From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Subject: Re: [PATCH RFC 0/7] KVM: nVMX: enlightened VMCS initial implementation Date: Thu, 21 Dec 2017 16:08:30 +0100 Message-ID: <87lghww235.fsf@vitty.brq.redhat.com> References: <20171218171742.5765-1-vkuznets@redhat.com> <87po7alupo.fsf@vitty.brq.redhat.com> <87vah0w8h9.fsf@vitty.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , Haiyang Zhang , x86@kernel.org, linux-kernel@vger.kernel.org, "Michael Kelley \(EOSG\)" , Bandan Das , Roman Kagan , devel@linuxdriverproject.org, Mohammed Gamal To: Paolo Bonzini Return-path: In-Reply-To: (Paolo Bonzini's message of "Thu, 21 Dec 2017 15:32:14 +0100") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" List-Id: kvm.vger.kernel.org Paolo Bonzini writes: > On 21/12/2017 13:50, Vitaly Kuznetsov wrote: >> I'm back with (somewhat frustrating) results (E5-2603): > > v4 (that would be Broadwell)? > Sorry, v3, actually. Haswell. (the first one supporting vmcs shadowing afaiu). >> 1) Windows on Hyper-V (no nesting): 1350 cycles >> >> 2) Windows on Hyper-V on Hyper-V: 8600 >> >> 3) Windows on KVM (no nesting): 1150 cycles >> >> 4) Windows on Hyper-V on KVM (no enlightened VMCS): 18200 >> >> 5) Windows on Hyper-V on KVM (enlightened VMCS): 17100 > > What version were you using for KVM? There are quite a few nested virt > optimizations in kvm/queue (which may make enlightened VMCS both more or > less efficient). This is kvm/queue and I rebased enlightened VMCS patches to it. > > In particular, with latest kvm/queue you could try tracing vmread and > vmwrite vmexits, and see if you get any. If you do, that might be an > easy few hundred cycles savings. Will do. -- Vitaly