On Sun, Apr 5, 2026 at 5:53 AM Muchun Song <[email protected]> wrote: > > Overview: > This patch series generalizes the HugeTLB Vmemmap Optimization (HVO) > into a generic vmemmap optimization framework that can be used by both > HugeTLB and DAX. > > Background: > Currently, the vmemmap optimization feature is highly coupled with > HugeTLB. However, DAX also has similar requirements for optimizing vmemmap > pages to save memory. The current implementation has separate vmemmap > optimization paths for HugeTLB and DAX, leading to duplicated logic, > complex initialization sequences, and architecture-specific flags. > > Implementation: > This series breaks down the optimization into a generic framework: > - Patch 1-6: Fix bugs related to sparse vmemmap initialization and DAX. > - Patch 7-13: Refactor the existing sparse vmemmap initialization. > - Patch 14-26: Decouple the vmemmap optimization from HugeTLB and > introduce generic optimization macros and functions. > - Patch 27-39: Switch HugeTLB and DAX to use the generic framework. > - Patch 40-49: Clean up the old HVO-specific code and simplify it. > > Benifit: > - When CONFIG_DEFERRED_STRUCT_PAGE_INIT is disabled, all struct pages > utilizing HVO (HugeTLB Vmemmap Optimization) skip initialization in > memmap_init, significantly accelerating boot times. > - All architectures supporting HVO benefit from the optimizations > provided by SPARSEMEM_VMEMMAP_PREINIT without requiring > architecture-specific adaptations. > - Device DAX struct page savings are further improved, saving an > additional 4KB of struct page memory for every 2MB huge page. > - Vmemmap tail pages used for Device DAX shared mappings are changed > from read-write to read-only, enhancing system security. > - HugeTLB and Device DAX now share a unified vmemmap optimization > framework, reducing long-term maintenance overhead. > > Testing: > - Verification: Compiled and tested on x86 architecture. > > > Chengkaitao (1): > mm: Convert vmemmap_p?d_populate() to static functions > > Muchun Song (48): > mm/sparse: fix vmemmap accounting imbalance on memory hotplug error > mm/sparse: add a @pgmap argument to memory deactivation paths > mm/sparse: fix vmemmap page accounting for HVOed DAX > mm/sparse: add a @pgmap parameter to arch vmemmap_populate() > mm/sparse: fix missing architecture-specific page table sync for HVO > DAX > mm/mm_init: fix uninitialized pageblock migratetype for ZONE_DEVICE > compound pages > mm/mm_init: use pageblock_migratetype_init_range() in > deferred_free_pages() > mm: panic on memory allocation failure in sparse_init_nid() > mm: move subsection_map_init() into sparse_init() > mm: defer sparse_init() until after zone initialization > mm: make set_pageblock_order() static > mm: integrate sparse_vmemmap_init_nid_late() into sparse_init_nid() > mm/cma: validate hugetlb CMA range by zone at reserve time > mm/hugetlb: free cross-zone bootmem gigantic pages after allocation > mm/hugetlb: initialize vmemmap optimization in early stage > mm: remove sparse_vmemmap_init_nid_late() > mm/mm_init: make __init_page_from_nid() static > mm/sparse-vmemmap: remove the VMEMMAP_POPULATE_PAGEREF flag > mm: rename vmemmap optimization macros to generic names > mm/sparse: drop power-of-2 size requirement for struct mem_section > mm/sparse: introduce compound page order to mem_section > mm/mm_init: skip initializing shared tail pages for compound pages > mm/sparse-vmemmap: initialize shared tail vmemmap page upon allocation > mm/sparse-vmemmap: support vmemmap-optimizable compound page > population > mm/hugetlb: use generic vmemmap optimization macros > mm: call memblocks_present() before HugeTLB initialization > mm/hugetlb: switch HugeTLB to use generic vmemmap optimization > mm: extract pfn_to_zone() helper > mm/sparse-vmemmap: remove unused SPARSEMEM_VMEMMAP_PREINIT feature > mm/hugetlb: remove HUGE_BOOTMEM_HVO flag and simplify pre-HVO logic > mm/sparse-vmemmap: consolidate shared tail page allocation > mm: introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION > mm/sparse-vmemmap: switch DAX to use generic vmemmap optimization > mm/sparse-vmemmap: introduce section zone to struct mem_section > powerpc/mm: use generic vmemmap_shared_tail_page() in compound vmemmap > mm/sparse-vmemmap: unify DAX and HugeTLB vmemmap optimization > mm/sparse-vmemmap: remap the shared tail pages as read-only > mm/sparse-vmemmap: remove unused ptpfn argument > mm/hugetlb_vmemmap: remove vmemmap_wrprotect_hvo() and related code > mm/sparse: simplify section_vmemmap_pages() > mm/sparse-vmemmap: introduce section_vmemmap_page_structs() > powerpc/mm: rely on generic vmemmap_can_optimize() to simplify code > mm/sparse-vmemmap: drop ARCH_WANT_OPTIMIZE_DAX_VMEMMAP and simplify > checks > mm/sparse-vmemmap: drop @pgmap parameter from vmemmap populate APIs > mm/sparse: replace pgmap with order and zone in sparse_add_section() > mm: redefine HVO as Hugepage Vmemmap Optimization > Documentation/mm: restructure vmemmap_dedup.rst to reflect generalized > HVO > mm: consolidate struct page power-of-2 size checks for HVO > > .../admin-guide/kernel-parameters.txt | 2 +- > Documentation/admin-guide/sysctl/vm.rst | 2 +- > Documentation/mm/vmemmap_dedup.rst | 218 ++-------- > arch/powerpc/Kconfig | 1 - > arch/powerpc/include/asm/book3s/64/radix.h | 12 - > arch/powerpc/mm/book3s64/radix_pgtable.c | 114 +---- > arch/powerpc/mm/init_64.c | 1 + > arch/riscv/Kconfig | 1 - > arch/x86/Kconfig | 2 - > fs/Kconfig | 6 +- > include/linux/hugetlb.h | 7 +- > include/linux/memory_hotplug.h | 2 +- > include/linux/mm.h | 50 +-- > include/linux/mm_types.h | 2 + > include/linux/mm_types_task.h | 4 + > include/linux/mmzone.h | 143 ++++--- > include/linux/page-flags.h | 31 +- > kernel/bounds.c | 2 + > mm/Kconfig | 20 +- > mm/bootmem_info.c | 5 +- > mm/cma.c | 3 +- > mm/hugetlb.c | 143 +++---- > mm/hugetlb_cma.c | 3 +- > mm/hugetlb_vmemmap.c | 237 +---------- > mm/hugetlb_vmemmap.h | 35 +- > mm/internal.h | 26 +- > mm/memory_hotplug.c | 15 +- > mm/mm_init.c | 138 +++--- > mm/sparse-vmemmap.c | 392 +++++------------- > mm/sparse.c | 85 ++-- > mm/util.c | 2 +- > scripts/gdb/linux/mm.py | 6 +- > 32 files changed, 513 insertions(+), 1197 deletions(-) > > -- > 2.20.1
Thanks very much for doing this. This cleans up a lot of stuff. I did want to do some of this when I did the pre-HVO code, but I ended up not doing it to prevent perfect being the enemy of good. I haven't looked at all the individual patches yet, but overall this looks great to me. - Frank
