[PATCH 00/14] Reduce preallocations for maple tree

[Liam R. Howlett]

Initial work on preallocations showed no regression in performance
during testing, but recently some users (both on [1] and off [android]
list) have reported that preallocating the worst-case number of nodes
has caused some slow down.  This patch set addresses the number of
allocations in a few ways.

During munmap() most munmap() operations will remove a single VMA, so
leverage the fact that the maple tree can place a single pointer at
range 0 - 0 without allocating.  This is done by changing the index in
the 'sidetree'.

Re-introduce the entry argument to mas_preallocate() so that a more
intelligent guess of the node count can be made.

Patches are in the following order:
0001-0002: Testing framework for benchmarking some operations
0003-0004: Reduction of maple node allocation in sidetree
0005:      Small cleanup of do_vmi_align_munmap()
0006-0013: mas_preallocate() calculation change
0014:      Change the vma iterator order

[1] https://lore.kernel.org/linux-mm/202305061457.ac15990c-yujie.liu@xxxxxxxxx/

Liam R. Howlett (14):
  maple_tree: Add benchmarking for mas_for_each
  maple_tree: Add benchmarking for mas_prev()
  mm: Move unmap_vmas() declaration to internal header
  mm: Change do_vmi_align_munmap() side tree index
  mm: Remove prev check from do_vmi_align_munmap()
  maple_tree: Introduce __mas_set_range()
  mm: Remove re-walk from mmap_region()
  maple_tree: Re-introduce entry to mas_preallocate() arguments
  mm: Use vma_iter_clear_gfp() in nommu
  mm: Set up vma iterator for vma_iter_prealloc() calls
  maple_tree: Move mas_wr_end_piv() below mas_wr_extend_null()
  maple_tree: Update mas_preallocate() testing
  maple_tree: Refine mas_preallocate() node calculations
  mm/mmap: Change vma iteration order in do_vmi_align_munmap()

 fs/exec.c                        |   1 +
 include/linux/maple_tree.h       |  23 ++++-
 include/linux/mm.h               |   4 -
 lib/maple_tree.c                 |  78 ++++++++++----
 lib/test_maple_tree.c            |  74 +++++++++++++
 mm/internal.h                    |  40 ++++++--
 mm/memory.c                      |  16 ++-
 mm/mmap.c                        | 171 ++++++++++++++++---------------
 mm/nommu.c                       |  45 ++++----
 tools/testing/radix-tree/maple.c |  59 ++++++-----
 10 files changed, 331 insertions(+), 180 deletions(-)

-- 
2.39.2