Comment by xyzzyz

My understanding (let me know if I'm wrong) is that Hyperthread aware OSes (which is like what, everything since WinXP/Linux kernel 2.4?) will schedule lower priority tasks to the logical cores and higher priority tasks to the real cores.

You understand it wrong, even though you’re somewhat correct as to what scheduler actually does. In a single physical core, both logical processors are equivalent, and neither one has higher internal priority over the other. The hyper threading aware scheduler will take extra care in scheduling in this scenario, but not in a sense you describe — if you have 2 physical cores, and thus 4 logical processors, and 2 CPU intensive tasks, the scheduler might attempt to schedule them on different physical cores, instead of stuffing them on the two logical processors of a single physical core. It’s not because one logical core is better than the other, but rather it’s because the two tasks would simply compete with each other in a way they wouldn’t if they were on physically separate cores.