Sanity check, CoreOS supports multi-socket servers right? CPU's showing offline

Ask Fedora
1

HTOP shows the following…

2f2959b4173488a93ec47431af52ef76aabb5c8d.png
2f2959b4173488a93ec47431af52ef76aabb5c8d.png3745×480 33.7 KB

But I see this across the board in portainer, grafana, etc. Everything only sees half my logical cores, it seems the second socket isn’t being used.

I haven’t migrated my heavier software over yet, so load is light. Is this some kind of powersaving feature maybe? Does it spin up the CPU if/when it really is needed? Or did I miss a configuration step somewhere?

EDIT also handy to see (it does recognize the socket is there)…

cb759087b9bb7799178f89983a00c9825fe49561.png
cb759087b9bb7799178f89983a00c9825fe49561.png1755×825 33.1 KB

Maybe a command other than chcpu to manage this (offline/online the cpu)?

2

Default installations of Fedora CoreOS boot with the mitigations=auto,nosmt kernel argument, which instructs the kernel to disable SMT (hyperthreading) on systems where this is needed to mitigate CPU security vulnerabilities. If you only run trusted workloads, you can remove this kernel argument, which will cause the kernel to mitigate vulnerabilities as far as possible without disabling SMT. Example Butane config:

variant: fcos
version: 1.4.0
kernel_arguments:
  should_not_exist:
    - mitigations=auto,nosmt
3

Ah, that makes sense. I wasn’t seeing the whole CPU offline, just hyperthreading for both offline. Thanks!

Alternatively to your butane config you can use rpm-ostree kargs --editor to pull up the kernel params in a text editor (vi/vim) and remove the mitigations=auto,nosmt entry (which was the first entry in my kernel argument list).

Thanks again!