Andi Kleen wrote:
Matt LaPlante <[email protected]> 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.
--Andy
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