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=-0.6 required=3.0 tests=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=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 B05A2C43218 for ; Tue, 11 Jun 2019 01:48:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81CCF20652 for ; Tue, 11 Jun 2019 01:48:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TKKFa09Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390811AbfFKBsT (ORCPT ); Mon, 10 Jun 2019 21:48:19 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:36628 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726532AbfFKBsT (ORCPT ); Mon, 10 Jun 2019 21:48:19 -0400 Received: by mail-pg1-f194.google.com with SMTP id a3so5995607pgb.3; Mon, 10 Jun 2019 18:48:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=j+N/oz9ewSf1uzJtrwZj4fSW3UaedXAd0tvAVxxwGDQ=; b=TKKFa09YIMxRKoPIribOASB9kzjZArL2NWoHTraN60xpIXbpHyiEAyWwLbx8Kj4xoQ qYZIHAG+2gvyq9E6Q5KPrk8Dv/xAEkpoAhLr8aV1Ss6OjVeyq/y4v+VacT6y4Ie955ce vBQR2n1E/0ud36tnqNK3RVaqdfX2O58yYIo9HLv8j/Xj9fZoz3mBS5WvnKrrq9XZL5Y5 jMA5DeSa3Fne1z8uVfqgiU9QuXZ2NRJQNHi1+aDule9ctnyJG0YyvTF3T7MCTS2WiXI/ HjXmyV+A5I4w+pZbWRpkSay8bl+Xdf6UZ4qRP29t+579hp79bu6s9fAF0I/TEjiPiuni Wf+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=j+N/oz9ewSf1uzJtrwZj4fSW3UaedXAd0tvAVxxwGDQ=; b=LxQN9KfnZeERewAfVh5/bn+BQUSYFAE81OqtXsZ56QCohqzawTPRVg5bNbeHSlBzgM dTYbgxaRbRtjMq78Dh3SWzQymlZFvS2G96tbSOQNTmZlEcEfmUb35qOwEcK4iicRjDB2 melxnZ6DU/Mgss0YZxkPSF2G9MepiqzW7MmpgowajRFjbd3dwnO2FeQXFI+1lX3WjVjT k0f9nnUEoTT+voXC5jgJsh7h2+ufetO9x5X8gqdnD55hPdKtmKg7dYCiOsUStlRpo5P3 LcUPkfN8AhyPynDIffi/uJan41ySv3gAMAFIQ2xs1ZxfD34QK2vjIhekB/BETj09Rrs4 X2aw== X-Gm-Message-State: APjAAAU5T25Vvd+COVI5TiDwzNUdOGdqP2Qw7L3eK2t0q+Fe8zntWnap qXn70Y3mwBVWvFjFX0btSdA= X-Google-Smtp-Source: APXvYqzyXO4RciUwJXuZZNwWj1WdybwXH77yRQGcRE/YdfxOTDjdUbWhVoj7iFc3COVOyguQapBhpw== X-Received: by 2002:a62:e917:: with SMTP id j23mr71948692pfh.55.1560217698427; Mon, 10 Jun 2019 18:48:18 -0700 (PDT) Received: from [10.2.189.129] ([66.170.99.2]) by smtp.gmail.com with ESMTPSA id e20sm11402106pfi.35.2019.06.10.18.48.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jun 2019 18:48:17 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: [PATCH v3 0/3] KVM: Yield to IPI target if necessary From: Nadav Amit In-Reply-To: Date: Mon, 10 Jun 2019 18:48:15 -0700 Cc: Sean Christopherson , =?utf-8?B?UmFkaW0gS3LEjW3DocWZ?= , LKML , kvm , Paolo Bonzini Content-Transfer-Encoding: quoted-printable Message-Id: References: <1559178307-6835-1-git-send-email-wanpengli@tencent.com> <20190610143420.GA6594@flask> <20190611011100.GB24835@linux.intel.com> To: Wanpeng Li X-Mailer: Apple Mail (2.3445.104.11) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 10, 2019, at 6:45 PM, Wanpeng Li wrote: >=20 > On Tue, 11 Jun 2019 at 09:11, Sean Christopherson > wrote: >> On Mon, Jun 10, 2019 at 04:34:20PM +0200, Radim Kr=C4=8Dm=C3=A1=C5=99 = wrote: >>> 2019-05-30 09:05+0800, Wanpeng Li: >>>> The idea is from Xen, when sending a call-function IPI-many to = vCPUs, >>>> yield if any of the IPI target vCPUs was preempted. 17% performance >>>> increasement of ebizzy benchmark can be observed in an = over-subscribe >>>> environment. (w/ kvm-pv-tlb disabled, testing TLB flush = call-function >>>> IPI-many since call-function is not easy to be trigged by userspace >>>> workload). >>>=20 >>> Have you checked if we could gain performance by having the yield as = an >>> extension to our PV IPI call? >>>=20 >>> It would allow us to skip the VM entry/exit overhead on the caller. >>> (The benefit of that might be negligible and it also poses a >>> complication when splitting the target mask into several PV IPI >>> hypercalls.) >>=20 >> Tangetially related to splitting PV IPI hypercalls, are there any = major >> hurdles to supporting shorthand? Not having to generate the mask for >> ->send_IPI_allbutself and ->kvm_send_ipi_all seems like an easy to = way >> shave cycles for affected flows. >=20 > Not sure why shorthand is not used for native x2apic mode. Why do you say so? native_send_call_func_ipi() checks if allbutself shorthand should be used and does so (even though the check can be more efficient - I=E2=80=99m looking at that code right now=E2=80=A6)=