camel@mindpipe> <20060113185533.GA18301@hockin.org> Content-Type: text/plain Organization: MontaVista Software, Inc. Date: Fri, 13 Jan 2006 10:56:13 -0800 Message-Id: <1137178574.2536.13.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2006-01-13 at 10:55 -0800, thockin@hockin.org wrote: > On Fri, Jan 13, 2006 at 01:09:51PM -0500, Lee Revell wrote: > > > Some apps/users need higher resolution and lower overhead that only rdtsc > > > can offer currently. > > > > But obviously if the TSC gives wildly inaccurate results, it cannot be > > used no matter how low the overhead. > > unless we can re-sync the TSCs often enough that apps don't notice. > You'd have to quantify that somehow, in terms of the max drift rate (ppm), and the max resolution available (< tsc frequency). Either that, or track an offset, and use one TSC as truth, and update the correction factor for the other TSCs as often as needed, maybe? This is kind of analogous to the "drift" NTP calculates against a free-running oscillator. So you'd be pushing that functionality deeper into the OS-core. Dave Mills had that "hardpps" stuff in there for a while, it might be a starting point. Just some thoughts for now... Sven > - > 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/ -- *********************************** Sven-Thorsten Dietrich Real-Time Software Architect MontaVista Software, Inc. 1237 East Arques Ave. Sunnyvale, CA 94085 Phone: 408.992.4515 Fax: 408.328.9204 http://www.mvista.com Platform To Innovate ***********************************