[Haskell-cafe] why is haddock so slow

[Johannes Waldmann]

I have a larg-ish project (800 modules) and these ghc compilation times:

cabal install                : 19 min
cabal install --disable-doc  : 13 min

the compilation includes the profiling build.

That is, running haddock takes the same 6 minutes
as running the compiler (with optimization)

I also built with "optimization: False library-profiling: False"
and this takes 3 min.

I understand that haddockification goes via the compiler's front-end
to resolve names and infer types. 
This takes 3 min (as the non-optimizing compiler run shows).

What does haddock do in the other 3 min? 

What could I do to help analyze this?

- J.W.

(ghc-7.8.3, haddock 2.15.0, rotating disk (not SSD), Fedora 20, x86_64)