1 /*
2 * Copyright (c) 2000, 2015, 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 #include "precompiled.hpp"
26 #include "gc/shared/cardTableModRefBS.inline.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "gc/shared/genCollectedHeap.hpp"
29 #include "gc/shared/space.inline.hpp"
30 #include "memory/virtualspace.hpp"
31 #include "services/memTracker.hpp"
32 #include "utilities/macros.hpp"
33
34 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
35 // enumerate ref fields that have been modified (since the last
36 // enumeration.)
37
38 size_t CardTableModRefBS::compute_byte_map_size()
39 {
40 assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
41 "uninitialized, check declaration order");
42 assert(_page_size != 0, "uninitialized, check declaration order");
43 const size_t granularity = os::vm_allocation_granularity();
44 return align_size_up(_guard_index + 1, MAX2(_page_size, granularity));
45 }
46
47 CardTableModRefBS::CardTableModRefBS(
48 MemRegion whole_heap,
49 const BarrierSet::FakeRtti& fake_rtti) :
50 ModRefBarrierSet(fake_rtti.add_tag(BarrierSet::CardTableModRef)),
51 _whole_heap(whole_heap),
52 _guard_index(0),
53 _guard_region(),
54 _last_valid_index(0),
55 _page_size(os::vm_page_size()),
56 _byte_map_size(0),
57 _covered(NULL),
58 _committed(NULL),
59 _cur_covered_regions(0),
60 _byte_map(NULL),
61 byte_map_base(NULL)
62 {
63 assert((uintptr_t(_whole_heap.start()) & (card_size - 1)) == 0, "heap must start at card boundary");
64 assert((uintptr_t(_whole_heap.end()) & (card_size - 1)) == 0, "heap must end at card boundary");
65
66 assert(card_size <= 512, "card_size must be less than 512"); // why?
67
68 _covered = new MemRegion[_max_covered_regions];
69 if (_covered == NULL) {
70 vm_exit_during_initialization("Could not allocate card table covered region set.");
71 }
72 }
73
74 void CardTableModRefBS::initialize() {
75 _guard_index = cards_required(_whole_heap.word_size()) - 1;
76 _last_valid_index = _guard_index - 1;
77
78 _byte_map_size = compute_byte_map_size();
79
80 HeapWord* low_bound = _whole_heap.start();
81 HeapWord* high_bound = _whole_heap.end();
82
83 _cur_covered_regions = 0;
84 _committed = new MemRegion[_max_covered_regions];
85 if (_committed == NULL) {
86 vm_exit_during_initialization("Could not allocate card table committed region set.");
87 }
88
89 const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
90 MAX2(_page_size, (size_t) os::vm_allocation_granularity());
91 ReservedSpace heap_rs(_byte_map_size, rs_align, false);
92
93 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
94
95 os::trace_page_sizes("card table", _guard_index + 1, _guard_index + 1,
96 _page_size, heap_rs.base(), heap_rs.size());
97 if (!heap_rs.is_reserved()) {
98 vm_exit_during_initialization("Could not reserve enough space for the "
99 "card marking array");
100 }
101
102 // The assembler store_check code will do an unsigned shift of the oop,
103 // then add it to byte_map_base, i.e.
104 //
105 // _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
106 _byte_map = (jbyte*) heap_rs.base();
107 byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
108 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
109 assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
110
111 jbyte* guard_card = &_byte_map[_guard_index];
112 uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
113 _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
114 os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
115 !ExecMem, "card table last card");
116 *guard_card = last_card;
117
118 if (TraceCardTableModRefBS) {
119 gclog_or_tty->print_cr("CardTableModRefBS::CardTableModRefBS: ");
120 gclog_or_tty->print_cr(" "
121 " &_byte_map[0]: " INTPTR_FORMAT
122 " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
123 p2i(&_byte_map[0]),
124 p2i(&_byte_map[_last_valid_index]));
125 gclog_or_tty->print_cr(" "
126 " byte_map_base: " INTPTR_FORMAT,
127 p2i(byte_map_base));
128 }
129 }
130
131 CardTableModRefBS::~CardTableModRefBS() {
132 if (_covered) {
133 delete[] _covered;
134 _covered = NULL;
135 }
136 if (_committed) {
137 delete[] _committed;
138 _committed = NULL;
139 }
140 }
141
142 int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
143 int i;
144 for (i = 0; i < _cur_covered_regions; i++) {
145 if (_covered[i].start() == base) return i;
146 if (_covered[i].start() > base) break;
147 }
148 // If we didn't find it, create a new one.
