1 /*
2 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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).
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24
25 #ifndef SHARE_MEMORY_METASPACE_CHUNKMANAGER_HPP
26 #define SHARE_MEMORY_METASPACE_CHUNKMANAGER_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/metaspace/chunkLevel.hpp"
30 #include "memory/metaspace/counter.hpp"
31 #include "memory/metaspace/metachunk.hpp"
32
33 namespace metaspace {
34
35 class VirtualSpaceList;
36 class ChunkManagerStatistics;
37
38 // class ChunkManager
39 //
40 // The ChunkManager has a central role. Callers request chunks from it.
41 // It keeps the freelists for chunks. If the freelist is exhausted it
42 // allocates new chunks from a connected VirtualSpaceList.
43 //
44 class ChunkManager : public CHeapObj<mtInternal> {
45
46 // A chunk manager is connected to a virtual space list which is used
47 // to allocate new root chunks when no free chunks are found.
48 VirtualSpaceList* const _vslist;
49
50 // Name
51 const char* const _name;
52
53 // Freelist
54 MetachunkList _chunks [chklvl::NUM_CHUNK_LEVELS];
55
56 // Total size, in words, of all chunks.
57 SizeCounter _total_word_size;
58
59 // Total size, in words, of the committed parts of all chunks.
60 SizeCounter _committed_word_size;
61
62 // Returns true if this manager contains the given chunk. Slow (walks free list) and
63 // only needed for verifications.
64 DEBUG_ONLY(bool contains_chunk(Metachunk* metachunk) const;)
65
66 // Given a chunk we are about to handout to the caller, make sure it is committed
67 // according to constants::committed_words_on_fresh_chunks.
68 // May fail if we hit the commit limit.
69 static bool commit_chunk_before_handout(Metachunk* c);
70
71 // Return a single chunk to the freelist and adjust accounting. No merge is attempted.
72 void return_chunk_simple(Metachunk* c);
73
74 // Take a single chunk from the given freelist and adjust counters. Returns NULL
75 // if there is no fitting chunk for this level.
76 Metachunk* remove_first_chunk_at_level(chklvl_t l);
77
78
79 // Given a chunk which must be outside of a freelist and must be free, split it to
80 // meet a target level and return it. Splinters are added to the freelist.
81 Metachunk* split_chunk_and_add_splinters(Metachunk* c, chklvl_t target_level);
82
83 public:
84
85 // Creates a chunk manager with a given name (which is for debug purposes only)
86 // and an associated space list which will be used to request new chunks from
87 // (see get_chunk())
88 ChunkManager(const char* name, VirtualSpaceList* space_list);
89
90 // Get a chunk and be smart about it.
91 // - 1) Attempt to find a free chunk of exactly the pref_level level
92 // - 2) Failing that, attempt to find a chunk smaller or equal the minimal level.
93 // - 3) Failing that, attempt to find a free chunk of larger size and split it.
94 // - 4) Failing that, attempt to allocate a new chunk from the connected virtual space.
95 // - Failing that, give up and return NULL.
96 // Note: this is not guaranteed to return a *committed* chunk. The chunk manager will
97 // attempt to commit the returned chunk according to constants::committed_words_on_fresh_chunks;
98 // but this may fail if we hit a commit limit. In that case, a partly uncommitted chunk
99 // will be returned, and the commit is attempted again when we allocate from the chunk's
100 // uncommitted area. See also Metachunk::allocate.
101 Metachunk* get_chunk(chklvl_t min_level, chklvl_t pref_level);
102
103 // Return a single chunk to the ChunkManager and adjust accounting. May merge chunk
104 // with neighbors.
105 // Happens after a Classloader was unloaded and releases its metaspace chunks.
106 // !! Note: this may invalidate the chunk. Do not access the chunk after
107 // this function returns !!
108 void return_chunk(Metachunk* c);
109
110 // Uncommit payload area of free chunks. Will be called during Metaspace GC.
111 void uncommit_free_chunks();
112
113 // Run verifications. slow=true: verify chunk-internal integrity too.
114 DEBUG_ONLY(void verify(bool slow) const;)
115 DEBUG_ONLY(void verify_locked(bool slow) const;)
116
117 // Returns the name of this chunk manager.
118 const char* name() const { return _name; }
119
120 // Returns number of words in all free chunks.
121 size_t total_word_size() const { return _total_word_size.get(); }
122
123 // Update statistics.
124 void add_to_statistics(ChunkManagerStatistics* out) const;
125
126 private:
127
128 static ChunkManager* _chunkmanager_class;
129 static ChunkManager* _chunkmanager_nonclass;
130
131 public:
132
133 static ChunkManager* chunkmanager_class() { return _chunkmanager_class; }
134 static ChunkManager* chunkmanager_nonclass() { return _chunkmanager_nonclass; }
135
136 static void set_chunkmanager_class(ChunkManager* cm);
137 static void set_chunkmanager_nonclass(ChunkManager* cm);
138
139 };
140
141 } // namespace metaspace
142
143 #endif // SHARE_MEMORY_METASPACE_CHUNKMANAGER_HPP