[pacman-dev] [PATCH] pkgdelta: use highest compression ratio when creating deltas with xdelta3

Matthias Krüger matthias.krueger at famsik.de
Wed Mar 5 19:45:13 EST 2014

On 03/06/2014 01:14 AM, Matthias Krüger wrote:
> On 03/06/2014 12:33 AM, Allan McRae wrote:
>> On 06/03/14 09:25, Matthias Krüger wrote:
>>> Looking how pkgdelta works, I found this line
>>>      xdelta3  -q -f -s "$oldfile" "$newfile" "$deltafile" || ret=$?
>>> which seemed to be responsible for the actual delta generation, however
>>>      man xdelta3
>>> revealed that there were different compression levels (0-9) (not sure
>>> which one is default).
>>> To make it short, we could have had smaller deltas since pkgdelta was
>>> introduced!
>>> Examples:
>>> -9          16660K
>>> blender-12:2.69.c7ac0e-1_to_13:2.69.13290d-1-x86_64.delta
>>>   default  17832K 
>>> blender-12:2.69.c7ac0e-1_to_13:2.69.13290d-1-x86_64.delta
>>> -9         504K    xbmc-12.3-10_to_12.3-11-x86_64.delta
>>> default  572K   xbmc-12.3-10_to_12.3-11-x86_64.delta
>> How is memory usage changed?   Mainly when regenerating the package from
>> deltas?
> Surprisingly, for blender both runs took ~96MB and 1:50m (+- a second).
Mmh, just to clear out potential misunderstanding: both runs = 
decompression of normal and -9-compressed delta.
Compression ate around 140M and ~16s for normal, and 236M and ~26s for 
-9 level.

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