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