1 /*
2 * Copyright (c) 2017, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25 #ifndef SHARE_VM_GC_SHARED_CARDTABLE_HPP
26 #define SHARE_VM_GC_SHARED_CARDTABLE_HPP
27
28 #include "memory/memRegion.hpp"
29
30 class CardTable: public CHeapObj<mtGC> {
31 friend class VMStructs;
32 protected:
33 // The declaration order of these const fields is important; see the
34 // constructor before changing.
35 const bool _scanned_concurrently;
36 const MemRegion _whole_heap; // the region covered by the card table
37 size_t _guard_index; // index of very last element in the card
38 // table; it is set to a guard value
39 // (last_card) and should never be modified
40 size_t _last_valid_index; // index of the last valid element
41 const size_t _page_size; // page size used when mapping _byte_map
42 size_t _byte_map_size; // in bytes
43 jbyte* _byte_map; // the card marking array
44 jbyte* _byte_map_base;
45
46 int _cur_covered_regions;
47 // The covered regions should be in address order.
48 MemRegion* _covered;
49 // The committed regions correspond one-to-one to the covered regions.
50 // They represent the card-table memory that has been committed to service
51 // the corresponding covered region. It may be that committed region for
52 // one covered region corresponds to a larger region because of page-size
53 // roundings. Thus, a committed region for one covered region may
54 // actually extend onto the card-table space for the next covered region.
55 MemRegion* _committed;
56
57 // The last card is a guard card, and we commit the page for it so
58 // we can use the card for verification purposes. We make sure we never
59 // uncommit the MemRegion for that page.
60 MemRegion _guard_region;
61
62 inline size_t compute_byte_map_size();
63
64 // Finds and return the index of the region, if any, to which the given
65 // region would be contiguous. If none exists, assign a new region and
66 // returns its index. Requires that no more than the maximum number of
67 // covered regions defined in the constructor are ever in use.
68 int find_covering_region_by_base(HeapWord* base);
69
70 // Same as above, but finds the region containing the given address
71 // instead of starting at a given base address.
72 int find_covering_region_containing(HeapWord* addr);
73
74 // Returns the leftmost end of a committed region corresponding to a
75 // covered region before covered region "ind", or else "NULL" if "ind" is
76 // the first covered region.
77 HeapWord* largest_prev_committed_end(int ind) const;
78
79 // Returns the part of the region mr that doesn't intersect with
80 // any committed region other than self. Used to prevent uncommitting
81 // regions that are also committed by other regions. Also protects
82 // against uncommitting the guard region.
83 MemRegion committed_unique_to_self(int self, MemRegion mr) const;
84
85 // Some barrier sets create tables whose elements correspond to parts of
86 // the heap; the CardTableModRefBS is an example. Such barrier sets will
87 // normally reserve space for such tables, and commit parts of the table
88 // "covering" parts of the heap that are committed. At most one covered
89 // region per generation is needed.
90 static const int _max_covered_regions = 2;
91
92 enum CardValues {
93 clean_card = -1,
94 // The mask contains zeros in places for all other values.
95 clean_card_mask = clean_card - 31,
96
97 dirty_card = 0,
98 precleaned_card = 1,
99 claimed_card = 2,
100 deferred_card = 4,
101 last_card = 8,
102 CT_MR_BS_last_reserved = 16
103 };
104
105 // a word's worth (row) of clean card values
106 static const intptr_t clean_card_row = (intptr_t)(-1);
107
108 public:
109 CardTable(MemRegion whole_heap, bool conc_scan);
110 virtual ~CardTable();
111 virtual void initialize();
112
113 // The kinds of precision a CardTableModRefBS may offer.
114 enum PrecisionStyle {
115 Precise,
116 ObjHeadPreciseArray
117 };
118
119 // Tells what style of precision this card table offers.
120 PrecisionStyle precision() {
121 return ObjHeadPreciseArray; // Only one supported for now.
122 }
123
124 // *** Barrier set functions.
125
126 // Initialization utilities; covered_words is the size of the covered region
127 // in, um, words.
128 inline size_t cards_required(size_t covered_words) {
129 // Add one for a guard card, used to detect errors.
130 const size_t words = align_size_up(covered_words, card_size_in_words);
131 return words / card_size_in_words + 1;
132 }
133
134 // Dirty the bytes corresponding to "mr" (not all of which must be
135 // covered.)
136 void dirty_MemRegion(MemRegion mr);
137
138 // Clear (to clean_card) the bytes entirely contained within "mr" (not
139 // all of which must be covered.)
