1 /*
2 * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2018, 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
21 * or visit www.oracle.com if you need additional information or have any
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24 */
25
26 #ifndef SHARE_MEMORY_METASPACE_MSVIRTUALSPACENODE_HPP
27 #define SHARE_MEMORY_METASPACE_MSVIRTUALSPACENODE_HPP
28
29 #include "memory/allocation.hpp"
30 #include "memory/metaspace/msCommitMask.hpp"
31 #include "memory/metaspace/msCounter.hpp"
32 #include "memory/metaspace/msRootChunkArea.hpp"
33 #include "memory/metaspace/msSettings.hpp"
34 #include "memory/memRegion.hpp"
35 #include "memory/virtualspace.hpp"
36 #include "utilities/debug.hpp"
37 #include "utilities/bitMap.hpp"
38 #include "utilities/globalDefinitions.hpp"
39
40 class outputStream;
41
42 namespace metaspace {
43
44 class CommitLimiter;
45 class FreeChunkListVector;
46
47 // VirtualSpaceNode manages a single contiguous address range of metaspace. Logically that memory
48 // region is split up into a sequence of "root chunk areas", each one containing one root chunk
49 // or splinters of a root chunk.
50 //
51 // The underlying memory is also logically divided into a number of "commit granules", units of memory
52 // which may be committed or uncommitted independently from each other.
53 //
54 // (Both root chunk areas and commit granules have not much to do with each other - one is a way to
55 // reserve memory for the upper regions, see ChunkManager. One is a way to manage commited memory.)
56 //
57 // VirtualSpaceNode:
58 // - exposes a function to allocate a new root chunk (see VirtualSpaceNode::allocate_root_chunk()).
59 //
60 // - knows about the commit state of the memory region - which commit granule are committed, which
61 // are not. It exposes functions to commit and uncommit regions (without actively committing
62 // itself)
63 //
64 // - It has a reference to a "CommitLimiter", an interface to query whether committing is
65 // possible. That interface hides the various ways committing may be limited (GC threshold,
66 // MaxMetaspaceSize, ...)
67 //
68 // - It uses ReservedSpace to reserve its memory. It either owns the ReservedSpace or that
69 // space got handed in from outside (ccs).
70 //
71 //
72 //
73 //
74 // | root chunk area | root chunk area | root chunk area | <-- root chunk areas
75 //
76 // +-----------------------------------------------------------------------------------------------+
77 // | |
78 // | `VirtualSpaceNode` memory |
79 // | |
80 // +-----------------------------------------------------------------------------------------------+
81 //
82 // |x| |x|x|x| | | | |x|x|x| | | |x|x| | | |x|x|x|x| | | | | | | | |x| | | |x|x|x|x| | | |x| | | |x| <-- commit granules
83 //
84 // (x = committed)
85 //
86
87 class VirtualSpaceNode : public CHeapObj<mtClass> {
88
89 // Link to next VirtualSpaceNode
90 VirtualSpaceNode* _next;
91
92 // The underlying space. This has been either created by this node
93 // and is owned by it, or has been handed in from outside (e.g. in
94 // case of CompressedClassSpace).
95 ReservedSpace _rs;
96
97 // True if the node owns the reserved space, false if not.
98 const bool _owns_rs;
99
100 // Start pointer of the area.
101 MetaWord* const _base;
102
103 // Size, in words, of the whole node
104 const size_t _word_size;
105
106 // Size, in words, of the range of this node which has been handed out in
107 // the form of root chunks.
108 size_t _used_words;
109
110 // The bitmap describing the commit state of the region:
111 // Each bit covers a region of 64K (see constants::commit_granule_size).
112 CommitMask _commit_mask;
113
114 // An array/lookup table of RootChunkArea objects. Each one describes a root chunk area.
115 RootChunkAreaLUT _root_chunk_area_lut;
116
117 // Limiter object to ask before expanding the committed size of this node.
118 CommitLimiter* const _commit_limiter;
119
120 // Points to outside size counters which we are to increase/decrease when we commit/uncommit
121 // space from this node.
122 SizeCounter* const _total_reserved_words_counter;
123 SizeCounter* const _total_committed_words_counter;
124
125 /// committing, uncommitting ///
126
127 // Given a pointer into this node, calculate the start of the commit granule
128 // the pointer points into.
129 MetaWord* calc_start_of_granule(MetaWord* p) const {
130 DEBUG_ONLY(check_pointer(p));
131 return align_down(p, Settings::commit_granule_bytes());
132 }
133
134 // Given an address range, ensure it is committed.
135 //
136 // The range has to be aligned to granule size.
137 //
138 // Function will:
139 // - check how many granules in that region are uncommitted; If all are committed, it
140 // returns true immediately.
141 // - check if committing those uncommitted granules would bring us over the commit limit
142 // (GC threshold, MaxMetaspaceSize). If true, it returns false.
143 // - commit the memory.
144 // - mark the range as committed in the commit mask
145 //
146 // Returns true if success, false if it did hit a commit limit.
147 bool commit_range(MetaWord* p, size_t word_size);
148
149 //// creation ////
150
151 // Create a new empty node spanning the given given reserved space.
152 VirtualSpaceNode(ReservedSpace rs, bool owns_rs, CommitLimiter* limiter,
153 SizeCounter* reserve_counter, SizeCounter* commit_counter);
154
155 public:
156
157 // Create a node of a given size (it will create its own space).
