ThirdPartyHeap.md

OpenJDK's Third-Party Heap Design

Build System Integration

0. Suppose our implementation of third-party heap is under folder $PWD/my_third_party_heap/

1. Enable build with third-party heap

• Build with command make THIRD_PARTY_HEAP=$PWD/my_third_party_heap.
• This will search for, and include $PWD/my_third_party_heap/CompileThirdPartyHeap.gmk

2. Setup my_third_party_heap/CompileThirdPartyHeap.gmk

# TOPDIR points to openjdk root directory
JVM_SRC_DIRS += $(TOPDIR)/my_third_party_heap
JVM_CFLAGS += -DINCLUDE_THIRD_PARTY_HEAP -DTHIRD_PARTY_HEAP_SRC=$(TOPDIR)/my_third_party_heap

This will compile every .cpp files under $PWD/my_third_party_heap and link to libjava.so.

3. (Optional) Add custom build target before building libjava.so

This is useful for mmtk to build the libmmtk.so building libjava.so

Add this to CompileThirdPartyHeap.gmk:

lib_mmtk:
	echo "your build commands here"

$(BUILD_LIBJVM): lib_mmtk

Third-Party Heap Interface

Currently, we need to add a cpp file in my_third_party_heap and implement 2 interfaces:

#include "gc/shared/thirdPartyHeap.hpp"

namespace third_party_heap {

class MutatorContext;

MutatorContext* bind_mutator(::Thread* current) {
    // Returns a pointer of a thread-local storage
}

GCArguments* new_gc_arguments() {
    // Return your inherited GCArguments instance
}

};

• An implementation of GCArguments is responsible for create a CollectedHeap*.
  1. So you need to define a implementation of CollectedHeap as well.
  2. And implement CollectedHeap::mem_allocate method for object allocation
     1. Allocate objects either by:
        • Allocate with global synchronization
        • Get pre-created MutatorContext*, and allocate without synchronization.
     2. (Possibly) triggers a gc manually within this method

TODO: Barrier Support for Third-party Heap

We only have no-barrier support...

TODO: Performance

CollectedHeap::mem_allocate without UseTLAB seems have bad performance...