Changing dpkg-deb default compression from gzip to lzma for Hardy

Emmet Hikory emmet.hikory at
Tue Dec 18 00:51:50 UTC 2007

On Dec 18, 2007 9:09 AM, Thilo Six wrote:
> comparation of a whole install (download time + extract time):
> download time gz (39084/384)= 101.78s +  14.278s = 116.06s
> download time 7z (27358/384)=  71.24s + 143.783s = 215.02s

    Comparisons like this have far too many factors (as you mentioned
separately).  I've seen Ubuntu used on a 3GHz Core2 Duo over ISDN and
on a 400MHz Pentium IIIs with ethernet connectivity to the mirrors,
which lead to compltely different results to the tests above.

    Bandwidth will always be location dependent, so package size
related to bandwidth is not an easy item for discussion.  Smaller is
nice, but for some it doesn't matter very much, as their connections
are either fast enough that it's not important, or slow enough that
they download overnight (or otherwise deeply backgrounded) anyway.

    Processor speed is similarly variable.  Not that benchmarks (1)
mean much, but the interesting point is only relative time for
decompression, as for most packages the IO load delay is concentrated
on unpack rather than decompress (and further that packing happens
once per revision per architecture, and unpacking happens a lot).  Is
3-5 times as long acceptable?  Maybe.  Is 10-15 times as long
acceptable?  Probably not (so we shouldn't use bzip2 unless it gets a
lot faster).

    The largest factor is the ship size: what fits on a CD.  Yes, DVDs
exist, and yes, Ubuntu ships DVD images, but they aren't as popular as
the CDs for a variety of reasons not relevant to a compression
discussion.  If the set of software considered interesting for a
default installation is larger than fits on a CD (which is often the
case), something must be cut: fonts, translations, and niche
applications tend to be early candidates.  If an alternate compression
scheme allows for more to fit on the CD, this is a win (see the
specification (2) for more details).  Further, more widespread
adoption of lzma may allow the integration of squashfs-lzma (3), which
would similarly improve the volume of material available on the



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