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24
25#ifndef SHARE_GC_SHARED_SPACEDECORATOR_HPP
26#define SHARE_GC_SHARED_SPACEDECORATOR_HPP
27
28#include "gc/parallel/mutableSpace.hpp"
29#include "gc/shared/space.hpp"
30#include "utilities/globalDefinitions.hpp"
31
32class 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
73class 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
122class ContiguousSpace;
123
124// For use with GenCollectedHeap's
125class GenSpaceMangler: public SpaceMangler {
126 ContiguousSpace* _sp;
127
128 ContiguousSpace* sp() { return _sp; }
129
130 HeapWord* top() const { return _sp->top(); }
131 HeapWord* end() const { return _sp->end(); }
132
133 public:
134 GenSpaceMangler(ContiguousSpace* sp) : SpaceMangler(), _sp(sp) {}
135};
136
137// For use with ParallelScavengeHeap's.
138class MutableSpaceMangler: public SpaceMangler {
139 MutableSpace* _sp;
140
141 MutableSpace* sp() { return _sp; }
142
143 HeapWord* top() const { return _sp->top(); }
144 HeapWord* end() const { return _sp->end(); }
145
146 public:
147 MutableSpaceMangler(MutableSpace* sp) : SpaceMangler(), _sp(sp) {}
148};
149
150#endif // SHARE_GC_SHARED_SPACEDECORATOR_HPP
151