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split compact + adjust phase
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Thomas Schatzl committed Feb 13, 2024
1 parent fc07978 commit c2c6c29
Showing 1 changed file with 68 additions and 55 deletions.
123 changes: 68 additions & 55 deletions src/hotspot/share/gc/serial/serialCompressor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -151,7 +151,7 @@ class SCCompacter {

// Given a heap word (usually the start of an object), compute the forwarding address.
inline HeapWord* forwardee(HeapWord* addr) const {
assert(_mark_bitmap.is_marked(addr), "must be marked");
//assert(_mark_bitmap.is_marked(addr), "must be marked");
HeapWord* block_base = align_down(addr, bytes_per_block());
size_t block = addr_to_block_idx(addr);
assert(_bot[block] != nullptr, "must have initialized BOT entry");
Expand Down Expand Up @@ -212,8 +212,8 @@ class SCCompacter {
// Build the block-offset-table for space at index.
void build_table_for_space(uint idx) {
ContiguousSpace* space = get_space(idx);
HeapWord* bottom = space->bottom();
HeapWord* top = space->top();
HeapWord* const bottom = space->bottom();
HeapWord* const top = space->top();

// Clear table (only required for assertion in forwardee()).
DEBUG_ONLY(clear(bottom, top);)
Expand All @@ -223,6 +223,7 @@ class SCCompacter {
SCDeadSpacer dead_spacer(space);

HeapWord* compact_top = get_compaction_top(_index);
HeapWord* const start_compact_top = compact_top;
HeapWord* current = bottom;

// Scan all live blocks in the space.
Expand Down Expand Up @@ -256,6 +257,7 @@ class SCCompacter {
size_t live_in_block = _mark_bitmap.count_marked_words(first_obj_this_block, first_obj_after_block);
while (live_in_block > pointer_delta(_spaces[_index]._space->end(),
compact_top)) {
log_info(gc)("split!");
// out-of-memory in this space
_spaces[_index]._compaction_top = compact_top;
_index++;
Expand All @@ -274,6 +276,7 @@ class SCCompacter {
record_first_dead(idx, top);
}
_spaces[_index]._compaction_top = compact_top;
//log_info(gc)("compacted [" PTR_FORMAT ", " PTR_FORMAT ") to [" PTR_FORMAT " to " PTR_FORMAT ")", p2i(bottom), p2i(top), p2i(start_compact_top), p2i(compact_top));
}

// Reserves memory for the block-offset-table (does not commit any memory, yet).
Expand Down Expand Up @@ -342,11 +345,15 @@ class SCCompacter {

// Compact live objects in a space.
void compact_space(uint idx) const;
void adjust_space(uint idx);

void phase3_compact() {
for (uint i = 0; i < _num_spaces; ++i) {
compact_space(i);
}
for (uint i = 0; i < _num_spaces; ++i) {
adjust_space(i);
}
}
};

Expand Down Expand Up @@ -405,68 +412,74 @@ static ContiguousSpace* space_containing(HeapWord* addr) {
// Compact live objects in a space.
void SCCompacter::compact_space(uint idx) const {
ContiguousSpace* space = get_space(idx);
HeapWord* bottom = space->bottom();
HeapWord* top = space->top();
HeapWord* const bottom = space->bottom();
HeapWord* const top = space->top();
HeapWord* current = _mark_bitmap.get_next_marked_addr(bottom, top);

SCUpdateRefsClosure cl(*this);

TenuredSpace* tenured_space = SerialHeap::heap()->old_gen()->space();

HeapWord* last_compact_end = nullptr;

// Visit all live objects in the space.
while (current < top) {
assert(_mark_bitmap.is_marked(current), "must be marked");
// Copy the whole chunk.
HeapWord* compact_to = forwardee(current);
HeapWord* next_dead = _mark_bitmap.get_next_unmarked_addr(current, top);
size_t size = pointer_delta(next_dead, current);
if (compact_to != current) {
assert(last_compact_end == nullptr || current < get_first_dead(idx) || compact_to == last_compact_end || space_containing(last_compact_end) != space_containing(compact_to),
"must compact without gaps, except when switching spaces: current: " PTR_FORMAT ", first_dead: " PTR_FORMAT ", compact_to: " PTR_FORMAT ", last_compact_end: " PTR_FORMAT, p2i(current), p2i(get_first_dead(idx)), p2i(compact_to), p2i(last_compact_end));
Copy::aligned_conjoint_words(current, compact_to, size);
}
last_compact_end = compact_to + size;

