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comparison src/share/vm/memory/metablock.hpp @ 6885:685df3c6f84b

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7045397: NPG: Add freelists to class loader arenas. Reviewed-by: coleenp, stefank, jprovino, ohair
author jmasa
date Tue, 18 Sep 2012 23:35:42 -0700
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children 335b388c4b28
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6877:d0e7716b179e 6885:685df3c6f84b
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_METABLOCK_HPP
25 #define SHARE_VM_MEMORY_METABLOCK_HPP
26
27 // Metablock are the unit of allocation from a Chunk. It is initialized
28 // with the size of the requested allocation. That size is overwritten
29 // once the allocation returns.
30 //
31 // A Metablock may be reused by its SpaceManager but are never moved between
32 // SpaceManagers. There is no explicit link to the Metachunk
33 // from which it was allocated. Metablock may be deallocated and
34 // put on a freelist but the space is never freed, rather
35 // the Metachunk it is a part of will be deallocated when it's
36 // associated class loader is collected.
37
38 class Metablock VALUE_OBJ_CLASS_SPEC {
39 friend class VMStructs;
40 private:
41 // Used to align the allocation (see below).
42 union block_t {
43 void* _data[3];
44 struct header_t {
45 size_t _word_size;
46 Metablock* _next;
47 Metablock* _prev;
48 } _header;
49 } _block;
50 static size_t _min_block_byte_size;
51 static size_t _overhead;
52
53 typedef union block_t Block;
54 typedef struct header_t Header;
55 const Block* block() const { return &_block; }
56 const Block::header_t* header() const { return &(block()->_header); }
57 public:
58
59 static Metablock* initialize(MetaWord* p, size_t word_size);
60
61 // This places the body of the block at a 2 word boundary
62 // because every block starts on a 2 word boundary. Work out
63 // how to make the body on a 2 word boundary if the block
64 // starts on a arbitrary boundary. JJJ
65
66 size_t word_size() const { return header()->_word_size; }
67 void set_word_size(size_t v) { _block._header._word_size = v; }
68 size_t size() const volatile { return _block._header._word_size; }
69 void set_size(size_t v) { _block._header._word_size = v; }
70 Metablock* next() const { return header()->_next; }
71 void set_next(Metablock* v) { _block._header._next = v; }
72 Metablock* prev() const { return header()->_prev; }
73 void set_prev(Metablock* v) { _block._header._prev = v; }
74
75 static size_t min_block_byte_size() { return _min_block_byte_size; }
76 static size_t overhead() { return _overhead; }
77
78 bool is_free() { return header()->_word_size != 0; }
79 void clear_next() { set_next(NULL); }
80 void link_prev(Metablock* ptr) { set_prev(ptr); }
81 uintptr_t* end() { return ((uintptr_t*) this) + size(); }
82 bool cantCoalesce() const { return false; }
83 void link_next(Metablock* ptr) { set_next(ptr); }
84 void link_after(Metablock* ptr){
85 link_next(ptr);
86 if (ptr != NULL) ptr->link_prev(this);
87 }
88
89 // Should not be needed in a free list of Metablocks
90 void markNotFree() { ShouldNotReachHere(); }
91
92 // Debug support
93 #ifdef ASSERT
94 void* prev_addr() const { return (void*)&_block._header._prev; }
95 void* next_addr() const { return (void*)&_block._header._next; }
96 void* size_addr() const { return (void*)&_block._header._word_size; }
97 #endif
98 bool verify_chunk_in_free_list(Metablock* tc) const { return true; }
99 bool verify_par_locked() { return true; }
100
101 void assert_is_mangled() const {/* Don't check "\*/}
102 };
103 #endif // SHARE_VM_MEMORY_METABLOCK_HPP