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comparison: src/share/vm/gc_implementation/parallelScavenge/psPromotionLAB.hpp

src/share/vm/gc_implementation/parallelScavenge/psPromotionLAB.hpp

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1 /*
2 * Copyright (c) 2002, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP
27
28 #include "gc_implementation/parallelScavenge/objectStartArray.hpp"
29 #include "memory/allocation.hpp"
30
31 //
32 // PSPromotionLAB is a parallel scavenge promotion lab. This class acts very
33 // much like a MutableSpace. We couldn't embed a MutableSpace, though, as
34 // it has a considerable number of asserts and invariants that are violated.
35 //
36
37 class ObjectStartArray;
38
39 class PSPromotionLAB : public CHeapObj<mtGC> {
40 protected:
41 static size_t filler_header_size;
42
43 enum LabState {
44 needs_flush,
45 flushed,
46 zero_size
47 };
48
49 HeapWord* _top;
50 HeapWord* _bottom;
51 HeapWord* _end;
52 LabState _state;
53
54 void set_top(HeapWord* value) { _top = value; }
55 void set_bottom(HeapWord* value) { _bottom = value; }
56 void set_end(HeapWord* value) { _end = value; }
57
58 // The shared initialize code invokes this.
59 debug_only(virtual bool lab_is_valid(MemRegion lab) { return false; });
60
61 PSPromotionLAB() : _top(NULL), _bottom(NULL), _end(NULL) { }
62
63 public:
64 // Filling and flushing.
65 void initialize(MemRegion lab);
66
67 virtual void flush();
68
69 // Accessors
70 HeapWord* bottom() const { return _bottom; }
71 HeapWord* end() const { return _end; }
72 HeapWord* top() const { return _top; }
73
74 bool is_flushed() { return _state == flushed; }
75
76 bool unallocate_object(HeapWord* obj, size_t obj_size);
77
78 // Returns a subregion containing all objects in this space.
79 MemRegion used_region() { return MemRegion(bottom(), top()); }
80
81 // Boolean querries.
82 bool is_empty() const { return used() == 0; }
83 bool not_empty() const { return used() > 0; }
84 bool contains(const void* p) const { return _bottom <= p && p < _end; }
85
86 // Size computations. Sizes are in bytes.
87 size_t capacity() const { return byte_size(bottom(), end()); }
88 size_t used() const { return byte_size(bottom(), top()); }
89 size_t free() const { return byte_size(top(), end()); }
90 };
91
92 class PSYoungPromotionLAB : public PSPromotionLAB {
93 public:
94 PSYoungPromotionLAB() { }
95
96 // Not MT safe
97 HeapWord* allocate(size_t size) {
98 // Can't assert this, when young fills, we keep the LAB around, but flushed.
99 // assert(_state != flushed, "Sanity");
100 HeapWord* obj = top();
101 HeapWord* new_top = obj + size;
102 // The 'new_top>obj' check is needed to detect overflow of obj+size.
103 if (new_top > obj && new_top <= end()) {
104 set_top(new_top);
105 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
106 "checking alignment");
107 return obj;
108 }
109
110 return NULL;
111 }
112
113 debug_only(virtual bool lab_is_valid(MemRegion lab));
114 };
115
116 class PSOldPromotionLAB : public PSPromotionLAB {
117 private:
118 ObjectStartArray* _start_array;
119
120 public:
121 PSOldPromotionLAB() : _start_array(NULL) { }
122 PSOldPromotionLAB(ObjectStartArray* start_array) : _start_array(start_array) { }
123
124 void set_start_array(ObjectStartArray* start_array) { _start_array = start_array; }
125
126 void flush();
127
128 // Not MT safe
129 HeapWord* allocate(size_t size) {
130 // Cannot test for this now that we're doing promotion failures
131 // assert(_state != flushed, "Sanity");
132 assert(_start_array != NULL, "Sanity");
133 HeapWord* obj = top();
134 HeapWord* new_top = obj + size;
135 // The 'new_top>obj' check is needed to detect overflow of obj+size.
136 if (new_top > obj && new_top <= end()) {
137 set_top(new_top);
138 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
139 "checking alignment");
140 _start_array->allocate_block(obj);
141 return obj;
142 }
143
144 return NULL;
145 }
146
147 debug_only(virtual bool lab_is_valid(MemRegion lab));
148 };
149
150 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP

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