Modified HotSpot VM 15 to support manual memory management outside of the garbage collected heap. The goal of this project is to enable novel compile-time memory management strategies for JVM languages.
Supports allocation/deallocation of:
- objects
- object arrays
- primitive int arrays
- primitive double arrays
Objects are allocated using malloc.
- Compatible only with EpsilonGC
- No support for pointer compression
- Build the JVM (for instructions see building.md)
- Compile source with javac
.../jdk/bin/javac Source.java - Run with command:
.../jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -XX:-UseCompressedOops -XX:-UseCompressedClassPointers Source
/**
* Allocates object in native memory.
* @param clazz Class of the object to be allocated.
* @return an allocated uninitialised object.
*/
public native static Object alloc(Class<?> clazz);
/**
* Allocates object array in native memory.
* @param clazz Class of the object array to be allocated.
* @param length The length of the array.
* @return an allocated object array.
*/
public native static Object[] allocObjArray(Class<?> clazz, int length);
/**
* Allocates primitive int array in native memory.
* @param length The length of the array.
* @return an allocated primitive array.
*/
public native static int[] allocIntArray(int length);
/**
* Allocates primitive double array in native memory.
* @param length The length of the array.
* @return an allocated primitive array.
*/
public native static double[] allocDoubleArray(int length);
/**
* Frees object allocated in native memory.
* @param obj object to be freed.
*/
public native static void free(Object obj);
/**
* Frees object array allocated in native memory.
* @param objArray object array to be freed.
*/
public native static void freeObjArray(Object[] objArray);
Foo obj = (Foo) Runtime.alloc(Foo.class);
obj.a = 42;
System.out.println(obj.a);
Runtime.free(obj);
See here for more examples.