very slow "git gc --aggressive" in GIT-1.6.4.4

very slow "git gc --aggressive" in GIT-1.6.4.4

[Leo Razoumov]

I noticed that "git gc --agressive" takes 5 times longer with
git-1.6.4.4 than with git-1.6.2.5.

Below are benchmarks on my Linux Ubuntu-9.04 laptop (Core2 Duo 2.54GHz).
As a test repo I use a mirror of the official GIT upstream.

GIT-v1.6.4.4
-----------------
git.upstream> time git gc --agressive
Counting objects: 105217, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (103507/103507), done.
Writing objects: 100% (105217/105217), done.
Total 105217 (delta 77228), reused 0 (delta 0)
git gc --aggressive  168.31s user 0.58s system 180% cpu 1:33.52 total

GIT-1.6.2.5.LR1
---------------------
git.upstream> time git gc --aggressive
Counting objects: 105217, done.
Delta compression using 2 threads.
Compressing objects: 100% (103507/103507), done.
Writing objects: 100% (105217/105217), done.
Total 105217 (delta 76235), reused 0 (delta 0)
git gc --aggressive  30.97s user 0.48s system 141% cpu 22.177 total
==========================================

168 seconds for git-1.6.4.4 versus 22 seconds for git-1.6.2.5.

What gives?

--Leo--

Re: very slow "git gc --aggressive" in GIT-1.6.4.4

[Michael Andreen]

On Friday 18 September 2009 21:23:59 Leo Razoumov wrote:
> I noticed that "git gc --agressive" takes 5 times longer with
> git-1.6.4.4 than with git-1.6.2.5.
> 
> Below are benchmarks on my Linux Ubuntu-9.04 laptop (Core2 Duo 2.54GHz).
> As a test repo I use a mirror of the official GIT upstream.

git-1.6.3 and later changed the settings for --aggressive to window=250 and 
depth=250, which produces a tighter pack. The earlier setting wasn't really 
aggressive.

/Michael