1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)freeBlockDictionary.hpp 1.32 07/05/05 17:05:47 JVM"
3 #endif
4 /*
5 * Copyright 2001-2005 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 //
29 // Free block maintenance for Concurrent Mark Sweep Generation
30 //
31 // The main data structure for free blocks are
32 // . an indexed array of small free blocks, and
33 // . a dictionary of large free blocks
34 //
35
36 // No virtuals in FreeChunk (don't want any vtables).
37
38 // A FreeChunk is merely a chunk that can be in a doubly linked list
39 // and has a size field. NOTE: FreeChunks are distinguished from allocated
40 // objects in two ways (by the sweeper). The second word (prev) has the
41 // LSB set to indicate a free chunk; allocated objects' klass() pointers
42 // don't have their LSB set. The corresponding bit in the CMSBitMap is
43 // set when the chunk is allocated. There are also blocks that "look free"
44 // but are not part of the free list and should not be coalesced into larger
45 // free blocks. These free blocks have their two LSB's set.
46
47 class FreeChunk VALUE_OBJ_CLASS_SPEC {
48 friend class VMStructs;
49 FreeChunk* _next;
50 FreeChunk* _prev;
51 size_t _size;
52
53 public:
54 NOT_PRODUCT(static const size_t header_size();)
55 // Returns "true" if the "wrd", which is required to be the second word
56 // of a block, indicates that the block represents a free chunk.
57 static bool secondWordIndicatesFreeChunk(intptr_t wrd) {
58 return (wrd & 0x1) == 0x1;
59 }
60 bool isFree() const {
61 return secondWordIndicatesFreeChunk((intptr_t)_prev);
62 }
63 bool cantCoalesce() const { return (((intptr_t)_prev) & 0x3) == 0x3; }
64 FreeChunk* next() const { return _next; }
65 FreeChunk* prev() const { return (FreeChunk*)(((intptr_t)_prev) & ~(0x3)); }
66 debug_only(void* prev_addr() const { return (void*)&_prev; })
67
68 void linkAfter(FreeChunk* ptr) {
69 linkNext(ptr);
70 if (ptr != NULL) ptr->linkPrev(this);
71 }
72 void linkAfterNonNull(FreeChunk* ptr) {
73 assert(ptr != NULL, "precondition violation");
74 linkNext(ptr);
75 ptr->linkPrev(this);
76 }
77 void linkNext(FreeChunk* ptr) { _next = ptr; }
78 void linkPrev(FreeChunk* ptr) { _prev = (FreeChunk*)((intptr_t)ptr | 0x1); }
79 void clearPrev() { _prev = NULL; }
80 void clearNext() { _next = NULL; }
81 void dontCoalesce() {
82 // the block should be free
83 assert(isFree(), "Should look like a free block");
84 _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
85 }
86 void markFree() { _prev = (FreeChunk*)((intptr_t)_prev | 0x1); }
87 void markNotFree() { _prev = NULL; }
88
89 size_t size() const { return _size; }
90 void setSize(size_t size) { _size = size; }
91
92 // For volatile reads:
93 size_t* size_addr() { return &_size; }
94
95 // Return the address past the end of this chunk
96 HeapWord* end() const { return ((HeapWord*) this) + _size; }
97
98 // debugging
99 void verify() const PRODUCT_RETURN;
100 void verifyList() const PRODUCT_RETURN;
101 void mangleAllocated(size_t size) PRODUCT_RETURN;
102 void mangleFreed(size_t size) PRODUCT_RETURN;
103 };
104
105 // Alignment helpers etc.
106 #define numQuanta(x,y) ((x+y-1)/y)
107 enum AlignmentConstants {
108 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
109 };
110
111 // A FreeBlockDictionary is an abstract superclass that will allow
112 // a number of alternative implementations in the future.
113 class FreeBlockDictionary: public CHeapObj {
114 public:
115 enum Dither {
116 atLeast,
117 exactly,
118 roughly
119 };
120 enum DictionaryChoice {
121 dictionaryBinaryTree = 0,
122 dictionarySplayTree = 1,
123 dictionarySkipList = 2
124 };
125
126 private:
127 NOT_PRODUCT(Mutex* _lock;)
128
129 public:
130 virtual void removeChunk(FreeChunk* fc) = 0;
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1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)freeBlockDictionary.hpp 1.32 07/05/05 17:05:47 JVM"
3 #endif
4 /*
5 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 // A FreeBlockDictionary is an abstract superclass that will allow
29 // a number of alternative implementations in the future.
30 class FreeBlockDictionary: public CHeapObj {
31 public:
32 enum Dither {
33 atLeast,
34 exactly,
35 roughly
36 };
37 enum DictionaryChoice {
38 dictionaryBinaryTree = 0,
39 dictionarySplayTree = 1,
40 dictionarySkipList = 2
41 };
42
43 private:
44 NOT_PRODUCT(Mutex* _lock;)
45
46 public:
47 virtual void removeChunk(FreeChunk* fc) = 0;
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