Re: Git and GCC

From: Jon Smirl <jonsmirl@gmail.com>
Date: Dec 6, 2007, 06:47 UTC
Message-ID: <9e4733910712052247x116cabb4q48ebafffb93f7e03@mail.gmail.com>
In-Reply-To: <4aca3dc20712052117j3ef5cf99y848d4962ae8ddf33@mail.gmail.com>

On 12/6/07, Daniel Berlin <dberlin@dberlin.org> wrote:

Show 5 quoted lines

> > While you won't get the git svn metadata if you clone the infradead
> > repo, it can be recreated on the fly by git svn if you want to start
> > commiting directly to gcc svn.
> >
> I will give this a try :)

Back when I was working on the Mozilla repository we were able to convert the full 4GB CVS repository complete with all history into a 450MB pack file. That work is where the git-fastimport tool came from. But it took a month of messing with the import tools to achieve this and Mozilla still chose another VCS (mainly because of poor Windows support in git).

Like Linus says, this type of command will yield the smallest pack file:
 git repack -a -d --depth=250 --window=250

I do agree that importing multi-gigabyte repositories is not a daily occurrence nor a turn-key operation. There are significant issues when translating from one VCS to another. The lack of global branch tracking in CVS causes extreme problems on import. Hand editing of CVS files also caused endless trouble.

The key to converting repositories of this size is RAM. 4GB minimum, more would be better. git-repack is not multi-threaded. There were a few attempts at making it multi-threaded but none were too successful. If I remember right, with loads of RAM, a repack on a 450MB repository was taking about five hours on a 2.8Ghz Core2. But this is something you only have to do once for the import. Later repacks will reuse the original deltas.

-- 
Jon Smirl
jonsmirl@gmail.com