--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp Mon Dec 10 15:47:44 2018 +0100
@@ -0,0 +1,844 @@
+/*
+ * Copyright (c) 2014, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+
+#include "code/codeCache.hpp"
+#include "gc/shared/gcTraceTime.inline.hpp"
+#include "gc/shenandoah/shenandoahBrooksPointer.hpp"
+#include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
+#include "gc/shenandoah/shenandoahCollectionSet.hpp"
+#include "gc/shenandoah/shenandoahFreeSet.hpp"
+#include "gc/shenandoah/shenandoahPhaseTimings.hpp"
+#include "gc/shenandoah/shenandoahMarkCompact.hpp"
+#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahHeap.inline.hpp"
+#include "gc/shenandoah/shenandoahHeuristics.hpp"
+#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
+#include "gc/shenandoah/shenandoahRootProcessor.hpp"
+#include "gc/shenandoah/shenandoahTraversalGC.hpp"
+#include "gc/shenandoah/shenandoahTaskqueue.hpp"
+#include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
+#include "gc/shenandoah/shenandoahUtils.hpp"
+#include "gc/shenandoah/shenandoahVerifier.hpp"
+#include "gc/shenandoah/shenandoahVMOperations.hpp"
+#include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
+#include "memory/metaspace.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/thread.hpp"
+#include "utilities/copy.hpp"
+#include "utilities/growableArray.hpp"
+#include "gc/shared/workgroup.hpp"
+
+void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
+ _gc_timer = gc_timer;
+}
+
+void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) {
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_before_fullgc();
+ }
+
+ if (VerifyBeforeGC) {
+ Universe::verify();
+ }
+
+ heap->set_full_gc_in_progress(true);
+
+ assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
+ assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
+
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
+ heap->pre_full_gc_dump(_gc_timer);
+ }
+
+ {
+ ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
+ // Full GC is supposed to recover from any GC state:
+
+ // a0. Remember if we have forwarded objects
+ bool has_forwarded_objects = heap->has_forwarded_objects();
+
+ // a1. Cancel evacuation, if in progress
+ if (heap->is_evacuation_in_progress()) {
+ heap->set_evacuation_in_progress(false);
+ }
+ assert(!heap->is_evacuation_in_progress(), "sanity");
+
+ // a2. Cancel update-refs, if in progress
+ if (heap->is_update_refs_in_progress()) {
+ heap->set_update_refs_in_progress(false);
+ }
+ assert(!heap->is_update_refs_in_progress(), "sanity");
+
+ // a3. Cancel concurrent traversal GC, if in progress
+ if (heap->is_concurrent_traversal_in_progress()) {
+ heap->traversal_gc()->reset();
+ heap->set_concurrent_traversal_in_progress(false);
+ }
+
+ // b. Cancel concurrent mark, if in progress
+ if (heap->is_concurrent_mark_in_progress()) {
+ heap->concurrent_mark()->cancel();
+ heap->stop_concurrent_marking();
+ }
+ assert(!heap->is_concurrent_mark_in_progress(), "sanity");
+
+ // c. Reset the bitmaps for new marking
+ heap->reset_mark_bitmap();
+ assert(heap->marking_context()->is_bitmap_clear(), "sanity");
+ assert(!heap->marking_context()->is_complete(), "sanity");
+
+ // d. Abandon reference discovery and clear all discovered references.
+ ReferenceProcessor* rp = heap->ref_processor();
+ rp->disable_discovery();
+ rp->abandon_partial_discovery();
+ rp->verify_no_references_recorded();
+
+ // e. Set back forwarded objects bit back, in case some steps above dropped it.
+ heap->set_has_forwarded_objects(has_forwarded_objects);
+ }
+
+ heap->make_parsable(true);
+
+ CodeCache::gc_prologue();
+
+ OrderAccess::fence();
+
+ phase1_mark_heap();
+
+ // Once marking is done, which may have fixed up forwarded objects, we can drop it.
+ // Coming out of Full GC, we would not have any forwarded objects.
+ // This also prevents read barrier from kicking in while adjusting pointers in phase3.
