1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)cardTableModRefBS.cpp 1.60 07/12/05 23:34:34 JVM"
3 #endif
4 /*
5 * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
29 // enumerate ref fields that have been modified (since the last
30 // enumeration.)
31
32 # include "incls/_precompiled.incl"
33 # include "incls/_cardTableModRefBS.cpp.incl"
34
35 size_t CardTableModRefBS::cards_required(size_t covered_words)
36 {
37 // Add one for a guard card, used to detect errors.
38 const size_t words = align_size_up(covered_words, card_size_in_words);
39 return words / card_size_in_words + 1;
40 }
41
42 size_t CardTableModRefBS::compute_byte_map_size()
43 {
44 assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
45 "unitialized, check declaration order");
46 assert(_page_size != 0, "unitialized, check declaration order");
47 const size_t granularity = os::vm_allocation_granularity();
48 return align_size_up(_guard_index + 1, MAX2(_page_size, granularity));
49 }
50
51 CardTableModRefBS::CardTableModRefBS(MemRegion whole_heap,
52 int max_covered_regions):
53 ModRefBarrierSet(max_covered_regions),
54 _whole_heap(whole_heap),
55 _guard_index(cards_required(whole_heap.word_size()) - 1),
56 _last_valid_index(_guard_index - 1),
57 _page_size(os::vm_page_size()),
58 _byte_map_size(compute_byte_map_size())
59 {
60 _kind = BarrierSet::CardTableModRef;
61
62 HeapWord* low_bound = _whole_heap.start();
63 HeapWord* high_bound = _whole_heap.end();
64 assert((uintptr_t(low_bound) & (card_size - 1)) == 0, "heap must start at card boundary");
65 assert((uintptr_t(high_bound) & (card_size - 1)) == 0, "heap must end at card boundary");
66
67 assert(card_size <= 512, "card_size must be less than 512"); // why?
68
69 _covered = new MemRegion[max_covered_regions];
70 _committed = new MemRegion[max_covered_regions];
71 if (_covered == NULL || _committed == NULL)
72 vm_exit_during_initialization("couldn't alloc card table covered region set.");
73 int i;
74 for (i = 0; i < max_covered_regions; i++) {
75 _covered[i].set_word_size(0);
76 _committed[i].set_word_size(0);
77 }
78 _cur_covered_regions = 0;
79
80 const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
81 MAX2(_page_size, (size_t) os::vm_allocation_granularity());
82 ReservedSpace heap_rs(_byte_map_size, rs_align, false);
83 os::trace_page_sizes("card table", _guard_index + 1, _guard_index + 1,
84 _page_size, heap_rs.base(), heap_rs.size());
85 if (!heap_rs.is_reserved()) {
86 vm_exit_during_initialization("Could not reserve enough space for the "
87 "card marking array");
88 }
89
90 // The assember store_check code will do an unsigned shift of the oop,
91 // then add it to byte_map_base, i.e.
92 //
93 // _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
94 _byte_map = (jbyte*) heap_rs.base();
95 byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
96 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
97 assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
98
99 jbyte* guard_card = &_byte_map[_guard_index];
100 uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
101 _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
102 if (!os::commit_memory((char*)guard_page, _page_size, _page_size)) {
103 // Do better than this for Merlin
104 vm_exit_out_of_memory(_page_size, "card table last card");
105 }
106 *guard_card = last_card;
107
108 _lowest_non_clean =
109 NEW_C_HEAP_ARRAY(CardArr, max_covered_regions);
110 _lowest_non_clean_chunk_size =
111 NEW_C_HEAP_ARRAY(size_t, max_covered_regions);
112 _lowest_non_clean_base_chunk_index =
113 NEW_C_HEAP_ARRAY(uintptr_t, max_covered_regions);
114 _last_LNC_resizing_collection =
115 NEW_C_HEAP_ARRAY(int, max_covered_regions);
116 if (_lowest_non_clean == NULL
117 || _lowest_non_clean_chunk_size == NULL
118 || _lowest_non_clean_base_chunk_index == NULL
119 || _last_LNC_resizing_collection == NULL)
120 vm_exit_during_initialization("couldn't allocate an LNC array.");
121 for (i = 0; i < max_covered_regions; i++) {
122 _lowest_non_clean[i] = NULL;
123 _lowest_non_clean_chunk_size[i] = 0;
124 _last_LNC_resizing_collection[i] = -1;
125 }
126
127 if (TraceCardTableModRefBS) {
128 gclog_or_tty->print_cr("CardTableModRefBS::CardTableModRefBS: ");
129 gclog_or_tty->print_cr(" "
130 " &_byte_map[0]: " INTPTR_FORMAT
131 " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
132 &_byte_map[0],
133 &_byte_map[_last_valid_index]);
134 gclog_or_tty->print_cr(" "
135 " byte_map_base: " INTPTR_FORMAT,
136 byte_map_base);
137 }
138 }
139
140 int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
141 int i;
142 for (i = 0; i < _cur_covered_regions; i++) {
143 if (_covered[i].start() == base) return i;
144 if (_covered[i].start() > base) break;
145 }
146 // If we didn't find it, create a new one.
