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Re: Experiment with using 7z for gzip compression of packages



OK, so another results, I used different data, because the apt cache is moving target and I not do backup of the last data...

0) 129 files: 268 706 070B - 100%
1) xz for control.tar.xz and data.tar.xz, all *.gz inside debs ungziped: 186 814 608B - 69.5%
2) 7z-gzip for control.tar.gz, xz for data.tar.xz, all *.gz inside debs ungziped: 186 822 308B - 69.5%
3) 7z-gzip for control.tar.gz, xz for data.tar.xz, all *.gz inside debs recompressed to xz: 187 681 956B - 69.8%
4) like 1) + PNG optimization (advdef, optipng, pngcrush, pngopt): 186 750 504B - 69.5%

Decompression of all gzip files inside the deb will save 0.3%.
Recompression of control.tar to xz gives little smaller size overall (some files bigger some smaller).
PNG optimization gives also little smaller size.

Note that I am not dpkg developer either zlib developer, I am only user.
TonyMi

> ------------ Původní zpráva ------------
> Od: Christian Leber <christian@leber.de>
> Předmět: Re: Experiment with using 7z for gzip compression of packages
> Datum: 17.4.2011 23:14:57
> ----------------------------------------
> On Sun, Apr 17, 2011 at 10:05:53PM +0200, tonda.misek@post.cz wrote:
>
> Hello Tonda
>
> > 0) 1132 packages (I used my apt cache):			1 076 539kB - 100%
> > 1) recompress the control.tar.gz and data.tar.gz:	1 038 391kB - 96.5%
> > 2) + recompress all *.gz files inside the data.tar.gz:	1 022 712kB - 95.0%
> > 3) like 1) but with xz:					  752 202kB - 69.9%
> > 4) like 2) but with xz:					  727 946kB - 67.6%
> >
> > Are the numbers for 1) and 2) interesting enough to do something in this
> direction?
>
> Surprising that the 7zip gzip compression is not more well known, it is
> available since serveal years as advancecomp.
> (i just looked it up and i used to 2004 to reduce the live filesystem size of
> knoppix)
>
> Afaik the difference is that is tries out a few parameters for each junk and
> uses the best one.
>
> It would be nice if you could try out something else:
> decompress all *.gz files in the data.tar and compress the .tar with xz,
> this could possibly yield better compression due to the big directory size of
> lzma.
> (after extraction the file would have to be gziped... but nevertheless it would
> be interesting)
>
> Christian
>
> --
>   Christian Leber <christian@leber.de> or <leber@uni-hd.de>
>
>
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>
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