/*

 * Copyright (c) 2014, 2019, 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/shared/preservedMarks.inline.hpp"

#include "gc/shenandoah/shenandoahForwarding.inline.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.inline.hpp"

#include "gc/shenandoah/shenandoahHeuristics.hpp"

#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"

#include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"

#include "gc/shenandoah/shenandoahTraversalGC.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 "memory/universe.hpp"

#include "oops/compressedOops.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/biasedLocking.hpp"

#include "runtime/thread.hpp"

#include "utilities/copy.hpp"

#include "utilities/growableArray.hpp"

#include "gc/shared/workgroup.hpp"

ShenandoahMarkCompact::ShenandoahMarkCompact() :

  _gc_timer(NULL),

  _preserved_marks(new PreservedMarksSet(true)) {}

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->set_concurrent_mark_in_progress(false);

    }

    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);

    // f. Sync pinned region status from the CP marks

    heap->sync_pinned_region_status();

    // The rest of prologue:

    BiasedLocking::preserve_marks();

    _preserved_marks->init(heap->workers()->active_workers());

  }

  heap->make_parsable(true);

  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 resolves with fwdptr 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);

  }

  {

    // Epilogue

    SharedRestorePreservedMarksTaskExecutor exec(heap->workers());

    _preserved_marks->restore(&exec);

    BiasedLocking::restore_marks();

    _preserved_marks->reclaim();

  }

  // 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);

  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();

  heap->parallel_cleaning(true /* full_gc */);

}

class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {

private:

  PreservedMarks*          const _preserved_marks;

  ShenandoahHeap*          const _heap;

  GrowableArray<ShenandoahHeapRegion*>& _empty_regions;

  int _empty_regions_pos;

  ShenandoahHeapRegion*          _to_region;

  ShenandoahHeapRegion*          _from_region;

  HeapWord* _compact_point;

public:

  ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,

                                              GrowableArray<ShenandoahHeapRegion*>& empty_regions,

                                              ShenandoahHeapRegion* to_region) :

    _preserved_marks(preserved_marks),

    _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();

    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);

    _preserved_marks->push_if_necessary(p, p->mark_raw());

    p->forward_to(oop(_compact_point));

    _compact_point += obj_size;

  }

};

class ShenandoahPrepareForCompactionTask : public AbstractGangTask {

private:

  PreservedMarksSet*        const _preserved_marks;

  ShenandoahHeap*           const _heap;

  ShenandoahHeapRegionSet** const _worker_slices;

  ShenandoahRegionIterator        _heap_regions;

  ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {

    ShenandoahHeapRegion* from_region = _heap_regions.next();

    // Look for next candidate for this slice:

    while (from_region != NULL) {

      // Empty region: get it into the slice to defragment the slice itself.

      // We could have skipped this without violating correctness, but we really

      // want to compact all live regions to the start of the heap, which sometimes

      // means moving them into the fully empty regions.

      if (from_region->is_empty()) break;

      // Can move the region, and this is not the humongous region. Humongous

      // moves are special cased here, because their moves are handled separately.

      if (from_region->is_stw_move_allowed() && !from_region->is_humongous()) break;

      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_empty() || from_region->is_stw_move_allowed(), "only regions that can be moved in mark-compact");

      slice->add_region(from_region);

    }

    return from_region;

  }

public:

  ShenandoahPrepareForCompactionTask(PreservedMarksSet* preserved_marks, ShenandoahHeapRegionSet** worker_slices) :

    AbstractGangTask("Shenandoah Prepare For Compaction Task"),

    _preserved_marks(preserved_marks),

    _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(_preserved_marks->get(worker_id), 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(); c > 0; c--) {

    ShenandoahHeapRegion *r = heap->get_region(c - 1);

    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_stw_move_allowed()) {

      // From-region candidate: movable humongous region

      oop old_obj = oop(r->bottom());

      size_t words_size = old_obj->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.

        _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark_raw());

        old_obj->forward_to(oop(heap->get_region(start)->bottom()));

        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());

      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();

  // About to figure out which regions can be compacted, make sure pinning status

  // had been updated in GC prologue.

  heap->assert_pinned_region_status();

  {

    // 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.