src/share/vm/gc_implementation/g1/heapRegion.inline.hpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP

#include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
#include "gc_implementation/g1/g1CollectedHeap.hpp"
#include "gc_implementation/g1/heapRegion.hpp"
#include "memory/space.hpp"
#include "runtime/atomic.inline.hpp"

// This version requires locking.
inline HeapWord* G1OffsetTableContigSpace::allocate_impl(size_t size,
                                                HeapWord* const end_value) {
  HeapWord* obj = top();
  if (pointer_delta(end_value, obj) >= size) {
    HeapWord* new_top = obj + size;
    set_top(new_top);
    assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
    return obj;
  } else {
    return NULL;
  }
}

// This version is lock-free.
inline HeapWord* G1OffsetTableContigSpace::par_allocate_impl(size_t size,
                                                    HeapWord* const end_value) {
  do {
    HeapWord* obj = top();
    if (pointer_delta(end_value, obj) >= size) {
      HeapWord* new_top = obj + size;
      HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
      // result can be one of two:
      //  the old top value: the exchange succeeded
      //  otherwise: the new value of the top is returned.
      if (result == obj) {
        assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
        return obj;
      }
    } else {
      return NULL;
    }
  } while (true);
}

inline HeapWord* G1OffsetTableContigSpace::allocate(size_t size) {
  HeapWord* res = allocate_impl(size, end());
  if (res != NULL) {
    _offsets.alloc_block(res, size);
  }
  return res;
}

// Because of the requirement of keeping "_offsets" up to date with the
// allocations, we sequentialize these with a lock.  Therefore, best if
// this is used for larger LAB allocations only.
inline HeapWord* G1OffsetTableContigSpace::par_allocate(size_t size) {
  MutexLocker x(&_par_alloc_lock);
  return allocate(size);
}

inline HeapWord* G1OffsetTableContigSpace::block_start(const void* p) {
  return _offsets.block_start(p);
}

inline HeapWord*
G1OffsetTableContigSpace::block_start_const(const void* p) const {
  return _offsets.block_start_const(p);
}

inline bool
HeapRegion::block_is_obj(const HeapWord* p) const {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  if (ClassUnloadingWithConcurrentMark) {
    return !g1h->is_obj_dead(oop(p), this);
  }
  return p < top();
}

inline size_t
HeapRegion::block_size(const HeapWord *addr) const {
  if (addr == top()) {
    return pointer_delta(end(), addr);
  }

  if (block_is_obj(addr)) {
    return oop(addr)->size();
  }

  assert(ClassUnloadingWithConcurrentMark,
      err_msg("All blocks should be objects if G1 Class Unloading isn't used. "
              "HR: ["PTR_FORMAT", "PTR_FORMAT", "PTR_FORMAT") "
              "addr: " PTR_FORMAT,
              p2i(bottom()), p2i(top()), p2i(end()), p2i(addr)));

  // Old regions' dead objects may have dead classes
  // We need to find the next live object in some other
  // manner than getting the oop size
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  HeapWord* next = g1h->concurrent_mark()->prevMarkBitMap()->
      getNextMarkedWordAddress(addr, prev_top_at_mark_start());

  assert(next > addr, "must get the next live object");
  return pointer_delta(next, addr);
}

inline HeapWord* HeapRegion::par_allocate_no_bot_updates(size_t word_size) {
  assert(is_young(), "we can only skip BOT updates on young regions");
  return par_allocate_impl(word_size, end());
}

inline HeapWord* HeapRegion::allocate_no_bot_updates(size_t word_size) {
  assert(is_young(), "we can only skip BOT updates on young regions");
  return allocate_impl(word_size, end());
}

inline void HeapRegion::note_start_of_marking() {
  _next_marked_bytes = 0;
  _next_top_at_mark_start = top();
}

inline void HeapRegion::note_end_of_marking() {
  _prev_top_at_mark_start = _next_top_at_mark_start;
  _prev_marked_bytes = _next_marked_bytes;
  _next_marked_bytes = 0;

  assert(_prev_marked_bytes <=
         (size_t) pointer_delta(prev_top_at_mark_start(), bottom()) *
         HeapWordSize, "invariant");
}

inline void HeapRegion::note_start_of_copying(bool during_initial_mark) {
  if (is_survivor()) {
    // This is how we always allocate survivors.
    assert(_next_top_at_mark_start == bottom(), "invariant");
  } else {
    if (during_initial_mark) {
      // During initial-mark we'll explicitly mark any objects on old
      // regions that are pointed to by roots. Given that explicit
      // marks only make sense under NTAMS it'd be nice if we could
      // check that condition if we wanted to. Given that we don't
      // know where the top of this region will end up, we simply set
      // NTAMS to the end of the region so all marks will be below
      // NTAMS. We'll set it to the actual top when we retire this region.
      _next_top_at_mark_start = end();
    } else {
      // We could have re-used this old region as to-space over a
      // couple of GCs since the start of the concurrent marking
      // cycle. This means that [bottom,NTAMS) will contain objects
      // copied up to and including initial-mark and [NTAMS, top)
      // will contain objects copied during the concurrent marking cycle.
      assert(top() >= _next_top_at_mark_start, "invariant");
    }
  }
}

inline void HeapRegion::note_end_of_copying(bool during_initial_mark) {
  if (is_survivor()) {
    // This is how we always allocate survivors.
    assert(_next_top_at_mark_start == bottom(), "invariant");
  } else {
    if (during_initial_mark) {
      // See the comment for note_start_of_copying() for the details
      // on this.
      assert(_next_top_at_mark_start == end(), "pre-condition");
      _next_top_at_mark_start = top();
    } else {
      // See the comment for note_start_of_copying() for the details
      // on this.
      assert(top() >= _next_top_at_mark_start, "invariant");
    }
  }
}

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP