From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader Date: Tue, 06 Jan 2015 09:39:57 +0100 Message-ID: <54AB9F5D.6070504__3949.45775992728$1420534203$gmane$org@redhat.com> References: <8d09c16eb39cbe264417cc66c4aca730af10b70b.1419295081.git.luto@amacapital.net> <20150105152511.GA9172@amt.cnet> <20150105191756.GA31201@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Y8PgK-00007l-I9 for xen-devel@lists.xenproject.org; Tue, 06 Jan 2015 08:40:06 +0000 Received: by mail-wg0-f50.google.com with SMTP id a1so28822260wgh.23 for ; Tue, 06 Jan 2015 00:40:02 -0800 (PST) In-Reply-To: <20150105191756.GA31201@amt.cnet> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Marcelo Tosatti , Andy Lutomirski Cc: Gleb Natapov , "xen-devel@lists.xenproject.org" , "linux-kernel@vger.kernel.org" , kvm list List-Id: xen-devel@lists.xenproject.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