[PATCH v6 00/12] lib/find_bit: fast path for small bitmaps

Yury Norov
2021-04-01T00:33:01Z

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.

v6 is mostly a resend. The only change comparing to v5 is a fix of
small_const_nbits() synchronization patch.

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/20210316015424.1999082-1-yury.norov@gmail.com/
v5: https://lore.kernel.org/linux-arch/20210321215457.588554-1-yury.norov@gmail.com/T/
v6: - sync small_const_nbits() properly (patch 6).
- Rasmus' ack added.

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(-)

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2.25.1