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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * 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.

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#include "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1OopStarChunkedList.inline.hpp"

#include "gc/g1/g1ParScanThreadState.hpp"

#include "gc/g1/g1RemSet.hpp"

#include "oops/access.inline.hpp"

#include "oops/oop.inline.hpp"

template <class T> void G1ParScanThreadState::do_oop_evac(T* p) {

  // Reference should not be NULL here as such are never pushed to the task queue.

  oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);

  // Although we never intentionally push references outside of the collection

  // set, due to (benign) races in the claim mechanism during RSet scanning more

  // than one thread might claim the same card. So the same card may be

  // processed multiple times, and so we might get references into old gen here.

  // So we need to redo this check.

  const InCSetState in_cset_state = _g1h->in_cset_state(obj);

  // References pushed onto the work stack should never point to a humongous region

  // as they are not added to the collection set due to above precondition.

  assert(!in_cset_state.is_humongous(),

         "Obj " PTR_FORMAT " should not refer to humongous region %u from " PTR_FORMAT,

         p2i(obj), _g1h->addr_to_region((HeapWord*)obj), p2i(p));

  if (!in_cset_state.is_in_cset()) {

    // In this case somebody else already did all the work.

    return;

  }

  markOop m = obj->mark_raw();

  if (m->is_marked()) {

    obj = (oop) m->decode_pointer();

  } else {

    obj = copy_to_survivor_space(in_cset_state, obj, m);

  }

  RawAccess<IS_NOT_NULL>::oop_store(p, obj);

  assert(obj != NULL, "Must be");

  if (HeapRegion::is_in_same_region(p, obj)) {

    return;

  }

  HeapRegion* from = _g1h->heap_region_containing(p);

  if (!from->is_young()) {

    enqueue_card_if_tracked(p, obj);

  }

}

template <class T> inline void G1ParScanThreadState::push_on_queue(T* ref) {

  assert(verify_ref(ref), "sanity");

  _refs->push(ref);

}

inline void G1ParScanThreadState::do_oop_partial_array(oop* p) {

  assert(has_partial_array_mask(p), "invariant");

  oop from_obj = clear_partial_array_mask(p);

  assert(_g1h->is_in_reserved(from_obj), "must be in heap.");

  assert(from_obj->is_objArray(), "must be obj array");

  objArrayOop from_obj_array = objArrayOop(from_obj);

  // The from-space object contains the real length.

  int length                 = from_obj_array->length();

  assert(from_obj->is_forwarded(), "must be forwarded");

  oop to_obj                 = from_obj->forwardee();

  assert(from_obj != to_obj, "should not be chunking self-forwarded objects");

  objArrayOop to_obj_array   = objArrayOop(to_obj);

  // We keep track of the next start index in the length field of the

  // to-space object.

  int next_index             = to_obj_array->length();

  assert(0 <= next_index && next_index < length,

         "invariant, next index: %d, length: %d", next_index, length);

  int start                  = next_index;

  int end                    = length;

  int remainder              = end - start;

  // We'll try not to push a range that's smaller than ParGCArrayScanChunk.

  if (remainder > 2 * ParGCArrayScanChunk) {

    end = start + ParGCArrayScanChunk;

    to_obj_array->set_length(end);

    // Push the remainder before we process the range in case another

    // worker has run out of things to do and can steal it.

    oop* from_obj_p = set_partial_array_mask(from_obj);

    push_on_queue(from_obj_p);

  } else {

    assert(length == end, "sanity");

    // We'll process the final range for this object. Restore the length

    // so that the heap remains parsable in case of evacuation failure.

    to_obj_array->set_length(end);

  }

  HeapRegion* hr = _g1h->heap_region_containing(to_obj);

  G1ScanInYoungSetter x(&_scanner, hr->is_young());

  // Process indexes [start,end). It will also process the header

  // along with the first chunk (i.e., the chunk with start == 0).

