Re: [RFC PATCH 02/12] khugepaged: Generalize alloc_charge_folio()

[Ryan Roberts]

On 20/12/2024 17:41, Christoph Lameter (Ampere) wrote:
> On Tue, 17 Dec 2024, Ryan Roberts wrote:
> 
>> We previously decided that all existing THP stats would continue to only count
>> PMD-sized THP for fear of breaking userspace in subtle ways, and instead would
>> introduce new mTHP stats that can count for each order. We already have
>> MTHP_STAT_ANON_FAULT_ALLOC and MTHP_STAT_ANON_FAULT_FALLBACK (amongst others) so
>> these new stats fit the pattern well, IMHO.
> 
> Could we move all the stats somewhere into sysfs where we can get them by
> page order? /proc/vmstat keeps getting new counters.

This is exactly what has been done already for mthp stats. They live at:

/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/stats/.

So there is a directory per size, and there is a file per stat.