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dc9715ebf1
hotspot/src/share/vm/gc
@ -82,6 +82,8 @@ class CompactibleFreeListSpace: public CompactibleSpace {
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template <typename SpaceType>
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friend void CompactibleSpace::scan_and_compact(SpaceType* space);
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template <typename SpaceType>
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friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
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template <typename SpaceType>
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friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
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// "Size" of chunks of work (executed during parallel remark phases
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@ -411,22 +411,6 @@ HeapWord* CompactibleSpace::forward(oop q, size_t size,
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return compact_top;
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}
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bool CompactibleSpace::insert_deadspace(size_t& allowed_deadspace_words,
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HeapWord* q, size_t deadlength) {
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if (allowed_deadspace_words >= deadlength) {
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allowed_deadspace_words -= deadlength;
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CollectedHeap::fill_with_object(q, deadlength);
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oop(q)->set_mark(oop(q)->mark()->set_marked());
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assert((int) deadlength == oop(q)->size(), "bad filler object size");
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// Recall that we required "q == compaction_top".
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return true;
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} else {
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allowed_deadspace_words = 0;
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return false;
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}
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}
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void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
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scan_and_forward(this, cp);
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}
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@ -362,6 +362,12 @@ private:
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inline size_t obj_size(const HeapWord* addr) const;
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template <class SpaceType>
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static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN;
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template <class SpaceType>
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static inline void clear_empty_region(SpaceType* space);
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public:
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CompactibleSpace() :
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_compaction_top(NULL), _next_compaction_space(NULL) {}
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@ -455,16 +461,6 @@ protected:
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return end();
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}
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// Requires "allowed_deadspace_words > 0", that "q" is the start of a
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// free block of the given "word_len", and that "q", were it an object,
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// would not move if forwarded. If the size allows, fill the free
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// block with an object, to prevent excessive compaction. Returns "true"
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// iff the free region was made deadspace, and modifies
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// "allowed_deadspace_words" to reflect the number of available deadspace
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// words remaining after this operation.
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bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
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size_t word_len);
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// Below are template functions for scan_and_* algorithms (avoiding virtual calls).
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// The space argument should be a subclass of CompactibleSpace, implementing
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// scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
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@ -31,6 +31,7 @@
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#include "gc/shared/space.hpp"
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#include "gc/shared/spaceDecorator.hpp"
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#include "memory/universe.hpp"
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#include "oops/oopsHierarchy.hpp"
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#include "runtime/prefetch.inline.hpp"
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#include "runtime/safepoint.hpp"
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@ -75,11 +76,61 @@ size_t CompactibleSpace::obj_size(const HeapWord* addr) const {
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return oop(addr)->size();
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}
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class DeadSpacer : StackObj {
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size_t _allowed_deadspace_words;
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bool _active;
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CompactibleSpace* _space;
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public:
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DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) {
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size_t ratio = _space->allowed_dead_ratio();
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_active = ratio > 0;
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if (_active) {
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assert(!UseG1GC, "G1 should not be using dead space");
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// We allow some amount of garbage towards the bottom of the space, so
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// we don't start compacting before there is a significant gain to be made.
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// Occasionally, we want to ensure a full compaction, which is determined
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// by the MarkSweepAlwaysCompactCount parameter.
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if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) {
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_allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
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} else {
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_active = false;
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}
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}
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}
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bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
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if (!_active) {
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return false;
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}
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size_t dead_length = pointer_delta(dead_end, dead_start);
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if (_allowed_deadspace_words >= dead_length) {
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_allowed_deadspace_words -= dead_length;
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CollectedHeap::fill_with_object(dead_start, dead_length);
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oop obj = oop(dead_start);
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obj->set_mark(obj->mark()->set_marked());
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assert(dead_length == (size_t)obj->size(), "bad filler object size");
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log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",
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p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
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return true;
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} else {
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_active = false;
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return false;
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}
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}
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};
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template <class SpaceType>
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inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
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// Compute the new addresses for the live objects and store it in the mark
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// Used by universe::mark_sweep_phase2()
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HeapWord* compact_top; // This is where we are currently compacting to.
