|
187
|
1 /*
|
|
196
|
2 * Copyright 2001-2008 Sun Microsystems, Inc. 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 *
|
|
|
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), 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; })
|
|
|
88
|
|
|
89 size_t size() const volatile {
|
|
|
90 LP64_ONLY(if (UseCompressedOops) return mark()->get_size(); else )
|
|
|
91 return _size;
|
|
|
92 }
|
|
|
93 void setSize(size_t sz) {
|
|
|
94 LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::set_size_and_free(sz)); else )
|
|
|
95 _size = sz;
|
|
|
96 }
|
|
|
97
|
|
|
98 FreeChunk* next() const { return _next; }
|
|
|
99
|
|
|
100 void linkAfter(FreeChunk* ptr) {
|
|
|
101 linkNext(ptr);
|
|
|
102 if (ptr != NULL) ptr->linkPrev(this);
|
|
|
103 }
|
|
|
104 void linkAfterNonNull(FreeChunk* ptr) {
|
|
|
105 assert(ptr != NULL, "precondition violation");
|
|
|
106 linkNext(ptr);
|
|
|
107 ptr->linkPrev(this);
|
|
|
108 }
|
|
|
109 void linkNext(FreeChunk* ptr) { _next = ptr; }
|
|
|
110 void linkPrev(FreeChunk* ptr) {
|
|
|
111 LP64_ONLY(if (UseCompressedOops) _prev = ptr; else)
|
|
|
112 _prev = (FreeChunk*)((intptr_t)ptr | 0x1);
|
|
|
113 }
|
|
|
114 void clearPrev() { _prev = NULL; }
|
|
|
115 void clearNext() { _next = NULL; }
|
|
|
116 void markNotFree() {
|
|
|
117 LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::prototype());)
|
|
|
118 // Also set _prev to null
|
|
|
119 _prev = NULL;
|
|
|
120 }
|
|
|
121
|
|
|
122 // Return the address past the end of this chunk
|
|
|
123 HeapWord* end() const { return ((HeapWord*) this) + size(); }
|
|
|
124
|
|
|
125 // debugging
|
|
|
126 void verify() const PRODUCT_RETURN;
|
|
|
127 void verifyList() const PRODUCT_RETURN;
|
|
|
128 void mangleAllocated(size_t size) PRODUCT_RETURN;
|
|
|
129 void mangleFreed(size_t size) PRODUCT_RETURN;
|
|
|
130 };
|
|
|
131
|
|
|
132 // Alignment helpers etc.
|
|
|
133 #define numQuanta(x,y) ((x+y-1)/y)
|
|
|
134 enum AlignmentConstants {
|
|
|
135 MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
|
|
|
136 };
|
|
|
137
|
