pack during fastimport of kernel uses too much memory

On the weekend, I tried importing the Linux kernel into Bazaar via bzr-fastimport. While packing at the 120K revision point, my desktop with 6G of memory had 100% dedicated to programs and nothing else was running. Not good.

I can try this again and collect more diagnostics if required but it's probably quicker for the person fixing this to run it themselves. To reproduce, grab the latest stable Linux kernel (2.6.30.y) using git. Then run:

  bzr fast-export-from-git linux-2.6.30.y linux-2.6.30.y.fi
  gzip linux-2.6.30.y.fi
  bzr fast-import linux-2.6.30.y.fi.gz linux-2.6.30.y.bzr

Note: The export from git is pretty quick - 15 minutes or so on my desktop. After gzipping, the exported data requires around 2.6G, though you'll need a lot more free space than that for the raw file. The import into Bazaar takes around 13 hours.

FWIW, the import isn't clean as a subsequent bzr fast-export runs into a problem. I suspect this packing memory use problem is independent of the import bugs though.