Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752933AbXJ2XCq (ORCPT ); Mon, 29 Oct 2007 19:02:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752216AbXJ2XCi (ORCPT ); Mon, 29 Oct 2007 19:02:38 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:43983 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751863AbXJ2XCi (ORCPT ); Mon, 29 Oct 2007 19:02:38 -0400 Date: Tue, 30 Oct 2007 00:02:13 +0100 From: Ingo Molnar To: Zachary Amsden Cc: Glauber de Oliveira Costa , linux-kernel@vger.kernel.org, tglx@linutronix.de, rusty@rustcorp.com.au, jeremy@goop.org, --cc@redhat.com, avi@quramnet.com, kvm-devel@lists.sourceforge.net, Glauber de Oliveira Costa , Dan Hecht , Garrett Smith Subject: Re: [PATCH] raise tsc clocksource rating Message-ID: <20071029230213.GA1982@elte.hu> References: <11936994092607-git-send-email-gcosta@redhat.com> <1193697734.9793.86.camel@bodhitayantram.eng.vmware.com> <20071029224852.GA27547@elte.hu> <1193698505.9793.90.camel@bodhitayantram.eng.vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1193698505.9793.90.camel@bodhitayantram.eng.vmware.com> User-Agent: Mutt/1.5.16 (2007-06-09) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1027 Lines: 26 * Zachary Amsden wrote: > On Mon, 2007-10-29 at 23:48 +0100, Ingo Molnar wrote: > > * Zachary Amsden wrote: > > > if it's inaccurate why are you exposing it to the guest then? Native > > only uses the TSC if it's safe and accurate to do so. > > Not every guest support paravirt, but for correctness, all guests > require TSC, which must be exposed all the way up to userspace, no > matter what the efficiency or accuracy may be. but if there's a perfect TSC available (there is such hardware) then the TSC _is_ the best clocksource. Paravirt now turns it off unconditionally in essence. anyway, that's at most an optimization issue. No strong feelings here, and we can certainly delay this patch until this gets all sorted out. Ingo - 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/