[fedora-virt] Different cpu usage between Fedora and SL6 guests - SOLVED

[Orion Poplawski]

On 07/18/2012 11:04 AM, Cole Robinson wrote:
> On 07/18/2012 11:17 AM, Orion Poplawski wrote:
>> On 07/17/2012 04:50 PM, Orion Poplawski wrote:
>>> While staring at top on my SL6 kvm server waiting for it to crash, I noticed
>>> that my idle Fedora kvm guests appear to be consuming between 8-12% cpu while
>>> my idle SL6 guests appear to be consuming between 0.3-2% cpu as shown in the
>>> qemu-kvm processes in top.  In fact I have a Fedora 17 instance running now
>>> with nothing but kernel processes and the qemu-kvm process still shows it
>>> using 7-8% cpu.
>>>
>>> Does anyone have any insight as to why this would be the case?
>>>
>>
>>   It appears that toggling the Autosuspend for USB device QEMU USB Tablet [QEMU
>> 0.12.1] tunable has a big effect and brings it in line with SL6.
>>
>> SL6:
>> usb 1-1: Product: QEMU USB Tablet
>> input: QEMU 0.12.1 QEMU USB Tablet as
>> /devices/pci0000:00/0000:00:01.2/usb1/1-1/1-1:1.0/input/input4
>> generic-usb 0003:0627:0001.0001: input,hidraw0: USB HID v0.01 Pointer [QEMU
>> 0.12.1 QEMU USB Tablet] on usb-0000:00:01.2-1/input0
>>
>> # cat /sys/devices/pci0000:00/0000:00:01.2/usb1/1-1/power/autosuspend
>> 2
>> # cat  /sys/devices/pci0000:00/0000:00:01.2/usb1/1-1/power/level
>> auto
>>
>> F17:
>> [    3.015642] usb 1-1: Product: QEMU USB Tablet
>> [    3.117125] input: QEMU 0.12.1 QEMU USB Tablet as
>> /devices/pci0000:00/0000:00:01.2/usb1/1-1/1-1:1.0/input/input3
>> [    3.117827] generic-usb 0003:0627:0001.0001: input,hidraw0: USB HID v0.01
>> Pointer [QEMU 0.12.1 QEMU USB Tablet] on usb-0000:00:01.2-1/input0
>>
>> # cat /sys/devices/pci0000:00/0000:00:01.2/usb1/power/autosuspend
>> 2
>> # cat  /sys/devices/pci0000:00/0000:00:01.2/usb1/1-1/power/level
>> on
>>
>> So it appears that SL6 is setting to auto automatically, but Fedora is not.  I
>> wonder why.
>>
>
> Hmm, could you please open a bug for that? I guess against F17 qemu for now,
> might be kernel or udev though. I think this is a regression from previous
> releases, tablet autosuspend is supposed to work out of the box.
>
> Thanks,
> Cole
>

Filed against udev since that is where it was fixed in EL6.

https://bugzilla.redhat.com/show_bug.cgi?id=841368
-- 
Orion Poplawski
Technical Manager                     303-415-9701 x222
NWRA, Boulder Office                  FAX: 303-415-9702
3380 Mitchell Lane                       orion at nwra.com
Boulder, CO 80301                   http://www.nwra.com