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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 632EEC18E5B for ; Tue, 17 Mar 2020 08:17:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46948206EC for ; Tue, 17 Mar 2020 08:17:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725906AbgCQIRb (ORCPT ); Tue, 17 Mar 2020 04:17:31 -0400 Received: from mga11.intel.com ([192.55.52.93]:17620 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725536AbgCQIRa (ORCPT ); Tue, 17 Mar 2020 04:17:30 -0400 IronPort-SDR: JWpHzikvSX4FPH3+JvEfRalfolr5JXzm/ewvSdi61VKpicIbCcgt6CQHzPNDv1oJpKq/XdR1Oq s2g0FZz6rOnA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2020 01:17:30 -0700 IronPort-SDR: PogRVo52L4c/bHJT8ZMdD3bunGoSsLhHQc/kjfz1lqeJ2kBhfpOnK+G1yBjX10VJVMqJyVoXWX HHJzp5nQh2ig== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,563,1574150400"; d="scan'208";a="445419123" Received: from sqa-gate.sh.intel.com (HELO clx-ap-likexu.tsp.org) ([10.239.48.212]) by fmsmga006.fm.intel.com with ESMTP; 17 Mar 2020 01:17:27 -0700 From: Like Xu To: pbonzini@redhat.com, like.xu@linux.intel.com Cc: ehankland@google.com, jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com, vkuznets@redhat.com, wanpengli@tencent.com Subject: [PATCH v2] KVM: x86/pmu: Reduce counter period change overhead and delay the effective time Date: Tue, 17 Mar 2020 16:14:58 +0800 Message-Id: <20200317081458.88714-1-like.xu@linux.intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200317075315.70933-1-like.xu@linux.intel.com> References: <20200317075315.70933-1-like.xu@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The cost of perf_event_period() is unstable, and when the guest samples multiple events, the overhead increases dramatically (5378 ns on E5-2699). For a non-running counter, the effective time of the new period is when its corresponding enable bit is enabled. Calling perf_event_period() in advance is superfluous. For a running counter, it's safe to delay the effective time until the KVM_REQ_PMU event is handled. If there are multiple perf_event_period() calls before handling KVM_REQ_PMU, it helps to reduce the total cost. Signed-off-by: Like Xu --- arch/x86/kvm/pmu.c | 11 ----------- arch/x86/kvm/pmu.h | 11 +++++++++++ arch/x86/kvm/vmx/pmu_intel.c | 10 ++++------ 3 files changed, 15 insertions(+), 17 deletions(-) diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index d1f8ca57d354..527a8bb85080 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -437,17 +437,6 @@ void kvm_pmu_init(struct kvm_vcpu *vcpu) kvm_pmu_refresh(vcpu); } -static inline bool pmc_speculative_in_use(struct kvm_pmc *pmc) -{ - struct kvm_pmu *pmu = pmc_to_pmu(pmc); - - if (pmc_is_fixed(pmc)) - return fixed_ctrl_field(pmu->fixed_ctr_ctrl, - pmc->idx - INTEL_PMC_IDX_FIXED) & 0x3; - - return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE; -} - /* Release perf_events for vPMCs that have been unused for a full time slice. */ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu) { diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h index d7da2b9e0755..cd112e825d2c 100644 --- a/arch/x86/kvm/pmu.h +++ b/arch/x86/kvm/pmu.h @@ -138,6 +138,17 @@ static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value) return sample_period; } +static inline bool pmc_speculative_in_use(struct kvm_pmc *pmc) +{ + struct kvm_pmu *pmu = pmc_to_pmu(pmc); + + if (pmc_is_fixed(pmc)) + return fixed_ctrl_field(pmu->fixed_ctr_ctrl, + pmc->idx - INTEL_PMC_IDX_FIXED) & 0x3; + + return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE; +} + void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel); void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int fixed_idx); void reprogram_counter(struct kvm_pmu *pmu, int pmc_idx); diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 7c857737b438..20f654a0c09b 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -263,15 +263,13 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (!msr_info->host_initiated) data = (s64)(s32)data; pmc->counter += data - pmc_read_counter(pmc); - if (pmc->perf_event) - perf_event_period(pmc->perf_event, - get_sample_period(pmc, data)); + if (pmc_speculative_in_use(pmc)) + kvm_make_request(KVM_REQ_PMU, vcpu); return 0; } else if ((pmc = get_fixed_pmc(pmu, msr))) { pmc->counter += data - pmc_read_counter(pmc); - if (pmc->perf_event) - perf_event_period(pmc->perf_event, - get_sample_period(pmc, data)); + if (pmc_speculative_in_use(pmc)) + kvm_make_request(KVM_REQ_PMU, vcpu); return 0; } else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) { if (data == pmc->eventsel) -- 2.21.1