Please repeat the test using a tarball created from a reiserfs
partition, you'll get better numbers for reiserfs. Not as good as
reiser4, but still much better than these.
File order from readdir matters a lot.
It is a bit amazing how many obscurities can bite you with seemingly
simple tests like this. We recently ran into one with tar recognizing
that it was writing to /dev/null, and optimizing for it.
Hans