From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422750AbWAMR6k (ORCPT ); Fri, 13 Jan 2006 12:58:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422754AbWAMR6k (ORCPT ); Fri, 13 Jan 2006 12:58:40 -0500 Received: from viper.oldcity.dca.net ([216.158.38.4]:45257 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S1422750AbWAMR6j (ORCPT ); Fri, 13 Jan 2006 12:58:39 -0500 Subject: Re: Dual core Athlons and unsynced TSCs From: Lee Revell To: thockin@hockin.org Cc: linux-kernel In-Reply-To: <20060113180620.GA14382@hockin.org> References: <1137104260.2370.85.camel@mindpipe> <20060113180620.GA14382@hockin.org> Content-Type: text/plain Date: Fri, 13 Jan 2006 12:58:36 -0500 Message-Id: <1137175117.15108.18.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.5.4 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 10:06 -0800, thockin@hockin.org wrote: > On Thu, Jan 12, 2006 at 05:17:39PM -0500, Lee Revell wrote: > > It's been known for quite some time that the TSCs are not synced between > > cores on Athlon X2 machines and this screws up the kernel's timekeeping, > > as it still uses the TSC as the default time source on these machines. > > > > This problem still seems to be present in the latest kernels. What is > > the plan to fix it? Is the fix simply to make the kernel use the ACPI > > PM timer by default on Athlon X2? > > If your BIOS has an ACPI "HPET" table, then the kernel can use the HPET > timer instead. It doesn't solve the problem for apps or other kernel bits > that use rdtsc directly, but there are other fixes for that floating > around which will hopefully get consideration when they're mature. > The apps can be converted to use clock_gettime(), but that does not help if the kernel can't keep reasonable time on these machines. But if we just use "clock=pmtmr" by default on these machines the TSC is not a problem right? Lee