Hyperthreading & IRQ affinity

[John Reuning]

There have been several questions about the virtual cpus that result
from hyperthreading P4 processors.  For a dual cpu system, which lists
cpus 0-3, which cpu numbers correspond to which actual processor?  Are
cpu01 & cpu03 the virtual cpus, meaning that cpu00 & cpu01 represent the
first processor and cpu02 & cpu03 represent the second processor?  Or is
it an even-odd split: cpu00 & cpu02, cpu01 & cpu03?  Or does the
physical processor id value in /proc/cpuinfo indicate which cpu number
is which?

I'm curious because it seems possible to mess up and set irq affinity
(for dual network adapters, for example) to the same physical processor.

Thanks,

John R.
ibiblio.org