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comparison src/share/vm/memory/metachunk.hpp @ 12902:bdfbb1fb19ca

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8026391: The Metachunk header wastes memory Reviewed-by: coleenp, jmasa
author stefank
date Tue, 15 Oct 2013 14:28:51 +0200
parents c23dbf0e8ab7
children 28df60a5badf
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12901:f16726924734 12902:bdfbb1fb19ca
1 /* 1 /*
2 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. 2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 * 4 *
5 * This code is free software; you can redistribute it and/or modify it 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 6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. 7 * published by the Free Software Foundation.
22 * 22 *
23 */ 23 */
24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP 24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
25 #define SHARE_VM_MEMORY_METACHUNK_HPP 25 #define SHARE_VM_MEMORY_METACHUNK_HPP
26 26
27 // Metachunk - Quantum of allocation from a Virtualspace 27 #include "memory/allocation.hpp"
28 // Metachunks are reused (when freed are put on a global freelist) and 28 #include "utilities/debug.hpp"
29 // have no permanent association to a SpaceManager. 29 #include "utilities/globalDefinitions.hpp"
30
31 // +--------------+ <- end
32 // | | --+ ---+
33 // | | | free |
34 // | | | |
35 // | | | | capacity
36 // | | | |
37 // | | <- top --+ |
38 // | | ---+ |
39 // | | | used |
40 // | | | |
41 // | | | |
42 // +--------------+ <- bottom ---+ ---+
43 30
44 class VirtualSpaceNode; 31 class VirtualSpaceNode;
45 32
46 class Metachunk VALUE_OBJ_CLASS_SPEC { 33 // Super class of Metablock and Metachunk to allow them to
47 // link to support lists of chunks 34 // be put on the FreeList and in the BinaryTreeDictionary.
48 Metachunk* _next; 35 template <class T>
49 Metachunk* _prev; 36 class Metabase VALUE_OBJ_CLASS_SPEC {
50 VirtualSpaceNode* _container; 37 size_t _word_size;
38 T* _next;
39 T* _prev;
51 40
52 MetaWord* _bottom; 41 protected:
53 MetaWord* _end; 42 Metabase(size_t word_size) : _word_size(word_size), _next(NULL), _prev(NULL) {}
54 MetaWord* _top;
55 size_t _word_size;
56 // Used in a guarantee() so included in the Product builds
57 // even through it is only for debugging.
58 bool _is_free;
59
60 // Metachunks are allocated out of a MetadataVirtualSpace and
61 // and use some of its space to describe itself (plus alignment
62 // considerations). Metadata is allocated in the rest of the chunk.
63 // This size is the overhead of maintaining the Metachunk within
64 // the space.
65 static size_t _overhead;
66 43
67 public: 44 public:
68 Metachunk(size_t word_size , VirtualSpaceNode* container); 45 T* next() const { return _next; }
46 T* prev() const { return _prev; }
47 void set_next(T* v) { _next = v; assert(v != this, "Boom");}
48 void set_prev(T* v) { _prev = v; assert(v != this, "Boom");}
49 void clear_next() { set_next(NULL); }
50 void clear_prev() { set_prev(NULL); }
69 51
70 // Used to add a Metachunk to a list of Metachunks
71 void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
72 void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
73 void set_container(VirtualSpaceNode* v) { _container = v; }
74
75 MetaWord* allocate(size_t word_size);
76
77 // Accessors
78 Metachunk* next() const { return _next; }
79 Metachunk* prev() const { return _prev; }
80 VirtualSpaceNode* container() const { return _container; }
81 MetaWord* bottom() const { return _bottom; }
82 MetaWord* end() const { return _end; }
83 MetaWord* top() const { return _top; }
84 size_t word_size() const { return _word_size; }
85 size_t size() const volatile { return _word_size; } 52 size_t size() const volatile { return _word_size; }
86 void set_size(size_t v) { _word_size = v; } 53 void set_size(size_t v) { _word_size = v; }
87 bool is_free() { return _is_free; } 54
88 void set_is_free(bool v) { _is_free = v; } 55 void link_next(T* ptr) { set_next(ptr); }
89 static size_t overhead() { return _overhead; } 56 void link_prev(T* ptr) { set_prev(ptr); }
90 void clear_next() { set_next(NULL); } 57 void link_after(T* ptr) {
91 void link_prev(Metachunk* ptr) { set_prev(ptr); }
92 uintptr_t* end() { return ((uintptr_t*) this) + size(); }
93 bool cantCoalesce() const { return false; }
94 void link_next(Metachunk* ptr) { set_next(ptr); }
95 void link_after(Metachunk* ptr){
96 link_next(ptr); 58 link_next(ptr);
97 if (ptr != NULL) ptr->link_prev(this); 59 if (ptr != NULL) ptr->link_prev((T*)this);
98 } 60 }
99 61
100 // Reset top to bottom so chunk can be reused. 62 uintptr_t* end() const { return ((uintptr_t*) this) + size(); }
101 void reset_empty() { _top = (_bottom + _overhead); _next = NULL; _prev = NULL; }
102 bool is_empty() { return _top == (_bottom + _overhead); }
103 63
104 // used (has been allocated) 64 bool cantCoalesce() const { return false; }
105 // free (available for future allocations)
106 // capacity (total size of chunk)
107 size_t used_word_size() const;
108 size_t free_word_size() const;
109 size_t capacity_word_size()const;
110 65
111 // Debug support 66 // Debug support
112 #ifdef ASSERT 67 #ifdef ASSERT
113 void* prev_addr() const { return (void*)&_prev; } 68 void* prev_addr() const { return (void*)&_prev; }
114 void* next_addr() const { return (void*)&_next; } 69 void* next_addr() const { return (void*)&_next; }
115 void* size_addr() const { return (void*)&_word_size; } 70 void* size_addr() const { return (void*)&_word_size; }
116 #endif 71 #endif
117 bool verify_chunk_in_free_list(Metachunk* tc) const { return true; } 72 bool verify_chunk_in_free_list(T* tc) const { return true; }
118 bool verify_par_locked() { return true; } 73 bool verify_par_locked() { return true; }
119 74
120 void assert_is_mangled() const {/* Don't check "\*/} 75 void assert_is_mangled() const {/* Don't check "\*/}
121 76
122 NOT_PRODUCT(void mangle();) 77 bool is_free() { return true; }
78 };
79
80 // Metachunk - Quantum of allocation from a Virtualspace
81 // Metachunks are reused (when freed are put on a global freelist) and
82 // have no permanent association to a SpaceManager.
83
84 // +--------------+ <- end --+ --+
85 // | | | |
86 // | | | free |
87 // | | | |
88 // | | | | size | capacity
89 // | | | |
90 // | | <- top -- + |
91 // | | | |
92 // | | | used |
93 // | | | |
94 // | | | |
95 // +--------------+ <- bottom --+ --+
96
97 class Metachunk : public Metabase<Metachunk> {
98 friend class TestMetachunk;
99 // The VirtualSpaceNode containing this chunk.
100 VirtualSpaceNode* _container;
101
102 // Current allocation top.
103 MetaWord* _top;
104
105 DEBUG_ONLY(bool _is_tagged_free;)
106
107 MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }
108 MetaWord* top() const { return _top; }
109
110 public:
111 // Metachunks are allocated out of a MetadataVirtualSpace and
112 // and use some of its space to describe itself (plus alignment
113 // considerations). Metadata is allocated in the rest of the chunk.
114 // This size is the overhead of maintaining the Metachunk within
115 // the space.
116
117 // Alignment of each allocation in the chunks.
118 static size_t object_alignment();
119
120 // Size of the Metachunk header, including alignment.
121 static size_t overhead();
122
123 Metachunk(size_t word_size , VirtualSpaceNode* container);
124
125 MetaWord* allocate(size_t word_size);
126
127 VirtualSpaceNode* container() const { return _container; }
128
129 MetaWord* bottom() const { return (MetaWord*) this; }
130
131 // Reset top to bottom so chunk can be reused.
132 void reset_empty() { _top = initial_top(); clear_next(); clear_prev(); }
133 bool is_empty() { return _top == initial_top(); }
134
135 // used (has been allocated)
136 // free (available for future allocations)
137 size_t word_size() const { return size(); }
138 size_t used_word_size() const;
139 size_t free_word_size() const;
140
141 #ifdef ASSERT
142 void mangle();
143 bool is_tagged_free() { return _is_tagged_free; }
144 void set_is_tagged_free(bool v) { _is_tagged_free = v; }
145 #endif
123 146
124 void print_on(outputStream* st) const; 147 void print_on(outputStream* st) const;
125 void verify(); 148 void verify();
126 }; 149 };
150
151 // Metablock is the unit of allocation from a Chunk.
152 //
153 // A Metablock may be reused by its SpaceManager but are never moved between
154 // SpaceManagers. There is no explicit link to the Metachunk
155 // from which it was allocated. Metablock may be deallocated and
156 // put on a freelist but the space is never freed, rather
157 // the Metachunk it is a part of will be deallocated when it's
158 // associated class loader is collected.
159
160 class Metablock : public Metabase<Metablock> {
161 friend class VMStructs;
162 public:
163 Metablock(size_t word_size) : Metabase<Metablock>(word_size) {}
164 };
165
127 #endif // SHARE_VM_MEMORY_METACHUNK_HPP 166 #endif // SHARE_VM_MEMORY_METACHUNK_HPP