158 static VirtualSpaceNode* create_node(size_t word_size, CommitLimiter* limiter, SizeCounter* reserve_words_counter,
159 SizeCounter* commit_words_counter);
160
161 // Create a node over an existing space
162 static VirtualSpaceNode* create_node(ReservedSpace rs, CommitLimiter* limiter, SizeCounter* reserve_words_counter,
163 SizeCounter* commit_words_counter);
164
165 ~VirtualSpaceNode();
166
167 // Note: public for gtests only, could be private.
168 MetaWord* base() const { return _base; }
169
170 // Reserved size of the whole node.
171 size_t word_size() const { return _word_size; }
172
173 //// Chunk allocation, splitting, merging /////
174
175 // Allocate a root chunk from this node. Will fail and return NULL if the node is full
176 // - if we used up the whole address space of this node's memory region.
177 // (in case this node backs compressed class space, this is how we hit
178 // CompressedClassSpaceSize).
179 // Note that this just returns reserved memory; caller must take care of committing this
180 // chunk before using it.
181 Metachunk* allocate_root_chunk();
182
183 // Given a chunk c, split it recursively until you get a chunk of the given target_level.
184 //
185 // The resulting target chunk resides at the same address as the original chunk.
186 // The resulting splinters are added to freelists.
187 void split(chunklevel_t target_level, Metachunk* c, FreeChunkListVector* freelists);
188
189 // Given a chunk, attempt to merge it recursively with its neighboring chunks.
190 //
191 // If successful (merged at least once), returns address of
192 // the merged chunk; NULL otherwise.
193 //
194 // The merged chunks are removed from the freelists.
195 //
196 // !!! Please note that if this method returns a non-NULL value, the
197 // original chunk will be invalid and should not be accessed anymore! !!!
198 Metachunk* merge(Metachunk* c, FreeChunkListVector* freelists);
199
200 // Given a chunk c, which must be "in use" and must not be a root chunk, attempt to
201 // enlarge it in place by claiming its trailing buddy.
202 //
203 // This will only work if c is the leader of the buddy pair and the trailing buddy is free.
204 //
205 // If successful, the follower chunk will be removed from the freelists, the leader chunk c will
206 // double in size (level decreased by one).
207 //
208 // On success, true is returned, false otherwise.
209 bool attempt_enlarge_chunk(Metachunk* c, FreeChunkListVector* freelists);
210
211 // Attempts to purge the node:
212 //
213 // If all chunks living in this node are free, they will all be removed from
214 // the freelist they currently reside in. Then, the node will be deleted.
215 //
216 // Returns true if the node has been deleted, false if not.
217 // !! If this returns true, do not access the node from this point on. !!
218 bool attempt_purge(FreeChunkListVector* freelists);
219
220 // Attempts to uncommit free areas according to the rules set in settings.
221 // Returns number of words uncommitted.
222 size_t uncommit_free_areas();
223
224 /// misc /////
225
226 // Returns size, in words, of the used space in this node alone.
227 // (Notes:
228 // - This is the space handed out to the ChunkManager, so it is "used" from the viewpoint of this node,
229 // but not necessarily used for Metadata.
230 // - This may or may not be committed memory.
231 size_t used_words() const { return _used_words; }
232
233 // Returns size, in words, of how much space is left in this node alone.
234 size_t free_words() const { return _word_size - _used_words; }
235
236 // Returns size, in words, of committed space in this node alone.
237 // Note: iterates over commit mask and hence may be a tad expensive on large nodes.
238 size_t committed_words() const;
239
240 //// Committing/uncommitting memory /////
241
242 // Given an address range, ensure it is committed.
243 //
244 // The range does not have to be aligned to granule size. However, the function will always commit
245 // whole granules.
246 //
247 // Function will:
248 // - check how many granules in that region are uncommitted; If all are committed, it
249 // returns true immediately.
250 // - check if committing those uncommitted granules would bring us over the commit limit
251 // (GC threshold, MaxMetaspaceSize). If true, it returns false.
252 // - commit the memory.
253 // - mark the range as committed in the commit mask
254 //
255 // Returns true if success, false if it did hit a commit limit.
256 bool ensure_range_is_committed(MetaWord* p, size_t word_size);
257
258 // Given an address range (which has to be aligned to commit granule size):
259 // - uncommit it
260 // - mark it as uncommitted in the commit mask
261 void uncommit_range(MetaWord* p, size_t word_size);
262
263 //// List stuff ////
264 VirtualSpaceNode* next() const { return _next; }
265 void set_next(VirtualSpaceNode* vsn) { _next = vsn; }
266
267 /// Debug stuff ////
268
269 // Print a description about this node.
270 void print_on(outputStream* st) const;
271
272 // Verify counters and basic structure. Slow mode: verify all chunks in depth
273 bool contains(const MetaWord* p) const {
274 return p >= _base && p < _base + _used_words;
275 }
276
277 #ifdef ASSERT
278 void check_pointer(const MetaWord* p) const {
279 assert(contains(p), "invalid pointer");
280 }
281 void verify() const;
282 void verify_locked() const;
283 #endif
284
285 };
286
287 } // namespace metaspace
288
289 #endif // SHARE_MEMORY_METASPACE_MSVIRTUALSPACENODE_HPP