1 /*
2 * Copyright (c) 2000, 2013, 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.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
26 #define SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
27
28 #include "memory/modRefBarrierSet.hpp"
29 #include "oops/oop.hpp"
30 #include "oops/oop.inline2.hpp"
31
32 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
33 // enumerate ref fields that have been modified (since the last
34 // enumeration.)
35
36 // As it currently stands, this barrier is *imprecise*: when a ref field in
37 // an object "o" is modified, the card table entry for the card containing
38 // the head of "o" is dirtied, not necessarily the card containing the
39 // modified field itself. For object arrays, however, the barrier *is*
40 // precise; only the card containing the modified element is dirtied.
41 // Any MemRegionClosures used to scan dirty cards should take these
42 // considerations into account.
43
44 class Generation;
45 class OopsInGenClosure;
46 class DirtyCardToOopClosure;
47 class ClearNoncleanCardWrapper;
48
49 class CardTableModRefBS: public ModRefBarrierSet {
50 // Some classes get to look at some private stuff.
51 friend class BytecodeInterpreter;
52 friend class VMStructs;
53 friend class CardTableRS;
54 friend class CheckForUnmarkedOops; // Needs access to raw card bytes.
55 friend class SharkBuilder;
56 #ifndef PRODUCT
57 // For debugging.
58 friend class GuaranteeNotModClosure;
59 #endif
60 protected:
61
62 enum CardValues {
63 clean_card = -1,
64 // The mask contains zeros in places for all other values.
65 clean_card_mask = clean_card - 31,
66
67 dirty_card = 0,
68 precleaned_card = 1,
69 claimed_card = 2,
70 deferred_card = 4,
71 last_card = 8,
72 CT_MR_BS_last_reserved = 16,
73 g1_young_gen = 32
74 };
75
76 // a word's worth (row) of clean card values
77 static const intptr_t clean_card_row = (intptr_t)(-1);
78
79 // dirty and precleaned are equivalent wrt younger_refs_iter.
80 static bool card_is_dirty_wrt_gen_iter(jbyte cv) {
81 return cv == dirty_card || cv == precleaned_card;
82 }
83
84 // Returns "true" iff the value "cv" will cause the card containing it
85 // to be scanned in the current traversal. May be overridden by
86 // subtypes.
87 virtual bool card_will_be_scanned(jbyte cv) {
88 return CardTableModRefBS::card_is_dirty_wrt_gen_iter(cv);
89 }
90
91 // Returns "true" iff the value "cv" may have represented a dirty card at
92 // some point.
93 virtual bool card_may_have_been_dirty(jbyte cv) {
94 return card_is_dirty_wrt_gen_iter(cv);
95 }
96
97 // The declaration order of these const fields is important; see the
98 // constructor before changing.
99 const MemRegion _whole_heap; // the region covered by the card table
100 const size_t _guard_index; // index of very last element in the card
101 // table; it is set to a guard value
102 // (last_card) and should never be modified
103 const size_t _last_valid_index; // index of the last valid element
104 const size_t _page_size; // page size used when mapping _byte_map
105 const size_t _byte_map_size; // in bytes
106 jbyte* _byte_map; // the card marking array
107
108 int _cur_covered_regions;
109 // The covered regions should be in address order.
110 MemRegion* _covered;
111 // The committed regions correspond one-to-one to the covered regions.
112 // They represent the card-table memory that has been committed to service
113 // the corresponding covered region. It may be that committed region for
114 // one covered region corresponds to a larger region because of page-size
115 // roundings. Thus, a committed region for one covered region may
116 // actually extend onto the card-table space for the next covered region.
117 MemRegion* _committed;
118
119 // The last card is a guard card, and we commit the page for it so
120 // we can use the card for verification purposes. We make sure we never
121 // uncommit the MemRegion for that page.
122 MemRegion _guard_region;
123
124 protected:
125 // Initialization utilities; covered_words is the size of the covered region
126 // in, um, words.
127 inline size_t cards_required(size_t covered_words);
128 inline size_t compute_byte_map_size();
129
130 // Finds and return the index of the region, if any, to which the given
131 // region would be contiguous. If none exists, assign a new region and
132 // returns its index. Requires that no more than the maximum number of
133 // covered regions defined in the constructor are ever in use.
134 int find_covering_region_by_base(HeapWord* base);
135
136 // Same as above, but finds the region containing the given address
137 // instead of starting at a given base address.
138 int find_covering_region_containing(HeapWord* addr);
139
140 // Resize one of the regions covered by the remembered set.
141 void resize_covered_region(MemRegion new_region);
142
143 // Returns the leftmost end of a committed region corresponding to a
144 // covered region before covered region "ind", or else "NULL" if "ind" is
145 // the first covered region.
