The buffer http://hpaste.org/68595 presents a simple code I tried to profile. I spotted what I strongly think to be an abusive memoization. The problem is that I don't see how to (simply) get rid of it. Compiled with -O2, it consumes 130MB of memory, however lines A and B executed separately consume each only 1MB. The infinite list (l 1), whatever I do, keeps being shared between lines A and B. I tried to wrap it in a function, as you can see, I also tried to make it explicitely polymorphic (bypassing monomorphic restriction), nothing solves it, GHC is just to good at memoizing. NB: When compiled without optimisations, the sharing does not happen (side note: but then lack of strictness analysis -- which is what I was testing at the first place -- makes line A (call to suminit2) consume a lot of memory, but this is normal).