Re: Decompression speed: zip vs lzo

[Sam Vilain <sam@vilain.net>]

Linus Torvalds wrote:
> 
> On Fri, 11 Jan 2008, Sam Vilain wrote:
>> Drat, guess that means I'll have to recompute the deltas - I was trying
>> to avoid that.
> 
> Well, you could try to reuse the delta base information itself, but then 
> recompute the actual delta data contents. It would require some 
> source-code changes, but that may be faster (and result in a more accurate 
> before/after picture) than actually recomputing the deltas.

Yes, it would - but my runs have finished.

Without compression of deltas:

wilber:~/src/perl-preview$ git-repack -a -d -f --window=250 --depth=100
Compressing objects: 100% (236554/236554), done.
Writing objects: 100% (244360/244360), done.
Total 244360 (delta 182343), reused 0 (delta 0)
wilber:~/src/perl-preview$ du -sk .git/objects/pack/
86781   .git/objects/pack/

With compression of deltas:

wilber:~/src/perl-preview$ time git-repack -a -d -f --window=250 --depth=100
Counting objects: 244360, done.
Compressing objects: 100% (236554/236554), done.
Writing objects: 100% (244360/244360), done.
Total 244360 (delta 182343), reused 0 (delta 0)

real    20m34.985s
user    20m1.003s
sys     0m25.558s
wilber:~/src/perl-preview$ du -sk .git/objects/pack/
72907   .git/objects/pack/

wilber:~/src/perl-preview$ git --version
git version 1.5.4.rc2.7.g079c9-dirty

Of course those compression parameters are quite insane.

And as a side note either repack-objects got significantly better about
memory use between 1.5.3.5 and that version (the OOM killer fired -
killing first firefox and thunderbird :)) or apparently running
git-repack with a ulimit stops it from allocating too much VM.

Sam.