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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 5A984C43141 for ; Thu, 28 Jun 2018 16:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 137D02767D for ; Thu, 28 Jun 2018 16:27:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 137D02767D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754128AbeF1Q1v (ORCPT ); Thu, 28 Jun 2018 12:27:51 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41652 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753040AbeF1Q1u (ORCPT ); Thu, 28 Jun 2018 12:27:50 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B49D076F9F; Thu, 28 Jun 2018 16:27:49 +0000 (UTC) Received: from vitty.brq.redhat.com.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A367E1116717; Thu, 28 Jun 2018 16:27:47 +0000 (UTC) From: Vitaly Kuznetsov To: Wanpeng Li Cc: "the arch\/x86 maintainers" , devel@linuxdriverproject.org, LKML , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Tianyu.Lan@microsoft.com, "Michael Kelley \(EOSG\)" Subject: Re: [PATCH 0/4] x86/hyper-v: optimize PV IPIs References: <20180622170625.30688-1-vkuznets@redhat.com> <8736x8h8wu.fsf@vitty.brq.redhat.com> Date: Thu, 28 Jun 2018 18:27:46 +0200 In-Reply-To: <8736x8h8wu.fsf@vitty.brq.redhat.com> (Vitaly Kuznetsov's message of "Wed, 27 Jun 2018 11:32:17 +0200") Message-ID: <87o9fuev0d.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 28 Jun 2018 16:27:49 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Thu, 28 Jun 2018 16:27:49 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'vkuznets@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > Wanpeng Li writes: > >> Hi Vitaly, (fix my reply mess this time) >> On Sat, 23 Jun 2018 at 01:09, Vitaly Kuznetsov wrote: >>> >>> When reviewing my "x86/hyper-v: use cheaper HVCALL_FLUSH_VIRTUAL_ADDRESS_ >>> {LIST,SPACE} hypercalls when possible" patch Michael suggested to apply the >>> same idea to PV IPIs. Here we go! >>> >>> Despite what Hyper-V TLFS says about HVCALL_SEND_IPI hypercall, it can >>> actually be 'fast' (passing parameters through registers). Use that too. >>> >>> This series can collide with my "KVM: x86: hyperv: PV IPI support for >>> Windows guests" series as I rename ipi_arg_non_ex/ipi_arg_ex structures >>> there. Depending on which one gets in first we may need to do tiny >>> adjustments. >> >> As hyperv PV TLB flush has already been merged, is there any other >> obvious multicast IPIs scenarios? qemu supports interrupt remapping >> since two years ago, I think windows guest can switch to cluster mode >> after entering x2APIC, so sending IPI per cluster. In addition, you >> can also post the benchmark result for this PV IPI optimization, >> although it also fixes the bug which you mentioned above. > > I got confused, which of my patch series are you actually looking at? > :-) > > This particular one ("x86/hyper-v: optimize PV IPIs") is not about > KVM/qemu, it is for Linux running on top on real Hyper-V server. We > already support PV IPIs and here I'm just trying to optimize the way how > we send them by switching to a cheaper hypercall (and using 'fast' > version of it) when possible. I don't actually have a good benchmark > (and I don't remember seeing one when K.Y. posted PV IPI support) but > this can be arranged I guess: I can write a dump 'IPI sender' in kernel > and send e.g. 1000 IPIs. So I used the IPI benchmark (https://lkml.org/lkml/2017/12/19/141, thanks for the tip!) on this series. On a 16 vCPU guest (WS2016) I'm getting the following: Before: Dry-run: 0 203110 Self-IPI: 6167430 11645550 Normal IPI: 380479300 475881820 Broadcast IPI: 0 2557371420 After: Dry-run: 0 214280 (not interesting) Self-IPI: 5706210 10697640 (- 8%) Normal IPI: 379330010 450158830 (- 5%) Broadcast IPI: 0 2340427160 (- 8%) -- Vitaly