+ heap->set_has_forwarded_objects(false);
+
+ heap->set_full_gc_move_in_progress(true);
+
+ // Setup workers for the rest
+ OrderAccess::fence();
+
+ // Initialize worker slices
+ ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
+ for (uint i = 0; i < heap->max_workers(); i++) {
+ worker_slices[i] = new ShenandoahHeapRegionSet();
+ }
+
+ {
+ // The rest of code performs region moves, where region status is undefined
+ // until all phases run together.
+ ShenandoahHeapLocker lock(heap->lock());
+
+ phase2_calculate_target_addresses(worker_slices);
+
+ OrderAccess::fence();
+
+ phase3_update_references();
+
+ phase4_compact_objects(worker_slices);
+ }
+
+ // Resize metaspace
+ MetaspaceGC::compute_new_size();
+
+ // Free worker slices
+ for (uint i = 0; i < heap->max_workers(); i++) {
+ delete worker_slices[i];
+ }
+ FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
+
+ CodeCache::gc_epilogue();
+ JvmtiExport::gc_epilogue();
+
+ heap->set_full_gc_move_in_progress(false);
+ heap->set_full_gc_in_progress(false);
+
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_after_fullgc();
+ }
+
+ if (VerifyAfterGC) {
+ Universe::verify();
+ }
+
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
+ heap->post_full_gc_dump(_gc_timer);
+ }
+}
+
+class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
+private:
+ ShenandoahMarkingContext* const _ctx;
+
+public:
+ ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
+
+ void heap_region_do(ShenandoahHeapRegion *r) {
+ _ctx->capture_top_at_mark_start(r);
+ r->clear_live_data();
+ r->set_concurrent_iteration_safe_limit(r->top());
+ }
+};
+
+void ShenandoahMarkCompact::phase1_mark_heap() {
+ GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
+ ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
+
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ ShenandoahPrepareForMarkClosure cl;
+ heap->heap_region_iterate(&cl);
+
+ ShenandoahConcurrentMark* cm = heap->concurrent_mark();
+
+ heap->set_process_references(heap->heuristics()->can_process_references());
+ heap->set_unload_classes(heap->heuristics()->can_unload_classes());
+
+ ReferenceProcessor* rp = heap->ref_processor();
+ // enable ("weak") refs discovery
+ rp->enable_discovery(true /*verify_no_refs*/);
+ rp->setup_policy(true); // forcefully purge all soft references
+ rp->set_active_mt_degree(heap->workers()->active_workers());
+
+ cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
+ cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
+ cm->finish_mark_from_roots(/* full_gc = */ true);
+
+ heap->mark_complete_marking_context();
+}
+
+class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
+private:
+ ShenandoahHeap* const _heap;
+ GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
+ int _empty_regions_pos;
+ ShenandoahHeapRegion* _to_region;
+ ShenandoahHeapRegion* _from_region;
+ HeapWord* _compact_point;
+
+public:
+ ShenandoahPrepareForCompactionObjectClosure(GrowableArray<ShenandoahHeapRegion*>& empty_regions, ShenandoahHeapRegion* to_region) :
+ _heap(ShenandoahHeap::heap()),
+ _empty_regions(empty_regions),
+ _empty_regions_pos(0),
+ _to_region(to_region),
+ _from_region(NULL),
+ _compact_point(to_region->bottom()) {}
+
+ void set_from_region(ShenandoahHeapRegion* from_region) {
+ _from_region = from_region;
+ }
+
+ void finish_region() {
+ assert(_to_region != NULL, "should not happen");
+ _to_region->set_new_top(_compact_point);
+ }
+
+ bool is_compact_same_region() {
+ return _from_region == _to_region;
+ }
+
+ int empty_regions_pos() {
+ return _empty_regions_pos;
+ }
+
+ void do_object(oop p) {
+ assert(_from_region != NULL, "must set before work");
+ assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
+ assert(!_heap->complete_marking_context()->allocated_after_mark_start((HeapWord*) p), "must be truly marked");
+
+ size_t obj_size = p->size() + ShenandoahBrooksPointer::word_size();
+ if (_compact_point + obj_size > _to_region->end()) {
+ finish_region();
+
+ // Object doesn't fit. Pick next empty region and start compacting there.
