[v4,00/13] lib/find_bit: fast path for small bitmaps

Message

Yury Norov March 16, 2021, 1:54 a.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: - move le.h header together with find.h for m68 and sh;
    - preserve small_const_nbits() macro;
    - drop FAST_PATH config option as this series doesn't increase .text,
      instead, it compacts it;
    - add Andy and Rasmus as reviewers of BITMAP API.

Yury Norov (13):
  tools: disable -Wno-type-limits
  tools: bitmap: sync function declarations with the kernel
  arch: rearrange headers inclusion order in asm/bitops for m68k and sh
  lib: introduce BITS_{FIRST,LAST} macro
  tools: sync BITS_MASK macros with the kernel
  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       |   9 ++
 include/linux/bitmap.h                  |  30 +++----
 include/linux/bitops.h                  |  12 ---
 include/linux/bits.h                    |   6 ++
 include/linux/cpumask.h                 |   8 +-
 include/linux/netdev_features.h         |   2 +-
 include/linux/nodemask.h                |   2 +-
 lib/bitmap.c                            |  26 +++---
 lib/find_bit.c                          |  72 +++-------------
 lib/genalloc.c                          |   8 +-
 tools/include/asm-generic/bitops/find.h |  85 +++++++++++++++++--
 tools/include/asm-generic/bitsperlong.h |   3 +
 tools/include/linux/bitmap.h            |  31 +++----
 tools/include/linux/bits.h              |   6 ++
 tools/lib/bitmap.c                      |  10 +--
 tools/lib/find_bit.c                    |  56 +++++-------
 tools/scripts/Makefile.include          |   1 +
 tools/testing/radix-tree/bitmap.c       |   4 +-
 23 files changed, 340 insertions(+), 204 deletions(-)