149 assert(_cur_covered_regions < _max_covered_regions,
150 "too many covered regions");
151 // Move the ones above up, to maintain sorted order.
152 for (int j = _cur_covered_regions; j > i; j--) {
153 _covered[j] = _covered[j-1];
154 _committed[j] = _committed[j-1];
155 }
156 int res = i;
157 _cur_covered_regions++;
158 _covered[res].set_start(base);
159 _covered[res].set_word_size(0);
160 jbyte* ct_start = byte_for(base);
161 uintptr_t ct_start_aligned = align_size_down((uintptr_t)ct_start, _page_size);
162 _committed[res].set_start((HeapWord*)ct_start_aligned);
163 _committed[res].set_word_size(0);
164 return res;
165 }
166
167 int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
168 for (int i = 0; i < _cur_covered_regions; i++) {
169 if (_covered[i].contains(addr)) {
170 return i;
171 }
172 }
173 assert(0, "address outside of heap?");
174 return -1;
175 }
176
177 HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
178 HeapWord* max_end = NULL;
179 for (int j = 0; j < ind; j++) {
180 HeapWord* this_end = _committed[j].end();
181 if (this_end > max_end) max_end = this_end;
182 }
183 return max_end;
184 }
185
186 MemRegion CardTableModRefBS::committed_unique_to_self(int self,
187 MemRegion mr) const {
188 MemRegion result = mr;
189 for (int r = 0; r < _cur_covered_regions; r += 1) {
190 if (r != self) {
191 result = result.minus(_committed[r]);
192 }
193 }
194 // Never include the guard page.
195 result = result.minus(_guard_region);
196 return result;
197 }
198
199 void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
200 // We don't change the start of a region, only the end.
201 assert(_whole_heap.contains(new_region),
202 "attempt to cover area not in reserved area");
203 debug_only(verify_guard();)
204 // collided is true if the expansion would push into another committed region
205 debug_only(bool collided = false;)
206 int const ind = find_covering_region_by_base(new_region.start());
207 MemRegion const old_region = _covered[ind];
208 assert(old_region.start() == new_region.start(), "just checking");
209 if (new_region.word_size() != old_region.word_size()) {
210 // Commit new or uncommit old pages, if necessary.
211 MemRegion cur_committed = _committed[ind];
212 // Extend the end of this _committed region
213 // to cover the end of any lower _committed regions.
214 // This forms overlapping regions, but never interior regions.
215 HeapWord* const max_prev_end = largest_prev_committed_end(ind);
216 if (max_prev_end > cur_committed.end()) {
217 cur_committed.set_end(max_prev_end);
218 }
219 // Align the end up to a page size (starts are already aligned).
220 jbyte* const new_end = byte_after(new_region.last());
221 HeapWord* new_end_aligned =
222 (HeapWord*) align_size_up((uintptr_t)new_end, _page_size);
223 assert(new_end_aligned >= (HeapWord*) new_end,
224 "align up, but less");
225 // Check the other regions (excludes "ind") to ensure that
226 // the new_end_aligned does not intrude onto the committed
227 // space of another region.
228 int ri = 0;
229 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
230 if (new_end_aligned > _committed[ri].start()) {
231 assert(new_end_aligned <= _committed[ri].end(),
232 "An earlier committed region can't cover a later committed region");
233 // Any region containing the new end
234 // should start at or beyond the region found (ind)
235 // for the new end (committed regions are not expected to
236 // be proper subsets of other committed regions).
