Eliminating External Fragmentation in a Non-Moving Garbage Collector for Java

Fragmentation can cause serious loss of memory in systems that are using dynamic memory management. Any useful memory management system must therefore provide means to limit fragmentation. Today’s garbage collector implementations often do this by moving objects in a way that free memory is non-fragmented. This paper presents a new object model that is based on fixed size blocks. The model eliminates external fragmentation without the need to move objects. A Java virtual machine and a static Java bytecode compiler that use this object model have been implemented and analysed using the SPECjvm98 benchmark suite. This Java implementation allows for deterministic memory management as needed in real-time systems that is difficult to achieve with moving collectors and unparalleled by current implementations