linux-kernel - [RESEND PATCH v2 0/6] lib/find_bit: fast path for small bitmaps

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Message-Id: <20210130191719.7085-1-yury.norov@gmail.com>
Date:   Sat, 30 Jan 2021 11:17:11 -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>,
        Joe Perches <joe@...ches.com>
Subject: [RESEND PATCH v2 0/6] lib/find_bit: fast path for small bitmaps

Bitmap operations are much simpler and faster in case of small bitmaps
which 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 are small and their 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.

v1: https://www.spinics.net/lists/kernel/msg3804727.html
v2: - employ GENMASK() for bitmaps;
    - unify find_bit inliners in;
    - address comments to v1;



Yury Norov (8):
  tools: disable -Wno-type-limits
  tools: bitmap: sync function declarations with linux kernel
  arch: rearrange headers inclusion order in asm/bitops for m68k and sh
  lib: introduce BITS_{FIRST,LAST} macro
  bitsperlong.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            |  47 ++++-------
 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 +-
 22 files changed, 337 insertions(+), 225 deletions(-)

-- 
2.25.1