From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock Date: Mon, 19 Apr 2010 13:49:04 +0300 Message-ID: <4BCC3520.6090305@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> <1271673975.1674.763.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jeremy Fitzhardinge , Marcelo Tosatti , Zachary Amsden To: Peter Zijlstra Return-path: In-Reply-To: <1271673975.1674.763.camel@laptop> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/19/2010 01:46 PM, Peter Zijlstra wrote: > 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. > > Sockets and boards too? (IOW, how reliable is TSC_RELIABLE)? -- error compiling committee.c: too many arguments to function