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    SubjectRe: A little coding style nugget of joy
    Andi Kleen wrote:
    > Matt LaPlante <> writes:
    >> Since everyone loves random statistics, here are a few gems to give you a break from your busy day:
    >> Number of lines in the 2.6.22 Linux kernel source that include one or more trailing whitespaces: 135209
    >> Bytes saved by removing said whitespace: 151809
    > You don't actually save anything on disk on most file systems
    > (essentially everything except reiserfs on current Linux)
    > because all files are rounded to block size (normally 4K)
    > Same in page cache.

    This is a terrible assumption in general (i.e. if filesize % blocksize
    is close to uniformly distributed). If you remove one byte and the data
    is stored with blocksize B, then you either save zero bytes with
    probability 1-1/B or you save B bytes with probability 1/B. The
    expected number of bytes saved is B*1/B=1. Since expectation is linear,
    if you remove x bytes, the expected number of bytes saved is x (even if
    there is more than one byte removed per file).

    In my tree, about half of the files have size >= 4k, so the assumption
    is probably not _that_ far off the mark.

    Alternatively, there are an average of about 16 bytes removed per file,
    and there are 11 which are <= 16 bytes short of a 4k boundary, so it's
    not at all unreasonable that we'd save 40-50k.

    > And in tar files bzip2/gzip is very good at compacting them.

    That's true.

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      Last update: 2007-09-19 23:47    [W:0.023 / U:13.232 seconds]
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