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    SubjectRe: [RFC] Breaking data compatibility with userspace bzlib
    On Fri, Jun 20, 2003 at 08:59:15PM +0200, J?rn Engel wrote:
    > Now, the cost of the underlying BWT is O(n) in memory and O(n*ln(n))
    > in time. That given, I consider it odd to use a linear semantic of
    > blockSizeXXXX and would prefer an exponential one, as the zlib uses
    > here and there. Thus blockSizeBits would now give the blockSize as
    > 1 << blockSizeBits, allowing to go well below 100k, resulting in lower
    > memory consumption for some and well above 900k, giving better
    > compression ratios.
    >
    >
    > Long intro, short question: Jay O Nay?

    The big question is whether the bzip2 better compression is actually
    useful in a kernel context? Patches to do bzip2 for initrd, for
    example, have been around for ages:

    http://gtf.org/garzik/kernel/files/initrd-bzip2-2.2.13-2.patch.gz

    But the compression and decompression overhead is _much_ larger
    than gzip. It was so huge for maximal compression that dialing back
    compression reaching a point of diminishing returns rather quickly,
    when compared to gzip memory usage and compression.

    I talked a bit with the bzip2 author a while ago about memory usage.
    He eventually added the capability to only require small blocks
    for decompression (64K IIRC?), but there was a significant loss in
    compression factor.

    So... even in 2003, I really don't know of many (any?) tasks which
    would benefit from bzip2, considering the additional memory and
    cpu overhead.

    Jeff



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