[Libreoffice] Windows installer size reduction effort - the compression theory

Hi,

I am sure we can shrink the installer more with better compression
settings. Unfortunately I am not able to try these theory now because I
have problem with Windows based build system. So any participation
related to this topic is welcome

The current situation:
We are using double compression for creating LibreOffice install kit for
Windows:

1) Compressed CAB file contains the installable files
2) The installation system is packed into the NSIS based preinstaller.

According to
    solenv/bin/modules/installer/globals.pm
    solenv/bin/modules/installer/windows/msiglobal.pm
    setup_native/source/win32/nsis/downloadtemplate.nsi

For cab file compression we are using:
globals.pm
    cabfilecompressionlevel = 7

and

msiglobal.pm
    .Set CompressionType=LZX
    .Set Compress=ON
    .Set CompressionLevel=cabfilecompressionlevel=7
options.

For NSIS based presintaller we are using:
    SetCompressor lzma
option.

So currently we use a high compression for cab file generation which
produces small file but takes more time. Then recompress it with lzma
that may not able to compress so much but takes long time. However we
use NSIS in SetCompress auto mode that might causes compression test and
if it is not enough good it drops the compressed file and use the
original cab file.

My idea is to use only one tight compressor and the other archiver
should used in store or zip mode. So there is to way to rethink the
compression practice:

1) Maximize the compression of CAB files and minimalize NSIS compression:
    This produces a smaller cab file but if the installer request files
in non other sequence as compressed may we pay penalty in uncompression
time.

For this we can use CAB compression settings:
    .Set CompressionType=LZX
    .Set Compress=ON
    .Set CompressionMemory= 21

(We can eliminate .Set CompressionLevel=cabfilecompressionlevel=7 maybe
it is useful for MSZIP compression (or not))

For NSIS we use simple store or small compression:

a)
    SetCompress Off
    SetDatablockOptimize On

b)
    SetCompress Force
    SetCompressor zlib
    SetDatablockOptimize On

OR

2) CAB file only store the installer's files and NSIS compression set to
high:
    This may produces the smallest installer so I would try this for
first. The compression of NSIS takes time but decompression speed is and
also the installation is fast. The    preinstallation may takes
dictionary equivalent memory usage so we should not set Dictionary size
larger than 32-64 MB. The only negative effect, the preinstalled
(unpacked) installer uses same diskspace as the fully installed package
(For installation we need at least twice space of full installation).

For this we can use CAB store setting:
    .Set Compress=OFF

For NSIS we use simple store or small compression:

SetCompress Auto
SetCompressor /SOLID lzma
SetCompressorDictSize 64
SetDatablockOptimize On


References:

    http://msdn.microsoft.com/en-us/library/bb417343.aspx

    http://www.symantec.com/connect/articles/advanced-nsis-scripting-part-1

"The SetCompressorDictSize accepts one setting, which is the number of
megabytes to use for the dictionary size. The greater this number, the
more memory is required to execute the installation. The memory
requirement to run the installer will be the dictionary size plus about
4 megabytes or so. The default dictionary size is 8 megabytes. You can
get a slightly better compression ratio by changing this to 16, 32, or
64. You can set this up to 128 or possibly higher, but you won't notice
much difference when you use a dictionary size greater than 64.

With that in mind, I suggest that you use "SetCompressorDictSize 64",
but you can experiment with this value to see what works best for your
particular installer."

    http://nsis.sourceforge.net/Docs/Chapter4.html#4.8.2.3

What is your opinion? Can somebody test it on a real Windows build system?

-- 

Best regards,

Kálmán „KAMI” Szalai | 神 | kami911 [at] gmail [dot] com


My favorite projects:

OxygenOffice Professional <http://ooop.sf.net/> - office suite - for everybody | Magyarul 
<http://hun.sf.net/> - In Hungarian

Blog <http://bit.ly/10ucTR> | Support <http://bit.ly/eYZO6> 

Follow me <http://bit.ly/gJuJZ>, if you can <http://bit.ly/kDocB>

Attachment: signature.asc
Description: OpenPGP digital signature