From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial Date: Mon, 01 Sep 2014 15:29:03 +0200 Message-ID: <5404749F.7050606@redhat.com> References: <201408291545282753855@sangfor.com>, <20140829143849.GA8909@grmbl.mre>, <201409012038178763909@sangfor.com> <201409012052442706397@sangfor.com> <5404701F.5070302@de.ibm.com> <540470CD.9060800@redhat.com> <5404731A.8020405@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 7bit Cc: qemu-devel , kvm To: Christian Borntraeger , Zhang Haoyu , Amit Shah Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40150 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753410AbaIAN33 (ORCPT ); Mon, 1 Sep 2014 09:29:29 -0400 In-Reply-To: <5404731A.8020405@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: Il 01/09/2014 15:22, Christian Borntraeger ha scritto: > > > If virtio-blk and virtio-serial share an IRQ, the guest operating system has to check each virtqueue for activity. Maybe there is some inefficiency doing that. > > > AFAIK virtio-serial registers 64 virtqueues (on 31 ports + console) even if everything is unused. > > > > That could be the case if MSI is disabled. > > Do the windows virtio drivers enable MSIs, in their inf file? It depends on the version of the drivers, but it is a reasonable guess at what differs between Linux and Windows. Haoyu, can you give us the output of lspci from a Linux guest? Paolo