I am running irqbalance with default configuration on an Atom 330 machine.  
This CPU has 2 physical cores + 2 SMT (aka Hyperthreading) cores.  

As shown below the interrupt for the eth0 device is always on CPUs 0 and 1, 
with CPUs 2 and 3 left idle.  But why?

Maybe irqbalance prefers physical cores?  My understanding, though, is that the 
even-numbered CPUs are the physical cores, with the odd-numbered one being the 
SMT cores.  If this understanding is correct, it means that irqbalance is 
toggling between a single physical core and its SMT sibling.

Any thoughts on why irqbalance is not using all 4 CPUs to distribute the eth0 
interrupts?

Thanks.

---------------------

# cat /proc/interrupts 
           CPU0       CPU1       CPU2       CPU3       
  0:        717        568          0          0   IO-APIC-edge      timer
  1:          0          2          0          0   IO-APIC-edge      i8042
  8:         26         33          0          0   IO-APIC-edge      rtc0
  9:          0          0          0          0   IO-APIC-fasteoi   acpi
 12:          1          3          0          0   IO-APIC-edge      i8042
 17:      11409      11661          0          0   IO-APIC-fasteoi   ahci
 18:        264        424          0          0   IO-APIC-fasteoi   
snd_hda_intel
 20:          0          0          0          0   IO-APIC-fasteoi   
ohci_hcd:usb2
 21:          0          0          0          0   IO-APIC-fasteoi   
ohci_hcd:usb3
 22:          0          0          0          0   IO-APIC-fasteoi   
ehci_hcd:usb1
 24:  686292451  685980205          0          0   PCI-MSI-edge      eth0


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