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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,T_HK_NAME_DR,USER_AGENT_MUTT 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 DF259C43143 for ; Mon, 1 Oct 2018 11:41:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A008B208AE for ; Mon, 1 Oct 2018 11:41:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A008B208AE 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 S1729277AbeJASTN (ORCPT ); Mon, 1 Oct 2018 14:19:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34234 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729047AbeJASTN (ORCPT ); Mon, 1 Oct 2018 14:19:13 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BE0BF300197E; Mon, 1 Oct 2018 11:41:50 +0000 (UTC) Received: from work-vm (ovpn-117-221.ams2.redhat.com [10.36.117.221]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8C15E60162; Mon, 1 Oct 2018 11:41:49 +0000 (UTC) Date: Mon, 1 Oct 2018 12:41:47 +0100 From: "Dr. David Alan Gilbert" To: Feng Li Cc: linux-kernel , qemu-discuss@nongnu.org, qemu-devel@nongnu.org, "linux-scsi@vger.kernel.org" Subject: Re: [Qemu-devel] virtio-console downgrade the virtio-pci-blk performance Message-ID: <20181001114146.GA2508@work-vm> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Mon, 01 Oct 2018 11:41:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Feng Li (lifeng1519@gmail.com) wrote: > Hi, > I found an obvious performance downgrade when virtio-console combined > with virtio-pci-blk. > > This phenomenon exists in nearly all Qemu versions and all Linux > (CentOS7, Fedora 28, Ubuntu 18.04) distros. > > This is a disk cmd: > -drive file=iscsi://127.0.0.1:3260/iqn.2016-02.com.test:system:fl-iscsi/1,format=raw,if=none,id=drive-virtio-disk0,cache=none,aio=native > -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,write-cache=on > > If I add "-device > virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 ", the virtio > disk 4k iops (randread/randwrite) would downgrade from 60k to 40k. > > In VM, if I rmmod virtio-console, the performance will back to normal. > > Any idea about this issue? > > I don't know this is a qemu issue or kernel issue. It sounds odd; can you provide more details on: a) The benchmark you're using. b) the host and the guest config (number of cpus etc) c) Why are you running it with iscsi back to the same host - why not just simplify the test back to a simple file? Dave > > Thanks in advance. > -- > Thanks and Best Regards, > Alex > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK