1 /*
2 * Copyright (c) 2000, 2017, 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 "logging/log.hpp"
31 #include "memory/virtualspace.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "services/memTracker.hpp"
34 #include "utilities/align.hpp"
35 #include "utilities/macros.hpp"
36
37 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
38 // enumerate ref fields that have been modified (since the last
39 // enumeration.)
40
41 size_t CardTableModRefBS::compute_byte_map_size()
42 {
43 assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
44 "uninitialized, check declaration order");
45 assert(_page_size != 0, "uninitialized, check declaration order");
46 const size_t granularity = os::vm_allocation_granularity();
47 return align_up(_guard_index + 1, MAX2(_page_size, granularity));
48 }
49
50 CardTableModRefBS::CardTableModRefBS(
51 MemRegion whole_heap,
52 const BarrierSet::FakeRtti& fake_rtti) :
53 ModRefBarrierSet(fake_rtti.add_tag(BarrierSet::CardTableModRef)),
54 _whole_heap(whole_heap),
55 _guard_index(0),
56 _guard_region(),
57 _last_valid_index(0),
58 _page_size(os::vm_page_size()),
59 _byte_map_size(0),
60 _covered(NULL),
61 _committed(NULL),
62 _cur_covered_regions(0),
63 _byte_map(NULL),
64 byte_map_base(NULL)
65 {
66 assert((uintptr_t(_whole_heap.start()) & (card_size - 1)) == 0, "heap must start at card boundary");
67 assert((uintptr_t(_whole_heap.end()) & (card_size - 1)) == 0, "heap must end at card boundary");
68
69 assert(card_size <= 512, "card_size must be less than 512"); // why?
70
71 _covered = new MemRegion[_max_covered_regions];
72 if (_covered == NULL) {
73 vm_exit_during_initialization("Could not allocate card table covered region set.");
74 }
75 }
76
77 void CardTableModRefBS::initialize() {
78 _guard_index = cards_required(_whole_heap.word_size()) - 1;
79 _last_valid_index = _guard_index - 1;
80
81 _byte_map_size = compute_byte_map_size();
82
83 HeapWord* low_bound = _whole_heap.start();
84 HeapWord* high_bound = _whole_heap.end();
85
86 _cur_covered_regions = 0;
87 _committed = new MemRegion[_max_covered_regions];
88 if (_committed == NULL) {
89 vm_exit_during_initialization("Could not allocate card table committed region set.");
90 }
91
92 const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
93 MAX2(_page_size, (size_t) os::vm_allocation_granularity());
94 ReservedSpace heap_rs(_byte_map_size, rs_align, false);
95
96 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
97
98 os::trace_page_sizes("Card Table", _guard_index + 1, _guard_index + 1,
99 _page_size, heap_rs.base(), heap_rs.size());
100 if (!heap_rs.is_reserved()) {
101 vm_exit_during_initialization("Could not reserve enough space for the "
102 "card marking array");
103 }
104
105 // The assembler store_check code will do an unsigned shift of the oop,
106 // then add it to byte_map_base, i.e.
107 //
108 // _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
109 _byte_map = (jbyte*) heap_rs.base();
110 byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
111 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
112 assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
113
114 jbyte* guard_card = &_byte_map[_guard_index];
115 uintptr_t guard_page = align_down((uintptr_t)guard_card, _page_size);
116 _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
117 os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
118 !ExecMem, "card table last card");
119 *guard_card = last_card;
120
121 log_trace(gc, barrier)("CardTableModRefBS::CardTableModRefBS: ");
122 log_trace(gc, barrier)(" &_byte_map[0]: " INTPTR_FORMAT " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
123 p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
124 log_trace(gc, barrier)(" byte_map_base: " INTPTR_FORMAT, p2i(byte_map_base));
125 }
126
127 CardTableModRefBS::~CardTableModRefBS() {
128 if (_covered) {
129 delete[] _covered;
130 _covered = NULL;
131 }
132 if (_committed) {
133 delete[] _committed;
134 _committed = NULL;
135 }
136 }
137
138 int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
139 int i;
140 for (i = 0; i < _cur_covered_regions; i++) {
141 if (_covered[i].start() == base) return i;
142 if (_covered[i].start() > base) break;
143 }
144 // If we didn't find it, create a new one.
145 assert(_cur_covered_regions < _max_covered_regions,
146 "too many covered regions");
147 // Move the ones above up, to maintain sorted order.
148 for (int j = _cur_covered_regions; j > i; j--) {
149 _covered[j] = _covered[j-1];
150 _committed[j] = _committed[j-1];
151 }
152 int res = i;
153 _cur_covered_regions++;
154 _covered[res].set_start(base);
155 _covered[res].set_word_size(0);
156 jbyte* ct_start = byte_for(base);
157 uintptr_t ct_start_aligned = align_down((uintptr_t)ct_start, _page_size);
158 _committed[res].set_start((HeapWord*)ct_start_aligned);
159 _committed[res].set_word_size(0);
160 return res;
161 }
162
163 int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
164 for (int i = 0; i < _cur_covered_regions; i++) {
165 if (_covered[i].contains(addr)) {
166 return i;
167 }
168 }
169 assert(0, "address outside of heap?");
170 return -1;
171 }
172
173 HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
174 HeapWord* max_end = NULL;
175 for (int j = 0; j < ind; j++) {
176 HeapWord* this_end = _committed[j].end();
177 if (this_end > max_end) max_end = this_end;
178 }
179 return max_end;
180 }
181
182 MemRegion CardTableModRefBS::committed_unique_to_self(int self,
183 MemRegion mr) const {
184 MemRegion result = mr;
185 for (int r = 0; r < _cur_covered_regions; r += 1) {
186 if (r != self) {
187 result = result.minus(_committed[r]);
188 }
189 }
190 // Never include the guard page.
191 result = result.minus(_guard_region);
192 return result;
193 }
194
195 void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
196 // We don't change the start of a region, only the end.
197 assert(_whole_heap.contains(new_region),
198 "attempt to cover area not in reserved area");
199 debug_only(verify_guard();)
200 // collided is true if the expansion would push into another committed region
201 debug_only(bool collided = false;)
202 int const ind = find_covering_region_by_base(new_region.start());
203 MemRegion const 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 _committed region
209 // to cover the end of any lower _committed regions.
210 // This forms overlapping regions, but never interior regions.
211 HeapWord* const 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* const new_end = byte_after(new_region.last());
217 HeapWord* new_end_aligned = (HeapWord*) align_up(new_end, _page_size);
218 assert((void*)new_end_aligned >= (void*) new_end, "align up, but less");
219 // Check the other regions (excludes "ind") to ensure that
220 // the new_end_aligned does not intrude onto the committed
221 // space of another region.
222 int ri = 0;
223 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
224 if (new_end_aligned > _committed[ri].start()) {
225 assert(new_end_aligned <= _committed[ri].end(),
226 "An earlier committed region can't cover a later committed region");
227 // Any region containing the new end
228 // should start at or beyond the region found (ind)
229 // for the new end (committed regions are not expected to
230 // be proper subsets of other committed regions).
231 assert(_committed[ri].start() >= _committed[ind].start(),
232 "New end of committed region is inconsistent");
233 new_end_aligned = _committed[ri].start();
234 // new_end_aligned can be equal to the start of its
235 // committed region (i.e., of "ind") if a second
236 // region following "ind" also start at the same location
237 // as "ind".
238 assert(new_end_aligned >= _committed[ind].start(),
239 "New end of committed region is before start");
240 debug_only(collided = true;)
241 // Should only collide with 1 region
242 break;
243 }
244 }
245 #ifdef ASSERT
246 for (++ri; ri < _cur_covered_regions; ri++) {
247 assert(!_committed[ri].contains(new_end_aligned),
248 "New end of committed region is in a second committed region");
249 }
250 #endif
251 // The guard page is always committed and should not be committed over.
