Tuesday, January 31, 2023

Re: hw.ncpuonline

Janne Johansson <icepic.dz@gmail.com> wrote:

> Den ons 1 feb. 2023 kl 03:08 skrev Justin Muir <ve7utm@gmail.com>:
> > I've got an AMD A10 with 4 cores and only 2 are online. I'm not sure how to
> > enable the other 2.
> >
> > hw.ncpufound=4 btw
> > Any ideas out there?
>
> OpenBSD disables hyperthreading (or symmetric multithreading, smt), so
> if your "4-core" cpu is actually 2 real cores and 2 hyperthreads, then
> this sounds perfectly reasonable.
>
> For example, this box of mine (not the same cpu, but still), it looks like this:
>
> hw.ncpufound=8
> hw.smt=0
> hw.ncpuonline=4
>
> so I get the 4 real cores running out of possibly 8.


You can read up on the micro-architectural risks of the specific cpu you
have, and your usage pattern, and make your own decision. I have machines
where I enable it, but a safe default is the right choice for us to make.

No comments:

Post a Comment