Re: Decompression speed: zip vs lzo

From: Sam Vilain <sam@vilain.net>
Date: Jan 11, 2008, 01:01 UTC
Message-ID: <4786BFCD.1000303@vilain.net>
In-Reply-To: <alpine.LFD.1.00.0801101454440.3148@woody.linux-foundation.org>

Linus Torvalds wrote:

Show 9 quoted lines

> 
> 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.