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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 6113AC636C9 for ; Mon, 19 Jul 2021 07:37:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4595961019 for ; Mon, 19 Jul 2021 07:37:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235000AbhGSHks (ORCPT ); Mon, 19 Jul 2021 03:40:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233759AbhGSHkr (ORCPT ); Mon, 19 Jul 2021 03:40:47 -0400 Received: from mail-ot1-x329.google.com (mail-ot1-x329.google.com [IPv6:2607:f8b0:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE0B6C061762; Mon, 19 Jul 2021 00:37:46 -0700 (PDT) Received: by mail-ot1-x329.google.com with SMTP id f93-20020a9d03e60000b02904b1f1d7c5f4so17326100otf.9; Mon, 19 Jul 2021 00:37:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=KU35joaREKi8wYu27nSbbTlLzVUkngjyeSpBRqp8l7c=; b=ZhAtP9jq6ssyHpI49UT0cK4YAvAtrj6bw2VVxDWN1P8r+akwluUSu65GIEbpyL0p2P a3JOVSgo7nTywmhWBZIMNmrcWYHJpQx51kZWc5e2WVlTAxA+MEPQyrJTNcP7UZxGBR7y XdOd2CzFWMVuygQa8ynJH2k6Fz3xDR1fnKG0ihpleyx9/wA02Gj5CWvKttSayMTFv2sB S6Gq4rtLykxw7IFJhDVCnH/DHS5CgdcuuPPXCZGBBP972+tbE0Lbsr80WkmdhyS2YE/S Sdq4ThrXb0ImqzSm1/gvisFsqq18C2GMZkQpv1CbOmQXyAlDy/qTihjLvHJnkNDXzgpa Of+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=KU35joaREKi8wYu27nSbbTlLzVUkngjyeSpBRqp8l7c=; b=C/cp0Mn+onIzz50U/qOhHVg6m3ISmlfhO0w/cqzWsgcBoy46sajlsCz/5YWw4DwSQi GoXJ4NRHk+X40StpmKLTfaFMzbe0csk9TNhNbaCSX3q4UVxXa1ob3Ssx84AYh2DpdL7Z R2kvwWuI0LBA7RL8MGla/XV0sn3TcBpuVqp7koq2ZBjD89evg+2yaN8XpVvpLp31Vt5d ldeyKod2HOWeRAxMSoMnx68Mm5YfHtU91QxjJ4eHZZHySigAqp1DSZcK8UIoudzi83Yx vrrraSXhJt2Kl5u4pnweD2vzvpqf/HMis9KWdZM+lVRL3crJdR8NdGFtLEJf7E8vMi11 RlAg== X-Gm-Message-State: AOAM533q+FzCo7uZti0BWVVLrrT+U4H8efe8u0u+sMDbM9PSV69ZL0bd MSvseMJTGGO9KgA91OtaciJ6t7HjbwOMGZZifBg= X-Google-Smtp-Source: ABdhPJx/A2HSRknv97oVh/werPfkOH754gHACP5lmv08U10mFj0/qfdqEqassAcnwX7oR6Bt9vD5wv8tb7S04mrZITo= X-Received: by 2002:a05:6830:1c69:: with SMTP id s9mr17719718otg.185.1626680266412; Mon, 19 Jul 2021 00:37:46 -0700 (PDT) MIME-Version: 1.0 References: <20210716064808.14757-1-guang.zeng@intel.com> In-Reply-To: From: Wanpeng Li Date: Mon, 19 Jul 2021 15:37:35 +0800 Message-ID: Subject: Re: [PATCH 0/5] IPI virtualization support for VM To: Zeng Guang Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm , Dave Hansen , Tony Luck , Kan Liang , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Kim Phillips , Jarkko Sakkinen , Jethro Beekman , Kai Huang , "the arch/x86 maintainers" , LKML , Robert Hu , Gao Chao Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Jul 2021 at 15:26, Zeng Guang wrote: > > On 7/16/2021 5:25 PM, Wanpeng Li wrote: > > On Fri, 16 Jul 2021 at 15:14, Zeng Guang wrote: > >> Current IPI process in guest VM will virtualize the writing to interru= pt > >> command register(ICR) of the local APIC which will cause VM-exit anywa= y > >> on source vCPU. Frequent VM-exit could induce much overhead accumulate= d > >> if running IPI intensive task. > >> > >> IPI virtualization as a new VT-x feature targets to eliminate VM-exits > >> when issuing IPI on source vCPU. It introduces a new VM-execution > >> control - "IPI virtualization"(bit4) in the tertiary processor-based > >> VM-exection controls and a new data structure - "PID-pointer table > >> address" and "Last PID-pointer index" referenced by the VMCS. When "IP= I > >> virtualization" is enabled, processor emulateds following kind of writ= es > >> to APIC registers that would send IPIs, moreover without causing VM-ex= its. > >> - Memory-mapped ICR writes > >> - MSR-mapped ICR writes > >> - SENDUIPI execution > >> > >> This patch series implement IPI virtualization support in KVM. > >> > >> Patches 1-3 add tertiary processor-based VM-execution support > >> framework. > >> > >> Patch 4 implement interrupt dispatch support in x2APIC mode with > >> APIC-write VM exit. In previous platform, no CPU would produce > >> APIC-write VM exit with exit qulification 300H when the "virtual x2API= C > >> mode" VM-execution control was 1. > >> > >> Patch 5 implement IPI virtualization related function including > >> feature enabling through tertiary processor-based VM-execution in > >> various scenario of VMCS configuration, PID table setup in vCPU creati= on > >> and vCPU block consideration. > >> > >> Document for IPI virtualization is now available at the latest "Intel > >> Architecture Instruction Set Extensions Programming Reference". > >> > >> Document Link: > >> https://software.intel.com/content/www/us/en/develop/download/intel-ar= chitecture-instruction-set-extensions-programming-reference.html > >> > >> We did experiment to measure average time sending IPI from source vCPU > >> to the target vCPU completing the IPI handling by kvm unittest w/ and > >> w/o IPI virtualization. When IPI virtualizatin enabled, it will reduce > >> 22.21% and 15.98% cycles comsuming in xAPIC mode and x2APIC mode > >> respectly. > >> > >> KMV unittest:vmexit/ipi, 2 vCPU, AP runs without halt to ensure no VM > >> exit impact on target vCPU. > >> > >> Cycles of IPI > >> xAPIC mode x2APIC mode > >> test w/o IPIv w/ IPIv w/o IPIv w/ IPIv > >> 1 6106 4816 4265 3768 > >> 2 6244 4656 4404 3546 > >> 3 6165 4658 4233 3474 > >> 4 5992 4710 4363 3430 > >> 5 6083 4741 4215 3551 > >> 6 6238 4904 4304 3547 > >> 7 6164 4617 4263 3709 > >> 8 5984 4763 4518 3779 > >> 9 5931 4712 4645 3667 > >> 10 5955 4530 4332 3724 > >> 11 5897 4673 4283 3569 > >> 12 6140 4794 4178 3598 > >> 13 6183 4728 4363 3628 > >> 14 5991 4994 4509 3842 > >> 15 5866 4665 4520 3739 > >> 16 6032 4654 4229 3701 > >> 17 6050 4653 4185 3726 > >> 18 6004 4792 4319 3746 > >> 19 5961 4626 4196 3392 > >> 20 6194 4576 4433 3760 > >> > >> Average cycles 6059 4713.1 4337.85 3644.8 > >> %Reduction -22.21% -15.98% > > Commit a9ab13ff6e (KVM: X86: Improve latency for single target IPI > > fastpath) mentioned that the whole ipi fastpath feature reduces the > > latency from 4238 to 3293 around 22.3% on SKX server, why your IPIv > > hardware acceleration is worse than software emulation? In addition, > > Actually this performance data was measured on the basis of fastpath > optimization while cpu runs at base frequency. > > As a result, IPI virtualization could have extra 15.98% cost reduction > over IPI fastpath process in x2apic mode. I observed that adaptive advance lapic timer and adaptive halt-polling will influence kvm-unit-tests/vmexit.flat IPI testing score, could you post the score after disabling these features as commit a9ab13ff6e (KVM: X86: Improve latency for single target IPI fastpath) mentioned=EF=BC= =9F In addition, please post the hackbench(./hackbench -l 1000000) and ipi microbenchmark scores. Wanpeng