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// We're sure to be here before any objects are compacted into this
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// space, so this is a good time to initialize this:
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@ -90,89 +141,73 @@ inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* c
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assert(cp->threshold == NULL, "just checking");
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assert(cp->gen->first_compaction_space() == space, "just checking");
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cp->space = cp->gen->first_compaction_space();
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compact_top = cp->space->bottom();
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cp->space->set_compaction_top(compact_top);
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cp->threshold = cp->space->initialize_threshold();
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} else {
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compact_top = cp->space->compaction_top();
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cp->space->set_compaction_top(cp->space->bottom());
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}
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// We allow some amount of garbage towards the bottom of the space, so
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// we don't start compacting before there is a significant gain to be made.
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// Occasionally, we want to ensure a full compaction, which is determined
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// by the MarkSweepAlwaysCompactCount parameter.
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uint invocations = MarkSweep::total_invocations();
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bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);
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HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
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size_t allowed_deadspace = 0;
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if (skip_dead) {
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const size_t ratio = space->allowed_dead_ratio();
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allowed_deadspace = (space->capacity() * ratio / 100) / HeapWordSize;
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}
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DeadSpacer dead_spacer(space);
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HeapWord* q = space->bottom();
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HeapWord* t = space->scan_limit();
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HeapWord* end_of_live= q; // One byte beyond the last byte of the last
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// live object.
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HeapWord* first_dead = space->end(); // The first dead object.
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HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object.
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HeapWord* first_dead = NULL; // The first dead object.
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const intx interval = PrefetchScanIntervalInBytes;
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while (q < t) {
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assert(!space->scanned_block_is_obj(q) ||
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oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||
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oop(q)->mark()->has_bias_pattern(),
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HeapWord* cur_obj = space->bottom();
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HeapWord* scan_limit = space->scan_limit();
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while (cur_obj < scan_limit) {
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assert(!space->scanned_block_is_obj(cur_obj) ||
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oop(cur_obj)->mark()->is_marked() || oop(cur_obj)->mark()->is_unlocked() ||
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oop(cur_obj)->mark()->has_bias_pattern(),
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"these are the only valid states during a mark sweep");
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if (space->scanned_block_is_obj(q) && oop(q)->is_gc_marked()) {
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// prefetch beyond q
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Prefetch::write(q, interval);
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size_t size = space->scanned_block_size(q);
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compact_top = cp->space->forward(oop(q), size, cp, compact_top);
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q += size;
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end_of_live = q;
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if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) {
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// prefetch beyond cur_obj
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Prefetch::write(cur_obj, interval);
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size_t size = space->scanned_block_size(cur_obj);
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compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top);
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cur_obj += size;
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end_of_live = cur_obj;
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} else {
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// run over all the contiguous dead objects
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HeapWord* end = q;
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HeapWord* end = cur_obj;
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do {
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// prefetch beyond end
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Prefetch::write(end, interval);
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end += space->scanned_block_size(end);
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} while (end < t && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
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} while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
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// see if we might want to pretend this object is alive so that
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// we don't have to compact quite as often.
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if (allowed_deadspace > 0 && q == compact_top) {
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size_t sz = pointer_delta(end, q);
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if (space->insert_deadspace(allowed_deadspace, q, sz)) {
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compact_top = cp->space->forward(oop(q), sz, cp, compact_top);
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q = end;
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end_of_live = end;
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continue;
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if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
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oop obj = oop(cur_obj);
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compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);
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end_of_live = end;
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} else {
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// otherwise, it really is a free region.
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// cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
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*(HeapWord**)cur_obj = end;
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// see if this is the first dead region.
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if (first_dead == NULL) {
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first_dead = cur_obj;
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}
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}
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// otherwise, it really is a free region.
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// q is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
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(*(HeapWord**)q) = end;
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// see if this is the first dead region.
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if (q < first_dead) {
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first_dead = q;
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}
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// move on to the next object
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q = end;
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cur_obj = end;
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}
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}
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assert(q == t, "just checking");
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assert(cur_obj == scan_limit, "just checking");
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space->_end_of_live = end_of_live;
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if (end_of_live < first_dead) {
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first_dead = end_of_live;
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if (first_dead != NULL) {
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space->_first_dead = first_dead;
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} else {
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space->_first_dead = end_of_live;
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}
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space->_first_dead = first_dead;
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// save the compaction_top of the compaction space.
