Eric Lee / smarc-fsl-linux-kernel

12 Jan, 2010

1 commit

  • 7dd65feb6   lib: add support for LZO-compressed kernels ... Browse Code ยป

    This patch series adds generic support for creating and extracting
    LZO-compressed kernel images, as well as support for using such images on
    the x86 and ARM architectures, and support for creating and using
    LZO-compressed initrd and initramfs images.

    Russell King said:

    : Testing on a Cortex A9 model:
    : - lzo decompressor is 65% of the time gzip takes to decompress a kernel
    : - lzo kernel is 9% larger than a gzip kernel
    :
    : which I'm happy to say confirms your figures when comparing the two.
    :
    : However, when comparing your new gzip code to the old gzip code:
    : - new is 99% of the size of the old code
    : - new takes 42% of the time to decompress than the old code
    :
    : What this means is that for a proper comparison, the results get even better:
    : - lzo is 7.5% larger than the old gzip'd kernel image
    : - lzo takes 28% of the time that the old gzip code took
    :
    : So the expense seems definitely worth the effort. The only reason I
    : can think of ever using gzip would be if you needed the additional
    : compression (eg, because you have limited flash to store the image.)
    :
    : I would argue that the default for ARM should therefore be LZO.

    This patch:

    The lzo compressor is worse than gzip at compression, but faster at
    extraction. Here are some figures for an ARM board I'm working on:

    Uncompressed size: 3.24Mo
    gzip 1.61Mo 0.72s
    lzo 1.75Mo 0.48s

    So for a compression ratio that is still relatively close to gzip, it's
    much faster to extract, at least in that case.

    This part contains:
    - Makefile routine to support lzo compression
    - Fixes to the existing lzo compressor so that it can be used in
    compressed kernels
    - wrapper around the existing lzo1x_decompress, as it only extracts one
    block at a time, while we need to extract a whole file here
    - config dialog for kernel compression

    [akpm@linux-foundation.org: coding-style fixes]
    [akpm@linux-foundation.org: cleanup]
    Signed-off-by: Albin Tonnerre
    Tested-by: Wu Zhangjin
    Acked-by: "H. Peter Anvin"
    Cc: Ingo Molnar
    Cc: Thomas Gleixner
    Tested-by: Russell King
    Acked-by: Russell King
    Cc: Ralf Baechle
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Albin Tonnerre