From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 945EBC433F5 for ; Fri, 25 Mar 2022 13:59:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359091AbiCYOBX (ORCPT ); Fri, 25 Mar 2022 10:01:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358899AbiCYOBI (ORCPT ); Fri, 25 Mar 2022 10:01:08 -0400 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34B88606CA; Fri, 25 Mar 2022 06:59:33 -0700 (PDT) Received: by mail-pj1-x1033.google.com with SMTP id g9-20020a17090ace8900b001c7cce3c0aeso3597732pju.2; Fri, 25 Mar 2022 06:59:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=zFHRAV31Ch1tp+2iNpA7ALNISwTJjRRUfUkhPuq13Zo=; b=Cu4xcWiyozPIH5KA4agN/rdwpv5i8VxFgBjItP6j8wz9TTGY2XuJfrGQw+GTMtCW9T /ORB7tR1sdl/Q2caWDHAQLD00WcfLj/Q606h4CIpEdO2KXSfZ9epi8QKsbG4RrC27HCW 3bcl81VVQeIQU2umHw3Ml2DfmM9cksdbbAXFKXmAVCYkOjZUbl8WR/SoKc3xHU0i/42Z qNfFvvi8PJNXfrH9OZYWGhsUPsdWgKVzeXvo+qiDoC1NHkGRcUiMWqov+A8N+zmYPMvN pReCRc0a1pUtGV3hu6WFntKrJ/dt5aL5paVw+ZjZUcCKD5WEcyr7E4+H3R6phBGZCNmb NX4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=zFHRAV31Ch1tp+2iNpA7ALNISwTJjRRUfUkhPuq13Zo=; b=YWRaIob8XCMvb8TyPiyEwR/IQPB5SnxSoM/QJ9EgglA5mclhAL20D/hD3ab5iV4Mkt dM13p00ITYXkLmgoTM38h4wsfcwO4x+PzXLL1powV6P7mA+RjIQ5i+frQ/O5li1v9A+S XmA44ZLpILVgUhYGAmTzH7R3Zjkfpw6hWVdbaDNqss1L8JzgaGXXgTpmST2XKnG8BHuD bIYQepicZHtSq8o5uMkZC7K6/KDUPab1Xy4cg2uFR6GmTFjJII2S7Os/IC6O32OGG79q gugVlmciZnk2LHNvFXlAjYiWMCHSx0+O2H9Dx+8+4fYg+njkMuVltBe4VKElur3YlPjM wm+g== X-Gm-Message-State: AOAM5305/nHeDuhksIINso8nrjFJjjEf2KPxHPu1H3IBnNKp98wjwfei CFE86V35fsucKpkrHwaWKYlWWFsVusM= X-Google-Smtp-Source: ABdhPJwLEuM4gsxnbwwEPABdOHYRI14l6NbAdRqXSGJjqYX+3gfuV43mgriZl0bNGYiGc+e7x+iErg== X-Received: by 2002:a17:90b:1809:b0:1c7:2032:4b34 with SMTP id lw9-20020a17090b180900b001c720324b34mr25034960pjb.4.1648216772580; Fri, 25 Mar 2022 06:59:32 -0700 (PDT) Received: from localhost.localdomain ([203.205.141.113]) by smtp.googlemail.com with ESMTPSA id lw4-20020a17090b180400b001c7327d09c3sm14470875pjb.53.2022.03.25.06.59.30 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Mar 2022 06:59:32 -0700 (PDT) From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: [PATCH RESEND 3/5] KVM: X86: Boost vCPU which is in critical section Date: Fri, 25 Mar 2022 06:58:27 -0700 Message-Id: <1648216709-44755-4-git-send-email-wanpengli@tencent.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1648216709-44755-1-git-send-email-wanpengli@tencent.com> References: <1648216709-44755-1-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li The missing semantic gap that occurs when a guest OS is preempted when executing its own critical section, this leads to degradation of application scalability. We try to bridge this semantic gap in some ways, by passing guest preempt_count to the host and checking guest irq disable state, the hypervisor now knows whether guest OSes are running in the critical section, the hypervisor yield-on-spin heuristics can be more smart this time to boost the vCPU candidate who is in the critical section to mitigate this preemption problem, in addition, it is more likely to be a potential lock holder. Testing on 96 HT 2 socket Xeon CLX server, with 96 vCPUs VM 100GB RAM, one VM running benchmark, the other(none-2) VMs running cpu-bound workloads, There is no performance regression for other benchmarks like Unixbench etc. 1VM vanilla optimized improved hackbench -l 50000 28 21.45 30.5% ebizzy -M 12189 12354 1.4% dbench 712 MB/sec 722 MB/sec 1.4% 2VM: vanilla optimized improved hackbench -l 10000 29.4 26 13% ebizzy -M 3834 4033 5% dbench 42.3 MB/sec 44.1 MB/sec 4.3% 3VM: vanilla optimized improved hackbench -l 10000 47 35.46 33% ebizzy -M 3828 4031 5% dbench 30.5 MB/sec 31.16 MB/sec 2.3% Signed-off-by: Wanpeng Li --- arch/x86/kvm/x86.c | 22 ++++++++++++++++++++++ include/linux/kvm_host.h | 1 + virt/kvm/kvm_main.c | 7 +++++++ 3 files changed, 30 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 425fd7f38fa9..6b300496bbd0 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10375,6 +10375,28 @@ static int vcpu_run(struct kvm_vcpu *vcpu) return r; } +static int kvm_vcpu_non_preemptable(struct kvm_vcpu *vcpu) +{ + int count; + + if (!vcpu->arch.pv_pc.preempt_count_enabled) + return 0; + + if (!kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_pc.preempt_count_cache, + &count, sizeof(int))) + return (count & ~PREEMPT_NEED_RESCHED); + + return 0; +} + +bool kvm_arch_boost_candidate(struct kvm_vcpu *vcpu) +{ + if (vcpu->arch.irq_disabled || kvm_vcpu_non_preemptable(vcpu)) + return true; + + return false; +} + static inline int complete_emulated_io(struct kvm_vcpu *vcpu) { int r; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 252ee4a61b58..9f1a7d9540de 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1428,6 +1428,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu); int kvm_arch_post_init_vm(struct kvm *kvm); void kvm_arch_pre_destroy_vm(struct kvm *kvm); int kvm_arch_create_vm_debugfs(struct kvm *kvm); +bool kvm_arch_boost_candidate(struct kvm_vcpu *vcpu); #ifndef __KVM_HAVE_ARCH_VM_ALLOC /* diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9581a24c3d17..ee5a788892e0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3545,6 +3545,11 @@ bool __weak kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu) return false; } +bool __weak kvm_arch_boost_candidate(struct kvm_vcpu *vcpu) +{ + return true; +} + void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) { struct kvm *kvm = me->kvm; @@ -3580,6 +3585,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) !kvm_arch_dy_has_pending_interrupt(vcpu) && !kvm_arch_vcpu_in_kernel(vcpu)) continue; + if (!kvm_arch_boost_candidate(vcpu)) + continue; if (!kvm_vcpu_eligible_for_directed_yield(vcpu)) continue; -- 2.25.1