Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp @ 1562:dfe27f03244a
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date | Tue, 01 Jun 2010 11:48:33 -0700 |
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2 * Copyright (c) 2001, 2008, Oracle and/or its affiliates. All rights reserved. |
187 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
187 | 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), depending on whether the VM is 32 or | |
38 // 64 bits. | |
39 // In 32 bits or 64 bits without CompressedOops, the second word (prev) has the | |
40 // LSB set to indicate a free chunk; allocated objects' klass() pointers | |
41 // don't have their LSB set. The corresponding bit in the CMSBitMap is | |
42 // set when the chunk is allocated. There are also blocks that "look free" | |
43 // but are not part of the free list and should not be coalesced into larger | |
44 // free blocks. These free blocks have their two LSB's set. | |
45 | |
46 class FreeChunk VALUE_OBJ_CLASS_SPEC { | |
47 friend class VMStructs; | |
48 // For 64 bit compressed oops, the markOop encodes both the size and the | |
49 // indication that this is a FreeChunk and not an object. | |
50 volatile size_t _size; | |
51 FreeChunk* _prev; | |
52 FreeChunk* _next; | |
53 | |
54 markOop mark() const volatile { return (markOop)_size; } | |
55 void set_mark(markOop m) { _size = (size_t)m; } | |
56 | |
57 public: | |
58 NOT_PRODUCT(static const size_t header_size();) | |
59 | |
60 // Returns "true" if the address indicates that the block represents | |
61 // a free chunk. | |
62 static bool indicatesFreeChunk(const HeapWord* addr) { | |
63 // Force volatile read from addr because value might change between | |
64 // calls. We really want the read of _mark and _prev from this pointer | |
65 // to be volatile but making the fields volatile causes all sorts of | |
66 // compilation errors. | |
67 return ((volatile FreeChunk*)addr)->isFree(); | |
68 } | |
69 | |
70 bool isFree() const volatile { | |
71 LP64_ONLY(if (UseCompressedOops) return mark()->is_cms_free_chunk(); else) | |
72 return (((intptr_t)_prev) & 0x1) == 0x1; | |
73 } | |
74 bool cantCoalesce() const { | |
75 assert(isFree(), "can't get coalesce bit on not free"); | |
76 return (((intptr_t)_prev) & 0x2) == 0x2; | |
77 } | |
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 FreeChunk* prev() const { | |
84 return (FreeChunk*)(((intptr_t)_prev) & ~(0x3)); | |
85 } | |
86 | |
87 debug_only(void* prev_addr() const { return (void*)&_prev; }) | |
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88 debug_only(void* next_addr() const { return (void*)&_next; }) |
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89 debug_only(void* size_addr() const { return (void*)&_size; }) |
187 | 90 |
91 size_t size() const volatile { | |
92 LP64_ONLY(if (UseCompressedOops) return mark()->get_size(); else ) | |
93 return _size; | |
94 } | |
95 void setSize(size_t sz) { | |
96 LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::set_size_and_free(sz)); else ) | |
97 _size = sz; | |
98 } | |
99 | |
100 FreeChunk* next() const { return _next; } | |
101 | |
102 void linkAfter(FreeChunk* ptr) { | |
103 linkNext(ptr); | |
104 if (ptr != NULL) ptr->linkPrev(this); | |
105 } | |
106 void linkAfterNonNull(FreeChunk* ptr) { | |
107 assert(ptr != NULL, "precondition violation"); | |
108 linkNext(ptr); | |
109 ptr->linkPrev(this); | |
110 } | |
111 void linkNext(FreeChunk* ptr) { _next = ptr; } | |
112 void linkPrev(FreeChunk* ptr) { | |
113 LP64_ONLY(if (UseCompressedOops) _prev = ptr; else) | |
114 _prev = (FreeChunk*)((intptr_t)ptr | 0x1); | |
115 } | |
116 void clearPrev() { _prev = NULL; } | |
117 void clearNext() { _next = NULL; } | |
118 void markNotFree() { | |
119 LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::prototype());) | |
120 // Also set _prev to null | |
121 _prev = NULL; | |
122 } | |
123 | |
124 // Return the address past the end of this chunk | |
125 HeapWord* end() const { return ((HeapWord*) this) + size(); } | |
126 | |
127 // debugging | |
128 void verify() const PRODUCT_RETURN; | |
129 void verifyList() const PRODUCT_RETURN; | |
130 void mangleAllocated(size_t size) PRODUCT_RETURN; | |
131 void mangleFreed(size_t size) PRODUCT_RETURN; | |
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133 void print_on(outputStream* st); |
187 | 134 }; |
135 | |
136 // Alignment helpers etc. | |
137 #define numQuanta(x,y) ((x+y-1)/y) | |
138 enum AlignmentConstants { | |
139 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment | |
140 }; | |
141 |