140 void clear_MemRegion(MemRegion mr);
141
142 // Return true if "p" is at the start of a card.
143 bool is_card_aligned(HeapWord* p) {
144 jbyte* pcard = byte_for(p);
145 return (addr_for(pcard) == p);
146 }
147
148 // Mapping from address to card marking array entry
149 jbyte* byte_for(const void* p) const {
150 assert(_whole_heap.contains(p),
151 "Attempt to access p = " PTR_FORMAT " out of bounds of "
152 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
153 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
154 jbyte* result = &_byte_map_base[uintptr_t(p) >> card_shift];
155 assert(result >= _byte_map && result < _byte_map + _byte_map_size,
156 "out of bounds accessor for card marking array");
157 return result;
158 }
159
160 // The card table byte one after the card marking array
161 // entry for argument address. Typically used for higher bounds
162 // for loops iterating through the card table.
163 jbyte* byte_after(const void* p) const {
164 return byte_for(p) + 1;
165 }
166
167 virtual void invalidate(MemRegion mr);
168 void clear(MemRegion mr);
169 void dirty(MemRegion mr);
170
171 // Provide read-only access to the card table array.
172 const jbyte* byte_for_const(const void* p) const {
173 return byte_for(p);
174 }
175 const jbyte* byte_after_const(const void* p) const {
176 return byte_after(p);
177 }
178
179 // Mapping from card marking array entry to address of first word
180 HeapWord* addr_for(const jbyte* p) const {
181 assert(p >= _byte_map && p < _byte_map + _byte_map_size,
182 "out of bounds access to card marking array");
183 size_t delta = pointer_delta(p, _byte_map_base, sizeof(jbyte));
184 HeapWord* result = (HeapWord*) (delta << card_shift);
185 assert(_whole_heap.contains(result),
186 "Returning result = " PTR_FORMAT " out of bounds of "
187 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
188 p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
189 return result;
190 }
191
192 // Mapping from address to card marking array index.
193 size_t index_for(void* p) {
194 assert(_whole_heap.contains(p),
195 "Attempt to access p = " PTR_FORMAT " out of bounds of "
196 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
197 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
198 return byte_for(p) - _byte_map;
199 }
200
201 const jbyte* byte_for_index(const size_t card_index) const {
202 return _byte_map + card_index;
203 }
204
205 // Resize one of the regions covered by the remembered set.
206 virtual void resize_covered_region(MemRegion new_region);
207
208 // *** Card-table-RemSet-specific things.
209
210 static uintx ct_max_alignment_constraint();
211
212 // Apply closure "cl" to the dirty cards containing some part of
213 // MemRegion "mr".
214 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);
215
216 // Return the MemRegion corresponding to the first maximal run
217 // of dirty cards lying completely within MemRegion mr.
218 // If reset is "true", then sets those card table entries to the given
219 // value.
220 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
221 int reset_val);
222 void verify();
223
224 void verify_guard();
225
226 // val_equals -> it will check that all cards covered by mr equal val
227 // !val_equals -> it will check that all cards covered by mr do not equal val
228 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
229 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
230 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
231
232 // Print a description of the memory for the card table
233 virtual void print_on(outputStream* st) const;
234
235 // Constants
236 enum SomePublicConstants {
237 card_shift = 9,
238 card_size = 1 << card_shift,
239 card_size_in_words = card_size / sizeof(HeapWord)
240 };
241
242 static jbyte clean_card_val() { return clean_card; }
243 static jbyte clean_card_mask_val() { return clean_card_mask; }
244 static jbyte dirty_card_val() { return dirty_card; }
245 static jbyte claimed_card_val() { return claimed_card; }
246 static jbyte precleaned_card_val() { return precleaned_card; }
247 static jbyte deferred_card_val() { return deferred_card; }
248 static intptr_t clean_card_row_val() { return clean_card_row; }
249
250 // Card marking array base (adjusted for heap low boundary)
251 // This would be the 0th element of _byte_map, if the heap started at 0x0.
252 // But since the heap starts at some higher address, this points to somewhere
253 // before the beginning of the actual _byte_map.
254 jbyte* byte_map_base() const { return _byte_map_base; }
255 bool scanned_concurrently() const { return _scanned_concurrently; }
256
257 virtual bool is_in_young(void* addr) const = 0;
258 };
259
260 #endif // SHARE_VM_GC_SHARED_CARDTABLE_HPP