Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755010AbYJUQsZ (ORCPT ); Tue, 21 Oct 2008 12:48:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753431AbYJUQsL (ORCPT ); Tue, 21 Oct 2008 12:48:11 -0400 Received: from smtp-outbound-1.vmware.com ([65.115.85.69]:60720 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342AbYJUQsJ (ORCPT ); Tue, 21 Oct 2008 12:48:09 -0400 Subject: Re: [PATCH 0/3] Improve TSC as a clocksource under VMware From: Alok Kataria Reply-To: akataria@vmware.com To: Pavel Machek Cc: "H. Peter Anvin" , LKML , the arch/x86 maintainers , Daniel Hecht In-Reply-To: <20081021095002.GA5880@atrey.karlin.mff.cuni.cz> References: <1224552902.2640.88.camel@alok-dev1> <20081021095002.GA5880@atrey.karlin.mff.cuni.cz> Content-Type: text/plain Organization: VMware INC. Date: Tue, 21 Oct 2008 09:48:08 -0700 Message-Id: <1224607688.6161.25.camel@alok-dev1> Mime-Version: 1.0 X-Mailer: Evolution 2.8.0 (2.8.0-40.el5_1.1) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1335 Lines: 34 On Tue, 2008-10-21 at 02:50 -0700, Pavel Machek wrote: > > Hi, > > > > This patch set makes some changes to the TSC code, so that it is always > > used as the default clocksource when running under VMware. > > The first 2 patches do the ground work of adding code to detect if we > > are running under VMware. > > The third patch adds a tsc_reliable flag which tells us that TSC is > > reliable on this system, so that we can skip some tests which can > > potentially mark TSC as unstable. Details under individual patch > > headers. > > How do you _know_ TSC is stable under VMWare? Since we implement it that way :) The hypervisor takes care of providing a constant rate TSC to the guest on such systems which have variable frequency. Thanks, Alok > AFAICT, accesses to TSC > are not virtualized and system VMWare runs on may still use frequency > scaling, no? > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/