Asymmetric Dual-Space Collectors

In Modern Computer Systems, automatic memory management is used in operating systems, programming languages and virtual machines. Automatic memory management, also referred to as garbage collection (GC), is a mechanism to recycle objects in the memory which will never be used again. In addition to high-performance hardware and fully optimization for software designation, improving the efficiency of garbage collection algorithm is also a way to improving mutator’s performance.Traditional semi-space collector with the conservative reserved space policy is lack of adaptability. This article focuses on the semi-space collector and the work can be described as follows:1. We study each kind of garbage collection algorithms, analyze their characteristics, give different collectors’ realizations, and discuss the development of the collectors.2. Cheney copy algorithm and Lisp2mark-compact algorithm are analyzed in several aspects such as the theory, the space design and the advantages and disadvantages. To overcome semi-space collector’s shortcoming of inefficient memory utilization, we propose the asymmetric dual-space copy algorithm according to the weak generational hypothesis and predictability of mutators’behaviors.3. The space design of asymmetric dual-space copy collector is given, the copy algorithm and mark-compact algorithm are modified, a brand-new space adjusting module is designed in order to combine the two collection algorithms together. Then the asymmetric dual-space copy collector and a detailed experimental program are developed. The collector is tested in different benchmarks to prove our collector can effectively improve the efficiency of garbage collection.4. As all the collectors which are based on copy algorithm suffers a severe recession when the total size of alive objects has been close to half the size of the heap, while mark-compact collectors still perform well at this point, we design a mode switching module and realize the asymmetric dual-space hybrid collector based on the asymmetric dual-space copy collector and mark-compact collector. We also test the collector to prove its high performance in the case of high survival rate.