From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752728AbdKJMnT (ORCPT ); Fri, 10 Nov 2017 07:43:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50914 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750835AbdKJMnR (ORCPT ); Fri, 10 Nov 2017 07:43:17 -0500 Subject: Re: [PATCH v3 0/4] KVM: Paravirt remote TLB flush To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Peter Zijlstra , Wanpeng Li References: <1510307387-14812-1-git-send-email-wanpeng.li@hotmail.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <64f35b5e-63b0-20b4-c3d0-85258e32c0ad@redhat.com> Date: Fri, 10 Nov 2017 13:43:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1510307387-14812-1-git-send-email-wanpeng.li@hotmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 10 Nov 2017 12:43:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10.11.2017 10:49, Wanpeng Li wrote: > Remote flushing api's does a busy wait which is fine in bare-metal > scenario. But with-in the guest, the vcpus might have been pre-empted > or blocked. In this scenario, the initator vcpu would end up > busy-waiting for a long amount of time. > > This patch set implements para-virt flush tlbs making sure that it > does not wait for vcpus that are sleeping. And all the sleeping vcpus > flush the tlb on guest enter. Idea was discussed here: > https://lkml.org/lkml/2012/2/20/157 > > The best result is achieved when we're overcommiting the host by running > multiple vCPUs on each pCPU. In this case PV tlb flush avoids touching > vCPUs which are not scheduled and avoid the wait on the main CPU. > > In addition, thanks for commit 9e52fc2b50d ("x86/mm: Enable RCU based > page table freeing (CONFIG_HAVE_RCU_TABLE_FREE=y)") > > Test on a Haswell i7 desktop 4 cores (2HT), so 8 pCPUs, running ebizzy in > one linux guest. > > ebizzy -M > vanilla optimized boost > 8 vCPUs 10152 10083 -0.68% > 16 vCPUs 1224 4866 297.5% > 24 vCPUs 1109 3871 249% > 32 vCPUs 1025 3375 229.3% > > Note: The patchset is rebased against "locking/qspinlock/x86: Avoid > test-and-set when PV_DEDICATED is set" v3 > > v2 -> v3: > * percpu cpumask > > v1 -> v2: > * a new CPUID feature bit > * fix cmpxchg check > * use kvm_vcpu_flush_tlb() to get the statistics right > * just OR the KVM_VCPU_PREEMPTED in kvm_steal_time_set_preempted > * add a new bool argument to kvm_x86_ops->tlb_flush > * __cpumask_clear_cpu() instead of cpumask_clear_cpu() > * not put cpumask_t on stack > * rebase the patchset against "locking/qspinlock/x86: Avoid > test-and-set when PV_DEDICATED is set" v3 > > Wanpeng Li (4): > KVM: Add vCPU running/preempted state > KVM: Add paravirt remote TLB flush > KVM: X86: introduce invalidate_gpa argument to tlb flush > KVM: Add flush_on_enter before guest enter > > Documentation/virtual/kvm/cpuid.txt | 10 +++++++++ > arch/x86/include/asm/kvm_host.h | 2 +- > arch/x86/include/uapi/asm/kvm_para.h | 6 +++++ > arch/x86/kernel/kvm.c | 43 ++++++++++++++++++++++++++++++++++-- > arch/x86/kvm/cpuid.c | 3 ++- > arch/x86/kvm/svm.c | 14 ++++++------ > arch/x86/kvm/vmx.c | 21 +++++++++--------- > arch/x86/kvm/x86.c | 24 ++++++++++++-------- > 8 files changed, 93 insertions(+), 30 deletions(-) > Minor thing: Ass all patches are x86 specific, they should all have the prefix "KVM: x86". -- Thanks, David / dhildenb