1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_GC_SHARED_SPACEDECORATOR_HPP
26 #define SHARE_GC_SHARED_SPACEDECORATOR_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/memRegion.hpp"
30 #include "utilities/globalDefinitions.hpp"
31
32 class SpaceDecorator: public AllStatic {
33 public:
34 // Initialization flags.
35 static const bool Clear = true;
36 static const bool DontClear = false;
37 static const bool Mangle = true;
38 static const bool DontMangle = false;
39 };
40
41 // Functionality for use with class Space and class MutableSpace.
42 // The approach taken with the mangling is to mangle all
43 // the space initially and then to mangle areas that have
44 // been allocated since the last collection. Mangling is
45 // done in the context of a generation and in the context
46 // of a space.
47 // The space in a generation is mangled when it is first
48 // initialized and when the generation grows. The spaces
49 // are not necessarily up-to-date when this mangling occurs
50 // and the method mangle_region() is used.
51 // After allocations have been done in a space, the space generally
52 // need to be remangled. Remangling is only done on the
53 // recently allocated regions in the space. Typically, that is
54 // the region between the new top and the top just before a
55 // garbage collection.
56 // An exception to the usual mangling in a space is done when the
57 // space is used for an extraordinary purpose. Specifically, when
58 // to-space is used as scratch space for a mark-sweep-compact
59 // collection.
60 // Spaces are mangled after a collection. If the generation
61 // grows after a collection, the added space is mangled as part of
62 // the growth of the generation. No additional mangling is needed when the
63 // spaces are resized after an expansion.
64 // The class SpaceMangler keeps a pointer to the top of the allocated
65 // area and provides the methods for doing the piece meal mangling.
66 // Methods for doing sparces and full checking of the mangling are
67 // included. The full checking is done if DEBUG_MANGLING is defined.
68 // GenSpaceMangler is used with the GenCollectedHeap collectors and
69 // MutableSpaceMangler is used with the ParallelScavengeHeap collectors.
70 // These subclasses abstract the differences in the types of spaces used
71 // by each heap.
72
73 class SpaceMangler: public CHeapObj<mtGC> {
74 friend class VMStructs;
75
76 // High water mark for allocations. Typically, the space above
77 // this point have been mangle previously and don't need to be
78 // touched again. Space below this point has been allocated
79 // and remangling is needed between the current top and this
80 // high water mark.
81 HeapWord* _top_for_allocations;
82 HeapWord* top_for_allocations() { return _top_for_allocations; }
83
84 public:
85
86 // Setting _top_for_allocations to NULL at initialization
87 // makes it always below top so that mangling done as part
88 // of the initialize() call of a space does nothing (as it
89 // should since the mangling is done as part of the constructor
90 // for the space.
91 SpaceMangler() : _top_for_allocations(NULL) {}
92
93 // Methods for top and end that delegate to the specific
94 // space type.
95 virtual HeapWord* top() const = 0;
96 virtual HeapWord* end() const = 0;
97
98 // Return true if q matches the mangled pattern.
99 static bool is_mangled(HeapWord* q) PRODUCT_RETURN0;
100
101 // Used to save the an address in a space for later use during mangling.
102 void set_top_for_allocations(HeapWord* v);
103
104 // Overwrites the unused portion of this space.
105 // Mangle only the region not previously mangled [top, top_previously_mangled)
106 void mangle_unused_area();
107 // Mangle all the unused region [top, end)
108 void mangle_unused_area_complete();
109 // Do some sparse checking on the area that should have been mangled.
110 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
111 // Do a complete check of the area that should be mangled.
112 void check_mangled_unused_area_complete() PRODUCT_RETURN;
113
114 // Mangle the MemRegion. This is a non-space specific mangler. It
115 // is used during the initial mangling of a space before the space
116 // is fully constructed. Also is used when a generation is expanded
117 // and possibly before the spaces have been reshaped to to the new
118 // size of the generation.
119 static void mangle_region(MemRegion mr) PRODUCT_RETURN;
120 };
121
122 class ContiguousSpace;
123 class MutableSpace;
124
125 // For use with GenCollectedHeap's
126 class GenSpaceMangler: public SpaceMangler {
127 ContiguousSpace* _sp;
128
129 ContiguousSpace* sp() { return _sp; }
130
131 HeapWord* top() const;
132 HeapWord* end() const;
133
134 public:
135 GenSpaceMangler(ContiguousSpace* sp) : SpaceMangler(), _sp(sp) {}
136 };
137
138 // For use with ParallelScavengeHeap's.
139 class MutableSpaceMangler: public SpaceMangler {
140 MutableSpace* _sp;
141
142 MutableSpace* sp() { return _sp; }
143
144 HeapWord* top() const;
145 HeapWord* end() const;
146
147 public:
148 MutableSpaceMangler(MutableSpace* sp) : SpaceMangler(), _sp(sp) {}
149 };
150
151 #endif // SHARE_GC_SHARED_SPACEDECORATOR_HPP