[v2,00/34] Split ptdesc from struct page

Message

Vishal Moola May 1, 2023, 7:27 p.m. UTC

The MM subsystem is trying to shrink struct page. This patchset
introduces a memory descriptor for page table tracking - struct ptdesc.

This patchset introduces ptdesc, splits ptdesc from struct page, and
converts many callers of page table constructor/destructors to use ptdescs.

Ptdesc is a foundation to further standardize page tables, and eventually
allow for dynamic allocation of page tables independent of struct page.
However, the use of pages for page table tracking is quite deeply
ingrained and varied across archictectures, so there is still a lot of
work to be done before that can happen.

This is rebased on next-20230428.

v2:
  Fix a lot of compiler warning/errors
  Moved definition of ptdesc to outside CONFIG_MMU
  Revert commit 7e25de77bc5ea which had gmap use pmd_pgtable_page()
  Allow functions to preserve const-ness where applicable
  Define folio equivalents for PAGE_TYPE_OPS page functions

Vishal Moola (Oracle) (34):
  mm: Add PAGE_TYPE_OP folio functions
  s390: Use _pt_s390_gaddr for gmap address tracking
  s390: Use pt_frag_refcount for pagetables
  pgtable: Create struct ptdesc
  mm: add utility functions for ptdesc
  mm: Convert pmd_pgtable_page() to pmd_ptdesc()
  mm: Convert ptlock_alloc() to use ptdescs
  mm: Convert ptlock_ptr() to use ptdescs
  mm: Convert pmd_ptlock_init() to use ptdescs
  mm: Convert ptlock_init() to use ptdescs
  mm: Convert pmd_ptlock_free() to use ptdescs
  mm: Convert ptlock_free() to use ptdescs
  mm: Create ptdesc equivalents for pgtable_{pte,pmd}_page_{ctor,dtor}
  powerpc: Convert various functions to use ptdescs
  x86: Convert various functions to use ptdescs
  s390: Convert various gmap functions to use ptdescs
  s390: Convert various pgalloc functions to use ptdescs
  mm: Remove page table members from struct page
  pgalloc: Convert various functions to use ptdescs
  arm: Convert various functions to use ptdescs
  arm64: Convert various functions to use ptdescs
  csky: Convert __pte_free_tlb() to use ptdescs
  hexagon: Convert __pte_free_tlb() to use ptdescs
  loongarch: Convert various functions to use ptdescs
  m68k: Convert various functions to use ptdescs
  mips: Convert various functions to use ptdescs
  nios2: Convert __pte_free_tlb() to use ptdescs
  openrisc: Convert __pte_free_tlb() to use ptdescs
  riscv: Convert alloc_{pmd, pte}_late() to use ptdescs
  sh: Convert pte_free_tlb() to use ptdescs
  sparc64: Convert various functions to use ptdescs
  sparc: Convert pgtable_pte_page_{ctor, dtor}() to ptdesc equivalents
  um: Convert {pmd, pte}_free_tlb() to use ptdescs
  mm: Remove pgtable_{pmd, pte}_page_{ctor, dtor}() wrappers

 Documentation/mm/split_page_table_lock.rst    |  12 +-
 .../zh_CN/mm/split_page_table_lock.rst        |  14 +-
 arch/arm/include/asm/tlb.h                    |  12 +-
 arch/arm/mm/mmu.c                             |   6 +-
 arch/arm64/include/asm/tlb.h                  |  14 +-
 arch/arm64/mm/mmu.c                           |   7 +-
 arch/csky/include/asm/pgalloc.h               |   4 +-
 arch/hexagon/include/asm/pgalloc.h            |   8 +-
 arch/loongarch/include/asm/pgalloc.h          |  27 ++-
 arch/loongarch/mm/pgtable.c                   |   7 +-
 arch/m68k/include/asm/mcf_pgalloc.h           |  41 ++--
 arch/m68k/include/asm/sun3_pgalloc.h          |   8 +-
 arch/m68k/mm/motorola.c                       |   4 +-
 arch/mips/include/asm/pgalloc.h               |  31 +--
 arch/mips/mm/pgtable.c                        |   7 +-
 arch/nios2/include/asm/pgalloc.h              |   8 +-
 arch/openrisc/include/asm/pgalloc.h           |   8 +-
 arch/powerpc/mm/book3s64/mmu_context.c        |  10 +-
 arch/powerpc/mm/book3s64/pgtable.c            |  32 +--
 arch/powerpc/mm/pgtable-frag.c                |  46 ++--
 arch/riscv/include/asm/pgalloc.h              |   8 +-
 arch/riscv/mm/init.c                          |  16 +-
 arch/s390/include/asm/pgalloc.h               |   4 +-
 arch/s390/include/asm/tlb.h                   |   4 +-
 arch/s390/mm/gmap.c                           | 222 +++++++++++-------
 arch/s390/mm/pgalloc.c                        | 126 +++++-----
 arch/sh/include/asm/pgalloc.h                 |   9 +-
 arch/sparc/mm/init_64.c                       |  17 +-
 arch/sparc/mm/srmmu.c                         |   5 +-
 arch/um/include/asm/pgalloc.h                 |  18 +-
 arch/x86/mm/pgtable.c                         |  46 ++--
 arch/x86/xen/mmu_pv.c                         |   2 +-
 include/asm-generic/pgalloc.h                 |  62 +++--
 include/asm-generic/tlb.h                     |  11 +
 include/linux/mm.h                            | 138 +++++++----
 include/linux/mm_types.h                      |  14 --
 include/linux/page-flags.h                    |  20 +-
 include/linux/pgtable.h                       |  61 +++++
 mm/memory.c                                   |   8 +-
 39 files changed, 648 insertions(+), 449 deletions(-)

Comments

Jason Gunthorpe May 18, 2023, 12:12 p.m. UTC | #1

On Mon, May 01, 2023 at 12:27:55PM -0700, Vishal Moola (Oracle) wrote:
> The MM subsystem is trying to shrink struct page. This patchset
> introduces a memory descriptor for page table tracking - struct ptdesc.
> 
> This patchset introduces ptdesc, splits ptdesc from struct page, and
> converts many callers of page table constructor/destructors to use ptdescs.

Lightly related food for future thought - based on some discussions at
LSF/MM it would be really nice if an end result of this was that a
rcu_head was always available in the ptdesc so we don't need to
allocate memory to free a page table.

Jason