// Scan all consecutive live objects in the current live chunk and update their references.
HeapWord* obj_start = compact_to;
while (obj_start < last_compact_end) {
oop obj = cast_to_oop(obj_start);
// Update references of object.
obj->oop_iterate(&cl);

// We need to update the offset table so that the beginnings of objects can be
// found during scavenge. Note that we are updating the offset table based on
// where the object will be once the compaction phase finishes.
HeapWord* next_obj = obj_start + obj->size();
if (tenured_space->is_in_reserved(obj_start)) {
tenured_space->update_for_block(obj_start, next_obj);
//log_info(gc)("compact_space [" PTR_FORMAT ", " PTR_FORMAT ")", p2i(bottom), p2i(top));
HeapWord* last_compact_end = nullptr;
{
GCTraceTime(Info, gc) x("Move objects");

// Visit all live objects in the space.
while (current < top) {
assert(_mark_bitmap.is_marked(current), "must be marked");
// Copy the whole chunk.
HeapWord* compact_to = forwardee(current);
HeapWord* next_dead = _mark_bitmap.get_next_unmarked_addr(current, top);
size_t size = pointer_delta(next_dead, current);
if (compact_to != current) {
assert(last_compact_end == nullptr || current < get_first_dead(idx) || compact_to == last_compact_end || space_containing(last_compact_end) != space_containing(compact_to),
"must compact without gaps, except when switching spaces: current: " PTR_FORMAT ", first_dead: " PTR_FORMAT ", compact_to: " PTR_FORMAT ", last_compact_end: " PTR_FORMAT, p2i(current), p2i(get_first_dead(idx)), p2i(compact_to), p2i(last_compact_end));
Copy::aligned_conjoint_words(current, compact_to, size);
}

// Advance to next object in chunk.
obj_start = next_obj;
}

// Advance to next live object.
if (next_dead >= top) {
break;
}
assert(!_mark_bitmap.is_marked(next_dead), "must not be live");
if (next_dead < get_first_dead(idx)) {
last_compact_end = compact_to + size;

// Advance to next live object.
if (next_dead >= top) {
break;
}
assert(!_mark_bitmap.is_marked(next_dead), "must not be live");
assert(next_dead < get_first_dead(idx), "must be, deadspacer not supoprted");
// Dead-spacer object, not a record of next live object.
current = _mark_bitmap.get_next_marked_addr(next_dead, top);
} else {
// We stored the address of the next live object in the first unmarked word
// after the current live chunk.
HeapWord* next = *(HeapWord**)next_dead;
assert(next == _mark_bitmap.get_next_marked_addr(next_dead, top), "must match");
current = next;
}
}

// Reset top and unused memory
space->set_top(get_compaction_top(idx));
}

void SCCompacter::adjust_space(uint idx) {
// Scan all consecutive live objects in the current live chunk and update their references.
ContiguousSpace* space = get_space(idx);
{
GCTraceTime(Info, gc) a("Adjust pointers");
SCUpdateRefsClosure cl(*this);

TenuredSpace* tenured_space = SerialHeap::heap()->old_gen()->space();
bool needs_bot_update = space == tenured_space;
HeapWord* obj_start = space->bottom();
HeapWord* obj_top = space->top();
//log_info(gc)("Adjust [" PTR_FORMAT ", " PTR_FORMAT ")", p2i(obj_start), p2i(obj_top));

while (obj_start < obj_top) {
oop obj = cast_to_oop(obj_start);
// Update references of object.
obj->oop_iterate(&cl);

// We need to update the offset table so that the beginnings of objects can be
// found during scavenge. Note that we are updating the offset table based on
// where the object will be once the compaction phase finishes.
HeapWord* next_obj = obj_start + obj->size();
if (needs_bot_update) {
tenured_space->update_for_block(obj_start, next_obj);
}

// Advance to next object in chunk.
obj_start = next_obj;
}
}
if (ZapUnusedHeapArea) {
space->mangle_unused_area();
}
Expand Down

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