Clone / pull from github very slow

I have recently noticed that cloning or pulling from github with hg / hggit is very slow.

If I clone a small (800 K) repository with git, my times are:

real 0m3.117s
user 0m0.091s
sys 0m0.293s

If I use hg with hggit, my times are:

real 10m20.517s
user 0m0.000s
sys 0m0.000s

This is a huge difference. Does anyone know the reason?