psPromotionLAB.hpp revision 8413:92457dfb91bd 
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24
25#ifndef SHARE_VM_GC_PARALLEL_PSPROMOTIONLAB_HPP
26#define SHARE_VM_GC_PARALLEL_PSPROMOTIONLAB_HPP
27
28#include "gc/parallel/objectStartArray.hpp"
29#include "gc/shared/collectedHeap.hpp"
30#include "memory/allocation.hpp"
31
32//
33// PSPromotionLAB is a parallel scavenge promotion lab. This class acts very
34// much like a MutableSpace. We couldn't embed a MutableSpace, though, as
35// it has a considerable number of asserts and invariants that are violated.
36//
37
38class ObjectStartArray;
39
40class PSPromotionLAB : public CHeapObj<mtGC> {
41 protected:
42  static size_t filler_header_size;
43
44  enum LabState {
45    needs_flush,
46    flushed,
47    zero_size
48  };
49
50  HeapWord* _top;
51  HeapWord* _bottom;
52  HeapWord* _end;
53  LabState _state;
54
55  void set_top(HeapWord* value)    { _top = value; }
56  void set_bottom(HeapWord* value) { _bottom = value; }
57  void set_end(HeapWord* value)    { _end = value; }
58
59  // The shared initialize code invokes this.
60  debug_only(virtual bool lab_is_valid(MemRegion lab) { return false; });
61
62  PSPromotionLAB() : _top(NULL), _bottom(NULL), _end(NULL), _state(zero_size) { }
63
64 public:
65  // Filling and flushing.
66  void initialize(MemRegion lab);
67
68  virtual void flush();
69
70  // Accessors
71  HeapWord* bottom() const           { return _bottom; }
72  HeapWord* end() const              { return _end;    }
73  HeapWord* top() const              { return _top;    }
74
75  bool is_flushed()                  { return _state == flushed; }
76
77  bool unallocate_object(HeapWord* obj, size_t obj_size);
78
79  // Returns a subregion containing all objects in this space.
80  MemRegion used_region()            { return MemRegion(bottom(), top()); }
81
82  // Boolean queries.
83  bool is_empty() const              { return used() == 0; }
84  bool not_empty() const             { return used() > 0; }
85  bool contains(const void* p) const { return _bottom <= p && p < _end; }
86
87  // Size computations.  Sizes are in bytes.
88  size_t capacity() const            { return byte_size(bottom(), end()); }
89  size_t used() const                { return byte_size(bottom(), top()); }
90  size_t free() const                { return byte_size(top(),    end()); }
91};
92
93class PSYoungPromotionLAB : public PSPromotionLAB {
94 public:
95  PSYoungPromotionLAB() { }
96
97  // Not MT safe
98  inline HeapWord* allocate(size_t size);
99
100  debug_only(virtual bool lab_is_valid(MemRegion lab);)
101};
102
103class PSOldPromotionLAB : public PSPromotionLAB {
104 private:
105  ObjectStartArray* _start_array;
106
107 public:
108  PSOldPromotionLAB() : _start_array(NULL) { }
109  PSOldPromotionLAB(ObjectStartArray* start_array) : _start_array(start_array) { }
110
111  void set_start_array(ObjectStartArray* start_array) { _start_array = start_array; }
112
113  void flush();
114
115  // Not MT safe
116  HeapWord* allocate(size_t size) {
117    // Cannot test for this now that we're doing promotion failures
118    // assert(_state != flushed, "Sanity");
119    assert(_start_array != NULL, "Sanity");
120    HeapWord* obj = top();
121    HeapWord* new_top = obj + size;
122    // The 'new_top>obj' check is needed to detect overflow of obj+size.
123    if (new_top > obj && new_top <= end()) {
124      set_top(new_top);
125      assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
126             "checking alignment");
127      _start_array->allocate_block(obj);
128      return obj;
129    }
130
131    return NULL;
132  }
133
134  debug_only(virtual bool lab_is_valid(MemRegion lab));
135};
136
137#endif // SHARE_VM_GC_PARALLEL_PSPROMOTIONLAB_HPP
138