src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp

/*
 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * 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.
 *
 */

#ifndef SHARE_VM_GC_G1_G1CONCURRENTMARK_INLINE_HPP
#define SHARE_VM_GC_G1_G1CONCURRENTMARK_INLINE_HPP

#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1ConcurrentMark.hpp"
#include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
#include "gc/g1/g1ConcurrentMarkObjArrayProcessor.inline.hpp"
#include "gc/g1/suspendibleThreadSet.hpp"
#include "gc/shared/taskqueue.inline.hpp"
#include "utilities/bitMap.inline.hpp"

inline bool G1ConcurrentMark::mark_in_next_bitmap(oop const obj) {
  HeapRegion* const hr = _g1h->heap_region_containing(obj);
  return mark_in_next_bitmap(hr, obj);
}

inline bool G1ConcurrentMark::mark_in_next_bitmap(HeapRegion* const hr, oop const obj) {
  assert(hr != NULL, "just checking");
  assert(hr->is_in_reserved(obj), "Attempting to mark object at " PTR_FORMAT " that is not contained in the given region %u", p2i(obj), hr->hrm_index());

  if (hr->obj_allocated_since_next_marking(obj)) {
    return false;
  }

  // Some callers may have stale objects to mark above nTAMS after humongous reclaim.
  // Can't assert that this is a valid object at this point, since it might be in the process of being copied by another thread.
  assert(!hr->is_continues_humongous(), "Should not try to mark object " PTR_FORMAT " in Humongous continues region %u above nTAMS " PTR_FORMAT, p2i(obj), hr->hrm_index(), p2i(hr->next_top_at_mark_start()));

  HeapWord* const obj_addr = (HeapWord*)obj;
  // Dirty read to avoid CAS.
  if (_nextMarkBitMap->is_marked(obj_addr)) {
    return false;
  }

  return _nextMarkBitMap->par_mark(obj_addr);
}

#ifndef PRODUCT
template<typename Fn>
inline void G1CMMarkStack::iterate(Fn fn) const {
  assert_at_safepoint(true);

  size_t num_chunks = 0;

  TaskQueueEntryChunk* cur = _chunk_list;
  while (cur != NULL) {
    guarantee(num_chunks <= _chunks_in_chunk_list, "Found " SIZE_FORMAT " oop chunks which is more than there should be", num_chunks);

    for (size_t i = 0; i < EntriesPerChunk; ++i) {
      if (cur->data[i].is_null()) {
        break;
      }
      fn(cur->data[i]);
    }
    cur = cur->next;
    num_chunks++;
  }
}
#endif

// It scans an object and visits its children.
inline void G1CMTask::scan_task_entry(G1TaskQueueEntry task_entry) { process_grey_task_entry<true>(task_entry); }

inline void G1CMTask::push(G1TaskQueueEntry task_entry) {
  assert(task_entry.is_array_slice() || _g1h->is_in_g1_reserved(task_entry.obj()), "invariant");
  assert(task_entry.is_array_slice() || !_g1h->is_on_master_free_list(
              _g1h->heap_region_containing(task_entry.obj())), "invariant");
  assert(task_entry.is_array_slice() || !_g1h->is_obj_ill(task_entry.obj()), "invariant");  // FIXME!!!
  assert(task_entry.is_array_slice() || _nextMarkBitMap->is_marked((HeapWord*)task_entry.obj()), "invariant");

  if (!_task_queue->push(task_entry)) {
    // The local task queue looks full. We need to push some entries
    // to the global stack.
    move_entries_to_global_stack();

    // this should succeed since, even if we overflow the global
    // stack, we should have definitely removed some entries from the
    // local queue. So, there must be space on it.
    bool success = _task_queue->push(task_entry);
    assert(success, "invariant");
  }
}

inline bool G1CMTask::is_below_finger(oop obj, HeapWord* global_finger) const {
  // If obj is above the global finger, then the mark bitmap scan
  // will find it later, and no push is needed.  Similarly, if we have
  // a current region and obj is between the local finger and the
  // end of the current region, then no push is needed.  The tradeoff
  // of checking both vs only checking the global finger is that the
  // local check will be more accurate and so result in fewer pushes,
  // but may also be a little slower.
  HeapWord* objAddr = (HeapWord*)obj;
  if (_finger != NULL) {
    // We have a current region.