+ ShenandoahHeapRegion* new_to_region;
+ if (_empty_regions_pos < _empty_regions.length()) {
+ new_to_region = _empty_regions.at(_empty_regions_pos);
+ _empty_regions_pos++;
+ } else {
+ // Out of empty region? Compact within the same region.
+ new_to_region = _from_region;
+ }
+
+ assert(new_to_region != _to_region, "must not reuse same to-region");
+ assert(new_to_region != NULL, "must not be NULL");
+ _to_region = new_to_region;
+ _compact_point = _to_region->bottom();
+ }
+
+ // Object fits into current region, record new location:
+ assert(_compact_point + obj_size <= _to_region->end(), "must fit");
+ shenandoah_assert_not_forwarded(NULL, p);
+ ShenandoahBrooksPointer::set_raw(p, _compact_point + ShenandoahBrooksPointer::word_size());
+ _compact_point += obj_size;
+ }
+};
+
+class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahHeapRegionSet** const _worker_slices;
+ ShenandoahRegionIterator _heap_regions;
+
+ ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
+ ShenandoahHeapRegion* from_region = _heap_regions.next();
+
+ while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) {
+ from_region = _heap_regions.next();
+ }
+
+ if (from_region != NULL) {
+ assert(slice != NULL, "sanity");
+ assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
+ assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact");
+ slice->add_region(from_region);
+ }
+
+ return from_region;
+ }
+
+public:
+ ShenandoahPrepareForCompactionTask(ShenandoahHeapRegionSet** worker_slices) :
+ AbstractGangTask("Shenandoah Prepare For Compaction Task"),
+ _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
+ }
+
+ void work(uint worker_id) {
+ ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
+ ShenandoahHeapRegion* from_region = next_from_region(slice);
+ // No work?
+ if (from_region == NULL) {
+ return;
+ }
+
+ // Sliding compaction. Walk all regions in the slice, and compact them.
+ // Remember empty regions and reuse them as needed.
+ ResourceMark rm;
+ GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
+ ShenandoahPrepareForCompactionObjectClosure cl(empty_regions, from_region);
+ while (from_region != NULL) {
+ cl.set_from_region(from_region);
+ if (from_region->has_live()) {
+ _heap->marked_object_iterate(from_region, &cl);
+ }
+
+ // Compacted the region to somewhere else? From-region is empty then.
+ if (!cl.is_compact_same_region()) {
+ empty_regions.append(from_region);
+ }
+ from_region = next_from_region(slice);
+ }
+ cl.finish_region();
+
+ // Mark all remaining regions as empty
+ for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
+ ShenandoahHeapRegion* r = empty_regions.at(pos);
+ r->set_new_top(r->bottom());
+ }
+ }
+};
+
+void ShenandoahMarkCompact::calculate_target_humongous_objects() {
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ // Compute the new addresses for humongous objects. We need to do this after addresses
+ // for regular objects are calculated, and we know what regions in heap suffix are
+ // available for humongous moves.
+ //
+ // Scan the heap backwards, because we are compacting humongous regions towards the end.
+ // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
+ // humongous start there.
+ //
+ // The complication is potential non-movable regions during the scan. If such region is
+ // detected, then sliding restarts towards that non-movable region.
+
+ size_t to_begin = heap->num_regions();
+ size_t to_end = heap->num_regions();
+
+ for (size_t c = heap->num_regions() - 1; c > 0; c--) {
+ ShenandoahHeapRegion *r = heap->get_region(c);
+ if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
+ // To-region candidate: record this, and continue scan
+ to_begin = r->region_number();
+ continue;
+ }
+
+ if (r->is_humongous_start() && r->is_move_allowed()) {
+ // From-region candidate: movable humongous region
+ oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
+ size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size();
+ size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
+
+ size_t start = to_end - num_regions;
+
+ if (start >= to_begin && start != r->region_number()) {
+ // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
+ ShenandoahBrooksPointer::set_raw(old_obj, heap->get_region(start)->bottom() + ShenandoahBrooksPointer::word_size());
+ to_end = start;
+ continue;
+ }
+ }
+
+ // Failed to fit. Scan starting from current region.
