1 /*
2 * Copyright (c) 2000, 2018, 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.
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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_VM_GC_SHARED_CARDTABLE_HPP
26 #define SHARE_VM_GC_SHARED_CARDTABLE_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/oopsHierarchy.hpp"
31 #include "utilities/align.hpp"
32
33 class CardTable: public CHeapObj<mtGC> {
34 friend class VMStructs;
35 protected:
36 // The declaration order of these const fields is important; see the
37 // constructor before changing.
38 const bool _scanned_concurrently;
39 const MemRegion _whole_heap; // the region covered by the card table
40 size_t _guard_index; // index of very last element in the card
41 // table; it is set to a guard value
42 // (last_card) and should never be modified
43 size_t _last_valid_index; // index of the last valid element
44 const size_t _page_size; // page size used when mapping _byte_map
45 size_t _byte_map_size; // in bytes
46 jbyte* _byte_map; // the card marking array
47 jbyte* _byte_map_base;
48
49 int _cur_covered_regions;
50
51 // The covered regions should be in address order.
52 MemRegion* _covered;
53 // The committed regions correspond one-to-one to the covered regions.
54 // They represent the card-table memory that has been committed to service
55 // the corresponding covered region. It may be that committed region for
56 // one covered region corresponds to a larger region because of page-size
57 // roundings. Thus, a committed region for one covered region may
58 // actually extend onto the card-table space for the next covered region.
59 MemRegion* _committed;
60
61 // The last card is a guard card, and we commit the page for it so
62 // we can use the card for verification purposes. We make sure we never
63 // uncommit the MemRegion for that page.
64 MemRegion _guard_region;
65
66 inline size_t compute_byte_map_size();
67
68 // Finds and return the index of the region, if any, to which the given
69 // region would be contiguous. If none exists, assign a new region and
70 // returns its index. Requires that no more than the maximum number of
71 // covered regions defined in the constructor are ever in use.
72 int find_covering_region_by_base(HeapWord* base);
73
74 // Same as above, but finds the region containing the given address
75 // instead of starting at a given base address.
76 int find_covering_region_containing(HeapWord* addr);
77
78 // Returns the leftmost end of a committed region corresponding to a
79 // covered region before covered region "ind", or else "NULL" if "ind" is
80 // the first covered region.
81 HeapWord* largest_prev_committed_end(int ind) const;
82
83 // Returns the part of the region mr that doesn't intersect with
84 // any committed region other than self. Used to prevent uncommitting
85 // regions that are also committed by other regions. Also protects
86 // against uncommitting the guard region.
87 MemRegion committed_unique_to_self(int self, MemRegion mr) const;
88
89 // Some barrier sets create tables whose elements correspond to parts of
90 // the heap; the CardTableBarrierSet is an example. Such barrier sets will
91 // normally reserve space for such tables, and commit parts of the table
92 // "covering" parts of the heap that are committed. At most one covered
93 // region per generation is needed.
94 static const int _max_covered_regions = 2;
95
96 enum CardValues {
97 clean_card = -1,
98 // The mask contains zeros in places for all other values.
99 clean_card_mask = clean_card - 31,
100
101 dirty_card = 0,
102 precleaned_card = 1,
103 claimed_card = 2,
104 deferred_card = 4,
105 last_card = 8,
106 CT_MR_BS_last_reserved = 16
107 };
108
109 // a word's worth (row) of clean card values
110 static const intptr_t clean_card_row = (intptr_t)(-1);
111
112 public:
113 CardTable(MemRegion whole_heap, bool conc_scan);
114 virtual ~CardTable();
115 virtual void initialize();
116
117 // The kinds of precision a CardTable may offer.
118 enum PrecisionStyle {
119 Precise,
120 ObjHeadPreciseArray
121 };
122
123 // Tells what style of precision this card table offers.
124 PrecisionStyle precision() {
125 return ObjHeadPreciseArray; // Only one supported for now.
126 }
127
128 // *** Barrier set functions.
129
130 // Initialization utilities; covered_words is the size of the covered region
131 // in, um, words.
132 inline size_t cards_required(size_t covered_words) {
133 // Add one for a guard card, used to detect errors.
134 const size_t words = align_up(covered_words, card_size_in_words);
135 return words / card_size_in_words + 1;
136 }
137
138 // Dirty the bytes corresponding to "mr" (not all of which must be
139 // covered.)
140 void dirty_MemRegion(MemRegion mr);
141
142 // Clear (to clean_card) the bytes entirely contained within "mr" (not
143 // all of which must be covered.)