146 HeapWord* largest_prev_committed_end(int ind) const;
147
148 // Returns the part of the region mr that doesn't intersect with
149 // any committed region other than self. Used to prevent uncommitting
150 // regions that are also committed by other regions. Also protects
151 // against uncommitting the guard region.
152 MemRegion committed_unique_to_self(int self, MemRegion mr) const;
153
154 // Mapping from address to card marking array entry
155 jbyte* byte_for(const void* p) const {
156 assert(_whole_heap.contains(p),
157 err_msg("Attempt to access p = "PTR_FORMAT" out of bounds of "
158 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
159 p, _whole_heap.start(), _whole_heap.end()));
160 jbyte* result = &byte_map_base[uintptr_t(p) >> card_shift];
161 assert(result >= _byte_map && result < _byte_map + _byte_map_size,
162 "out of bounds accessor for card marking array");
163 return result;
164 }
165
166 // The card table byte one after the card marking array
167 // entry for argument address. Typically used for higher bounds
168 // for loops iterating through the card table.
169 jbyte* byte_after(const void* p) const {
170 return byte_for(p) + 1;
171 }
172
173 // Iterate over the portion of the card-table which covers the given
174 // region mr in the given space and apply cl to any dirty sub-regions
175 // of mr. Dirty cards are _not_ cleared by the iterator method itself,
176 // but closures may arrange to do so on their own should they so wish.
177 void non_clean_card_iterate_serial(MemRegion mr, MemRegionClosure* cl);
178
179 // A variant of the above that will operate in a parallel mode if
180 // worker threads are available, and clear the dirty cards as it
181 // processes them.
182 // XXX ??? MemRegionClosure above vs OopsInGenClosure below XXX
183 // XXX some new_dcto_cl's take OopClosure's, plus as above there are
184 // some MemRegionClosures. Clean this up everywhere. XXX
185 void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,
186 OopsInGenClosure* cl, CardTableRS* ct);
187
188 private:
189 // Work method used to implement non_clean_card_iterate_possibly_parallel()
190 // above in the parallel case.
191 void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
192 OopsInGenClosure* cl, CardTableRS* ct,
193 int n_threads);
194
195 protected:
196 // Dirty the bytes corresponding to "mr" (not all of which must be
197 // covered.)
198 void dirty_MemRegion(MemRegion mr);
199
200 // Clear (to clean_card) the bytes entirely contained within "mr" (not
201 // all of which must be covered.)
202 void clear_MemRegion(MemRegion mr);
203
204 // *** Support for parallel card scanning.
205
206 // This is an array, one element per covered region of the card table.
207 // Each entry is itself an array, with one element per chunk in the
208 // covered region. Each entry of these arrays is the lowest non-clean
209 // card of the corresponding chunk containing part of an object from the
210 // previous chunk, or else NULL.
211 typedef jbyte* CardPtr;
212 typedef CardPtr* CardArr;
213 CardArr* _lowest_non_clean;
214 size_t* _lowest_non_clean_chunk_size;
215 uintptr_t* _lowest_non_clean_base_chunk_index;
216 int* _last_LNC_resizing_collection;
217
218 // Initializes "lowest_non_clean" to point to the array for the region
219 // covering "sp", and "lowest_non_clean_base_chunk_index" to the chunk
220 // index of the corresponding to the first element of that array.
221 // Ensures that these arrays are of sufficient size, allocating if necessary.
222 // May be called by several threads concurrently.
223 void get_LNC_array_for_space(Space* sp,
224 jbyte**& lowest_non_clean,
225 uintptr_t& lowest_non_clean_base_chunk_index,
226 size_t& lowest_non_clean_chunk_size);
227
228 // Returns the number of chunks necessary to cover "mr".
229 size_t chunks_to_cover(MemRegion mr) {
230 return (size_t)(addr_to_chunk_index(mr.last()) -
231 addr_to_chunk_index(mr.start()) + 1);
232 }
233
234 // Returns the index of the chunk in a stride which
235 // covers the given address.
236 uintptr_t addr_to_chunk_index(const void* addr) {
237 uintptr_t card = (uintptr_t) byte_for(addr);
238 return card / ParGCCardsPerStrideChunk;
239 }
240
241 // Apply cl, which must either itself apply dcto_cl or be dcto_cl,
242 // to the cards in the stride (of n_strides) within the given space.
243 void process_stride(Space* sp,
244 MemRegion used,
245 jint stride, int n_strides,
246 OopsInGenClosure* cl,
247 CardTableRS* ct,
248 jbyte** lowest_non_clean,
249 uintptr_t lowest_non_clean_base_chunk_index,
250 size_t lowest_non_clean_chunk_size);
251
252 // Makes sure that chunk boundaries are handled appropriately, by
253 // adjusting the min_done of dcto_cl, and by using a special card-table
254 // value to indicate how min_done should be set.
