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    SubjectRe: [PATCH 3/5] Add support for LZO-compressed kernels
    On Wed, Jul 22, 2009 at 03:28:09PM +0000, wrote :
    > On Jul 22, 2009 9:01am, Albin Tonnerre <>
    > wrote:
    > > This is the first part of the lzo 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.
    > Is that "time to run the extraction algorithm", or "time to read in image from
    > media and extract"? I think the time to read from the media would tend to
    > dominate the decompression time.
    > Either way, could you provide the other time for each algorithm in order to
    > give a sense of how this might scale to other CPU speeds/media read speeds?

    That's the time to run the extraction algorithm. As H. Peter Anvin pointed out,
    you can have a fast media and a somewhat slow CPU, for which lzo makes sense.
    As for other data, I don't have all the figures handy, but:

    - LZMA: compressed size 1.19Mo, decompression time: several *seconds* (that's
    on a 180MHz ARM9 board, using a patch to implement LZMA compression similar
    to this one)
    - Bzip2 eats a lot of RAM, and head.S only gives 64Ko of malloc() space on
    ARM, so I didn't try.

    Albin Tonnerre, Free Electrons
    Kernel, drivers and embedded Linux development,
    consulting, training and support.
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