• Kyungsik Lee's avatar
    decompressor: add LZ4 decompressor module · cffb78b0
    Kyungsik Lee authored
    Add support for LZ4 decompression in the Linux Kernel.  LZ4 Decompression
    APIs for kernel are based on LZ4 implementation by Yann Collet.
    Benchmark Results(PATCH v3)
    Compiler: Linaro ARM gcc 4.6.2
    1. ARMv7, 1.5GHz based board
       Kernel: linux 3.4
       Uncompressed Kernel Size: 14MB
            Compressed Size  Decompression Speed
       LZO  6.7MB            20.1MB/s, 25.2MB/s(UA)
       LZ4  7.3MB            29.1MB/s, 45.6MB/s(UA)
    2. ARMv7, 1.7GHz based board
       Kernel: linux 3.7
       Uncompressed Kernel Size: 14MB
            Compressed Size  Decompression Speed
       LZO  6.0MB            34.1MB/s, 52.2MB/s(UA)
       LZ4  6.5MB            86.7MB/s
    - UA: Unaligned memory Access support
    - Latest patch set for LZO applied
    This patch set is for adding support for LZ4-compressed Kernel.  LZ4 is a
    very fast lossless compression algorithm and it also features an extremely
    fast decoder [1].
    But we have five of decompressors already and one question which does
    arise, however, is that of where do we stop adding new ones?  This issue
    had been discussed and came to the conclusion [2].
    Russell King said that we should have:
     - one decompressor which is the fastest
     - one decompressor for the highest compression ratio
     - one popular decompressor (eg conventional gzip)
    If we have a replacement one for one of these, then it should do exactly
    that: replace it.
    The benchmark shows that an 8% increase in image size vs a 66% increase
    in decompression speed compared to LZO(which has been known as the
    fastest decompressor in the Kernel).  Therefore the "fast but may not be
    small" compression title has clearly been taken by LZ4 [3].
    [1] http://code.google.com/p/lz4/
    [2] http://thread.gmane.org/gmane.linux.kbuild.devel/9157
    [3] http://thread.gmane.org/gmane.linux.kbuild.devel/9347
    LZ4 homepage: http://fastcompression.blogspot.com/p/lz4.html
    LZ4 source repository: http://code.google.com/p/lz4/Signed-off-by: default avatarKyungsik Lee <kyungsik.lee@lge.com>
    Signed-off-by: default avatarYann Collet <yann.collet.73@gmail.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Russell King <rmk@arm.linux.org.uk>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Florian Fainelli <florian@openwrt.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
lz4defs.h 2.03 KB