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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 902ABC43613 for ; Wed, 19 Jun 2019 21:04:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6BF9B21537 for ; Wed, 19 Jun 2019 21:04:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730503AbfFSVEN (ORCPT ); Wed, 19 Jun 2019 17:04:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42416 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726175AbfFSVEM (ORCPT ); Wed, 19 Jun 2019 17:04:12 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 175BEC05A1D8; Wed, 19 Jun 2019 21:04:12 +0000 (UTC) Received: from amt.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id 899DE6013D; Wed, 19 Jun 2019 21:04:11 +0000 (UTC) Received: from amt.cnet (localhost [127.0.0.1]) by amt.cnet (Postfix) with ESMTP id B80E3105169; Wed, 19 Jun 2019 18:03:51 -0300 (BRT) Received: (from marcelo@localhost) by amt.cnet (8.14.7/8.14.7/Submit) id x5JL3lQR013428; Wed, 19 Jun 2019 18:03:47 -0300 Date: Wed, 19 Jun 2019 18:03:47 -0300 From: Marcelo Tosatti To: Wanpeng Li Cc: Paolo Bonzini , LKML , kvm , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH v4 2/5] KVM: LAPIC: inject lapic timer interrupt by posted interrupt Message-ID: <20190619210346.GA13033@amt.cnet> References: <1560770687-23227-1-git-send-email-wanpengli@tencent.com> <1560770687-23227-3-git-send-email-wanpengli@tencent.com> <20190618133541.GA3932@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 19 Jun 2019 21:04:12 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Li, On Wed, Jun 19, 2019 at 08:36:06AM +0800, Wanpeng Li wrote: > On Tue, 18 Jun 2019 at 21:36, Marcelo Tosatti wrote: > > > > 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... > > Here some new discussions: > https://lkml.org/lkml/2019/6/13/1423 Not sure what this has to do with injecting timer interrupts via posted interrupts ? > https://lkml.org/lkml/2019/6/13/1420 Two things (unrelated to the above): 1) hrtimer_reprogram is unable to wakeup a remote vCPU, therefore i believe execution of apic_timer_expired can be delayed. Should wakeup the CPU which hosts apic_timer_expired. /* * If the timer is not on the current cpu, we cannot reprogram * the other cpus clock event device. */ if (base->cpu_base != cpu_base) return; 2) Getting an oops when running cyclictest, debugging...