Re: [Qemu-devel] how to verify virtio is being used?

[Kevin Wolf <kwolf@redhat.com>]

Am 17.06.2011 13:39, schrieb al pat:
> Hi Kevin,
> 
> Thanks!
> 
> Yes, one disk is visible in guest as sdb (partitioned to sdb1),
> mounted and I write to it.
> 
> The virtio disk is visible as /dev/vda, (partitioned to vda1), mounted
> and I write to it.

Then it's using virtio-blk.

> Kernel log on guest - do you mean dmesg?
> 
> I was trying to trace through the virt io calls to confirm. and
> determine the invocation sequence.
> 
> My lspci output:
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 00:01.2 USB Controller: Intel Corporation 82371SB PIIX3 USB
> [Natoma/Triton II] (rev 01)
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
> 00:02.0 VGA compatible controller: Cirrus Logic GD 5446
> 00:03.0 Ethernet controller: Qumranet, Inc. Unknown device 1000
> 00:04.0 RAM memory: Qumranet, Inc. Unknown device 1002
> 00:06.0 SCSI storage controller: Qumranet, Inc. Unknown device 1001

This unknown device 1001 is your virtio-blk disk.

Kevin

> 
> lspci -k --- to show kernel drivers associated with the device does
> not work in the guest.
> 
> Thanks
> a
> 
> 
> On Fri, Jun 17, 2011 at 7:15 AM, Kevin Wolf <kwolf@redhat.com> wrote:
>> 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
>>