[MASTER] packages using a lot of memory at runtime should use lzma compression

[Jérôme]

Anyway, the software center requires a lot of memory.

Up to 3% of archive size could be saved :
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j@dt-X64:~/tmp$ 7z x /var/cache/apt/archives/app-install-data_0.12.04.4_all.deb

7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
p7zip Version 9.20 (locale=fr_FR.UTF-8,Utf16=on,HugeFiles=on,1 CPU)

Processing archive: /var/cache/apt/archives/app-install-data_0.12.04.4_all.deb

Extracting data.tar

Everything is Ok

Size: 11714560
Compressed: 7176706
j@dt-X64:~/tmp$ ls
data.tar
j@dt-X64:~/tmp$ gzip --best --stdout data.tar > data.tar.gz
j@dt-X64:~/tmp$ bzip2 --best --stdout data.tar > data.tar.bz2
j@dt-X64:~/tmp$ lzma --best --stdout data.tar > data.tar.lzma
j@dt-X64:~/tmp$ xz -9e --stdout data.tar > data.tar.xz
j@dt-X64:~/tmp$ ll -h
total 38M
drwxr-xr-x 2 j j 4,0K avril 21 09:31 ./
drwxr-xr-x 23 j j 4,0K avril 21 09:27 ../
-rw-rw-r-- 1 j j 12M avril 17 13:03 data.tar
-rw-rw-r-- 1 j j 6,7M avril 21 09:30 data.tar.bz2
-rw-rw-r-- 1 j j 6,7M avril 21 09:30 data.tar.gz
-rw-rw-r-- 1 j j 6,6M avril 21 09:30 data.tar.lzma
-rw-rw-r-- 1 j j 6,5M avril 21 09:31 data.tar.xz
j@dt-X64:~/tmp$
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ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: app-install-data 0.12.04.4
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic x86_64
ApportVersion: 2.0.1-0ubuntu5
Architecture: amd64
Date: Sun Apr 22 10:13:43 2012
Dependencies:

InstallationMedia: Xubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120328)
PackageArchitecture: all
SourcePackage: app-install-data-ubuntu
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel Letzeisen (dtl131)]

Jérôme, after confirming with other triagers, I've decided to combine your lzma bugs into one.

[Jérôme (jerome-bouat)]

Maybe you should use the "--extreme" option of the xz compression since it allows to save additionnal size for the archives.

[Jérôme (jerome-bouat)]

The only drawback of LZMA compression is the required memory while decompressing the archive. However this isn't a drawback for applications which require a lot of memory at runtime anyway (X.org, LibreOffice, Java Runtime Environnement, Firefox, ...).

On the contrary, applications which use only a few memory at runtime shouldn't use lzma compression (Linux image, initscripts, system daemons, ...). For the later applications, maybe their package should use bzip2 compression instead.

Such a compression method choice policy would ensure the same packages repository would fit a large range of computer, whatever is the physical host memory.

[Jérôme (jerome-bouat)]

A tradeoff would be the following : using LZMA compression of all packages. However, the "force" of the LZMA compression method would be chosen according to the required memory for decompression :
- for applications requiring a lot of memory (LibreOffice, Firefox, X.org, ...) : xz -9e
- for applications requiring less memory : xz -1e

[Jérôme (jerome-bouat)]

The 12.10 release of Ubuntu still have LibreOffice package which aren't compressed with LZMA.