[v5,00/12] lib/find_bit: fast path for small bitmaps

Message

Yury Norov March 21, 2021, 9:54 p.m. UTC

Bitmap operations are much simpler and faster in case of small bitmaps
which fit into a single word. In linux/bitmap.c we have a machinery that
allows compiler to replace actual function call with a few instructions
if bitmaps passed into the function are small and their size is known at
compile time.

find_*_bit() API lacks this functionality; but users will benefit from it
a lot. One important example is cpumask subsystem when
NR_CPUS <= BITS_PER_LONG.

v1: https://www.spinics.net/lists/kernel/msg3804727.html
v2: https://www.spinics.net/lists/linux-m68k/msg16945.html
v3: https://www.spinics.net/lists/kernel/msg3837020.html
v4: https://patchwork.kernel.org/project/linux-sh/cover/[e-mail]/
v5: - drop BITS_{FIRST,LAST} patch;
    - minor changes.

Yury Norov (12):
  tools: disable -Wno-type-limits
  tools: bitmap: sync function declarations with the kernel
  tools: sync BITMAP_LAST_WORD_MASK() macro with the kernel
  arch: rearrange headers inclusion order in asm/bitops for m68k and sh
  lib: extend the scope of small_const_nbits() macro
  tools: sync small_const_nbits() macro with the kernel
  lib: inline _find_next_bit() wrappers
  tools: sync find_next_bit implementation
  lib: add fast path for find_next_*_bit()
  lib: add fast path for find_first_*_bit() and find_last_bit()
  tools: sync lib/find_bit implementation
  MAINTAINERS: Add entry for the bitmap API

 MAINTAINERS                             |  16 ++++
 arch/m68k/include/asm/bitops.h          |   6 +-
 arch/sh/include/asm/bitops.h            |   5 +-
 include/asm-generic/bitops/find.h       | 108 +++++++++++++++++++++---
 include/asm-generic/bitops/le.h         |  38 ++++++++-
 include/asm-generic/bitsperlong.h       |  12 +++
 include/linux/bitmap.h                  |   8 --
 include/linux/bitops.h                  |  12 ---
 lib/find_bit.c                          |  68 ++-------------
 tools/include/asm-generic/bitops/find.h |  85 +++++++++++++++++--
 tools/include/asm-generic/bitsperlong.h |   3 +
 tools/include/linux/bitmap.h            |  18 ++--
 tools/lib/bitmap.c                      |   4 +-
 tools/lib/find_bit.c                    |  56 +++++-------
 tools/scripts/Makefile.include          |   1 +
 15 files changed, 284 insertions(+), 156 deletions(-)