#8255: GC Less Operation -------------------------------------+------------------------------------- Reporter: sirinath | Owner: Type: feature request | Status: closed Priority: lowest | Milestone: _|_ Component: Compiler | Version: 7.7 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Project (more performance bug | than a week) Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------- Comment (by sirinath): I am not saying you can get it right in one bang. Until you get it right you need a GC as a fall back. Lets take a simple case. In a function evocation which takes simple parameters and has closure on simple variable we can divide that what data came from the surrounding context (both closure and parameters), what actually is used in the local evaluation, and what needs to survive the function (return values, local created parameters which closures in locally defined function, etc.) This can translate to what memory needed to be allocated, what can de de allocated and what needs to be retained. This can be mapped into a set holding these symbols. For each function you maintain this information. If a function, a list of function etc. is passed to a function then these sets will hold some production of sets of the above 3. In the parent context functional application and closures will define what needs to survive this context if a function is returned. Based on this the compiler can build a region map on what needs allocating and when as well as when it can be freed. Some memory requirements sizes may not be know (e.g. input dependent) but allocation and de allocations can be inferred. Even if this is not globally optimised this requirement can be inferred in the functions context. When implementing something new like this it will not be perfect to handle all cases. Stating point may be 20% of the use cases which matter the most or used in a programme 80% of the time. In the rest fall back to GC as the safety net. Gradually can add more cases and some point you might not need the GC. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8255#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler