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=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 C6E20C48BD3 for ; Wed, 26 Jun 2019 16:44:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F08E2080C for ; Wed, 26 Jun 2019 16:44:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726620AbfFZQoe (ORCPT ); Wed, 26 Jun 2019 12:44:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbfFZQoe (ORCPT ); Wed, 26 Jun 2019 12:44:34 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1282C309175F; Wed, 26 Jun 2019 16:44:34 +0000 (UTC) Received: from amt.cnet (ovpn-112-3.gru2.redhat.com [10.97.112.3]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0B2A45D717; Wed, 26 Jun 2019 16:44:31 +0000 (UTC) Received: from amt.cnet (localhost [127.0.0.1]) by amt.cnet (Postfix) with ESMTP id A14F510517A; Wed, 26 Jun 2019 13:44:12 -0300 (BRT) Received: (from marcelo@localhost) by amt.cnet (8.14.7/8.14.7/Submit) id x5QGi8LV002573; Wed, 26 Jun 2019 13:44:08 -0300 Date: Wed, 26 Jun 2019 13:44:08 -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: <20190626164401.GA2211@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> <20190619210346.GA13033@amt.cnet> <20190621214205.GA4751@amt.cnet> <20190625190010.GA3377@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 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 26 Jun 2019 16:44:34 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Jun 26, 2019 at 07:02:13PM +0800, Wanpeng Li wrote: > On Wed, 26 Jun 2019 at 03:03, Marcelo Tosatti wrote: > > > > On Mon, Jun 24, 2019 at 04:53:53PM +0800, Wanpeng Li wrote: > > > On Sat, 22 Jun 2019 at 06:11, Marcelo Tosatti wrote: > > > > > > > > On Fri, Jun 21, 2019 at 09:42:39AM +0800, Wanpeng Li wrote: > > > > > On Thu, 20 Jun 2019 at 05:04, Marcelo Tosatti wrote: > > > > > > > > > > > > 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... > > > > > > > > > > https://lkml.org/lkml/2019/6/5/436 "Here you need to check > > > > > kvm_halt_in_guest, not kvm_mwait_in_guest, because you need to go > > > > > through kvm_apic_expired if the guest needs to be woken up from > > > > > kvm_vcpu_block." > > > > > > > > Ah, i think he means that a sleeping vcpu (in kvm_vcpu_block) must > > > > be woken up, if it receives a timer interrupt. > > > > > > > > But your patch will go through: > > > > > > > > kvm_apic_inject_pending_timer_irqs > > > > __apic_accept_irq -> > > > > vmx_deliver_posted_interrupt -> > > > > kvm_vcpu_trigger_posted_interrupt returns false > > > > (because vcpu->mode != IN_GUEST_MODE) -> > > > > kvm_vcpu_kick > > > > > > > > Which will wakeup the vcpu. > > > > > > Hi Marcelo, > > > > > > > > > > > Apart from this oops, which triggers when running: > > > > taskset -c 1 ./cyclictest -D 3600 -p 99 -t 1 -h 30 -m -n -i 50000 -b 40 > > > > > > I try both host and guest use latest kvm/queue w/ CONFIG_PREEMPT > > > enabled, and expose mwait as your config, however, there is no oops. > > > Can you reproduce steadily or encounter casually? Can you reproduce > > > w/o the patchset? > > > > Hi Li, > > Hi Marcelo, > > > > > Steadily. > > > > Do you have this as well: > > w/ or w/o below diff, testing on both SKX and HSW servers on hand, I > didn't see any oops. Could you observe the oops disappear when w/o > below diff? If the answer is yes, then the oops will not block to > merge the patchset since Paolo prefers to add the kvm_hlt_in_guest() > condition to guarantee be woken up from kvm_vcpu_block(). He agreed that its not necessary. Removing the HLT in guest widens the scope of the patch greatly. > For the > exitless injection if the guest is running(DPDK style workloads that > busy-spin on network card) scenarios, we can find a solution later. What is the use-case for HLT in guest again? I'll find the source for the oops (or confirm can't reproduce with kvm/queue RSN).