From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock Date: Tue, 20 Apr 2010 14:07:46 -1000 Message-ID: <4BCE41D2.5020005@redhat.com> References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BC8CA52.4090703@goop.org> <1271673545.1674.743.camel@laptop> <4BCC3584.1050501@redhat.com> <1271675100.1674.818.camel@laptop> <4BCC3A3E.9070909@redhat.com> <20100419142158.GD14158@mothafucka.localdomain> <4BCC69D5.3050209@redhat.com> <1271688411.1488.248.camel@laptop> <4BCC8246.9040202@goop.org> <4BCD748E.7080007@redhat.com> <4BCDF12C.1020702@goop.org> <4BCDF85C.3000004@redhat.com> <4BCE0399.2010708@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Peter Zijlstra , Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti To: Jeremy Fitzhardinge Return-path: In-Reply-To: <4BCE0399.2010708@goop.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/20/2010 09:42 AM, Jeremy Fitzhardinge wrote: > On 04/20/2010 11:54 AM, Avi Kivity wrote: > >> On 04/20/2010 09:23 PM, Jeremy Fitzhardinge wrote: >> >>> On 04/20/2010 02:31 AM, Avi Kivity wrote: >>> >>> >>>> btw, do you want this code in pvclock.c, or shall we keep it kvmclock >>>> specific? >>>> >>>> >>> I think its a pvclock-level fix. I'd been hoping to avoid having >>> something like this, but I think its ultimately necessary. >>> >>> >> Did you observe drift on Xen, or is this "ultimately" pointing at the >> future? >> > People are reporting weirdnesses that "clocksource=jiffies" apparently > resolves. Xen and KVM are faced with the same hardware constraints, and > it wouldn't surprise me if there were small measurable > non-monotonicities in the PV clock under Xen. May as well be safe. > Does the drift only occur on SMP VMs?