237 assert(_committed[ri].start() >= _committed[ind].start(),
238 "New end of committed region is inconsistent");
239 new_end_aligned = _committed[ri].start();
240 // new_end_aligned can be equal to the start of its
241 // committed region (i.e., of "ind") if a second
242 // region following "ind" also start at the same location
243 // as "ind".
244 assert(new_end_aligned >= _committed[ind].start(),
245 "New end of committed region is before start");
246 debug_only(collided = true;)
247 // Should only collide with 1 region
248 break;
249 }
250 }
251 #ifdef ASSERT
252 for (++ri; ri < _cur_covered_regions; ri++) {
253 assert(!_committed[ri].contains(new_end_aligned),
254 "New end of committed region is in a second committed region");
255 }
256 #endif
257 // The guard page is always committed and should not be committed over.
258 // "guarded" is used for assertion checking below and recalls the fact
259 // that the would-be end of the new committed region would have
260 // penetrated the guard page.
261 HeapWord* new_end_for_commit = new_end_aligned;
262
263 DEBUG_ONLY(bool guarded = false;)
264 if (new_end_for_commit > _guard_region.start()) {
265 new_end_for_commit = _guard_region.start();
266 DEBUG_ONLY(guarded = true;)
267 }
268
269 if (new_end_for_commit > cur_committed.end()) {
270 // Must commit new pages.
271 MemRegion const new_committed =
272 MemRegion(cur_committed.end(), new_end_for_commit);
273
274 assert(!new_committed.is_empty(), "Region should not be empty here");
275 os::commit_memory_or_exit((char*)new_committed.start(),
276 new_committed.byte_size(), _page_size,
277 !ExecMem, "card table expansion");
278 // Use new_end_aligned (as opposed to new_end_for_commit) because
279 // the cur_committed region may include the guard region.
280 } else if (new_end_aligned < cur_committed.end()) {
281 // Must uncommit pages.
282 MemRegion const uncommit_region =
283 committed_unique_to_self(ind, MemRegion(new_end_aligned,
284 cur_committed.end()));
285 if (!uncommit_region.is_empty()) {
286 // It is not safe to uncommit cards if the boundary between
287 // the generations is moving. A shrink can uncommit cards
288 // owned by generation A but being used by generation B.
289 if (!UseAdaptiveGCBoundary) {
290 if (!os::uncommit_memory((char*)uncommit_region.start(),
291 uncommit_region.byte_size())) {
292 assert(false, "Card table contraction failed");
293 // The call failed so don't change the end of the
294 // committed region. This is better than taking the
295 // VM down.
296 new_end_aligned = _committed[ind].end();
297 }
298 } else {
299 new_end_aligned = _committed[ind].end();
300 }
301 }
302 }
303 // In any case, we can reset the end of the current committed entry.
304 _committed[ind].set_end(new_end_aligned);
305
306 #ifdef ASSERT
307 // Check that the last card in the new region is committed according
308 // to the tables.
309 bool covered = false;
310 for (int cr = 0; cr < _cur_covered_regions; cr++) {
311 if (_committed[cr].contains(new_end - 1)) {
312 covered = true;
313 break;
314 }
315 }
316 assert(covered, "Card for end of new region not committed");
317 #endif
318
319 // The default of 0 is not necessarily clean cards.
320 jbyte* entry;
321 if (old_region.last() < _whole_heap.start()) {
322 entry = byte_for(_whole_heap.start());
323 } else {
324 entry = byte_after(old_region.last());
325 }
326 assert(index_for(new_region.last()) < _guard_index,
327 "The guard card will be overwritten");
328 // This line commented out cleans the newly expanded region and
329 // not the aligned up expanded region.
330 // jbyte* const end = byte_after(new_region.last());
331 jbyte* const end = (jbyte*) new_end_for_commit;
332 assert((end >= byte_after(new_region.last())) || collided || guarded,
333 "Expect to be beyond new region unless impacting another region");
334 // do nothing if we resized downward.
