From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wanpeng Li Subject: Re: Seeking a KVM benchmark Date: Mon, 17 Nov 2014 19:17:08 +0800 Message-ID: <5469D934.4080405@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> 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-pa0-f47.google.com ([209.85.220.47]:36990 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342AbaKQLRP (ORCPT ); Mon, 17 Nov 2014 06:17:15 -0500 Received: by mail-pa0-f47.google.com with SMTP id kq14so3112311pab.6 for ; Mon, 17 Nov 2014 03:17:15 -0800 (PST) In-Reply-To: <5460F5B9.8030902@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Hi Paolo, On 11/11/14, 1:28 AM, Paolo Bonzini wrote: > On 10/11/2014 15:23, Avi Kivity wrote: >> It's not surprising [1]. Since the meaning of some PTE bits change [2], >> the TLB has to be flushed. In VMX we have VPIDs, so we only need to flush >> if EFER changed between two invocations of the same VPID, which isn't the >> case. If there need a TLB flush if guest is UP? Regards, Wanpeng Li >> >> [1] after the fact >> [2] although those bits were reserved with NXE=0, so they shouldn't have >> any TLB footprint > You're right that this is not that surprising after the fact, and that > both Sandy Bridge and Ivy Bridge have VPIDs (even the non-Xeon ones). > This is also why I'm curious about the Nehalem. > > However note that even toggling the SCE bit is flushing the TLB. The > NXE bit is not being toggled here! That's the more surprising part. > > Paolo > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html