From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43001) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOSDO-00076T-JL for qemu-devel@nongnu.org; Mon, 01 Sep 2014 10:04:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XOSDD-0001Io-Rt for qemu-devel@nongnu.org; Mon, 01 Sep 2014 10:04:14 -0400 Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:40418) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOSDD-0001IO-In for qemu-devel@nongnu.org; Mon, 01 Sep 2014 10:04:03 -0400 Received: from /spool/local by e06smtp16.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 1 Sep 2014 15:04:01 +0100 Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 67E6B17D8047 for ; Mon, 1 Sep 2014 15:05:55 +0100 (BST) Received: from d06av09.portsmouth.uk.ibm.com (d06av09.portsmouth.uk.ibm.com [9.149.37.250]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s81E3wjh32964648 for ; Mon, 1 Sep 2014 14:03:58 GMT Received: from d06av09.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av09.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s81E3v5m012360 for ; Mon, 1 Sep 2014 08:03:57 -0600 Message-ID: <54047CCD.4000101@de.ibm.com> Date: Mon, 01 Sep 2014 16:03:57 +0200 From: Christian Borntraeger MIME-Version: 1.0 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> <5404749F.7050606@redhat.com> In-Reply-To: <5404749F.7050606@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Zhang Haoyu , Amit Shah Cc: qemu-devel , kvm On 01/09/14 15:29, Paolo Bonzini wrote: > 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 Zhang Haoyu, which virtio drivers did you use? I just checked the Fedora virtio driver. The INF file does not contain the MSI enablement as described in http://msdn.microsoft.com/en-us/library/windows/hardware/ff544246%28v=vs.85%29.aspx That would explain the performance issues - given that the link information is still true. Christian