We've been trying to track down a memory leak, and by adding SCC annotations, pinned it down to a very brief expression. Unfortunately, the expression is just a variable! We even looked at the generated core: (case ([Soutei.Term Logic.BodyVar] -> (...) -> Logic.Frame -> Logic.QState -> FBackTrackT.Stream m_aYsk Logic.QState) lookup_aYPK pred_aXVH ctxIdx_aYpI of wild_B1 { Data.Maybe.Nothing -> GHC.Err.patError ... Data.Maybe.Just x_aXVL -> __scc {pqzifoozq Assertions} x_aXVL }); Note the __scc annotation just before x_aXVL at the end of the expression. Yet in the time and allocation profile, this SCC is charged for a lot of time and allocations in the "individual" column; individual inherited COST CENTRE no. entries %time %alloc %time %alloc pq.foo' 466 50001 8.0 12.1 8.0 13.2 and in the heap profile, it is a major memory leak. The Haskell code looks like predQuery pred = case lookup pred ctxIdx of Just f -> {-# SCC "pq.foo'" #-} f Note that f is a function, which we expect to be expensive when it is called. However, that should be charged to the definition of the function, right? We tried pretty hard to reproduce this in a small test case, but never succeeded. Always, the cost was accounted to the definition of the function in the intuitive way. We're using ghc 6.4.1 and compiling without optimization. Can any ghc hacker suggest how this could happen, or give us any hints on what to try next? Andrew [1] http://haskell.org/ghc/docs/latest/html/users_guide/profiling.html