Exploring the Barrier to Entry: Incremental Generational Garbage Collection for {H}askell

(A.M. Cheadle, A.J. Field, S. Marlow, S.L. Peyton Jones, R.L. While) International Symposium on Memory Management, ACM, October 2004

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We document the design and implementation of a “production” incremental garbage collector for GHC 6.02. It builds on our earlier work (Non-stop Haskell) that exploited GHC’s dynamic dispatch mechanism to hijack object code pointers so that objects in to-space automatically scavenge themselves when the mutator attempts to " them. This paper details various optimisations based on code specialisation that remove the dynamic space, and associated time, overheads that accompanied our earlier scheme. We detail important implementation issues and provide a detailed evaluation of a range of design alternatives in comparison with Non-stop Haskell and GHC’s current generational collector. We also show how the same code specialisation techniques can be used to eliminate the write barrier in a generational collector.