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Date: Fri, 17 Jun 2011 13:15:00 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] how to verify virtio is being used?
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To: al pat <alps.oss@gmail.com>
Cc: qemu-devel@nongnu.org

Am 16.06.2011 20:57, schrieb al pat:
> I have posted this on kvm alias, but have not heard back. seeing some inputs.
> 
> seeking some pointers/guidance as to how to determine virtio is being used...
> 
> I configured a VM to use block device with if=virtio (create a 1GB
> disk using dd I exported this disk to the VM and am now doing scp from
> host to the
>  guest after creating partition/mkfs.
> 
> I created another 1GB disk and export it as a IDE disk. I use the same
> scp command from host to guest after creating partition/mkfs.
> 
> I am trying to determine if my block IO is indeed using virtio in the
> first case.
> 
> Empirically, I observe that with if=virtio, the throughput is about
> 30% more (in terms of mbps) and time taken is about 40% less than
> for the case where I passed the disk as a IDE disk.
> 
> My scp happens over virbr0 interface (and currently I am not concerned
> if networking is using virtio)
> 
> How do I confirm that virtio is being used? Are there any debugs that
> I can enable to do that.

Have a look at the guest kernel logs, lspci output or just at the device
name: IDE disks are called /dev/sda etc. whereas virtio-blk disks are
called /dev/vda etc.

Kevin