From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757239Ab2GKKyh (ORCPT ); Wed, 11 Jul 2012 06:54:37 -0400 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:37926 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757191Ab2GKKyf (ORCPT ); Wed, 11 Jul 2012 06:54:35 -0400 Message-ID: <4FFD5AED.3030307@linux.vnet.ibm.com> Date: Wed, 11 Jul 2012 16:22:29 +0530 From: Raghavendra K T Organization: IBM User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 MIME-Version: 1.0 To: Avi Kivity CC: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Marcelo Tosatti , Rik van Riel , S390 , Carsten Otte , Christian Borntraeger , KVM , chegu vinod , "Andrew M. Theurer" , LKML , X86 , Gleb Natapov , linux390@de.ibm.com, Srivatsa Vaddagiri , Joerg Roedel Subject: Re: [PATCH RFC 1/2] kvm vcpu: Note down pause loop exit References: <20120709062012.24030.37154.sendpatchset@codeblue> <20120709062032.24030.10454.sendpatchset@codeblue> <4FFD3F10.5020900@redhat.com> In-Reply-To: <4FFD3F10.5020900@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 12071100-7014-0000-0000-0000018A8B6F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2012 02:23 PM, Avi Kivity wrote: > On 07/09/2012 09:20 AM, Raghavendra K T wrote: >> Signed-off-by: Raghavendra K T >> >> Noting pause loop exited vcpu helps in filtering right candidate to yield. >> Yielding to same vcpu may result in more wastage of cpu. >> >> >> struct kvm_lpage_info { >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index f75af40..a492f5d 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -3264,6 +3264,7 @@ static int interrupt_window_interception(struct vcpu_svm *svm) >> >> static int pause_interception(struct vcpu_svm *svm) >> { >> + svm->vcpu.arch.plo.pause_loop_exited = true; >> kvm_vcpu_on_spin(&(svm->vcpu)); >> return 1; >> } >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 32eb588..600fb3c 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -4945,6 +4945,7 @@ out: >> static int handle_pause(struct kvm_vcpu *vcpu) >> { >> skip_emulated_instruction(vcpu); >> + vcpu->arch.plo.pause_loop_exited = true; >> kvm_vcpu_on_spin(vcpu); >> > > This code is duplicated. Should we move it to kvm_vcpu_on_spin? > > That means the .plo structure needs to be in common code, but that's not > too bad perhaps. > Since PLE is very much tied to x86, and proposed changes are very much specific to PLE handler, I thought it is better to make arch specific. So do you think it is good to move inside vcpu_on_spin and make ple structure belong to common code? >> index be6d549..07dbd14 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -5331,7 +5331,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) >> >> if (req_immediate_exit) >> smp_send_reschedule(vcpu->cpu); >> - >> + vcpu->arch.plo.pause_loop_exited = false; > > This adds some tiny overhead to vcpu entry. You could remove it by > using the vcpu->requests mechanism to clear the flag, since > vcpu->requests is already checked on every entry. So IIUC, let's have request bit for indicating PLE, pause_interception() /handle_pause() { make_request(PLE_REQUEST) vcpu_on_spin() } check_eligibility() { !test_request(PLE_REQUEST) || ( test_request(PLE_REQUEST) && dy_eligible()) . . } vcpu_run() { check_request(PLE_REQUEST) . . } Is this is the expected flow you had in mind? [ But my only concern was not resetting for cases where we do not do guest_enter(). will test how that goes]. > >> kvm_guest_enter(); >>