252 // "guarded" is used for assertion checking below and recalls the fact
253 // that the would-be end of the new committed region would have
254 // penetrated the guard page.
255 HeapWord* new_end_for_commit = new_end_aligned;
256
257 DEBUG_ONLY(bool guarded = false;)
258 if (new_end_for_commit > _guard_region.start()) {
259 new_end_for_commit = _guard_region.start();
260 DEBUG_ONLY(guarded = true;)
261 }
262
263 if (new_end_for_commit > cur_committed.end()) {
264 // Must commit new pages.
265 MemRegion const new_committed =
266 MemRegion(cur_committed.end(), new_end_for_commit);
267
268 assert(!new_committed.is_empty(), "Region should not be empty here");
269 os::commit_memory_or_exit((char*)new_committed.start(),
270 new_committed.byte_size(), _page_size,
271 !ExecMem, "card table expansion");
272 // Use new_end_aligned (as opposed to new_end_for_commit) because
273 // the cur_committed region may include the guard region.
274 } else if (new_end_aligned < cur_committed.end()) {
275 // Must uncommit pages.
276 MemRegion const uncommit_region =
277 committed_unique_to_self(ind, MemRegion(new_end_aligned,
278 cur_committed.end()));
279 if (!uncommit_region.is_empty()) {
280 // It is not safe to uncommit cards if the boundary between
281 // the generations is moving. A shrink can uncommit cards
282 // owned by generation A but being used by generation B.
283 if (!UseAdaptiveGCBoundary) {
284 if (!os::uncommit_memory((char*)uncommit_region.start(),
285 uncommit_region.byte_size())) {
286 assert(false, "Card table contraction failed");
287 // The call failed so don't change the end of the
288 // committed region. This is better than taking the
289 // VM down.
290 new_end_aligned = _committed[ind].end();
291 }
292 } else {
293 new_end_aligned = _committed[ind].end();
294 }
295 }
296 }
297 // In any case, we can reset the end of the current committed entry.
298 _committed[ind].set_end(new_end_aligned);
299
300 #ifdef ASSERT
301 // Check that the last card in the new region is committed according
302 // to the tables.
303 bool covered = false;
304 for (int cr = 0; cr < _cur_covered_regions; cr++) {
305 if (_committed[cr].contains(new_end - 1)) {
306 covered = true;
307 break;
308 }
309 }
310 assert(covered, "Card for end of new region not committed");
311 #endif
312
313 // The default of 0 is not necessarily clean cards.
314 jbyte* entry;
315 if (old_region.last() < _whole_heap.start()) {
316 entry = byte_for(_whole_heap.start());
317 } else {
318 entry = byte_after(old_region.last());
319 }
320 assert(index_for(new_region.last()) < _guard_index,
321 "The guard card will be overwritten");
322 // This line commented out cleans the newly expanded region and
323 // not the aligned up expanded region.
324 // jbyte* const end = byte_after(new_region.last());
325 jbyte* const end = (jbyte*) new_end_for_commit;
326 assert((end >= byte_after(new_region.last())) || collided || guarded,
327 "Expect to be beyond new region unless impacting another region");
328 // do nothing if we resized downward.
329 #ifdef ASSERT
330 for (int ri = 0; ri < _cur_covered_regions; ri++) {
331 if (ri != ind) {
332 // The end of the new committed region should not
333 // be in any existing region unless it matches
334 // the start of the next region.
335 assert(!_committed[ri].contains(end) ||
336 (_committed[ri].start() == (HeapWord*) end),
337 "Overlapping committed regions");
338 }
339 }
340 #endif
341 if (entry < end) {
342 memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
343 }
344 }
345 // In any case, the covered size changes.