144 void clear_MemRegion(MemRegion mr);
145
146 // Return true if "p" is at the start of a card.
147 bool is_card_aligned(HeapWord* p) {
148 jbyte* pcard = byte_for(p);
149 return (addr_for(pcard) == p);
150 }
151
152 // Mapping from address to card marking array entry
153 jbyte* byte_for(const void* p) const {
154 assert(_whole_heap.contains(p),
155 "Attempt to access p = " PTR_FORMAT " out of bounds of "
156 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
157 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
158 jbyte* result = &_byte_map_base[uintptr_t(p) >> card_shift];
159 assert(result >= _byte_map && result < _byte_map + _byte_map_size,
160 "out of bounds accessor for card marking array");
161 return result;
162 }
163
164 // The card table byte one after the card marking array
165 // entry for argument address. Typically used for higher bounds
166 // for loops iterating through the card table.
167 jbyte* byte_after(const void* p) const {
168 return byte_for(p) + 1;
169 }
170
171 virtual void invalidate(MemRegion mr);
172 void clear(MemRegion mr);
173 void dirty(MemRegion mr);
174
175 // Provide read-only access to the card table array.
176 const jbyte* byte_for_const(const void* p) const {
177 return byte_for(p);
178 }
179 const jbyte* byte_after_const(const void* p) const {
180 return byte_after(p);
181 }
182
183 // Mapping from card marking array entry to address of first word
184 HeapWord* addr_for(const jbyte* p) const {
185 assert(p >= _byte_map && p < _byte_map + _byte_map_size,
186 "out of bounds access to card marking array. p: " PTR_FORMAT
187 " _byte_map: " PTR_FORMAT " _byte_map + _byte_map_size: " PTR_FORMAT,
188 p2i(p), p2i(_byte_map), p2i(_byte_map + _byte_map_size));
189 size_t delta = pointer_delta(p, _byte_map_base, sizeof(jbyte));
190 HeapWord* result = (HeapWord*) (delta << card_shift);
191 assert(_whole_heap.contains(result),
192 "Returning result = " PTR_FORMAT " out of bounds of "
193 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
194 p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
195 return result;
196 }
197
198 // Mapping from address to card marking array index.
199 size_t index_for(void* p) {
200 assert(_whole_heap.contains(p),
201 "Attempt to access p = " PTR_FORMAT " out of bounds of "
202 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
203 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
204 return byte_for(p) - _byte_map;
205 }
206
207 const jbyte* byte_for_index(const size_t card_index) const {
208 return _byte_map + card_index;
209 }
210
211 // Resize one of the regions covered by the remembered set.
212 virtual void resize_covered_region(MemRegion new_region);
213
214 // *** Card-table-RemSet-specific things.
215
216 static uintx ct_max_alignment_constraint();
217
218 // Apply closure "cl" to the dirty cards containing some part of
219 // MemRegion "mr".
220 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);
221
222 // Return the MemRegion corresponding to the first maximal run
223 // of dirty cards lying completely within MemRegion mr.
224 // If reset is "true", then sets those card table entries to the given
225 // value.
226 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
227 int reset_val);
228
229 // Constants
230 enum SomePublicConstants {
231 card_shift = 9,
232 card_size = 1 << card_shift,
233 card_size_in_words = card_size / sizeof(HeapWord)
234 };
235
236 static jbyte clean_card_val() { return clean_card; }
237 static jbyte clean_card_mask_val() { return clean_card_mask; }
238 static jbyte dirty_card_val() { return dirty_card; }
239 static jbyte claimed_card_val() { return claimed_card; }
240 static jbyte precleaned_card_val() { return precleaned_card; }
241 static jbyte deferred_card_val() { return deferred_card; }
242 static intptr_t clean_card_row_val() { return clean_card_row; }
243
244 // Card marking array base (adjusted for heap low boundary)
245 // This would be the 0th element of _byte_map, if the heap started at 0x0.
246 // But since the heap starts at some higher address, this points to somewhere
247 // before the beginning of the actual _byte_map.
248 jbyte* byte_map_base() const { return _byte_map_base; }
249 bool scanned_concurrently() const { return _scanned_concurrently; }
250
251 virtual bool is_in_young(oop obj) const = 0;
252
253 // Print a description of the memory for the card table
254 virtual void print_on(outputStream* st) const;
255
256 void verify();
257 void verify_guard();
258
259 // val_equals -> it will check that all cards covered by mr equal val
260 // !val_equals -> it will check that all cards covered by mr do not equal val
261 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
262 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
263 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
264 };
265
266 #endif // SHARE_VM_GC_SHARED_CARDTABLE_HPP