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

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Date:   Fri, 29 Jan 2021 12:45:22 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-arch@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, Arnd Bergmann <arnd@...db.de>,
        Dennis Zhou <dennis@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        David Sterba <dsterba@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Stefano Brivio <sbrivio@...hat.com>,
        "Ma, Jianpeng" <jianpeng.ma@...el.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: [PATCH 0/6] lib/find_bit: fast path for small bitmaps

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_*_bit() API lacks this functionality; despite users will benefit from it
a lot. One important example is cpumask subsystem, when 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.

Tools is synchronized with new implementation where needed.

Yury Norov (6):
  arch: rearrange headers inclusion order in asm/bitops for m68k and sh
  lib: inttroduce BITS_{FIRST,LAST}() macro
  bits_per_long.h: introduce SMALL_CONST() macro
  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       | 108 +++++++++++++++++++++---
 include/asm-generic/bitops/le.h         |  38 ++++++++-
 include/asm-generic/bitsperlong.h       |   2 +
 include/linux/bitmap.h                  |  60 ++++++-------
 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 |   2 +
 tools/include/linux/bitmap.h            |  39 +++------
 tools/include/linux/bits.h              |   6 ++
 tools/lib/bitmap.c                      |   6 +-
 tools/lib/find_bit.c                    |  56 +++++-------
 tools/testing/radix-tree/bitmap.c       |   4 +-
 21 files changed, 330 insertions(+), 219 deletions(-)

-- 
2.25.1