335 #ifdef ASSERT
336 for (int ri = 0; ri < _cur_covered_regions; ri++) {
337 if (ri != ind) {
338 // The end of the new committed region should not
339 // be in any existing region unless it matches
340 // the start of the next region.
341 assert(!_committed[ri].contains(end) ||
342 (_committed[ri].start() == (HeapWord*) end),
343 "Overlapping committed regions");
344 }
345 }
346 #endif
347 if (entry < end) {
348 memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
349 }
350 }
351 // In any case, the covered size changes.
352 _covered[ind].set_word_size(new_region.word_size());
353 if (TraceCardTableModRefBS) {
354 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
355 gclog_or_tty->print_cr(" "
356 " _covered[%d].start(): " INTPTR_FORMAT
357 " _covered[%d].last(): " INTPTR_FORMAT,
358 ind, p2i(_covered[ind].start()),
359 ind, p2i(_covered[ind].last()));
360 gclog_or_tty->print_cr(" "
361 " _committed[%d].start(): " INTPTR_FORMAT
362 " _committed[%d].last(): " INTPTR_FORMAT,
363 ind, p2i(_committed[ind].start()),
364 ind, p2i(_committed[ind].last()));
365 gclog_or_tty->print_cr(" "
366 " byte_for(start): " INTPTR_FORMAT
367 " byte_for(last): " INTPTR_FORMAT,
368 p2i(byte_for(_covered[ind].start())),
369 p2i(byte_for(_covered[ind].last())));
370 gclog_or_tty->print_cr(" "
371 " addr_for(start): " INTPTR_FORMAT
372 " addr_for(last): " INTPTR_FORMAT,
373 p2i(addr_for((jbyte*) _committed[ind].start())),
374 p2i(addr_for((jbyte*) _committed[ind].last())));
375 }
376 // Touch the last card of the covered region to show that it
377 // is committed (or SEGV).
378 debug_only((void) (*byte_for(_covered[ind].last()));)
379 debug_only(verify_guard();)
380 }
381
382 // Note that these versions are precise! The scanning code has to handle the
383 // fact that the write barrier may be either precise or imprecise.
384
385 void CardTableModRefBS::write_ref_field_work(void* field, oop newVal, bool release) {
386 inline_write_ref_field(field, newVal, release);
387 }
388
389
390 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
391 assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
392 assert((HeapWord*)align_size_up ((uintptr_t)mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
393 jbyte* cur = byte_for(mr.start());
394 jbyte* last = byte_after(mr.last());
395 while (cur < last) {
396 *cur = dirty_card;
397 cur++;
398 }
399 }
400
401 void CardTableModRefBS::invalidate(MemRegion mr, bool whole_heap) {
402 assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
403 assert((HeapWord*)align_size_up ((uintptr_t)mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
404 for (int i = 0; i < _cur_covered_regions; i++) {
405 MemRegion mri = mr.intersection(_covered[i]);
406 if (!mri.is_empty()) dirty_MemRegion(mri);
407 }
408 }
409
410 void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
411 // Be conservative: only clean cards entirely contained within the
412 // region.
413 jbyte* cur;
414 if (mr.start() == _whole_heap.start()) {
415 cur = byte_for(mr.start());
416 } else {
417 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
418 cur = byte_after(mr.start() - 1);
419 }
420 jbyte* last = byte_after(mr.last());
421 memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
422 }
423
424 void CardTableModRefBS::clear(MemRegion mr) {
425 for (int i = 0; i < _cur_covered_regions; i++) {
426 MemRegion mri = mr.intersection(_covered[i]);
427 if (!mri.is_empty()) clear_MemRegion(mri);
428 }
429 }
430
431 void CardTableModRefBS::dirty(MemRegion mr) {
432 jbyte* first = byte_for(mr.start());
433 jbyte* last = byte_after(mr.last());
434 memset(first, dirty_card, last-first);
435 }
436
437 // Unlike several other card table methods, dirty_card_iterate()
438 // iterates over dirty cards ranges in increasing address order.
