git status: small difference between stating whole repository and small subdirectory

Hi,

I compared stating whole tree vs one small subdirectory, and I
expected that for the subdirectory status will be very very fast.
After all, it has only few files to stat. But it's not fast. Why?

With cold cache (echo 3 | sudo tee /proc/sys/vm/drop_caches):

$ time git status    > /dev/null
real	0m41.670s
user	0m0.980s
sys	0m2.908s

$ time git status -- src/.../somedir   > /dev/null
real	0m17.380s
user	0m0.748s
sys	0m0.328s

With warm cache:

$ time git status    > /dev/null
real	0m0.792s
user	0m0.404s
sys	0m0.384s

$ time git status -- src/.../somedir   > /dev/null
real	0m0.335s
user	0m0.288s
sys	0m0.048s

Repository/dir stats:

$ find * -type f | wc -l
127189
$ du -shc * | grep total
2.2G	total

$ find src/.../somedir -type f | wc -l
55
$ du -shc src/.../somedir | grep total
224K	total

$ git --version
git version 1.7.9.rc0.10.gbeecc

--

-- 
Piotr Krukowiecki