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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 C625CC76191 for ; Thu, 18 Jul 2019 13:45:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1340220873 for ; Thu, 18 Jul 2019 13:45:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390023AbfGRNpT (ORCPT ); Thu, 18 Jul 2019 09:45:19 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:28364 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726608AbfGRNpT (ORCPT ); Thu, 18 Jul 2019 09:45:19 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6IDhNh6172049 for ; Thu, 18 Jul 2019 09:45:18 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ttqxq57v2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 18 Jul 2019 09:45:17 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 18 Jul 2019 14:45:12 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6IDjBPi57606206 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 18 Jul 2019 13:45:11 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6615EA4062; Thu, 18 Jul 2019 13:45:11 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 29183A405B; Thu, 18 Jul 2019 13:45:11 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.115]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 18 Jul 2019 13:45:11 +0000 (GMT) Subject: Re: [PATCH 1/2] KVM: Boost vCPUs that are delivering interrupts To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: wanpengli@tencent.com, rkrcmar@redhat.com, paulus@ozlabs.org, maz@kernel.org References: <1563457031-21189-1-git-send-email-pbonzini@redhat.com> <1563457031-21189-2-git-send-email-pbonzini@redhat.com> From: Christian Borntraeger Openpgp: preference=signencrypt Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <1563457031-21189-2-git-send-email-pbonzini@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19071813-0016-0000-0000-0000029409E2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19071813-0017-0000-0000-000032F1E667 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-18_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=628 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907180144 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18.07.19 15:37, Paolo Bonzini wrote: > From: Wanpeng Li > > Inspired by commit 9cac38dd5d (KVM/s390: Set preempted flag during > vcpu wakeup and interrupt delivery), we want to also boost not just > lock holders but also vCPUs that are delivering interrupts. Most > smp_call_function_many calls are synchronous, so the IPI target vCPUs > are also good yield candidates. This patch introduces vcpu->ready to > boost vCPUs during wakeup and interrupt delivery time; unlike s390 we do > not reuse vcpu->preempted so that voluntarily preempted vCPUs are taken > into account by kvm_vcpu_on_spin, but vmx_vcpu_pi_put is not affected > (VT-d PI handles voluntary preemption separately, in pi_pre_block). > > Testing on 80 HT 2 socket Xeon Skylake server, with 80 vCPUs VM 80GB RAM: > ebizzy -M > > vanilla boosting improved > 1VM 21443 23520 9% > 2VM 2800 8000 180% > 3VM 1800 3100 72% > > Testing on my Haswell desktop 8 HT, with 8 vCPUs VM 8GB RAM, two VMs, > one running ebizzy -M, the other running 'stress --cpu 2': > > w/ boosting + w/o pv sched yield(vanilla) > > vanilla boosting improved > 1570 4000 155% > > w/ boosting + w/ pv sched yield(vanilla) > > vanilla boosting improved > 1844 5157 179% > > w/o boosting, perf top in VM: > > 72.33% [kernel] [k] smp_call_function_many > 4.22% [kernel] [k] call_function_i > 3.71% [kernel] [k] async_page_fault > > w/ boosting, perf top in VM: > > 38.43% [kernel] [k] smp_call_function_many > 6.31% [kernel] [k] async_page_fault > 6.13% libc-2.23.so [.] __memcpy_avx_unaligned > 4.88% [kernel] [k] call_function_interrupt > > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Christian Borntraeger > Cc: Paul Mackerras > Cc: Marc Zyngier > Signed-off-by: Wanpeng Li > Signed-off-by: Paolo Bonzini > --- > v2->v3: put it in kvm_vcpu_wake_up, use WRITE_ONCE Looks good. Some more comments > > arch/s390/kvm/interrupt.c | 2 +- > include/linux/kvm_host.h | 1 + > virt/kvm/kvm_main.c | 9 +++++++-- [...] > @@ -4205,6 +4206,8 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu) > > if (vcpu->preempted) > vcpu->preempted = false; > + if (vcpu->ready) > + WRITE_ONCE(vcpu->ready, false); What is the rationale of checking before writing. Avoiding writable cache line ping pong? > > kvm_arch_sched_in(vcpu, cpu); > > @@ -4216,8 +4219,10 @@ static void kvm_sched_out(struct preempt_notifier *pn, > { > struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn); > > - if (current->state == TASK_RUNNING) > + if (current->state == TASK_RUNNING) { > vcpu->preempted = true; WOuld it make sense to also use WRITE_ONCE for vcpu->preempted ? > + WRITE_ONCE(vcpu->ready, true); > + } > kvm_arch_vcpu_put(vcpu); > } > >