From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34492) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XORPp-0008Mu-C2 for qemu-devel@nongnu.org; Mon, 01 Sep 2014 09:13:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XORPe-00036k-Oz for qemu-devel@nongnu.org; Mon, 01 Sep 2014 09:13:01 -0400 Received: from mail-qc0-x22b.google.com ([2607:f8b0:400d:c01::22b]:51390) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XORPe-00036g-Ke for qemu-devel@nongnu.org; Mon, 01 Sep 2014 09:12:50 -0400 Received: by mail-qc0-f171.google.com with SMTP id x3so5425567qcv.30 for ; Mon, 01 Sep 2014 06:12:50 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <540470CD.9060800@redhat.com> Date: Mon, 01 Sep 2014 15:12:45 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <201408291545282753855@sangfor.com>, <20140829143849.GA8909@grmbl.mre>, <201409012038178763909@sangfor.com> <201409012052442706397@sangfor.com> <5404701F.5070302@de.ibm.com> In-Reply-To: <5404701F.5070302@de.ibm.com> Content-Type: text/plain; charset=gbk 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: Christian Borntraeger , Zhang Haoyu , Amit Shah Cc: qemu-devel , kvm Il 01/09/2014 15:09, Christian Borntraeger ha scritto: > This is just wild guessing: > 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. Paolo