Re: KVM power usage - high wakeup rates

[Anders <mail@flac.kalibalik.dk>]

Anthony Liguori wrote:
> 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.

According to powertop, I had about 15 kvm wakeups/sec with my previous 
setup (nohz, no display). Now I upgraded to kvm-70 and the timer 
interrupt has reappeared so I have this:

Top causes for wakeups:
  25,4% (112,4)      <kernel IPI> : function call interrupts
  22,6% (100,0)   qemu-system-x86 : kvm_arch_vcpu_ioctl_run (pit_timer_fn)
  22,6% (100,0)   qemu-system-x86 : __kvm_migrate_timers (apic_timer_fn)
   8,7% ( 38,5)   qemu-system-x86 : sys_timer_settime (posix_timer_fn)

What could be the cause for this change? The previous kvm was from 
Ubuntu 8.04, there are no changes in the guest.

In general, what are the best host/guest settings for a low number of 
wakeups?


Thanks,
Anders.