[mehrdadn]

Do you get the exact same performance characteristics by ignoring the extra virtual cores as you would have gotten if you could actually disable hyperthreading in the CPU via the firmware setup? Or does it result in some CPU resources becoming unusable that would otherwise be usable if HT were truly disabled?

[notaplumber]

Operating systems can't disable HT/SMT in the same way as the BIOS/firmware can, but presumably it will be fine if the kernel only schedules the idle process on HT "cores", it will spend much of, or all its time in a lower power state (MWAIT? C-states?), presumably the CPU is smart enough to handle that.

[mehrdadn]

I guess figuring out whether it's only "presumably" or actually "actually" was why I asked the question in the first place.

[notaplumber]

Hmm. This thread on the OpenBSD lists suggests it may be adequate, of course disabling in the BIOS is certainly a better option, if you can.

https://marc.info/?t=152938773300027&r=1&w=2

[blattimwind]

At least in previous generations some resources where statically shared, but most were dynamically shared.