147 assert(_cur_covered_regions < _max_covered_regions,
148 "too many covered regions");
149 // Move the ones above up, to maintain sorted order.
150 for (int j = _cur_covered_regions; j > i; j--) {
151 _covered[j] = _covered[j-1];
152 _committed[j] = _committed[j-1];
153 }
154 int res = i;
155 _cur_covered_regions++;
156 _covered[res].set_start(base);
157 _covered[res].set_word_size(0);
158 jbyte* ct_start = byte_for(base);
159 uintptr_t ct_start_aligned = align_size_down((uintptr_t)ct_start, _page_size);
160 _committed[res].set_start((HeapWord*)ct_start_aligned);
161 _committed[res].set_word_size(0);
162 return res;
163 }
164
165 int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
166 for (int i = 0; i < _cur_covered_regions; i++) {
167 if (_covered[i].contains(addr)) {
168 return i;
169 }
170 }
171 assert(0, "address outside of heap?");
172 return -1;
173 }
174
175 HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
176 HeapWord* max_end = NULL;
177 for (int j = 0; j < ind; j++) {
178 HeapWord* this_end = _committed[j].end();
179 if (this_end > max_end) max_end = this_end;
180 }
181 return max_end;
182 }
183
184 MemRegion CardTableModRefBS::committed_unique_to_self(int self,
185 MemRegion mr) const {
186 MemRegion result = mr;
187 for (int r = 0; r < _cur_covered_regions; r += 1) {
188 if (r != self) {
189 result = result.minus(_committed[r]);
190 }
191 }
192 // Never include the guard page.
193 result = result.minus(_guard_region);
194 return result;
195 }
196
197 void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
198 // We don't change the start of a region, only the end.
199 assert(_whole_heap.contains(new_region),
200 "attempt to cover area not in reserved area");
201 debug_only(verify_guard();)
202 int ind = find_covering_region_by_base(new_region.start());
203 MemRegion old_region = _covered[ind];
204 assert(old_region.start() == new_region.start(), "just checking");
205 if (new_region.word_size() != old_region.word_size()) {
206 // Commit new or uncommit old pages, if necessary.
207 MemRegion cur_committed = _committed[ind];
208 // Extend the end of this _commited region
209 // to cover the end of any lower _committed regions.
210 // This forms overlapping regions, but never interior regions.
211 HeapWord* max_prev_end = largest_prev_committed_end(ind);
212 if (max_prev_end > cur_committed.end()) {
213 cur_committed.set_end(max_prev_end);
214 }
215 // Align the end up to a page size (starts are already aligned).
216 jbyte* new_end = byte_after(new_region.last());
217 HeapWord* new_end_aligned =
218 (HeapWord*)align_size_up((uintptr_t)new_end, _page_size);
219 assert(new_end_aligned >= (HeapWord*) new_end,
220 "align up, but less");
221 // The guard page is always committed and should not be committed over.
222 HeapWord* new_end_for_commit = MIN2(new_end_aligned, _guard_region.start());
223 if (new_end_for_commit > cur_committed.end()) {
224 // Must commit new pages.
