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

Krzysztof Lichota krzysiek at lichota.net
Tue Dec 18 08:33:33 UTC 2007


Thilo Six napisał(a):
> Krzysztof Lichota wrote the following on 17.12.2007 13:05
> 
> recently i also tried 7z for my backups and in comparation to bz2 it seems to
> take a bit longer during compressing but is faster on extraction.
> Also the compressed file with 7z is ~30% compared to a bz2 one.

Thanks for performing these tests, they provide some hard data on which
we can discuss :)

Compression time is not an issue because it is done on server, not by user.

bzip2 is not currently used and it is really slow. Gzip is used.

So comparing decompression of gzip and lzma, we have:

$ time untargz oo.tar.gz
real    0m0.636s
user    0m0.484s
sys     0m0.128s

$ time 7za x -so oo.tar.7z | tar xf -
real    0m5.849s
user    0m5.616s
sys     0m0.176s


So for lzma the time is over 5 seconds. And for 5 seconds system
responsiveness might be affected. Thus I suggested to run decompression
with nice to limit its effect on foreground tasks. ionice should also be
used to limit effect from I/O bandwidth point of view.

	Krzysztof Lichota


	

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