From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754069AbbAFIkG (ORCPT ); Tue, 6 Jan 2015 03:40:06 -0500 Received: from mail-we0-f175.google.com ([74.125.82.175]:39676 "EHLO mail-we0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753348AbbAFIkD (ORCPT ); Tue, 6 Jan 2015 03:40:03 -0500 Message-ID: <54AB9F5D.6070504@redhat.com> Date: Tue, 06 Jan 2015 09:39:57 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 Newsgroups: gmane.comp.emulators.kvm.devel,gmane.linux.kernel To: Marcelo Tosatti , Andy Lutomirski CC: Gleb Natapov , kvm list , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xenproject.org" Subject: Re: [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader References: <8d09c16eb39cbe264417cc66c4aca730af10b70b.1419295081.git.luto@amacapital.net> <20150105152511.GA9172@amt.cnet> <20150105191756.GA31201@amt.cnet> In-Reply-To: <20150105191756.GA31201@amt.cnet> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/01/2015 20:17, Marcelo Tosatti wrote: > But there is no guarantee that vCPU-N has updated its pvti when > vCPU-M resumes guest instruction execution. You're right. > So the cost this patch removes is mainly from __getcpu (==RDTSCP?) ? > Perhaps you can use Gleb's idea to stick vcpu id into version field ? Or just replace __getcpu with rdtscp. Paolo