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Re: [Qemu-devel] [question] virtio-blk performance degradationhappened w
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial |
Date: |
Mon, 01 Sep 2014 16:03:57 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.0 |
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
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial, Zhang Haoyu, 2014/09/01
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial, Amit Shah, 2014/09/01
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial, Zhang Haoyu, 2014/09/01
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappenedwith virito-serial, Zhang Haoyu, 2014/09/04
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappenedwith virito-serial, Zhang Haoyu, 2014/09/07
- Re: [Qemu-devel] [question] virtio-blk performance degradationhappenedwith virito-serial, Amit Shah, 2014/09/11
- Re: [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial, Zhang Haoyu, 2014/09/11
- Re: [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial, Stefan Hajnoczi, 2014/09/12
- Re: [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial, Max Reitz, 2014/09/13
- Re: [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial, Zhang Haoyu, 2014/09/16
Re: [Qemu-devel] [question] virtio-blk performance degradationhappened with virito-serial, Amit Shah, 2014/09/02