Re: Something is broken in repack

[Nicolas Pitre <nico@cam.org>]

On Tue, 11 Dec 2007, David Miller wrote:

> From: Nicolas Pitre <nico@cam.org>
> Date: Tue, 11 Dec 2007 12:21:11 -0500 (EST)
> 
> > BUT.  The point is that repacking the gcc repo using "git repack -a -f 
> > --window=250" has a radically different memory usage profile whether you 
> > do the repack on the earlier 2.1GB pack or the later 300MB pack.  
> 
> If you repack on the smaller pack file, git has to expand more stuff
> internally in order to search the deltas, whereas with the larger pack
> file I bet git has to less often undelta'ify to get base objects blobs
> for delta search.

Of course.  I came to that conclusion two days ago.  And despite being 
pretty familiar with the involved code (I wrote part of it myself) I 
just can't spot anything wrong with it so far.

But somehow the threading code keep distracting people from that issue 
since it gets to do the same work whether or not the source pack is 
densely packed or not.

Nicolas 
(who wish he had access to a much faster machine to investigate this issue)