+ to_begin = r->region_number();
+ to_end = r->region_number();
+ }
+}
+
+class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
+private:
+ ShenandoahHeap* const _heap;
+
+public:
+ ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
+ void heap_region_do(ShenandoahHeapRegion* r) {
+ if (r->is_trash()) {
+ r->recycle();
+ }
+ if (r->is_cset()) {
+ r->make_regular_bypass();
+ }
+ if (r->is_empty_uncommitted()) {
+ r->make_committed_bypass();
+ }
+ assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number());
+
+ // Record current region occupancy: this communicates empty regions are free
+ // to the rest of Full GC code.
+ r->set_new_top(r->top());
+ }
+};
+
+class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahMarkingContext* const _ctx;
+
+public:
+ ShenandoahTrashImmediateGarbageClosure() :
+ _heap(ShenandoahHeap::heap()),
+ _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
+
+ void heap_region_do(ShenandoahHeapRegion* r) {
+ if (r->is_humongous_start()) {
+ oop humongous_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
+ if (!_ctx->is_marked(humongous_obj)) {
+ assert(!r->has_live(),
+ "Region " SIZE_FORMAT " is not marked, should not have live", r->region_number());
+ _heap->trash_humongous_region_at(r);
+ } else {
+ assert(r->has_live(),
+ "Region " SIZE_FORMAT " should have live", r->region_number());
+ }
+ } else if (r->is_humongous_continuation()) {
+ // If we hit continuation, the non-live humongous starts should have been trashed already
+ assert(r->humongous_start_region()->has_live(),
+ "Region " SIZE_FORMAT " should have live", r->region_number());
+ } else if (r->is_regular()) {
+ if (!r->has_live()) {
+ r->make_trash_immediate();
+ }
+ }
+ }
+};
+
+void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
+ GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
+ ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
+
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ {
+ // Trash the immediately collectible regions before computing addresses
+ ShenandoahTrashImmediateGarbageClosure tigcl;
+ heap->heap_region_iterate(&tigcl);
+
+ // Make sure regions are in good state: committed, active, clean.
+ // This is needed because we are potentially sliding the data through them.
+ ShenandoahEnsureHeapActiveClosure ecl;
+ heap->heap_region_iterate(&ecl);
+ }
+
+ // Compute the new addresses for regular objects
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
+ ShenandoahPrepareForCompactionTask prepare_task(worker_slices);
+ heap->workers()->run_task(&prepare_task);
+ }
+
+ // Compute the new addresses for humongous objects
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
+ calculate_target_humongous_objects();
+ }
+}
+
+class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahMarkingContext* const _ctx;
+
+ template <class T>
+ inline void do_oop_work(T* p) {
+ T o = RawAccess<>::oop_load(p);
+ if (!CompressedOops::is_null(o)) {
+ oop obj = CompressedOops::decode_not_null(o);
+ assert(_ctx->is_marked(obj), "must be marked");
+ oop forw = oop(ShenandoahBrooksPointer::get_raw(obj));
+ RawAccess<IS_NOT_NULL>::oop_store(p, forw);
+ }
+ }
+
+public:
+ ShenandoahAdjustPointersClosure() :
+ _heap(ShenandoahHeap::heap()),
+ _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
+
+ void do_oop(oop* p) { do_oop_work(p); }
+ void do_oop(narrowOop* p) { do_oop_work(p); }
+};
+
+class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahAdjustPointersClosure _cl;
+
+public:
+ ShenandoahAdjustPointersObjectClosure() :
+ _heap(ShenandoahHeap::heap()) {
+ }
+ void do_object(oop p) {
+ assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
+ HeapWord* forw = ShenandoahBrooksPointer::get_raw(p);
+ p->oop_iterate(&_cl);
+ }
+};
+
+class ShenandoahAdjustPointersTask : public AbstractGangTask {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahRegionIterator _regions;
+
+public:
+ ShenandoahAdjustPointersTask() :
+ AbstractGangTask("Shenandoah Adjust Pointers Task"),
+ _heap(ShenandoahHeap::heap()) {
+ }
+
+ void work(uint worker_id) {
+ ShenandoahAdjustPointersObjectClosure obj_cl;
+ ShenandoahHeapRegion* r = _regions.next();
+ while (r != NULL) {
