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8271951: Consolidate preserved marks overflow stack in SerialGC

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@@ -167,8 +167,7 @@ void GenMarkSweep::deallocate_stacks() {
GenCollectedHeap* gch = GenCollectedHeap::heap();

@@ -49,8 +49,7 @@ uint MarkSweep::_total_invocations = 0;
Stack<oop, mtGC> MarkSweep::_marking_stack;
Stack<ObjArrayTask, mtGC> MarkSweep::_objarray_stack;

Stack<oop, mtGC> MarkSweep::_preserved_oop_stack;
Stack<markWord, mtGC> MarkSweep::_preserved_mark_stack;
Stack<PreservedMark, mtGC> MarkSweep::_preserved_overflow_stack;
size_t MarkSweep::_preserved_count = 0;
size_t MarkSweep::_preserved_count_max = 0;
PreservedMark* MarkSweep::_preserved_marks = NULL;
@@ -163,8 +162,7 @@ void MarkSweep::preserve_mark(oop obj, markWord mark) {
if (_preserved_count < _preserved_count_max) {
_preserved_marks[_preserved_count++].init(obj, mark);
} else {
_preserved_overflow_stack.push(PreservedMark(obj, mark));

@@ -176,37 +174,31 @@ void MarkSweep::set_ref_processor(ReferenceProcessor* rp) {
AdjustPointerClosure MarkSweep::adjust_pointer_closure;

void MarkSweep::adjust_marks() {
assert( _preserved_oop_stack.size() == _preserved_mark_stack.size(),
"inconsistent preserved oop stacks");

// adjust the oops we saved earlier
for (size_t i = 0; i < _preserved_count; i++) {

// deal with the overflow stack
StackIterator<oop, mtGC> iter(_preserved_oop_stack);
StackIterator<PreservedMark, mtGC> iter(_preserved_overflow_stack);
while (!iter.is_empty()) {
oop* p = iter.next_addr();
PreservedMark* p = iter.next_addr();

void MarkSweep::restore_marks() {
assert(_preserved_oop_stack.size() == _preserved_mark_stack.size(),
"inconsistent preserved oop stacks");
log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_oop_stack.size());
log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack.size());

// restore the marks we saved earlier
for (size_t i = 0; i < _preserved_count; i++) {

// deal with the overflow
while (!_preserved_oop_stack.is_empty()) {
oop obj = _preserved_oop_stack.pop();
markWord mark = _preserved_mark_stack.pop();
while (!_preserved_overflow_stack.is_empty()) {
PreservedMark p = _preserved_overflow_stack.pop();

@@ -100,8 +100,7 @@ class MarkSweep : AllStatic {
static Stack<ObjArrayTask, mtGC> _objarray_stack;

// Space for storing/restoring mark word
static Stack<markWord, mtGC> _preserved_mark_stack;
static Stack<oop, mtGC> _preserved_oop_stack;
static Stack<PreservedMark, mtGC> _preserved_overflow_stack;
static size_t _preserved_count;
static size_t _preserved_count_max;
static PreservedMark* _preserved_marks;
@@ -199,6 +198,8 @@ class PreservedMark {
markWord _mark;

PreservedMark(oop obj, markWord mark) : _obj(obj), _mark(mark) {}

void init(oop obj, markWord mark) {

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Do we even need this init function anymore? Even if such an assignment is still needed, it could just use assignment from a newly constructed object, e.g. pm = PreservedMark(obj, mark);. The only place I found where it is used is preserve_marks, which can use the assignment form instead.

_obj = obj;
_mark = mark;