From owner-freebsd-current@FreeBSD.ORG Fri Apr 18 00:35:33 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9FE071065673 for ; Fri, 18 Apr 2008 00:35:33 +0000 (UTC) (envelope-from obrien@NUXI.org) Received: from dragon.nuxi.org (trang.nuxi.org [74.95.12.85]) by mx1.freebsd.org (Postfix) with ESMTP id 768468FC1B for ; Fri, 18 Apr 2008 00:35:33 +0000 (UTC) (envelope-from obrien@NUXI.org) Received: from dragon.nuxi.org (obrien@localhost [127.0.0.1]) by dragon.nuxi.org (8.14.1/8.14.1) with ESMTP id m3I0ZGKO013288; Thu, 17 Apr 2008 17:35:16 -0700 (PDT) (envelope-from obrien@dragon.nuxi.org) Received: (from obrien@localhost) by dragon.nuxi.org (8.14.2/8.14.1/Submit) id m3I0ZGbI013287; Thu, 17 Apr 2008 17:35:16 -0700 (PDT) (envelope-from obrien) Date: Thu, 17 Apr 2008 17:35:16 -0700 From: "David O'Brien" To: David Malone Message-ID: <20080418003516.GD11705@dragon.NUXI.org> Mail-Followup-To: obrien@freebsd.org, David Malone , Jeff Roberson , gnn@freebsd.org, Andrew Gallatin , freebsd-current@freebsd.org References: <18431.23276.913397.188219@grasshopper.cs.duke.edu> <20080414215057.B959@desktop> <20080415084602.GA44129@walton.maths.tcd.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080415084602.GA44129@walton.maths.tcd.ie> X-Operating-System: FreeBSD 8.0-CURRENT User-Agent: Mutt/1.5.16 (2007-06-09) Cc: gnn@freebsd.org, freebsd-current@freebsd.org, Jeff Roberson , Andrew Gallatin Subject: Re: TSC Timecounter and multi-core/SMP X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: obrien@freebsd.org List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Apr 2008 00:35:33 -0000 On Tue, Apr 15, 2008 at 09:46:02AM +0100, David Malone wrote: > On Mon, Apr 14, 2008 at 09:51:42PM -1000, Jeff Roberson wrote: > > I think we should confirm whether this is the case with earlier opterson. > > I have seen two processors on the same die out of sync. > > This can definitely happen according to this note from AMD, which > someone posted a link to earlier in the thread: > > http://lkml.org/lkml/2005/11/4/173 > > it can happen when you hlt one core, but don't hlt the other on > some processors. Actually that is something slightly different. Even without HLT, RDTSC on the two cores of a dual-core processor can be out of sync. HLT can affect the delta between the two cores. -- -- David (obrien@FreeBSD.org)