Eric Lee / smarc-fsl-linux-kernel

17 Apr, 2015

1 commit

  • 2c57a0e23   lib: find_*_bit reimplementation ... Browse Code »

    This patchset does rework to find_bit function family to achieve better
    performance, and decrease size of text. All rework is done in patch 1.
    Patches 2 and 3 are about code moving and renaming.

    It was boot-tested on x86_64 and MIPS (big-endian) machines.
    Performance tests were ran on userspace with code like this:

    /* addr[] is filled from /dev/urandom */
    start = clock();
    while (ret < nbits)
    ret = find_next_bit(addr, nbits, ret + 1);

    end = clock();
    printf("%ld\t", (unsigned long) end - start);

    On Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz measurements are: (for
    find_next_bit, nbits is 8M, for find_first_bit - 80K)

    find_next_bit: find_first_bit:
    new current new current
    26932 43151 14777 14925
    26947 43182 14521 15423
    26507 43824 15053 14705
    27329 43759 14473 14777
    26895 43367 14847 15023
    26990 43693 15103 15163
    26775 43299 15067 15232
    27282 42752 14544 15121
    27504 43088 14644 14858
    26761 43856 14699 15193
    26692 43075 14781 14681
    27137 42969 14451 15061
    ... ...

    find_next_bit performance gain is 35-40%;
    find_first_bit - no measurable difference.

    On ARM machine, there is arch-specific implementation for find_bit.

    Thanks a lot to George Spelvin and Rasmus Villemoes for hints and
    helpful discussions.

    This patch (of 3):

    New implementations takes less space in source file (see diffstat) and in
    object. For me it's 710 vs 453 bytes of text. It also shows better
    performance.

    find_last_bit description fixed due to obvious typo.

    [akpm@linux-foundation.org: include linux/bitmap.h, per Rasmus]
    Signed-off-by: Yury Norov
    Reviewed-by: Rasmus Villemoes
    Reviewed-by: George Spelvin
    Cc: Alexey Klimov
    Cc: David S. Miller
    Cc: Daniel Borkmann
    Cc: Hannes Frederic Sowa
    Cc: Lai Jiangshan
    Cc: Mark Salter
    Cc: AKASHI Takahiro
    Cc: Thomas Graf
    Cc: Valentin Rothberg
    Cc: Chris Wilson
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Yury Norov
     

08 Mar, 2012

1 commit

27 May, 2011

1 commit

  • 19de85ef5   bitops: add #ifndef for each of find bitops ... Browse Code »

    The style that we normally use in asm-generic is to test the macro itself
    for existence, so in asm-generic, do:

    #ifndef find_next_zero_bit_le
    extern unsigned long find_next_zero_bit_le(const void *addr,
    unsigned long size, unsigned long offset);
    #endif

    and in the architectures, write

    static inline unsigned long find_next_zero_bit_le(const void *addr,
    unsigned long size, unsigned long offset)
    #define find_next_zero_bit_le find_next_zero_bit_le

    This adds the #ifndef for each of the find bitops in the generic header
    and source files.

    Suggested-by: Arnd Bergmann
    Signed-off-by: Akinobu Mita
    Acked-by: Russell King
    Cc: Martin Schwidefsky
    Cc: Heiko Carstens
    Cc: Greg Ungerer
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Akinobu Mita
     

01 Jan, 2009

1 commit