1 /*
2 * Copyright (c) 2012, 2019, 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
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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
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24 #ifndef SHARE_MEMORY_METASPACE_METACHUNK_HPP
25 #define SHARE_MEMORY_METASPACE_METACHUNK_HPP
26
27
28 #include "memory/metaspace/counter.hpp"
29 #include "memory/metaspace/abstractPool.hpp"
30 #include "memory/metaspace/chunkLevel.hpp"
31 #include "utilities/debug.hpp"
32 #include "utilities/globalDefinitions.hpp"
33
34
35
36 namespace metaspace {
37
38 class VirtualSpaceNode;
39
40 // Metachunk - Quantum of allocation from a Virtualspace
41 // Metachunks are reused (when freed are put on a global freelist) and
42 // have no permanent association to a SpaceManager.
43
44 // +--------------+ <- end ----+ --+
45 // | | | |
46 // | | | free |
47 // | | |
48 // | | | | size (aka capacity)
49 // | | | |
50 // | ----------- | <- top -- + |
51 // | | | |
52 // | | | used |
53 // +--------------+ <- start -- + -- +
54
55 // Note: this is a chunk **descriptor**. The real Payload area lives in metaspace,
56 // this class lives somewhere else.
57 class Metachunk {
58
59 // Todo: compact this node. A lot of things can be expressed more tighter.
60
61 // A chunk header is kept in a list:
62 // - in the list of used chunks inside a SpaceManager, if it is in use
63 // - in the list of free chunks inside a ChunkManager, if it is free
64 // - in the freelist of dead headers inside the MetaChunkHeaderPool,
65 // if it is dead (e.g. result of chunk merging).
66 Metachunk* _prev;
67 Metachunk* _next;
68
69 chklvl_t _level; // aka size.
70
71 // true: free, owned by ChunkManager
72 // false: in-use, owned by SpaceManager
73 // if dead, meaningless
74 bool _is_free;
75
76 // start of chunk memory; NULL if dead.
77 MetaWord* _base;
78
79 // Used words.
80 size_t _used_words;
81
82 // Guaranteed-to-be-committed-words, counted from base
83 // (This is a performance optimization. The underlying VirtualSpaceNode knows
84 // which granules are committed; but we want to avoid asking it unnecessarily
85 // in Metachunk::allocate(), so we keep a limit until which we are guaranteed
86 // to have committed memory under us.)
87 size_t _committed_words;
88
89 // the chunk tree node this header is hanging under; NULL if dead.
90 u2 _tree_node_ref;
91
92 // We need unfortunately a back link to the virtual space node
93 // for splitting and merging nodes.
94 VirtualSpaceNode* _vsnode;
95
96 MetaWord* top() const { return base() + _used_words; }
97
98 public:
99
100 Metachunk()
101 : _prev(NULL), _next(NULL),
102 _level(chklvl::ROOT_CHUNK_LEVEL),
103 _is_free(true),
104 _base(NULL),
105 _used_words(0),
106 _committed_words(0),
107 _tree_node_ref(0),
108 _vsnode(NULL)
109 {}
110
111 size_t word_size() const { return chklvl::word_size_for_level(_level); }
112
113 MetaWord* base() const { return _base; }
114 void set_base(MetaWord* p) { _base = p; }
115 MetaWord* end() const { return base() + word_size(); }
116
117 void set_prev(Metachunk* c) { _prev = c; }
118 Metachunk* prev() const { return _prev; }
119 void set_next(Metachunk* c) { _next = c; }
120 Metachunk* next() const { return _next; }
121 // Remove chunk from whatever list it lives in by wiring next with previous.
122 void remove_from_list();
123
124 bool is_free() const { return _is_free; }
125 bool is_in_use() const { return !_is_free; }
126 void set_free(bool v) { _is_free = v; }
127
128
129 void inc_level() { _level ++; DEBUG_ONLY(chklvl::is_valid_level(_level);) }
130 void dec_level() { _level --; DEBUG_ONLY(chklvl::is_valid_level(_level);) }
131 void set_level(chklvl_t v) { _level = v; DEBUG_ONLY(chklvl::is_valid_level(_level);) }
132 chklvl_t level() const { return _level; }
133
134 void set_tree_node_ref(u2 v) { _tree_node_ref = v; }
135 u2 tree_node_ref() const { return _tree_node_ref; }
136
137 VirtualSpaceNode* vsnode() const { return _vsnode; }
138 void set_vsnode(VirtualSpaceNode* n) { _vsnode = n; }
139
140 size_t used_words() const { return _used_words; }
141 size_t free_words() const { return word_size() - used_words(); }
142 size_t free_below_committed_words() const { return committed_words() - used_words(); }
143 void reset_used_words() { _used_words = 0; }
144
145 size_t committed_words() const { return _committed_words; }
146 void set_committed_words(size_t v) { _committed_words = v; }
147 bool is_fully_committed() const { return committed_words() == word_size(); }
148
149 // Ensure that chunk is committed up to at least word_size words.
150 // Fails if we hit a commit limit.
151 bool ensure_committed(size_t word_size);
152
153 // Alignment of an allocation.
154 static const size_t allocation_alignment_bytes = 8;
155 static const size_t allocation_alignment_words = allocation_alignment_bytes / BytesPerWord;
156
157 // Allocation from a chunk
158
159 // Allocate word_size words from this chunk.
160 //
161 // May cause memory to be committed. That may fail if we hit a commit limit. In that case,
162 // NULL is returned and p_did_hit_commit_limit will be set to true.
163 // If the remainder portion of the chunk was too small to hold the allocation,
164 // NULL is returned and p_did_hit_commit_limit will be set to false.
165 MetaWord* allocate(size_t word_size, bool* p_did_hit_commit_limit);
166
167 // Wipe this object to look as if it were default constructed.
168 void wipe() {
169 _prev = NULL; _next = NULL;
170 _level = chklvl::ROOT_CHUNK_LEVEL;
171 _is_free = true;
172 _base = NULL;
173 _used_words = 0;
174 _committed_words = 0;
175 _tree_node_ref = 0;
176 _vsnode = NULL;
177 }
178
179 //// Debug stuff ////
180 DEBUG_ONLY(void verify(bool slow) const;)
181
182 };
183
184
185 class MetachunkList {
186
187 Metachunk* _first;
188 IntCounter _num;
189
190 public:
191
192 MetachunkList() : _first(NULL), _num() {}
193
194 Metachunk* first() const { return _first; }
195 int size() const { return _num.get(); }
196
197 void add(Metachunk* c) {
198 c->set_next(_first);
199 _first = c;
200 _num.increment();
201 }
202
203 // Remove first node unless empty. Returns node or NULL.
204 Metachunk* remove_first() {
205 Metachunk* c = _first;
206 if (c != NULL) {
207 _first = c->next();
208 _num.decrement();
209 }
210 return c;
211 }
212
213 // Remove given chunk from list. List must contain that chunk.
214 void remove(Metachunk* c) {
215 assert(contains(c), "Does not contain this chunk");
216 c->remove_from_list();
217 _num.decrement();
218 }
219
220 // Manually decrement counter; needed for cases where chunks
221 // have been manually removed from the list without informing
222 // the list, e.g. chunk merging, see chunkManager::return_chunk().
223 void dec_counter_by(int v) {
224 _num.decrement_by(v);
225 }
226
227 #ifdef ASSERT
228 bool contains(const Metachunk* c) const;
229 void verify(bool slow) const;
230 #endif
231
232 };
233
234 } // namespace metaspace
235
236 #endif // SHARE_MEMORY_METASPACE_METACHUNK_HPP