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

[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.

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

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 <address@hidden> 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
>