#8027: Adding one call to getNumCapabilities triggers performance nose dive (6X slowdown) --------------------------------------+------------------------------------- Reporter: rrnewton | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Runtime System | Version: 7.6.3 Resolution: wontfix | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime performance bug | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: --------------------------------------+------------------------------------- Changes (by rrnewton): * status: new => closed * resolution: => wontfix Comment: Ah... my mistake. What was so apparently baffling is actually pretty reasonable. In this case adding more code to the function simply changes inlining decisions, which in turn determines whether dictionary elimination can be done. The 6X performance difference is just because of that. Perhaps such a function should be monomorphic to be safe... since the difference is so big. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/8027#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler