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comparison src/share/vm/gc_implementation/concurrentMarkSweep/freeBlockDictionary.hpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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1 /*
2 * Copyright 2001-2005 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 //
26 // Free block maintenance for Concurrent Mark Sweep Generation
27 //
28 // The main data structure for free blocks are
29 // . an indexed array of small free blocks, and
30 // . a dictionary of large free blocks
31 //
32
33 // No virtuals in FreeChunk (don't want any vtables).
34
35 // A FreeChunk is merely a chunk that can be in a doubly linked list
36 // and has a size field. NOTE: FreeChunks are distinguished from allocated
37 // objects in two ways (by the sweeper). The second word (prev) has the
38 // LSB set to indicate a free chunk; allocated objects' klass() pointers
39 // don't have their LSB set. The corresponding bit in the CMSBitMap is
40 // set when the chunk is allocated. There are also blocks that "look free"
41 // but are not part of the free list and should not be coalesced into larger
42 // free blocks. These free blocks have their two LSB's set.
43
44 class FreeChunk VALUE_OBJ_CLASS_SPEC {
45 friend class VMStructs;
46 FreeChunk* _next;
47 FreeChunk* _prev;
48 size_t _size;
49
50 public:
51 NOT_PRODUCT(static const size_t header_size();)
52 // Returns "true" if the "wrd", which is required to be the second word
53 // of a block, indicates that the block represents a free chunk.
54 static bool secondWordIndicatesFreeChunk(intptr_t wrd) {
55 return (wrd & 0x1) == 0x1;
56 }
57 bool isFree() const {
58 return secondWordIndicatesFreeChunk((intptr_t)_prev);
59 }
60 bool cantCoalesce() const { return (((intptr_t)_prev) & 0x3) == 0x3; }
61 FreeChunk* next() const { return _next; }
62 FreeChunk* prev() const { return (FreeChunk*)(((intptr_t)_prev) & ~(0x3)); }
63 debug_only(void* prev_addr() const { return (void*)&_prev; })
64
65 void linkAfter(FreeChunk* ptr) {
66 linkNext(ptr);
67 if (ptr != NULL) ptr->linkPrev(this);
68 }
69 void linkAfterNonNull(FreeChunk* ptr) {
70 assert(ptr != NULL, "precondition violation");
71 linkNext(ptr);
72 ptr->linkPrev(this);
73 }
74 void linkNext(FreeChunk* ptr) { _next = ptr; }
75 void linkPrev(FreeChunk* ptr) { _prev = (FreeChunk*)((intptr_t)ptr | 0x1); }
76 void clearPrev() { _prev = NULL; }
77 void clearNext() { _next = NULL; }
78 void dontCoalesce() {
79 // the block should be free
80 assert(isFree(), "Should look like a free block");
81 _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
82 }
83 void markFree() { _prev = (FreeChunk*)((intptr_t)_prev | 0x1); }
84 void markNotFree() { _prev = NULL; }
85
86 size_t size() const { return _size; }
87 void setSize(size_t size) { _size = size; }
88
89 // For volatile reads:
90 size_t* size_addr() { return &_size; }
91
92 // Return the address past the end of this chunk
93 HeapWord* end() const { return ((HeapWord*) this) + _size; }
94
95 // debugging
96 void verify() const PRODUCT_RETURN;
97 void verifyList() const PRODUCT_RETURN;
98 void mangleAllocated(size_t size) PRODUCT_RETURN;
99 void mangleFreed(size_t size) PRODUCT_RETURN;
100 };
101
102 // Alignment helpers etc.
103 #define numQuanta(x,y) ((x+y-1)/y)
104 enum AlignmentConstants {
105 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
106 };
107
108 // A FreeBlockDictionary is an abstract superclass that will allow
109 // a number of alternative implementations in the future.
110 class FreeBlockDictionary: public CHeapObj {
111 public:
112 enum Dither {
113 atLeast,
114 exactly,
115 roughly
116 };
117 enum DictionaryChoice {
118 dictionaryBinaryTree = 0,
119 dictionarySplayTree = 1,
120 dictionarySkipList = 2
121 };
122
123 private:
124 NOT_PRODUCT(Mutex* _lock;)
125
126 public:
127 virtual void removeChunk(FreeChunk* fc) = 0;
128 virtual FreeChunk* getChunk(size_t size, Dither dither = atLeast) = 0;
129 virtual void returnChunk(FreeChunk* chunk) = 0;
130 virtual size_t totalChunkSize(debug_only(const Mutex* lock)) const = 0;
131 virtual size_t maxChunkSize() const = 0;
132 virtual size_t minSize() const = 0;
133 // Reset the dictionary to the initial conditions for a single
134 // block.
135 virtual void reset(HeapWord* addr, size_t size) = 0;
136 virtual void reset() = 0;
137
138 virtual void dictCensusUpdate(size_t size, bool split, bool birth) = 0;
139 virtual bool coalDictOverPopulated(size_t size) = 0;
140 virtual void beginSweepDictCensus(double coalSurplusPercent,
141 float sweep_current, float sweep_ewstimate) = 0;
142 virtual void endSweepDictCensus(double splitSurplusPercent) = 0;
143 virtual FreeChunk* findLargestDict() const = 0;
144 // verify that the given chunk is in the dictionary.
145 virtual bool verifyChunkInFreeLists(FreeChunk* tc) const = 0;
146
147 // Sigma_{all_free_blocks} (block_size^2)
148 virtual double sum_of_squared_block_sizes() const = 0;
149
150 virtual FreeChunk* find_chunk_ends_at(HeapWord* target) const = 0;
151 virtual void inc_totalSize(size_t v) = 0;
152 virtual void dec_totalSize(size_t v) = 0;
153
154 NOT_PRODUCT (
155 virtual size_t sumDictReturnedBytes() = 0;
156 virtual void initializeDictReturnedBytes() = 0;
157 virtual size_t totalCount() = 0;
158 )
159
160 virtual void reportStatistics() const {
161 gclog_or_tty->print("No statistics available");
162 }
163
164 virtual void printDictCensus() const = 0;
165
166 virtual void verify() const = 0;
167
168 Mutex* par_lock() const PRODUCT_RETURN0;
169 void set_par_lock(Mutex* lock) PRODUCT_RETURN;
170 void verify_par_locked() const PRODUCT_RETURN;
171 };