255 void process_chunk_boundaries(Space* sp,
256 DirtyCardToOopClosure* dcto_cl,
257 MemRegion chunk_mr,
258 MemRegion used,
259 jbyte** lowest_non_clean,
260 uintptr_t lowest_non_clean_base_chunk_index,
261 size_t lowest_non_clean_chunk_size);
262
263 public:
264 // Constants
265 enum SomePublicConstants {
266 card_shift = 9,
267 card_size = 1 << card_shift,
268 card_size_in_words = card_size / sizeof(HeapWord)
269 };
270
271 static int clean_card_val() { return clean_card; }
272 static int clean_card_mask_val() { return clean_card_mask; }
273 static int dirty_card_val() { return dirty_card; }
274 static int claimed_card_val() { return claimed_card; }
275 static int precleaned_card_val() { return precleaned_card; }
276 static int deferred_card_val() { return deferred_card; }
277 static int g1_young_card_val() { return g1_young_gen; }
278
279 // For RTTI simulation.
280 bool is_a(BarrierSet::Name bsn) {
281 return bsn == BarrierSet::CardTableModRef || ModRefBarrierSet::is_a(bsn);
282 }
283
284 CardTableModRefBS(MemRegion whole_heap, int max_covered_regions);
285 ~CardTableModRefBS();
286
287 // *** Barrier set functions.
288
289 bool has_write_ref_pre_barrier() { return false; }
290
291 // Record a reference update. Note that these versions are precise!
292 // The scanning code has to handle the fact that the write barrier may be
293 // either precise or imprecise. We make non-virtual inline variants of
294 // these functions here for performance.
295 protected:
296 void write_ref_field_work(oop obj, size_t offset, oop newVal);
297 virtual void write_ref_field_work(void* field, oop newVal);
298 public:
299
300 bool has_write_ref_array_opt() { return true; }
301 bool has_write_region_opt() { return true; }
302
303 inline void inline_write_region(MemRegion mr) {
304 dirty_MemRegion(mr);
305 }
306 protected:
307 void write_region_work(MemRegion mr) {
308 inline_write_region(mr);
309 }
310 public:
311
312 inline void inline_write_ref_array(MemRegion mr) {
313 dirty_MemRegion(mr);
314 }
315 protected:
316 void write_ref_array_work(MemRegion mr) {
317 inline_write_ref_array(mr);
318 }
319 public:
320
321 bool is_aligned(HeapWord* addr) {
322 return is_card_aligned(addr);
323 }
324
325 // *** Card-table-barrier-specific things.
326
327 template <class T> inline void inline_write_ref_field_pre(T* field, oop newVal) {}
328
329 template <class T> inline void inline_write_ref_field(T* field, oop newVal) {
330 jbyte* byte = byte_for((void*)field);
331 *byte = dirty_card;
332 }
333
334 // These are used by G1, when it uses the card table as a temporary data
335 // structure for card claiming.
336 bool is_card_dirty(size_t card_index) {
337 return _byte_map[card_index] == dirty_card_val();
338 }
339
340 void mark_card_dirty(size_t card_index) {
341 _byte_map[card_index] = dirty_card_val();
342 }
343
344 bool is_card_claimed(size_t card_index) {
345 jbyte val = _byte_map[card_index];
346 return (val & (clean_card_mask_val() | claimed_card_val())) == claimed_card_val();
347 }
348
349 void set_card_claimed(size_t card_index) {
350 jbyte val = _byte_map[card_index];
351 if (val == clean_card_val()) {
352 val = (jbyte)claimed_card_val();
353 } else {
354 val |= (jbyte)claimed_card_val();
355 }
356 _byte_map[card_index] = val;
357 }
358
359 bool claim_card(size_t card_index);
360
361 bool is_card_clean(size_t card_index) {
362 return _byte_map[card_index] == clean_card_val();
363 }
364
365 bool is_card_deferred(size_t card_index) {
366 jbyte val = _byte_map[card_index];
367 return (val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val();
368 }
369
370 bool mark_card_deferred(size_t card_index);
371
372 // Card marking array base (adjusted for heap low boundary)
373 // This would be the 0th element of _byte_map, if the heap started at 0x0.
374 // But since the heap starts at some higher address, this points to somewhere
375 // before the beginning of the actual _byte_map.
376 jbyte* byte_map_base;
377
378 // Return true if "p" is at the start of a card.
