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[209.132.180.67]) by mx.google.com with ESMTP id x140si237094pgx.376.2019.06.18.06.36.46; Tue, 18 Jun 2019 06:37:03 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729543AbfFRNgZ (ORCPT + 99 others); Tue, 18 Jun 2019 09:36:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60010 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729493AbfFRNgX (ORCPT ); Tue, 18 Jun 2019 09:36:23 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5369430860A0; Tue, 18 Jun 2019 13:36:22 +0000 (UTC) Received: from amt.cnet (ovpn-112-7.gru2.redhat.com [10.97.112.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id CA61F1001DE7; Tue, 18 Jun 2019 13:36:21 +0000 (UTC) Received: from amt.cnet (localhost [127.0.0.1]) by amt.cnet (Postfix) with ESMTP id 07144105165; Tue, 18 Jun 2019 10:35:50 -0300 (BRT) Received: (from marcelo@localhost) by amt.cnet (8.14.7/8.14.7/Submit) id x5IDZkZI027558; Tue, 18 Jun 2019 10:35:46 -0300 Date: Tue, 18 Jun 2019 10:35:42 -0300 From: Marcelo Tosatti To: Wanpeng Li , Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH v4 2/5] KVM: LAPIC: inject lapic timer interrupt by posted interrupt Message-ID: <20190618133541.GA3932@amt.cnet> References: <1560770687-23227-1-git-send-email-wanpengli@tencent.com> <1560770687-23227-3-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1560770687-23227-3-git-send-email-wanpengli@tencent.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Tue, 18 Jun 2019 13:36:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 17, 2019 at 07:24:44PM +0800, Wanpeng Li wrote: > From: Wanpeng Li > > Dedicated instances are currently disturbed by unnecessary jitter due > to the emulated lapic timers fire on the same pCPUs which vCPUs resident. > There is no hardware virtual timer on Intel for guest like ARM. Both > programming timer in guest and the emulated timer fires incur vmexits. > This patch tries to avoid vmexit which is incurred by the emulated > timer fires in dedicated instance scenario. > > When nohz_full is enabled in dedicated instances scenario, the emulated > timers can be offload to the nearest busy housekeeping cpus since APICv > is really common in recent years. The guest timer interrupt is injected > by posted-interrupt which is delivered by housekeeping cpu once the emulated > timer fires. > > The host admin should fine tuned, e.g. dedicated instances scenario w/ > nohz_full cover the pCPUs which vCPUs resident, several pCPUs surplus > for busy housekeeping, disable mwait/hlt/pause vmexits to keep in non-root > mode, ~3% redis performance benefit can be observed on Skylake server. > > w/o patch: > > VM-EXIT Samples Samples% Time% Min Time Max Time Avg time > > EXTERNAL_INTERRUPT 42916 49.43% 39.30% 0.47us 106.09us 0.71us ( +- 1.09% ) > > w/ patch: > > VM-EXIT Samples Samples% Time% Min Time Max Time Avg time > > EXTERNAL_INTERRUPT 6871 9.29% 2.96% 0.44us 57.88us 0.72us ( +- 4.02% ) > > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Marcelo Tosatti > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/lapic.c | 33 ++++++++++++++++++++++++++------- > arch/x86/kvm/lapic.h | 1 + > arch/x86/kvm/vmx/vmx.c | 3 ++- > arch/x86/kvm/x86.c | 5 +++++ > arch/x86/kvm/x86.h | 2 ++ > include/linux/sched/isolation.h | 2 ++ > kernel/sched/isolation.c | 6 ++++++ > 7 files changed, 44 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 87ecb56..9ceeee5 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -122,6 +122,13 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) > return apic->vcpu->vcpu_id; > } > > +bool posted_interrupt_inject_timer(struct kvm_vcpu *vcpu) > +{ > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && > + kvm_hlt_in_guest(vcpu->kvm); > +} > +EXPORT_SYMBOL_GPL(posted_interrupt_inject_timer); Paolo, can you explain the reasoning behind this? Should not be necessary...