225 MemRegion new_committed =
226 MemRegion(cur_committed.end(), new_end_for_commit);
227
228 assert(!new_committed.is_empty(), "Region should not be empty here");
229 if (!os::commit_memory((char*)new_committed.start(),
230 new_committed.byte_size(), _page_size)) {
231 // Do better than this for Merlin
232 vm_exit_out_of_memory(new_committed.byte_size(),
233 "card table expansion");
234 }
235 // Use new_end_aligned (as opposed to new_end_for_commit) because
236 // the cur_committed region may include the guard region.
237 } else if (new_end_aligned < cur_committed.end()) {
238 // Must uncommit pages.
239 MemRegion uncommit_region =
240 committed_unique_to_self(ind, MemRegion(new_end_aligned,
241 cur_committed.end()));
242 if (!uncommit_region.is_empty()) {
243 if (!os::uncommit_memory((char*)uncommit_region.start(),
244 uncommit_region.byte_size())) {
245 // Do better than this for Merlin
246 vm_exit_out_of_memory(uncommit_region.byte_size(),
247 "card table contraction");
248 }
249 }
250 }
251 // In any case, we can reset the end of the current committed entry.
252 _committed[ind].set_end(new_end_aligned);
253
254 // The default of 0 is not necessarily clean cards.
255 jbyte* entry;
256 if (old_region.last() < _whole_heap.start()) {
257 entry = byte_for(_whole_heap.start());
258 } else {
259 entry = byte_after(old_region.last());
260 }
261 assert(index_for(new_region.last()) < (int) _guard_index,
262 "The guard card will be overwritten");
263 jbyte* end = byte_after(new_region.last());
264 // do nothing if we resized downward.
265 if (entry < end) {
266 memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
267 }
268 }
269 // In any case, the covered size changes.
270 _covered[ind].set_word_size(new_region.word_size());
271 if (TraceCardTableModRefBS) {
272 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
273 gclog_or_tty->print_cr(" "
274 " _covered[%d].start(): " INTPTR_FORMAT
275 " _covered[%d].last(): " INTPTR_FORMAT,
276 ind, _covered[ind].start(),
277 ind, _covered[ind].last());
278 gclog_or_tty->print_cr(" "
279 " _committed[%d].start(): " INTPTR_FORMAT
280 " _committed[%d].last(): " INTPTR_FORMAT,
281 ind, _committed[ind].start(),
282 ind, _committed[ind].last());
283 gclog_or_tty->print_cr(" "
284 " byte_for(start): " INTPTR_FORMAT
285 " byte_for(last): " INTPTR_FORMAT,
286 byte_for(_covered[ind].start()),
287 byte_for(_covered[ind].last()));
288 gclog_or_tty->print_cr(" "
289 " addr_for(start): " INTPTR_FORMAT
290 " addr_for(last): " INTPTR_FORMAT,
291 addr_for((jbyte*) _committed[ind].start()),
292 addr_for((jbyte*) _committed[ind].last()));
293 }
294 debug_only(verify_guard();)
295 }
296
297 // Note that these versions are precise! The scanning code has to handle the
298 // fact that the write barrier may be either precise or imprecise.
299
300 void CardTableModRefBS::write_ref_field_work(oop* field, oop newVal) {
301 inline_write_ref_field(field, newVal);
302 }
303
304
305 void CardTableModRefBS::non_clean_card_iterate(Space* sp,
306 MemRegion mr,
307 DirtyCardToOopClosure* dcto_cl,
308 MemRegionClosure* cl,
309 bool clear) {
310 if (!mr.is_empty()) {
311 int n_threads = SharedHeap::heap()->n_par_threads();
312 if (n_threads > 0) {
313 #ifndef SERIALGC
314 par_non_clean_card_iterate_work(sp, mr, dcto_cl, cl, clear, n_threads);
315 #else // SERIALGC
316 fatal("Parallel gc not supported here.");
317 #endif // SERIALGC
318 } else {
319 non_clean_card_iterate_work(mr, cl, clear);
320 }
321 }
322 }
323
324 // NOTE: For this to work correctly, it is important that
325 // we look for non-clean cards below (so as to catch those
326 // marked precleaned), rather than look explicitly for dirty
327 // cards (and miss those marked precleaned). In that sense,
328 // the name precleaned is currently somewhat of a misnomer.
