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Historically, these entries always > correspond to the smallest size we could encounter, not any current > usage of transparent huge pages or larger sizes used by the MMU. > > Ever since we added THP support many, many years ago, these entries > would keep reporting the smallest (fallback) granularity in a VMA. > > For this reason, they default to PAGE_SIZE for all VMAs except for > VMAs where we have the guarantee that the system and the MMU will > always use larger page sizes. hugetlb, for example, exposes a custom > vm_ops->pagesize callback to handle that. Similarly, dax/device > exposes a custom vm_ops->pagesize callback and provides similar > guarantees. > > Let's clarify the historical meaning of KernelPageSize / MMUPageSize, > and point at "AnonHugePages", "ShmemPmdMapped" and "FilePmdMapped" > regarding PMD entries. > > While at it, document "FilePmdMapped", clarify what the "AnonHugePages" > and "ShmemPmdMapped" entries really mean, and make it clear that there > are no other entries for other THP/folio sizes or mappings. > > Link: https://lore.kernel.org/all/20260225232708.87833-1-ak@linux.intel.com/ > Cc: Andrew Morton > Cc: Lorenzo Stoakes > Cc: Zi Yan > Cc: Baolin Wang > Cc: Liam R. Howlett > Cc: Nico Pache > Cc: Ryan Roberts Cc: Dev Jain > Cc: Barry Song > Cc: Lance Yang > Cc: Jonathan Corbet > Cc: Shuah Khan > Cc: Usama Arif > Cc: Andi Kleen > Signed-off-by: David Hildenbrand (Arm) > --- > Documentation/filesystems/proc.rst | 37 ++++++++++++++++++++++-------- > 1 file changed, 27 insertions(+), 10 deletions(-) > LGTM. Reviewed-by: Zi Yan Best Regards, Yan, Zi