This paper examines the use of generational garbage collection techniques for a lazy implementation of a non-strict functional language. Detailed measurements which demonstrate that a generational garbage collector can substantially out-perform non-generational collectors, despite the frequency of write operations in the underlying implementation, are presented. Our measurements are taken from a state-of-the-art compiled implementation for Haskell, running substantial benchmark programs. We make measurements of dynamic properties (such as object lifetimes) which affect generational collectors, study their interaction with a simple generational scheme, make direct performance comparisons with simpler collectors, and quantify the interaction with a paging system. The generational collector is demonstrably superior. At least for our benchmarks, it reduces the net storage management overhead, and it allows larger programs to be run on a given machine before thrashing ensues. 1 Introducti...

The garbage collector presented in this paper makes use of two well known compaction garbage collection algorithms with very different performance characteristics: Cheney's two-space copying collector and Jonker's sliding compaction collector. We propose a scheme which allows either collector to be used. The run-time memory requirements of the program being executed are used to determine the most appropriate collector. This enables us to achieve a fast collector for heap requirements less than half of the heap memory but allows the heap utilization to increase beyond this threshold. Using these ideas we develop a particularly attractive extension to Appel's generational collector. We also describe a particularly fast implementation of the garbage collector which avoids interpreting the structure and current state of closures by attaching specific code to heap objects. This code knows the structure and current state of the object and performs the appropriate actions without having to te...

This is the final report on the GRASP project, carried out under SERC grants GR/F34671 and GR/F98444, at Glasgow University 1 2 . The project supported two Principal Investigators (Simon Peyton Jones and Phil Wadler), and three Research Assistants (Kevin Hammond, Cordelia Hall and Will Partain). Four research students have worked in close association with the project. 1 Summary The purpose of GRASP was to help get the technology of functional programming out of the lab and into the hands of practitioners, by producing robust and usable compilers and profilers for these languages, on both sequential and parallel systems. The main achievements of the project are as follows: ffl We have played a key role in the development of a common international non-strict functional language, Haskell (Hudak et al. [1992]). This standardisation effort has led directly to a considerable focussing of the international research community in these languages. More details about Haskell are given in Sect...