Re: svn to git, N-squared?

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Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
> 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.

> 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
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