unfolding info as seen when building a module depends on flags in a previously-compiled module
I've observed a blowup in ghc memory usage when invoked with parallel build flags.
cabal get xmlhtml-0.2.3.2 cabal install xmlhtml-0.2.3.2 --only-dependencies cd xmlhtml-0.2.3.2
cabal clean ; cabal configure --ghc-options="-j4" ; time cabal build -j4 -v3
will take quite a while and use > 1gb of ram
cabal clean ; cabal configure --ghc-options="-j1 ; time cabal build -j1 -v3
will use < 150mb of ram.
Based upon the output of cabal build -j4 -v3, it looks like the parallel build is spending a lottt more time in the simplifier passes. I'm not sure what changes between the parallel and sequential builds to change this. I'll try to dig into this more in a few days, but recording this problem now before i forget. (though of course any insights would be appreciated)