Re: KVM power usage - high wakeup rates

[Anthony Liguori <anthony@codemonkey.ws>]

Haydn Solomon wrote:
> Hi List,
>
> When testing power usage of a windows xp guest using powertop utility,
> I'm noticing high wakeup rates. The following is the output of
> powertop for an idle windows xp guest.
>
>
> ==============================
> ===========================
> Wakeups-from-idle per second : 2716.6   interval: 10.0s
> no ACPI power usage estimate available
>
> Top causes for wakeups:
>   52.4% (2434.4)   qemu-system-x86 : sys_timer_settime (posix_timer_fn)
>   21.5% (996.7)   qemu-system-x86 : __kvm_migrate_pit_timer (pit_timer_fn)
>   15.0% (697.4)       <interrupt> : extra timer interrupt
>    4.9% (227.6)      <kernel IPI> : Rescheduling interrupts
>    1.6% ( 72.9)   USB device  6-2 : Optical USB Mouse (Logitech)
>    1.3% ( 61.7)       <interrupt> : nvidia
>    1.3% ( 59.0)       <interrupt> : uhci_hcd:usb4, uhci_hcd:usb6, HDA Intel
> ===================================================================
>
> I'm getting similar values when running a Fedora 9 guest.
>
> My host is running F9. Details of my /proc/cpuinfo :
>
> processor    : 1
> vendor_id    : GenuineIntel
> cpu family    : 6
> model        : 15
> model name    : Intel(R) Core(TM)2 Duo CPU     T7500  @ 2.20GHz
> stepping    : 10
> cpu MHz        : 2201.000
> cache size    : 4096 KB
> physical id    : 0
> siblings    : 2
> core id        : 1
> cpu cores    : 2
> fpu        : yes
> fpu_exception    : yes
> cpuid level    : 10
> wp        : yes
> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
> syscall nx lm constant_tsc arch_perfmon pebs bts rep_good pni monitor
> ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm ida
> bogomips    : 4387.73
> clflush size    : 64
> cache_alignment    : 64
> address sizes    : 36 bits physical, 48 bits virtual
> power management:
>
> The linux image I'm running is Linux localhost.localdomain
> 2.6.25.4-30.fc9.x86_64 #1 SMP Wed May 21 17:34:18 EDT 2008 x86_64
> x86_64 x86_64 GNU/Linux
>
> I'm starting my vm using the following command:
>
> /usr/local/kvm/bin/qemu-system-x86_64 \
> -hda windowsxp.img \
> -m 650 \
> -localtime \
> -net user \
> -net nic,model=e1000 \
> -smb /home/hsolomon \
> -std-vga \
> -soundhw all \
> -usb \
> -usbdevice tablet \
> -name StandardPC-NAT &
>   

USB tablet polls a lot.  You'll probably see far less wake ups if you 
don't use the tablet.

With the default options, my idle winxp guest causes about 550 
wakeups/sec which is pretty close to what I'd expect.  I don't think 
you'll get much better than that without using a dynticks guest.

Regards,

Anthony Liguori

> Thanks
>
> Haydn
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