Re: [PATCH] mm/thp: expose deferred split folio memory usage in meminfo

[David Hildenbrand (Arm)]

On 7/17/26 08:30, Ye Liu wrote:
> From: Ye Liu <liuye@xxxxxxxxxx>
> 
> Folios on the deferred split list hold physical memory that is
> invisible in meminfo. When a THP becomes partially mapped, the
> unmapped pages are removed from AnonPages but remain physically
> allocated until the shrinker splits the folio. This creates a
> memory accounting gap where used memory cannot be attributed to
> any meminfo field.
> 
> Add NR_DEFERRED_SPLIT_PAGES to track the total memory consumed by
> folios currently on the deferred_split_lru, updated via
> mod_node_page_state() at all enqueue/dequeue points. The new field
> DeferredSplitPages is visible in /proc/meminfo, /proc/vmstat, and
> per-node /sys/devices/system/node/node*/meminfo.
> 

Oh no.

This is really exposing a current implementation detail where we have this
information easily available in a way that we will not be able to change that
implementation later.

-- 
Cheers,

David