379 bool is_card_aligned(HeapWord* p) {
380 jbyte* pcard = byte_for(p);
381 return (addr_for(pcard) == p);
382 }
383
384 HeapWord* align_to_card_boundary(HeapWord* p) {
385 jbyte* pcard = byte_for(p + card_size_in_words - 1);
386 return addr_for(pcard);
387 }
388
389 // The kinds of precision a CardTableModRefBS may offer.
390 enum PrecisionStyle {
391 Precise,
392 ObjHeadPreciseArray
393 };
394
395 // Tells what style of precision this card table offers.
396 PrecisionStyle precision() {
397 return ObjHeadPreciseArray; // Only one supported for now.
398 }
399
400 // ModRefBS functions.
401 virtual void invalidate(MemRegion mr, bool whole_heap = false);
402 void clear(MemRegion mr);
403 void dirty(MemRegion mr);
404
405 // *** Card-table-RemSet-specific things.
406
407 // Invoke "cl.do_MemRegion" on a set of MemRegions that collectively
408 // includes all the modified cards (expressing each card as a
409 // MemRegion). Thus, several modified cards may be lumped into one
410 // region. The regions are non-overlapping, and are visited in
411 // *decreasing* address order. (This order aids with imprecise card
412 // marking, where a dirty card may cause scanning, and summarization
413 // marking, of objects that extend onto subsequent cards.)
414 void mod_card_iterate(MemRegionClosure* cl) {
415 non_clean_card_iterate_serial(_whole_heap, cl);
416 }
417
418 // Like the "mod_cards_iterate" above, except only invokes the closure
419 // for cards within the MemRegion "mr" (which is required to be
420 // card-aligned and sized.)
421 void mod_card_iterate(MemRegion mr, MemRegionClosure* cl) {
422 non_clean_card_iterate_serial(mr, cl);
423 }
424
425 static uintx ct_max_alignment_constraint();
426
427 // Apply closure "cl" to the dirty cards containing some part of
428 // MemRegion "mr".
429 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);
430
431 // Return the MemRegion corresponding to the first maximal run
432 // of dirty cards lying completely within MemRegion mr.
433 // If reset is "true", then sets those card table entries to the given
434 // value.
435 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
436 int reset_val);
437
438 // Provide read-only access to the card table array.
439 const jbyte* byte_for_const(const void* p) const {
440 return byte_for(p);
441 }
442 const jbyte* byte_after_const(const void* p) const {
443 return byte_after(p);
444 }
445
446 // Mapping from card marking array entry to address of first word
447 HeapWord* addr_for(const jbyte* p) const {
448 assert(p >= _byte_map && p < _byte_map + _byte_map_size,
449 "out of bounds access to card marking array");
450 size_t delta = pointer_delta(p, byte_map_base, sizeof(jbyte));
451 HeapWord* result = (HeapWord*) (delta << card_shift);
452 assert(_whole_heap.contains(result),
453 err_msg("Returning result = "PTR_FORMAT" out of bounds of "
454 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
455 result, _whole_heap.start(), _whole_heap.end()));
456 return result;
457 }
458
459 // Mapping from address to card marking array index.
460 size_t index_for(void* p) {
461 assert(_whole_heap.contains(p),
462 err_msg("Attempt to access p = "PTR_FORMAT" out of bounds of "
463 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
464 p, _whole_heap.start(), _whole_heap.end()));
465 return byte_for(p) - _byte_map;
466 }
467
468 const jbyte* byte_for_index(const size_t card_index) const {
469 return _byte_map + card_index;
470 }
471
472 // Print a description of the memory for the barrier set
473 virtual void print_on(outputStream* st) const;
474
475 void verify();
476 void verify_guard();
477
478 // val_equals -> it will check that all cards covered by mr equal val
479 // !val_equals -> it will check that all cards covered by mr do not equal val
480 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
481 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
482 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
483 void verify_g1_young_region(MemRegion mr) PRODUCT_RETURN;
484
485 static size_t par_chunk_heapword_alignment() {
486 return ParGCCardsPerStrideChunk * card_size_in_words;
487 }
488
489 };
490
491 class CardTableRS;
492
493 // A specialization for the CardTableRS gen rem set.
494 class CardTableModRefBSForCTRS: public CardTableModRefBS {
495 CardTableRS* _rs;
496 protected:
497 bool card_will_be_scanned(jbyte cv);
498 bool card_may_have_been_dirty(jbyte cv);
499 public:
500 CardTableModRefBSForCTRS(MemRegion whole_heap,
501 int max_covered_regions) :
502 CardTableModRefBS(whole_heap, max_covered_regions) {}
503
504 void set_CTRS(CardTableRS* rs) { _rs = rs; }
505 };
506
507
508 #endif // SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP