1 /*
2 * Copyright (c) 2001, 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.
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23 */
24
25 #ifndef SHARE_VM_MEMORY_FREELIST_HPP
26 #define SHARE_VM_MEMORY_FREELIST_HPP
27
28 #include "gc_implementation/shared/allocationStats.hpp"
29
30 class CompactibleFreeListSpace;
31
32 // A class for maintaining a free list of Chunk's. The FreeList
33 // maintains a the structure of the list (head, tail, etc.) plus
34 // statistics for allocations from the list. The links between items
35 // are not part of FreeList. The statistics are
36 // used to make decisions about coalescing Chunk's when they
37 // are swept during collection.
38 //
39 // See the corresponding .cpp file for a description of the specifics
40 // for that implementation.
41
42 class Mutex;
43
44 template <class Chunk_t>
45 class FreeList VALUE_OBJ_CLASS_SPEC {
46 friend class CompactibleFreeListSpace;
47 friend class VMStructs;
48
49 private:
50 Chunk_t* _head; // Head of list of free chunks
51 Chunk_t* _tail; // Tail of list of free chunks
52 size_t _size; // Size in Heap words of each chunk
53 ssize_t _count; // Number of entries in list
54
55 protected:
56
57 #ifdef ASSERT
58 Mutex* _protecting_lock;
59 #endif
60
61 // Asserts false if the protecting lock (if any) is not held.
62 void assert_proper_lock_protection_work() const PRODUCT_RETURN;
63 void assert_proper_lock_protection() const {
64 #ifdef ASSERT
65 if (_protecting_lock != NULL)
66 assert_proper_lock_protection_work();
67 #endif
68 }
69
70 void increment_count() {
71 _count++;
72 }
73
74 void decrement_count() {
75 _count--;
76 assert(_count >= 0, "Count should not be negative");
77 }
78
79 public:
80 // Constructor
81 // Construct a list without any entries.
82 FreeList();
83 // Construct a list with "fc" as the first (and lone) entry in the list.
84 FreeList(Chunk_t* fc);
85
86 // Do initialization
87 void initialize();
88
89 // Reset the head, tail, and count of a free list.
90 void reset();
91
92 // Declare the current free list to be protected by the given lock.
93 #ifdef ASSERT
94 Mutex* protecting_lock() const { return _protecting_lock; }
95 void set_protecting_lock(Mutex* v) {
96 _protecting_lock = v;
97 }
98 #endif
99
100 // Accessors.
101 Chunk_t* head() const {
102 assert_proper_lock_protection();
103 return _head;
104 }
105 void set_head(Chunk_t* v) {
106 assert_proper_lock_protection();
107 _head = v;
108 assert(!_head || _head->size() == _size, "bad chunk size");
109 }
110 // Set the head of the list and set the prev field of non-null
111 // values to NULL.
112 void link_head(Chunk_t* v);
113
114 Chunk_t* tail() const {
115 assert_proper_lock_protection();
116 return _tail;
117 }
118 void set_tail(Chunk_t* v) {
119 assert_proper_lock_protection();
120 _tail = v;
121 assert(!_tail || _tail->size() == _size, "bad chunk size");
122 }
123 // Set the tail of the list and set the next field of non-null
124 // values to NULL.
125 void link_tail(Chunk_t* v) {
126 assert_proper_lock_protection();
127 set_tail(v);
128 if (v != NULL) {
129 v->clear_next();
130 }
131 }
132
133 // No locking checks in read-accessors: lock-free reads (only) are benign.
134 // Readers are expected to have the lock if they are doing work that
135 // requires atomicity guarantees in sections of code.
136 size_t size() const {
137 return _size;
138 }
139 void set_size(size_t v) {
140 assert_proper_lock_protection();
141 _size = v;
142 }
143 ssize_t count() const { return _count; }
144 void set_count(ssize_t v) { _count = v;}
145
146 size_t get_better_size() { return size(); }
147
148 size_t returned_bytes() const { ShouldNotReachHere(); return 0; }
149 void set_returned_bytes(size_t v) {}
150 void increment_returned_bytes_by(size_t v) {}
151
152 // Unlink head of list and return it. Returns NULL if
153 // the list is empty.
154 Chunk_t* get_chunk_at_head();
155
156 // Remove the first "n" or "count", whichever is smaller, chunks from the
157 // list, setting "fl", which is required to be empty, to point to them.
158 void getFirstNChunksFromList(size_t n, FreeList<Chunk_t>* fl);
159
160 // Unlink this chunk from it's free list
161 void remove_chunk(Chunk_t* fc);
162
163 // Add this chunk to this free list.
164 void return_chunk_at_head(Chunk_t* fc);
165 void return_chunk_at_tail(Chunk_t* fc);
166
167 // Similar to returnChunk* but also records some diagnostic
168 // information.
169 void return_chunk_at_head(Chunk_t* fc, bool record_return, bool deallocate_pages);
170 void return_chunk_at_tail(Chunk_t* fc, bool record_return, bool deallocate_pages);
171
172 // Prepend "fl" (whose size is required to be the same as that of "this")
173 // to the front of "this" list.
174 void prepend(FreeList<Chunk_t>* fl);
175
176 // Verify that the chunk is in the list.
177 // found. Return NULL if "fc" is not found.
178 bool verify_chunk_in_free_list(Chunk_t* fc) const;
179
180 // Stats verification
181 // void verify_stats() const { ShouldNotReachHere(); };
182
183 // Printing support
184 static void print_labels_on(outputStream* st, const char* c);
185 void print_on(outputStream* st, const char* c = NULL) const;
186 };
187
188 #endif // SHARE_VM_MEMORY_FREELIST_HPP