1 /*
2 * Copyright (c) 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.
22 *
23 */
24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
25 #define SHARE_VM_MEMORY_METACHUNK_HPP
26
27 // Metachunk - Quantum of allocation from a Virtualspace
28 // Metachunks are reused (when freed are put on a global freelist) and
29 // have no permanent association to a SpaceManager.
30
31 // +--------------+ <- end
32 // | | --+ ---+
33 // | | | free |
34 // | | | |
35 // | | | | capacity
36 // | | | |
37 // | | <- top --+ |
38 // | | ---+ |
39 // | | | used |
40 // | | | |
41 // | | | |
42 // +--------------+ <- bottom ---+ ---+
43
44 class VirtualSpaceNode;
45
46 class Metachunk VALUE_OBJ_CLASS_SPEC {
47 // link to support lists of chunks
48 Metachunk* _next;
49 Metachunk* _prev;
50 VirtualSpaceNode* _container;
51
52 MetaWord* _bottom;
53 MetaWord* _end;
54 MetaWord* _top;
55 size_t _word_size;
56 // Used in a guarantee() so included in the Product builds
57 // even through it is only for debugging.
58 bool _is_free;
59
60 // Metachunks are allocated out of a MetadataVirtualSpace and
61 // and use some of its space to describe itself (plus alignment
62 // considerations). Metadata is allocated in the rest of the chunk.
63 // This size is the overhead of maintaining the Metachunk within
64 // the space.
65 static size_t _overhead;
66
67 public:
68 Metachunk(size_t word_size , VirtualSpaceNode* container);
69
70 // Used to add a Metachunk to a list of Metachunks
71 void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
72 void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
73 void set_container(VirtualSpaceNode* v) { _container = v; }
74
75 MetaWord* allocate(size_t word_size);
76
77 // Accessors
78 Metachunk* next() const { return _next; }
79 Metachunk* prev() const { return _prev; }
80 VirtualSpaceNode* container() const { return _container; }
81 MetaWord* bottom() const { return _bottom; }
82 MetaWord* end() const { return _end; }
83 MetaWord* top() const { return _top; }
84 size_t word_size() const { return _word_size; }
85 size_t size() const volatile { return _word_size; }
86 void set_size(size_t v) { _word_size = v; }
87 bool is_free() { return _is_free; }
88 void set_is_free(bool v) { _is_free = v; }
89 static size_t overhead() { return _overhead; }
90 void clear_next() { set_next(NULL); }
91 void link_prev(Metachunk* ptr) { set_prev(ptr); }
92 uintptr_t* end() { return ((uintptr_t*) this) + size(); }
93 bool cantCoalesce() const { return false; }
94 void link_next(Metachunk* ptr) { set_next(ptr); }
95 void link_after(Metachunk* ptr){
96 link_next(ptr);
97 if (ptr != NULL) ptr->link_prev(this);
98 }
99
100 // Reset top to bottom so chunk can be reused.
101 void reset_empty() { _top = (_bottom + _overhead); _next = NULL; _prev = NULL; }
102 bool is_empty() { return _top == (_bottom + _overhead); }
103
104 // used (has been allocated)
105 // free (available for future allocations)
106 // capacity (total size of chunk)
107 size_t used_word_size() const;
108 size_t free_word_size() const;
109 size_t capacity_word_size()const;
110
111 // Debug support
112 #ifdef ASSERT
113 void* prev_addr() const { return (void*)&_prev; }
114 void* next_addr() const { return (void*)&_next; }
115 void* size_addr() const { return (void*)&_word_size; }
116 #endif
117 bool verify_chunk_in_free_list(Metachunk* tc) const { return true; }
118 bool verify_par_locked() { return true; }
119
120 void assert_is_mangled() const {/* Don't check "\*/}
121
122 NOT_PRODUCT(void mangle();)
123
124 void print_on(outputStream* st) const;
125 void verify();
126 };
127 #endif // SHARE_VM_MEMORY_METACHUNK_HPP