[RFC 0/2] mm: thp: split time allocation of page table for THPs

[Usama Arif <usama.arif@linux.dev>]

This is an RFC patch to allocate the PTE page table at split time only
and not do pre-deposit for THPs as suggested by David [1].
The core patch is the first one. The second one is not needed and its
just vmstat counters I used to show that split doesn't fail. Its going to be
0 all the time and won't include it in future revisions.

It would have been ideal if all pre-deposit code was removed but its not
possible due to PowerPC. The rationale and further details are covered
in the commit message of the first patch, including why the patch is safe.

[1] https://lore.kernel.org/all/ee5bd77f-87ad-4640-a974-304b488e4c64@kernel.org/
 
Usama Arif (2):
  mm: thp: allocate PTE page tables lazily at split time
  mm: thp: add THP_SPLIT_PMD_PTE_ALLOC_FAILED counter

 include/linux/huge_mm.h       |   4 +-
 include/linux/vm_event_item.h |   1 +
 mm/huge_memory.c              | 145 ++++++++++++++++++++++++----------
 mm/khugepaged.c               |   7 +-
 mm/migrate_device.c           |  15 ++--
 mm/rmap.c                     |  42 +++++++++-
 mm/vmstat.c                   |   1 +
 7 files changed, 162 insertions(+), 53 deletions(-)

-- 
2.47.3