    // Finger and region values are all NULL or all non-NULL.  We
    // use _finger to check since we immediately use its value.
    assert(_curr_region != NULL, "invariant");
    assert(_region_limit != NULL, "invariant");
    assert(_region_limit <= global_finger, "invariant");

    // True if obj is less than the local finger, or is between
    // the region limit and the global finger.
    if (objAddr < _finger) {
      return true;
    } else if (objAddr < _region_limit) {
      return false;
    } // Else check global finger.
  }
  // Check global finger.
  return objAddr < global_finger;
}

template<bool scan>
inline void G1CMTask::process_grey_task_entry(G1TaskQueueEntry task_entry) {
  assert(scan || (task_entry.is_oop() && task_entry.obj()->is_typeArray()), "Skipping scan of grey non-typeArray");
  assert(task_entry.is_array_slice() || _nextMarkBitMap->is_marked((HeapWord*)task_entry.obj()),
         "Any stolen object should be a slice or marked");

  if (scan) {
    if (task_entry.is_array_slice()) {
      _words_scanned += _objArray_processor.process_slice(task_entry.slice());
    } else {
      oop obj = task_entry.obj();
      if (G1CMObjArrayProcessor::should_be_sliced(obj)) {
        _words_scanned += _objArray_processor.process_obj(obj);
      } else {
        _words_scanned += obj->oop_iterate_size(_cm_oop_closure);;
      }
    }
  }
  check_limits();
}

inline size_t G1CMTask::scan_objArray(objArrayOop obj, MemRegion mr) {
  obj->oop_iterate(_cm_oop_closure, mr);
  return mr.word_size();
}

inline void G1CMTask::make_reference_grey(oop obj) {
  if (!_cm->mark_in_next_bitmap(obj)) {
    return;
  }

  // No OrderAccess:store_load() is needed. It is implicit in the
  // CAS done in G1CMBitMap::parMark() call in the routine above.
  HeapWord* global_finger = _cm->finger();

  // We only need to push a newly grey object on the mark
  // stack if it is in a section of memory the mark bitmap
  // scan has already examined.  Mark bitmap scanning
  // maintains progress "fingers" for determining that.
  //
  // Notice that the global finger might be moving forward
  // concurrently. This is not a problem. In the worst case, we
  // mark the object while it is above the global finger and, by
  // the time we read the global finger, it has moved forward
  // past this object. In this case, the object will probably
  // be visited when a task is scanning the region and will also
  // be pushed on the stack. So, some duplicate work, but no
  // correctness problems.
  if (is_below_finger(obj, global_finger)) {
    G1TaskQueueEntry entry = G1TaskQueueEntry::from_oop(obj);
    if (obj->is_typeArray()) {
      // Immediately process arrays of primitive types, rather
      // than pushing on the mark stack.  This keeps us from
      // adding humongous objects to the mark stack that might
      // be reclaimed before the entry is processed - see
      // selection of candidates for eager reclaim of humongous
      // objects.  The cost of the additional type test is
      // mitigated by avoiding a trip through the mark stack,
      // by only doing a bookkeeping update and avoiding the
      // actual scan of the object - a typeArray contains no
      // references, and the metadata is built-in.
      process_grey_task_entry<false>(entry);
    } else {
      push(entry);
    }
  }
}

inline void G1CMTask::deal_with_reference(oop obj) {
  increment_refs_reached();
  if (obj == NULL) {
    return;
  }
  make_reference_grey(obj);
}

inline void G1ConcurrentMark::markPrev(oop p) {
  assert(!_prevMarkBitMap->is_marked((HeapWord*) p), "sanity");
 _prevMarkBitMap->mark((HeapWord*) p);
}

bool G1ConcurrentMark::isPrevMarked(oop p) const {
  assert(p != NULL && oopDesc::is_oop(p), "expected an oop");
  return _prevMarkBitMap->is_marked((HeapWord*)p);
}

inline bool G1ConcurrentMark::do_yield_check() {
  if (SuspendibleThreadSet::should_yield()) {
    SuspendibleThreadSet::yield();
    return true;
  } else {
    return false;
  }
}

#endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_INLINE_HPP