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cp->space->set_compaction_top(compact_top);
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@ -183,127 +218,58 @@ inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
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// adjust all the interior pointers to point at the new locations of objects
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// Used by MarkSweep::mark_sweep_phase3()
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HeapWord* q = space->bottom();
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HeapWord* t = space->_end_of_live; // Established by "prepare_for_compaction".
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HeapWord* cur_obj = space->bottom();
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HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward".
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HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward".
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assert(space->_first_dead <= space->_end_of_live, "Stands to reason, no?");
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if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {
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// we have a chunk of the space which hasn't moved and we've
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// reinitialized the mark word during the previous pass, so we can't
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// use is_gc_marked for the traversal.
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HeapWord* end = space->_first_dead;
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while (q < end) {
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// I originally tried to conjoin "block_start(q) == q" to the
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// assertion below, but that doesn't work, because you can't
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// accurately traverse previous objects to get to the current one
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// after their pointers have been
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// updated, until the actual compaction is done. dld, 4/00
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assert(space->block_is_obj(q), "should be at block boundaries, and should be looking at objs");
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// point all the oops to the new location
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size_t size = MarkSweep::adjust_pointers(oop(q));
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size = space->adjust_obj_size(size);
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q += size;
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}
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if (space->_first_dead == t) {
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q = t;
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} else {
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// The first dead object is no longer an object. At that memory address,
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// there is a pointer to the first live object that the previous phase found.
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q = *((HeapWord**)(space->_first_dead));
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}
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}
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assert(first_dead <= end_of_live, "Stands to reason, no?");
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const intx interval = PrefetchScanIntervalInBytes;
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debug_only(HeapWord* prev_q = NULL);
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while (q < t) {
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// prefetch beyond q
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Prefetch::write(q, interval);
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if (oop(q)->is_gc_marked()) {
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// q is alive
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debug_only(HeapWord* prev_obj = NULL);
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while (cur_obj < end_of_live) {
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Prefetch::write(cur_obj, interval);
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if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) {
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// cur_obj is alive
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// point all the oops to the new location
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size_t size = MarkSweep::adjust_pointers(oop(q));
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size_t size = MarkSweep::adjust_pointers(oop(cur_obj));
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size = space->adjust_obj_size(size);
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debug_only(prev_q = q);
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q += size;
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debug_only(prev_obj = cur_obj);
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cur_obj += size;
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} else {
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debug_only(prev_q = q);
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// q is not a live object, instead it points at the next live object
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q = *(HeapWord**)q;
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assert(q > prev_q, "we should be moving forward through memory, q: " PTR_FORMAT ", prev_q: " PTR_FORMAT, p2i(q), p2i(prev_q));
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debug_only(prev_obj = cur_obj);
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// cur_obj is not a live object, instead it points at the next live object
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cur_obj = *(HeapWord**)cur_obj;
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assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj));
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}
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}
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assert(q == t, "just checking");
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assert(cur_obj == end_of_live, "just checking");
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}
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#ifdef ASSERT
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template <class SpaceType>
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inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
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// Copy all live objects to their new location
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// Used by MarkSweep::mark_sweep_phase4()
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inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) {
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HeapWord* cur_obj = space->bottom();
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HeapWord* q = space->bottom();
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HeapWord* const t = space->_end_of_live;
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debug_only(HeapWord* prev_q = NULL);
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if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
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// we have a chunk of the space which hasn't moved and we've reinitialized
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// the mark word during the previous pass, so we can't use is_gc_marked for
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// the traversal.
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HeapWord* prev_obj = NULL;
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if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {
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#ifdef ASSERT // Debug only
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// we have a chunk of the space which hasn't moved and we've reinitialized
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// the mark word during the previous pass, so we can't use is_gc_marked for
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// the traversal.