  // Note that at this point the length field of to_obj_array is not

  // correct given that we are using it to keep track of the next

  // start index. oop_iterate_range() (thankfully!) ignores the length

  // field and only relies on the start / end parameters.  It does

  // however return the size of the object which will be incorrect. So

  // we have to ignore it even if we wanted to use it.

  to_obj_array->oop_iterate_range(&_scanner, start, end);

}

inline void G1ParScanThreadState::deal_with_reference(oop* ref_to_scan) {

  if (!has_partial_array_mask(ref_to_scan)) {

    do_oop_evac(ref_to_scan);

  } else {

    do_oop_partial_array(ref_to_scan);

  }

}

inline void G1ParScanThreadState::deal_with_reference(narrowOop* ref_to_scan) {

  assert(!has_partial_array_mask(ref_to_scan), "NarrowOop* elements should never be partial arrays.");

  do_oop_evac(ref_to_scan);

}

inline void G1ParScanThreadState::dispatch_reference(StarTask ref) {

  assert(verify_task(ref), "sanity");

  if (ref.is_narrow()) {

    deal_with_reference((narrowOop*)ref);

  } else {

    deal_with_reference((oop*)ref);

  }

}

void G1ParScanThreadState::steal_and_trim_queue(RefToScanQueueSet *task_queues) {

  StarTask stolen_task;

  while (task_queues->steal(_worker_id, stolen_task)) {

    assert(verify_task(stolen_task), "sanity");

    dispatch_reference(stolen_task);

    // We've just processed a reference and we might have made

    // available new entries on the queues. So we have to make sure

    // we drain the queues as necessary.

    trim_queue();

  }

}

inline bool G1ParScanThreadState::needs_partial_trimming() const {

  return !_refs->overflow_empty() || _refs->size() > _stack_trim_upper_threshold;

}

inline bool G1ParScanThreadState::is_partially_trimmed() const {

  return _refs->overflow_empty() && _refs->size() <= _stack_trim_lower_threshold;

}

inline void G1ParScanThreadState::trim_queue_to_threshold(uint threshold) {

  StarTask ref;

  // Drain the overflow stack first, so other threads can potentially steal.

  while (_refs->pop_overflow(ref)) {

    if (!_refs->try_push_to_taskqueue(ref)) {

      dispatch_reference(ref);

    }

  }

  while (_refs->pop_local(ref, threshold)) {

    dispatch_reference(ref);

  }

}

inline void G1ParScanThreadState::trim_queue_partially() {

  if (!needs_partial_trimming()) {

    return;

  }

  const Ticks start = Ticks::now();

  do {

    trim_queue_to_threshold(_stack_trim_lower_threshold);

  } while (!is_partially_trimmed());

  _trim_ticks += Ticks::now() - start;

}

inline Tickspan G1ParScanThreadState::trim_ticks() const {

  return _trim_ticks;

}

inline void G1ParScanThreadState::reset_trim_ticks() {

  _trim_ticks = Tickspan();

}

template <typename T>

inline void G1ParScanThreadState::remember_root_into_optional_region(T* p) {

  oop o = RawAccess<IS_NOT_NULL>::oop_load(p);

  uint index = _g1h->heap_region_containing(o)->index_in_opt_cset();

  _oops_into_optional_regions[index].push_root(p);

}

template <typename T>

inline void G1ParScanThreadState::remember_reference_into_optional_region(T* p) {

  oop o = RawAccess<IS_NOT_NULL>::oop_load(p);

  uint index = _g1h->heap_region_containing(o)->index_in_opt_cset();

  _oops_into_optional_regions[index].push_oop(p);

  DEBUG_ONLY(verify_ref(p);)

}

G1OopStarChunkedList* G1ParScanThreadState::oops_into_optional_region(const HeapRegion* hr) {

  return &_oops_into_optional_regions[hr->index_in_opt_cset()];

}