Re: svn to git, N-squared?

From: Eric Wong <normalperson@yhbt.net>
Date: Jun 12, 2006, 04:29 UTC
Message-ID: <20060612042934.GA12083@hand.yhbt.net>
In-Reply-To: <9e4733910606111902l709c71ccyf45070d55112739e@mail.gmail.com>

Jon Smirl <jonsmirl@gmail.com> wrote:

Show 6 quoted lines

> I have Mozilla CVS in a SVN repository. I've been using git-svnimport
> to import it. This time I am letting it run to completion; but the
> import has been running for four days now and it is only up to 2004.
> The import task is stable at 570MB and it is using about 50% of my
> CPU. It is constantly spawning off git write-tree, read-tree,
> hash-object, update-index. It is not doing excessive disk activity.

SVN itself seems to get much slower as you get towards newer revisions in a repository (FSFS) with lots of history. I've been experimenting a bit with a local copy of the gcc repo from November and git-svn SUCKED at importing it (it took over a week and I cancelled it out of frustration). I started repacking too, but, and it didn't help, Much of the performance defieciency was the svn sub process. being extremely slow at updating.

I also tried git-svnimport, of course, but I only had 512M on that machine and the machine became unusable due to heavy swapping.

Show 9 quoted lines

> The import seems to be getting n-squared slower. It is still making
> forward progress but the progress seems to be getting slower and
> slower.
> 
> It looks like it is doing write-tree, read-tree, hash-object,
> update-index once or more per change set. If these commands are
> n-proportional and they are getting run n times, then this is a
> n-squared process. Projecting this out, the import may take 10 days or
> more to completely finish.

I'm working on some improvements to git-svn to make it a bit more spiffy.

-- 
Eric Wong