--- /dev/null 2018-11-26 11:49:18.255023023 +0100 +++ new/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp 2018-11-26 21:29:01.937647585 +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/shenandoahWorkerPolicy.hpp" +#include "gc/shenandoah/vm_operations_shenandoah.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& _empty_regions; + int _empty_regions_pos; + ShenandoahHeapRegion* _to_region; + ShenandoahHeapRegion* _from_region; + HeapWord* _compact_point; + +public: + ShenandoahPrepareForCompactionObjectClosure(GrowableArray& 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 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 + 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::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(); +}