From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wanpeng Li Subject: Re: Seeking a KVM benchmark Date: Mon, 17 Nov 2014 20:14:19 +0800 Message-ID: <5469E69B.7050406@gmail.com> References: <545C7222.4070605@redhat.com> <20141108120125.GB2654@minantech.com> <20141109085238.GA26187@minantech.com> <54608D77.2090907@redhat.com> <20141110104531.GB26187@minantech.com> <5460AC7C.8040409@redhat.com> <5460CA71.2050701@gmail.com> <5460F5B9.8030902@redhat.com> <5469D934.4080405@gmail.com> <5469D974.4030008@redhat.com> <5469E361.60308@gmail.com> <5469E43F.5090301@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Andy Lutomirski , kvm list To: Paolo Bonzini , Avi Kivity , Gleb Natapov Return-path: Received: from mail-pd0-f173.google.com ([209.85.192.173]:63987 "EHLO mail-pd0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751473AbaKQMOd (ORCPT ); Mon, 17 Nov 2014 07:14:33 -0500 Received: by mail-pd0-f173.google.com with SMTP id ft15so168375pdb.18 for ; Mon, 17 Nov 2014 04:14:33 -0800 (PST) In-Reply-To: <5469E43F.5090301@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Hi Paolo, On 11/17/14, 8:04 PM, Paolo Bonzini wrote: > > On 17/11/2014 13:00, Wanpeng Li wrote: >> Sorry, maybe I didn't state my question clearly. As Avi mentioned above >> "In VMX we have VPIDs, so we only need to flush if EFER changed between >> two invocations of the same VPID", so there is only one VPID if the >> guest is UP, my question is if there need a TLB flush when guest's EFER >> has been changed? > Yes, because the meaning of the page table entries has changed. So both VMX EFER writes and non-VMX EFER writes cause a TLB flush for UP guest, is there still a performance improvement in this case? Regards, Wanpeng Li > > Paolo