+ if (!r->is_humongous_continuation() && r->has_live()) {
+ _heap->marked_object_iterate(r, &obj_cl);
+ }
+ r = _regions.next();
+ }
+ }
+};
+
+class ShenandoahAdjustRootPointersTask : public AbstractGangTask {
+private:
+ ShenandoahRootProcessor* _rp;
+
+public:
+ ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp) :
+ AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
+ _rp(rp) {}
+
+ void work(uint worker_id) {
+ ShenandoahAdjustPointersClosure cl;
+ CLDToOopClosure adjust_cld_closure(&cl, ClassLoaderData::_claim_strong);
+ MarkingCodeBlobClosure adjust_code_closure(&cl,
+ CodeBlobToOopClosure::FixRelocations);
+
+ _rp->process_all_roots(&cl, &cl,
+ &adjust_cld_closure,
+ &adjust_code_closure, NULL, worker_id);
+ }
+};
+
+void ShenandoahMarkCompact::phase3_update_references() {
+ GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
+ ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
+
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ WorkGang* workers = heap->workers();
+ uint nworkers = workers->active_workers();
+ {
+#if COMPILER2_OR_JVMCI
+ DerivedPointerTable::clear();
+#endif
+ ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots);
+ ShenandoahAdjustRootPointersTask task(&rp);
+ workers->run_task(&task);
+#if COMPILER2_OR_JVMCI
+ DerivedPointerTable::update_pointers();
+#endif
+ }
+
+ ShenandoahAdjustPointersTask adjust_pointers_task;
+ workers->run_task(&adjust_pointers_task);
+}
+
+class ShenandoahCompactObjectsClosure : public ObjectClosure {
+private:
+ ShenandoahHeap* const _heap;
+ uint const _worker_id;
+
+public:
+ ShenandoahCompactObjectsClosure(uint worker_id) :
+ _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
+
+ void do_object(oop p) {
+ assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
+ size_t size = (size_t)p->size();
+ HeapWord* compact_to = ShenandoahBrooksPointer::get_raw(p);
+ HeapWord* compact_from = (HeapWord*) p;
+ if (compact_from != compact_to) {
+ Copy::aligned_conjoint_words(compact_from, compact_to, size);
+ }
+ oop new_obj = oop(compact_to);
+ ShenandoahBrooksPointer::initialize(new_obj);
+ }
+};
+
+class ShenandoahCompactObjectsTask : public AbstractGangTask {
+private:
+ ShenandoahHeap* const _heap;
+ ShenandoahHeapRegionSet** const _worker_slices;
+
+public:
+ ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
+ AbstractGangTask("Shenandoah Compact Objects Task"),
+ _heap(ShenandoahHeap::heap()),
+ _worker_slices(worker_slices) {
+ }
+
+ void work(uint worker_id) {
+ ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
+
+ ShenandoahCompactObjectsClosure cl(worker_id);
+ ShenandoahHeapRegion* r = slice.next();
+ while (r != NULL) {
+ assert(!r->is_humongous(), "must not get humongous regions here");
+ if (r->has_live()) {
+ _heap->marked_object_iterate(r, &cl);
+ }
+ r->set_top(r->new_top());
+ r = slice.next();
+ }
+ }
+};
+
+class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
+private:
+ ShenandoahHeap* const _heap;
+ size_t _live;
+
+public:
+ ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
+ _heap->free_set()->clear();
+ }
+
+ void heap_region_do(ShenandoahHeapRegion* r) {
+ assert (!r->is_cset(), "cset regions should have been demoted already");
+
+ // Need to reset the complete-top-at-mark-start pointer here because
+ // the complete marking bitmap is no longer valid. This ensures
+ // size-based iteration in marked_object_iterate().
+ // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
+ // pinned regions.
+ if (!r->is_pinned()) {
+ _heap->complete_marking_context()->reset_top_at_mark_start(r);
+ }
+
+ size_t live = r->used();
+
+ // Make empty regions that have been allocated into regular
+ if (r->is_empty() && live > 0) {
+ r->make_regular_bypass();
+ }
+
+ // Reclaim regular regions that became empty
+ if (r->is_regular() && live == 0) {
+ r->make_trash();
+ }
+
+ // Recycle all trash regions
+ if (r->is_trash()) {
+ live = 0;
+ r->recycle();
+ }
+
+ r->set_live_data(live);
+ r->reset_alloc_metadata_to_shared();
+ _live += live;
+ }
+
+ size_t get_live() {
+ return _live;
+ }
+};
+
+void ShenandoahMarkCompact::compact_humongous_objects() {
+ // Compact humongous regions, based on their fwdptr objects.