329 void CardTableModRefBS::non_clean_card_iterate_work(MemRegion mr,
330 MemRegionClosure* cl,
331 bool clear) {
332 // Figure out whether we have to worry about parallelism.
333 bool is_par = (SharedHeap::heap()->n_par_threads() > 1);
334 for (int i = 0; i < _cur_covered_regions; i++) {
335 MemRegion mri = mr.intersection(_covered[i]);
336 if (mri.word_size() > 0) {
337 jbyte* cur_entry = byte_for(mri.last());
338 jbyte* limit = byte_for(mri.start());
339 while (cur_entry >= limit) {
340 jbyte* next_entry = cur_entry - 1;
341 if (*cur_entry != clean_card) {
342 size_t non_clean_cards = 1;
343 // Should the next card be included in this range of dirty cards.
344 while (next_entry >= limit && *next_entry != clean_card) {
345 non_clean_cards++;
346 cur_entry = next_entry;
347 next_entry--;
348 }
349 // The memory region may not be on a card boundary. So that
350 // objects beyond the end of the region are not processed, make
351 // cur_cards precise with regard to the end of the memory region.
352 MemRegion cur_cards(addr_for(cur_entry),
353 non_clean_cards * card_size_in_words);
354 MemRegion dirty_region = cur_cards.intersection(mri);
355 if (clear) {
356 for (size_t i = 0; i < non_clean_cards; i++) {
357 // Clean the dirty cards (but leave the other non-clean
358 // alone.) If parallel, do the cleaning atomically.
359 jbyte cur_entry_val = cur_entry[i];
360 if (card_is_dirty_wrt_gen_iter(cur_entry_val)) {
361 if (is_par) {
362 jbyte res = Atomic::cmpxchg(clean_card, &cur_entry[i], cur_entry_val);
363 assert(res != clean_card,
364 "Dirty card mysteriously cleaned");
365 } else {
366 cur_entry[i] = clean_card;
367 }
368 }
369 }
370 }
371 cl->do_MemRegion(dirty_region);
372 }
373 cur_entry = next_entry;
374 }
375 }
376 }
377 }
378
379 void CardTableModRefBS::mod_oop_in_space_iterate(Space* sp,
380 OopClosure* cl,
381 bool clear,
382 bool before_save_marks) {
383 // Note that dcto_cl is resource-allocated, so there is no
384 // corresponding "delete".
385 DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision());
386 MemRegion used_mr;
387 if (before_save_marks) {
388 used_mr = sp->used_region_at_save_marks();
389 } else {
390 used_mr = sp->used_region();
391 }
392 non_clean_card_iterate(sp, used_mr, dcto_cl, dcto_cl, clear);
393 }
394
395 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
396 jbyte* cur = byte_for(mr.start());
397 jbyte* last = byte_after(mr.last());
398 while (cur < last) {
399 *cur = dirty_card;
400 cur++;
401 }
402 }
403
404 void CardTableModRefBS::invalidate(MemRegion mr) {
405 for (int i = 0; i < _cur_covered_regions; i++) {
406 MemRegion mri = mr.intersection(_covered[i]);
407 if (!mri.is_empty()) dirty_MemRegion(mri);
408 }
409 }
410
411 void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
412 // Be conservative: only clean cards entirely contained within the
413 // region.
414 jbyte* cur;
415 if (mr.start() == _whole_heap.start()) {
416 cur = byte_for(mr.start());
417 } else {
418 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
419 cur = byte_after(mr.start() - 1);
420 }
421 jbyte* last = byte_after(mr.last());
422 memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
423 }
424
425 void CardTableModRefBS::clear(MemRegion mr) {
426 for (int i = 0; i < _cur_covered_regions; i++) {
427 MemRegion mri = mr.intersection(_covered[i]);
428 if (!mri.is_empty()) clear_MemRegion(mri);
429 }
430 }
431
432 // NOTES:
433 // (1) Unlike mod_oop_in_space_iterate() above, dirty_card_iterate()
434 // iterates over dirty cards ranges in increasing address order.
435 // (2) Unlike, e.g., dirty_card_range_after_preclean() below,
436 // this method does not make the dirty cards prelceaned.