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HeapWord* const end = space->_first_dead;
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while (q < end) {
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size_t size = space->obj_size(q);
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assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
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prev_q = q;
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q += size;
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}
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#endif
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if (space->_first_dead == t) {
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q = t;
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} else {
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// $$$ Funky
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q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer();
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}
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}
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const intx scan_interval = PrefetchScanIntervalInBytes;
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const intx copy_interval = PrefetchCopyIntervalInBytes;
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while (q < t) {
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if (!oop(q)->is_gc_marked()) {
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// mark is pointer to next marked oop
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debug_only(prev_q = q);
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q = (HeapWord*) oop(q)->mark()->decode_pointer();
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assert(q > prev_q, "we should be moving forward through memory");
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} else {
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// prefetch beyond q
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Prefetch::read(q, scan_interval);
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// size and destination
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size_t size = space->obj_size(q);
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HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();
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// prefetch beyond compaction_top
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Prefetch::write(compaction_top, copy_interval);
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// copy object and reinit its mark
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assert(q != compaction_top, "everything in this pass should be moving");
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Copy::aligned_conjoint_words(q, compaction_top, size);
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oop(compaction_top)->init_mark();
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assert(oop(compaction_top)->klass() != NULL, "should have a class");
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debug_only(prev_q = q);
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q += size;
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}
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while (cur_obj < space->_first_dead) {
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size_t size = space->obj_size(cur_obj);
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assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
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prev_obj = cur_obj;
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cur_obj += size;
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}
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}
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}
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#endif
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template <class SpaceType>
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inline void CompactibleSpace::clear_empty_region(SpaceType* space) {
|
||||
// Let's remember if we were empty before we did the compaction.
|
||||
bool was_empty = space->used_region().is_empty();
|
||||
// Reset space after compaction is complete
|
||||
@ -320,6 +286,65 @@ inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
|
||||
}
|
||||
}
|
||||
|
||||
template <class SpaceType>
|
||||
inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
|
||||
// Copy all live objects to their new location
|
||||
// Used by MarkSweep::mark_sweep_phase4()
|
||||
|
||||
verify_up_to_first_dead(space);
|
||||
|
||||
HeapWord* const end_of_live = space->_end_of_live;
|
||||
|
||||
assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live));
|
||||
if (space->_first_dead == end_of_live && !oop(space->bottom())->is_gc_marked()) {
|
||||
// Nothing to compact. The space is either empty or all live object should be left in place.
|
||||
clear_empty_region(space);
|
||||
return;
|
||||
}
|
||||
|
||||
const intx scan_interval = PrefetchScanIntervalInBytes;
|
||||
const intx copy_interval = PrefetchCopyIntervalInBytes;
|
||||
|
||||
assert(space->bottom() < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(space->bottom()), p2i(end_of_live));
|
||||
HeapWord* cur_obj = space->bottom();
|
||||
if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
|
||||
// All object before _first_dead can be skipped. They should not be moved.
|
||||
// A pointer to the first live object is stored at the memory location for _first_dead.
|
||||
cur_obj = *(HeapWord**)(space->_first_dead);
|
||||
}
|
||||
|
||||
debug_only(HeapWord* prev_obj = NULL);
|
||||
while (cur_obj < end_of_live) {
|
||||
if (!oop(cur_obj)->is_gc_marked()) {
|
||||
debug_only(prev_obj = cur_obj);
|
||||
// The first word of the dead object contains a pointer to the next live object or end of space.
|
||||
cur_obj = *(HeapWord**)cur_obj;
|
||||
assert(cur_obj > prev_obj, "we should be moving forward through memory");
|
||||
} else {
|
||||
// prefetch beyond q
|
||||
Prefetch::read(cur_obj, scan_interval);
|
||||
|
||||
// size and destination
|
||||
size_t size = space->obj_size(cur_obj);
|
||||
HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee();
|
||||
|
||||
// prefetch beyond compaction_top
|
||||
Prefetch::write(compaction_top, copy_interval);
|
||||
|
||||
// copy object and reinit its mark
|
||||
assert(cur_obj != compaction_top, "everything in this pass should be moving");
|
||||
Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
|
||||
oop(compaction_top)->init_mark();
|
||||
assert(oop(compaction_top)->klass() != NULL, "should have a class");
|
||||
|
||||
debug_only(prev_obj = cur_obj);
|
||||
cur_obj += size;
|
||||
}
|
||||
}
|
||||
|
||||
clear_empty_region(space);
|
||||
}
|
||||
|
||||
size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const {
|
||||
return oop(addr)->size();
|
||||
}
|
||||
|
Loading…
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Reference in New Issue
Block a user