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

[Cole Robinson]

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