/**
* An object has been marked (identifiged as live). Large objects are added to the to-space
* treadmill, while all other objects will have a mark bit set in the superpage header.
*
* @param object The object which has been marked.
*/
@Inline
private void internalMarkObject(ObjectReference object, boolean nurseryObject) {
Address cell = VM.objectModel.objectStartRef(object);
Address node = Treadmill.midPayloadToNode(cell);
treadmill.copy(node, nurseryObject);
}
/** Sweep through the large pages, releasing all superpages on the "from space" treadmill. */
private void sweepLargePages(boolean sweepNursery) {
while (true) {
Address cell = sweepNursery ? treadmill.popNursery() : treadmill.pop();
if (cell.isZero()) break;
release(getSuperPage(cell));
}
if (VM.VERIFY_ASSERTIONS)
VM.assertions._assert(sweepNursery ? treadmill.nurseryEmpty() : treadmill.fromSpaceEmpty());
}
/**
* Prepare for a new collection increment. For the mark-sweep collector we must flip the state of
* the mark bit between collections.
*/
public void prepare(boolean fullHeap) {
if (fullHeap) {
if (VM.VERIFY_ASSERTIONS) {
VM.assertions._assert(treadmill.fromSpaceEmpty());
}
markState = MARK_BIT.minus(markState);
}
treadmill.flip(fullHeap);
inNurseryGC = !fullHeap;
}
/**
* Perform any required initialization of the GC portion of the header.
*
* @param object the object ref to the storage to be initialized
* @param alloc is this initialization occuring due to (initial) allocation (true) or due to
* copying (false)?
*/
@Inline
public void initializeHeader(ObjectReference object, boolean alloc) {
Word oldValue = VM.objectModel.readAvailableBitsWord(object);
Word newValue = oldValue.and(LOS_BIT_MASK.not()).or(markState);
if (alloc) newValue = newValue.or(NURSERY_BIT);
if (Plan.NEEDS_LOG_BIT_IN_HEADER) newValue = newValue.or(Plan.UNLOGGED_BIT);
VM.objectModel.writeAvailableBitsWord(object, newValue);
Address cell = VM.objectModel.objectStartRef(object);
treadmill.addToTreadmill(Treadmill.midPayloadToNode(cell), alloc);
}
/**
* A new collection increment has completed. For the mark-sweep collector this means we can
* perform the sweep phase.
*/
public void release(boolean fullHeap) {
// sweep the large objects
sweepLargePages(true); // sweep the nursery
if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(treadmill.nurseryEmpty());
if (fullHeap) sweepLargePages(false); // sweep the mature space
}
/**
* Return the size of the per-superpage header required by this system. In this case it is just
* the underlying superpage header size.
*
* @return The size of the per-superpage header required by this system.
*/
@Inline
protected int superPageHeaderSize() {
return Treadmill.headerSize();
}