[PATCH 0/6] lib/find_bit: fast path for small bitmaps

From: Yury Norov
Date: Wed Jan 20 2021 - 20:44:12 EST

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

find_next_*_bit() lacks this functionality; despite users will
benefit from it a lot. One important example is cpumask subsystem if
NR_CPUS <= BITS_PER_LONG. In the very best case, the compiler may replace
a find_*_bit() call for such a bitmap with a single ffs or ffz instruction.

Yury Norov (6):
arch: rearrahge headers inclusion order in asm/bitops for m68k and sh
bitmap: move some macros from linux/bitmap.h to linux/bitops.h
tools: sync bitops macro definitions with the kernel
lib: inline _find_next_bit() wrappers
lib: add fast path for find_next_*_bit()
lib: add fast path for find_first_*_bit() and find_last_bit()

arch/m68k/include/asm/bitops.h | 4 +-
arch/sh/include/asm/bitops.h | 3 +-
include/asm-generic/bitops/find.h | 123 +++++++++++++++++++++++++++---
include/asm-generic/bitops/le.h | 45 ++++++++++-
include/linux/bitmap.h | 11 ---
include/linux/bitops.h | 23 +++---
lib/find_bit.c | 68 ++---------------
tools/include/linux/bitmap.h | 11 ---
tools/include/linux/bitops.h | 11 +++
9 files changed, 188 insertions(+), 111 deletions(-)