Bottlenecks in git merge

Hello, 

In connection with Ian Molton's question about merge have I played a
little with 'git merge' on the kernel sources.  What I find is that a
merge can take quite some time, but I'm not sure where that time exactly
goes to.  Here are the times I got:

Recursive (default):  4m22.282s
Resolve (-s resolve): 3m23.548s


What is taking so long?

Regards,

Peter


==============================>8==================
#!/bin/sh
#  Run from linux-2.6

change_readme() {
	sed -i "s/are much better/are better/" README
}

git checkout -f master
git branch -d test
git checkout -b test v2.6.12
change_readme
git commit -a -m "Work, work, work"
time git merge $STRATEGY "Merging happily." HEAD v2.6.15