Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754045Ab0DSKqU (ORCPT ); Mon, 19 Apr 2010 06:46:20 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:58491 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753899Ab0DSKqS (ORCPT ); Mon, 19 Apr 2010 06:46:18 -0400 Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock From: Peter Zijlstra To: Avi Kivity Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jeremy Fitzhardinge , Marcelo Tosatti , Zachary Amsden In-Reply-To: <4BCA026D.3070309@redhat.com> References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BCA026D.3070309@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 19 Apr 2010 12:46:15 +0200 Message-ID: <1271673975.1674.763.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 875 Lines: 22 On Sat, 2010-04-17 at 21:48 +0300, Avi Kivity wrote: > > After this patch is applied, I don't see a single warp in time during 5 days > > of execution, in any of the machines I saw them before. > > > > > > Please define a cpuid bit that makes this optional. When we eventually > enable it in the future, it will allow a wider range of guests to enjoy it. Right, so on x86 we have: X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency independent, not that it doesn't stop in C states and similar fun stuff. X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is constant and synced between cores. -- 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/