Re: [Qemu-devel] QEMU/KVM performance gets worser - high load - high interrupts - high context switches

[Gerhard Wiesinger]

On 11.01.2016 09:22, Paolo Bonzini wrote:
> On 09/01/2016 17:46, Gerhard Wiesinger wrote:
> > # Positive consequences via munin monitoring:
> > # Reduced fork rate: 40 => 13
> > # process states: running 15 => <1
> > # CÜU temperature: (core dependant) 65-70°C => 56-64°C
> > # CPU usage: system: 47% => 15%, user: 76% => 50%
> > # Context Switches: 20k => 7.5k
> > # Interrupts: 16k => 9k
> > # Load average: 2.8 => 1
> >
> > => back at the level before one year!!!!!!!
> >
> > Any idea why the serial device/PCI controller and the USB mouse tablet
> > consume so much CPU on latest kernel and/or qemu?
> For USB, it's possible that you're not using the USB autosuspend
> feature?  (As explained in Gerd's blog post, for Microsoft OSes you may
> need to fiddle with the registry).
>
> For virtio-serial, I have no idea.

Linux VMs: All VMs are Linux VM on this KVM host, so as per blog post 
udev rules should apply well for USB autosuspend. Most of the effect 
came from the virtio-serial and not from USB tablet.

For another KVM host with a Windows 7 VM:
I tried to find apply the blog post: But there is no option "Allow the 
computer to turn off the device to save power"
Nevertheless CPU usage could be reduced by removing the USB tablet from 
the Win7 VM.

Ciao,
Gerhard