KernelTrap: HyperThreading-Aware Scheduler

“Ingo Molnar, author of the O(1) scheduler and the original
preemptive kernel patch, has provided a patch to make the O(1)
scheduler fully aware of symmetric multithreading. Ingo

‘Symmetric multithreading (hyperthreading) is an
interesting new concept that IMO deserves full scheduler support.
Physical CPUs can have multiple (typically 2) logical CPUs
embedded, and can run multiple tasks ‘in parallel’ by utilizing
fast hardware-based context-switching between the two register sets
upon things like cache-misses or special instructions. To the OSs
the logical CPUs are almost undistinguishable from physical CPUs.
In fact the current scheduler treats each logical CPU as a separate
physical CPU – which works but does not maximize multiprocessing
performance on SMT/HT boxes…’


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