Hi,
Section-based vmemmap optimization is implemented in sparse-vmemmap.c,
while folio-based optimization currently lives in hugetlb_vmemmap.c.
The latter is tightly coupled to HugeTLB-specific state even though the
underlying page-table remapping operates on one folio at a time.
To make these interfaces easier to maintain, the folio-based remapping
mechanics first need a boundary that is independent of HugeTLB-specific
state and raw address ranges. This will allow the mechanics to be moved
into a common vmemmap optimization layer alongside the section-based
interface.
This series establishes that boundary through three folio-oriented
operations, each with a distinct role:
- vmemmap_optimize_folio() optimizes the vmemmap backing of a folio;
- vmemmap_restore_folio() restores the vmemmap backing of a folio; and
- vmemmap_pteify_folio() converts the vmemmap backing of a folio to
PTE mappings.
Together, these operations encapsulate the address-range calculation and
remapping mechanics for a folio. HugeTLB wrappers retain policy decisions
such as eligibility, optimized state, batching and TLB flush handling.
Patches 1-8 generalize the underlying vmemmap remapping infrastructure by
removing HugeTLB-specific assumptions and simplifying remap control and
resource handling. Patches 9-12 then establish folio-oriented operations
for optimization, restoration and PTE conversion.
The implementation remains in hugetlb_vmemmap.c for now. A follow-up can
move the folio-based operations into the common vmemmap optimization layer
once the interface boundary is in place.
v2:
- Rebase onto mm/mm-new at d42dfde37af7
- Rename the unified TLB flag to VMEMMAP_DEFER_TLB_FLUSH and clarify that
it defers only safely batchable flushes (suggested by Qi Zheng)
- Update the vmemmap page-list documentation to describe its input/output
contract (suggested by Lance Yang and Qi Zheng)
- Use page_address() instead of page_to_virt() when copying a vmemmap
replacement page
- Collect Reviewed-by tags from Lance Yang and Qi Zheng
v1: https://lore.kernel.org/20261020115306.813483-1-songmuchun@bytedance.com/ (local)
Muchun Song (12):
mm: hugetlb_vmemmap: remove HugeTLB-specific vmemmap optimization
macros
mm: hugetlb_vmemmap: unify VMEMMAP_{SPLIT,REMAP}_NO_TLB_FLUSH
mm: hugetlb_vmemmap: simplify vmemmap head page handling
mm: hugetlb_vmemmap: generalize vmemmap page allocation
mm: hugetlb_vmemmap: unify writable vmemmap page preparation
mm: hugetlb_vmemmap: rename vmemmap_remap_pte() to
vmemmap_optimize_pte()
mm: hugetlb_vmemmap: simplify shared tail page handling
mm: hugetlb_vmemmap: move alloc_vmemmap_page_list() next to its free
helper
mm: hugetlb_vmemmap: make vmemmap optimization folio-oriented
mm: hugetlb_vmemmap: make vmemmap restoration folio-oriented
mm: hugetlb_vmemmap: unify vmemmap range restoration
mm: hugetlb_vmemmap: make vmemmap PTE conversion folio-oriented
include/linux/vmemmap-optimization.h | 10 +-
mm/hugetlb.c | 4 +-
mm/hugetlb_vmemmap.c | 373 ++++++++++++---------------
mm/hugetlb_vmemmap.h | 10 +-
mm/mm_init.c | 6 +-
mm/sparse-vmemmap.c | 7 +-
6 files changed, 182 insertions(+), 228 deletions(-)
base-commit: d42dfde37af766d1c272467352c0a56d3169ee58
--
2.54.0