Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934194AbZJMUA6 (ORCPT ); Tue, 13 Oct 2009 16:00:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753466AbZJMUA6 (ORCPT ); Tue, 13 Oct 2009 16:00:58 -0400 Received: from claw.goop.org ([74.207.240.146]:42044 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752059AbZJMUA5 (ORCPT ); Tue, 13 Oct 2009 16:00:57 -0400 Message-ID: <4AD4DC52.8090508@goop.org> Date: Tue, 13 Oct 2009 13:00:18 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-2.7.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4 MIME-Version: 1.0 To: Avi Kivity CC: Dan Magenheimer , Jeremy Fitzhardinge , kurt.hackel@oracle.com, the arch/x86 maintainers , Linux Kernel Mailing List , Glauber de Oliveira Costa , Xen-devel , Keir Fraser , Zach Brown , Chris Mason , Ingo Molnar Subject: Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation References: <1254790211-15416-1-git-send-email-jeremy.fitzhardinge@citrix.com> <1254790211-15416-4-git-send-email-jeremy.fitzhardinge@citrix.com> <4ACB0833.2050203@redhat.com> <4ACB9074.1000804@goop.org> <4ACC6C9C.7080707@redhat.com> <4ACFD43E.6000506@goop.org> <4AD0CDFB.9030704@redhat.com> <4AD3738B.6050200@goop.org> <4AD375A5.8050205@redhat.com> <4AD37FE3.1010002@goop.org> <4AD420A4.7050508@redhat.com> In-Reply-To: <4AD420A4.7050508@redhat.com> X-Enigmail-Version: 0.97a Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1178 Lines: 29 On 10/12/09 23:39, Avi Kivity wrote: > On 10/12/2009 09:13 PM, Jeremy Fitzhardinge wrote: >> On 10/12/09 11:29, Avi Kivity wrote: >> >>> Good catch. Doesn't that invalidate rdtscp based vgettimeofday on >>> non-virt as well (assuming p == cpu)? >>> >> The tsc clocksource assumes the tsc is (mostly?) synced; it doesn't use >> rdtscp or make any attempt at per-cpu corrections. >> > > So it's broken or disabled when that assumption is wrong? We could > easily fix that now. Might even reuse the pvclock structures. Well, the kernel internally makes more or less the same assumption; the vsyscall clocksource is the same as the kernel's internal one. I think idea is that it just drops back to something like hpet if the tsc doesn't have very simple SMP characteristics. If the kernel could characterize the per-cpu properties of the tsc more accurately, then it could use the pvclock mechanism on native. J -- 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/