Re: [RFC PATCH v2] Introduce Hierarchical Per-CPU Counters

[Christoph Lameter (Ampere)]

On Tue, 8 Apr 2025, Paul E. McKenney wrote:

> RCU handles this by iterating from zero to nr_cpu_ids, which is set during
> early boot.  It also builds its tree-shaped data structures during early
> boot based on nr_cpu_ids.

nr_cpu_ids is better but there are funky things like the default bios of a
major server vendor indicating 256 or so possible cpus although only 2
were installed. Thus nr_cpu_id is 256. Presumably some hardware
configurations can support onlining 256 cpus....