Re: [PATCH] x86/cacheinfo: Define per-CPU num_cache_leaves

[Dave Hansen]

On 3/14/23 16:16, Ricardo Neri wrote:
> -static unsigned short num_cache_leaves;
> +static DEFINE_PER_CPU(unsigned short, num_cache_leaves);
> +
> +static inline unsigned short get_num_cache_leaves(unsigned int cpu)
> +{
> +	return per_cpu(num_cache_leaves, cpu);
> +}

I know it's in generic code, but we do already have this:

static DEFINE_PER_CPU(struct cpu_cacheinfo, ci_cpu_cacheinfo);

which has a num_leaves in it:

struct cpu_cacheinfo {
        struct cacheinfo *info_list;
        unsigned int num_levels;
        unsigned int num_leaves;
        bool cpu_map_populated;
};

That's currently _populated_ from the arch code that you are modifying.
Do we really need this data stored identically in two different per-cpu
locations?

I'd also love to hear some more background on "Intel Meteor Lake" and
_why_ it has an asymmetric cache topology.