From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christian Borntraeger <borntraeger@de.ibm.com>
Subject: Re: [Qemu-devel] [question] virtio-blk performance degradationhappened
 with virito-serial
Date: Mon, 01 Sep 2014 15:22:34 +0200
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References: <201408291545282753855@sangfor.com>, <20140829143849.GA8909@grmbl.mre>,	<201409012038178763909@sangfor.com> <201409012052442706397@sangfor.com> <5404701F.5070302@de.ibm.com> <540470CD.9060800@redhat.com>
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Cc: qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Zhang Haoyu <zhanghy@sangfor.com>,
	Amit Shah <amit.shah@redhat.com>
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On 01/09/14 15:12, Paolo Bonzini wrote:
> 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
> 

Do the windows virtio drivers enable MSIs, in their inf file?

Christian