+ //
+ // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
+ // humongous regions are already compacted, and do not require further moves, which alleviates
+ // sliding costs. We may consider doing this in parallel in future.
+
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ for (size_t c = heap->num_regions() - 1; c > 0; c--) {
+ ShenandoahHeapRegion* r = heap->get_region(c);
+ if (r->is_humongous_start()) {
+ oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
+ size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size();
+ size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
+
+ size_t old_start = r->region_number();
+ size_t old_end = old_start + num_regions - 1;
+ size_t new_start = heap->heap_region_index_containing(ShenandoahBrooksPointer::get_raw(old_obj));
+ size_t new_end = new_start + num_regions - 1;
+
+ if (old_start == new_start) {
+ // No need to move the object, it stays at the same slot
+ continue;
+ }
+
+ assert (r->is_move_allowed(), "should be movable");
+
+ Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
+ heap->get_region(new_start)->bottom(),
+ ShenandoahHeapRegion::region_size_words()*num_regions);
+
+ oop new_obj = oop(heap->get_region(new_start)->bottom() + ShenandoahBrooksPointer::word_size());
+ ShenandoahBrooksPointer::initialize(new_obj);
+
+ {
+ for (size_t c = old_start; c <= old_end; c++) {
+ ShenandoahHeapRegion* r = heap->get_region(c);
+ r->make_regular_bypass();
+ r->set_top(r->bottom());
+ }
+
+ for (size_t c = new_start; c <= new_end; c++) {
+ ShenandoahHeapRegion* r = heap->get_region(c);
+ if (c == new_start) {
+ r->make_humongous_start_bypass();
+ } else {
+ r->make_humongous_cont_bypass();
+ }
+
+ // Trailing region may be non-full, record the remainder there
+ size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
+ if ((c == new_end) && (remainder != 0)) {
+ r->set_top(r->bottom() + remainder);
+ } else {
+ r->set_top(r->end());
+ }
+
+ r->reset_alloc_metadata_to_shared();
+ }
+ }
+ }
+ }
+}
+
+// This is slightly different to ShHeap::reset_next_mark_bitmap:
+// we need to remain able to walk pinned regions.
+// Since pinned region do not move and don't get compacted, we will get holes with
+// unreachable objects in them (which may have pointers to unloaded Klasses and thus
+// cannot be iterated over using oop->size(). The only way to safely iterate over those is using
+// a valid marking bitmap and valid TAMS pointer. This class only resets marking
+// bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
+class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
+private:
+ ShenandoahRegionIterator _regions;
+
+public:
+ ShenandoahMCResetCompleteBitmapTask() :
+ AbstractGangTask("Parallel Reset Bitmap Task") {
+ }
+
+ void work(uint worker_id) {
+ ShenandoahHeapRegion* region = _regions.next();
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+ ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
+ while (region != NULL) {
+ if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
+ ctx->clear_bitmap(region);
+ }
+ region = _regions.next();
+ }
+ }
+};
+
+void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
+ GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
+ ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
+
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+ // Compact regular objects first
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
+ ShenandoahCompactObjectsTask compact_task(worker_slices);
+ heap->workers()->run_task(&compact_task);
+ }
+
+ // Compact humongous objects after regular object moves
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
+ compact_humongous_objects();
+ }
+
+ // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
+ // and must ensure the bitmap is in sync.
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
+ ShenandoahMCResetCompleteBitmapTask task;
+ heap->workers()->run_task(&task);
+ }
+
+ // Bring regions in proper states after the collection, and set heap properties.
+ {
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
+
+ ShenandoahPostCompactClosure post_compact;
+ heap->heap_region_iterate(&post_compact);
+ heap->set_used(post_compact.get_live());
+
+ heap->collection_set()->clear();
+ heap->free_set()->rebuild();
+ }
+
+ heap->clear_cancelled_gc();
+}