1 /*
2 * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2020 SAP SE. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26 #ifndef SHARE_MEMORY_METASPACE_METASPACECONTEXT_HPP
27 #define SHARE_MEMORY_METASPACE_METASPACECONTEXT_HPP
28
29 #include "memory/allocation.hpp"
30 #include "memory/metaspace/counters.hpp"
31 #include "memory/virtualspace.hpp"
32 #include "utilities/debug.hpp"
33
34 class outputStream;
35
36 namespace metaspace {
37
38 class ChunkManager;
39 class VirtualSpaceList;
40 class CommitLimiter;
41
42 // MetaspaceContext is a convenience bracket around:
43 //
44 // - a VirtualSpaceList managing a memory area used for Metaspace
45 // - a ChunkManager sitting atop of that which manages chunk freelists
46 //
47 // In a normal VM only one or two of these contexts ever exist: one for the metaspace, and
48 // optionally another one for the compressed class space.
49 //
50 // For tests more contexts may be created, and this would also be a way to use Metaspace
51 // for things other than class metadata. We would have to work on the naming then.
52 //
53 // - (Future TODO): Context should own a lock to guard it. Currently this stuff is guarded
54 // by one global lock, the slightly misnamed Metaspace_expandlock, but that one
55 // should be split into one per context.
56 // - (Future TODO): Context can/should have its own allocation alignment. That way we
57 // can have different alignment between class space and non-class metaspace. That could
58 // help optimize compressed class pointer encoding, see discussion for JDK-8244943).
59
60 class MetaspaceContext : public CHeapObj<mtMetaspace> {
61
62 const char* const _name;
63 VirtualSpaceList* const _vslist;
64 ChunkManager* const _cm;
65 SizeAtomicCounter _used_words_counter;
66
67 MetaspaceContext(const char* name, VirtualSpaceList* vslist, ChunkManager* cm) :
68 _name(name),
69 _vslist(vslist),
70 _cm(cm)
71 {}
72
73 static MetaspaceContext* _nonclass_space_context;
74 static MetaspaceContext* _class_space_context;
75
76 public:
77
78 // Destroys the context: deletes chunkmanager and virtualspacelist.
79 // If this is a non-expandable context over an existing space, that space remains
80 // untouched, otherwise all memory is unmapped.
81 ~MetaspaceContext();
82
83 VirtualSpaceList* vslist() { return _vslist; }
84 ChunkManager* cm() { return _cm; }
85 SizeAtomicCounter* used_words_counter() { return &_used_words_counter; }
86
87 // Create a new, empty, expandable metaspace context.
88 static MetaspaceContext* create_expandable_context(const char* name, CommitLimiter* commit_limiter);
89
90 // Create a new, empty, non-expandable metaspace context atop of an externally provided space.
91 static MetaspaceContext* create_nonexpandable_context(const char* name, ReservedSpace rs, CommitLimiter* commit_limiter);
92
93 void print_on(outputStream* st) const;
94
95 DEBUG_ONLY(void verify() const;)
96
97 static void initialize_class_space_context(ReservedSpace rs);
98 static void initialize_nonclass_space_context();
99
100 // Returns pointer to the global metaspace context.
101 // If compressed class space is active, this contains the non-class-space allocations.
102 // If compressed class space is inactive, this contains all metaspace allocations.
103 static MetaspaceContext* context_nonclass() { return _nonclass_space_context; }
104
105 // Returns pointer to the global class space context, if compressed class space is active,
106 // null otherwise.
107 static MetaspaceContext* context_class() { return _class_space_context; }
108
109 size_t used_words() const;
110 size_t committed_words() const;
111 size_t reserved_words() const;
112 };
113
114 } // end namespace
115
116 #endif // SHARE_MEMORY_METASPACE_METASPACECONTEXT_HPP
117