437 void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
438 MemRegionClosure* cl) {
439 for (int i = 0; i < _cur_covered_regions; i++) {
440 MemRegion mri = mr.intersection(_covered[i]);
441 if (!mri.is_empty()) {
442 jbyte *cur_entry, *next_entry, *limit;
443 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
444 cur_entry <= limit;
445 cur_entry = next_entry) {
446 next_entry = cur_entry + 1;
447 if (*cur_entry == dirty_card) {
448 size_t dirty_cards;
449 // Accumulate maximal dirty card range, starting at cur_entry
450 for (dirty_cards = 1;
451 next_entry <= limit && *next_entry == dirty_card;
452 dirty_cards++, next_entry++);
453 MemRegion cur_cards(addr_for(cur_entry),
454 dirty_cards*card_size_in_words);
455 cl->do_MemRegion(cur_cards);
456 }
457 }
458 }
459 }
460 }
461
462 MemRegion CardTableModRefBS::dirty_card_range_after_preclean(MemRegion mr) {
463 for (int i = 0; i < _cur_covered_regions; i++) {
464 MemRegion mri = mr.intersection(_covered[i]);
465 if (!mri.is_empty()) {
466 jbyte* cur_entry, *next_entry, *limit;
467 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
468 cur_entry <= limit;
469 cur_entry = next_entry) {
470 next_entry = cur_entry + 1;
471 if (*cur_entry == dirty_card) {
472 size_t dirty_cards;
473 // Accumulate maximal dirty card range, starting at cur_entry
474 for (dirty_cards = 1;
475 next_entry <= limit && *next_entry == dirty_card;
476 dirty_cards++, next_entry++);
477 MemRegion cur_cards(addr_for(cur_entry),
478 dirty_cards*card_size_in_words);
479 for (size_t i = 0; i < dirty_cards; i++) {
480 cur_entry[i] = precleaned_card;
481 }
482 return cur_cards;
483 }
484 }
485 }
486 }
487 return MemRegion(mr.end(), mr.end());
488 }
489
490 // Set all the dirty cards in the given region to "precleaned" state.
491 void CardTableModRefBS::preclean_dirty_cards(MemRegion mr) {
492 for (int i = 0; i < _cur_covered_regions; i++) {
493 MemRegion mri = mr.intersection(_covered[i]);
494 if (!mri.is_empty()) {
495 jbyte *cur_entry, *limit;
496 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
497 cur_entry <= limit;
498 cur_entry++) {
499 if (*cur_entry == dirty_card) {
500 *cur_entry = precleaned_card;
501 }
502 }
503 }
504 }
505 }
506
507 uintx CardTableModRefBS::ct_max_alignment_constraint() {
508 return card_size * os::vm_page_size();
509 }
510
511 void CardTableModRefBS::verify_guard() {
512 // For product build verification
513 guarantee(_byte_map[_guard_index] == last_card,
514 "card table guard has been modified");
515 }
516
517 void CardTableModRefBS::verify() {
518 verify_guard();
519 }
520
521 #ifndef PRODUCT
522 class GuaranteeNotModClosure: public MemRegionClosure {
523 CardTableModRefBS* _ct;
524 public:
525 GuaranteeNotModClosure(CardTableModRefBS* ct) : _ct(ct) {}
526 void do_MemRegion(MemRegion mr) {
527 jbyte* entry = _ct->byte_for(mr.start());
528 guarantee(*entry != CardTableModRefBS::clean_card,
529 "Dirty card in region that should be clean");
530 }
531 };
532
533 void CardTableModRefBS::verify_clean_region(MemRegion mr) {
534 GuaranteeNotModClosure blk(this);
535 non_clean_card_iterate_work(mr, &blk, false);
536 }
537 #endif
538
539 bool CardTableModRefBSForCTRS::card_will_be_scanned(jbyte cv) {
540 return
541 CardTableModRefBS::card_will_be_scanned(cv) ||
542 _rs->is_prev_nonclean_card_val(cv);
543 };
544
545 bool CardTableModRefBSForCTRS::card_may_have_been_dirty(jbyte cv) {
546 return
547 cv != clean_card &&
548 (CardTableModRefBS::card_may_have_been_dirty(cv) ||
549 CardTableRS::youngergen_may_have_been_dirty(cv));
550 };