439 void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
440 MemRegionClosure* cl) {
441 for (int i = 0; i < _cur_covered_regions; i++) {
442 MemRegion mri = mr.intersection(_covered[i]);
443 if (!mri.is_empty()) {
444 jbyte *cur_entry, *next_entry, *limit;
445 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
446 cur_entry <= limit;
447 cur_entry = next_entry) {
448 next_entry = cur_entry + 1;
449 if (*cur_entry == dirty_card) {
450 size_t dirty_cards;
451 // Accumulate maximal dirty card range, starting at cur_entry
452 for (dirty_cards = 1;
453 next_entry <= limit && *next_entry == dirty_card;
454 dirty_cards++, next_entry++);
455 MemRegion cur_cards(addr_for(cur_entry),
456 dirty_cards*card_size_in_words);
457 cl->do_MemRegion(cur_cards);
458 }
459 }
460 }
461 }
462 }
463
464 MemRegion CardTableModRefBS::dirty_card_range_after_reset(MemRegion mr,
465 bool reset,
466 int reset_val) {
467 for (int i = 0; i < _cur_covered_regions; i++) {
468 MemRegion mri = mr.intersection(_covered[i]);
469 if (!mri.is_empty()) {
470 jbyte* cur_entry, *next_entry, *limit;
471 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
472 cur_entry <= limit;
473 cur_entry = next_entry) {
474 next_entry = cur_entry + 1;
475 if (*cur_entry == dirty_card) {
476 size_t dirty_cards;
477 // Accumulate maximal dirty card range, starting at cur_entry
478 for (dirty_cards = 1;
479 next_entry <= limit && *next_entry == dirty_card;
480 dirty_cards++, next_entry++);
481 MemRegion cur_cards(addr_for(cur_entry),
482 dirty_cards*card_size_in_words);
483 if (reset) {
484 for (size_t i = 0; i < dirty_cards; i++) {
485 cur_entry[i] = reset_val;
486 }
487 }
488 return cur_cards;
489 }
490 }
491 }
492 }
493 return MemRegion(mr.end(), mr.end());
494 }
495
496 uintx CardTableModRefBS::ct_max_alignment_constraint() {
497 return card_size * os::vm_page_size();
498 }
499
500 void CardTableModRefBS::verify_guard() {
501 // For product build verification
502 guarantee(_byte_map[_guard_index] == last_card,
503 "card table guard has been modified");
504 }
505
506 void CardTableModRefBS::verify() {
507 verify_guard();
508 }
509
510 #ifndef PRODUCT
511 void CardTableModRefBS::verify_region(MemRegion mr,
512 jbyte val, bool val_equals) {
513 jbyte* start = byte_for(mr.start());
514 jbyte* end = byte_for(mr.last());
515 bool failures = false;
516 for (jbyte* curr = start; curr <= end; ++curr) {
517 jbyte curr_val = *curr;
518 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
519 if (failed) {
520 if (!failures) {
521 tty->cr();
522 tty->print_cr("== CT verification failed: [" INTPTR_FORMAT "," INTPTR_FORMAT "]", p2i(start), p2i(end));
523 tty->print_cr("== %sexpecting value: %d",
524 (val_equals) ? "" : "not ", val);
525 failures = true;
526 }
527 tty->print_cr("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], "
528 "val: %d", p2i(curr), p2i(addr_for(curr)),
529 p2i((HeapWord*) (((size_t) addr_for(curr)) + card_size)),
530 (int) curr_val);
531 }
532 }
533 guarantee(!failures, "there should not have been any failures");
534 }
535
536 void CardTableModRefBS::verify_not_dirty_region(MemRegion mr) {
537 verify_region(mr, dirty_card, false /* val_equals */);
538 }
539
540 void CardTableModRefBS::verify_dirty_region(MemRegion mr) {
541 verify_region(mr, dirty_card, true /* val_equals */);
542 }
543 #endif
544
545 void CardTableModRefBS::print_on(outputStream* st) const {
546 st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] byte_map_base: " INTPTR_FORMAT,
547 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(byte_map_base));
548 }
549