On Fri, Oct 08, 2021 at 04:22:27PM +0100, Valentin Schneider wrote:

So x86 has it default yes, and a lot of others (e.g. arm64) have it default
no.

IMO you don't gain much by disabling them. SCHED_MC and SCHED_CLUSTER only
control the presence of a sched_domain_topology_level - if it's useless it
gets degenerated at domain build time. Some valid reasons for not using
them is if the architecture defines its own topology table (e.g. powerpc
has CACHE and MC levels which are not gated behind any CONFIG).

SCHED_SMT has an impact on code generated in sched/core.c, but that is also
gated by a static key.

So I'd say having them default yes is sensible. I'd even say we should
change the "If unsure say N here." to "Y".

Right, so I tend to agree (and also that we should fix that Kconfig help
text). But it would be very nice to have feedback from the affected arch
maintainers.