346 _covered[ind].set_word_size(new_region.word_size());
347
348 log_trace(gc, barrier)("CardTableModRefBS::resize_covered_region: ");
349 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
350 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
351 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
352 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
353 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
354 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
355 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
356 p2i(addr_for((jbyte*) _committed[ind].start())), p2i(addr_for((jbyte*) _committed[ind].last())));
357
358 // Touch the last card of the covered region to show that it
359 // is committed (or SEGV).
360 debug_only((void) (*byte_for(_covered[ind].last()));)
361 debug_only(verify_guard();)
362 }
363
364 // Note that these versions are precise! The scanning code has to handle the
365 // fact that the write barrier may be either precise or imprecise.
366
367 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
368 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
369 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
370 jbyte* cur = byte_for(mr.start());
371 jbyte* last = byte_after(mr.last());
372 while (cur < last) {
373 *cur = dirty_card;
374 cur++;
375 }
376 }
377
378 void CardTableModRefBS::invalidate(MemRegion mr) {
379 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
380 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
381 for (int i = 0; i < _cur_covered_regions; i++) {
382 MemRegion mri = mr.intersection(_covered[i]);
383 if (!mri.is_empty()) dirty_MemRegion(mri);
384 }
385 }
386
387 void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
388 // Be conservative: only clean cards entirely contained within the
389 // region.
390 jbyte* cur;
391 if (mr.start() == _whole_heap.start()) {
392 cur = byte_for(mr.start());
393 } else {
394 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
395 cur = byte_after(mr.start() - 1);
396 }
397 jbyte* last = byte_after(mr.last());
398 memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
399 }
400
401 void CardTableModRefBS::clear(MemRegion mr) {
402 for (int i = 0; i < _cur_covered_regions; i++) {
403 MemRegion mri = mr.intersection(_covered[i]);
404 if (!mri.is_empty()) clear_MemRegion(mri);
405 }
406 }
407
408 void CardTableModRefBS::dirty(MemRegion mr) {
409 jbyte* first = byte_for(mr.start());
410 jbyte* last = byte_after(mr.last());
411 memset(first, dirty_card, last-first);
412 }
413
414 // Unlike several other card table methods, dirty_card_iterate()
415 // iterates over dirty cards ranges in increasing address order.
416 void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
417 MemRegionClosure* cl) {
418 for (int i = 0; i < _cur_covered_regions; i++) {
419 MemRegion mri = mr.intersection(_covered[i]);
420 if (!mri.is_empty()) {
421 jbyte *cur_entry, *next_entry, *limit;
422 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
423 cur_entry <= limit;
424 cur_entry = next_entry) {
425 next_entry = cur_entry + 1;
426 if (*cur_entry == dirty_card) {
427 size_t dirty_cards;
428 // Accumulate maximal dirty card range, starting at cur_entry
429 for (dirty_cards = 1;
430 next_entry <= limit && *next_entry == dirty_card;
431 dirty_cards++, next_entry++);
432 MemRegion cur_cards(addr_for(cur_entry),
433 dirty_cards*card_size_in_words);
434 cl->do_MemRegion(cur_cards);
435 }
436 }
437 }
438 }
439 }
440
441 MemRegion CardTableModRefBS::dirty_card_range_after_reset(MemRegion mr,
442 bool reset,
443 int reset_val) {
444 for (int i = 0; i < _cur_covered_regions; i++) {
445 MemRegion mri = mr.intersection(_covered[i]);
446 if (!mri.is_empty()) {
447 jbyte* cur_entry, *next_entry, *limit;
448 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
449 cur_entry <= limit;
450 cur_entry = next_entry) {
451 next_entry = cur_entry + 1;
452 if (*cur_entry == dirty_card) {
453 size_t dirty_cards;
454 // Accumulate maximal dirty card range, starting at cur_entry
455 for (dirty_cards = 1;
456 next_entry <= limit && *next_entry == dirty_card;
457 dirty_cards++, next_entry++);
458 MemRegion cur_cards(addr_for(cur_entry),
459 dirty_cards*card_size_in_words);
460 if (reset) {
461 for (size_t i = 0; i < dirty_cards; i++) {
462 cur_entry[i] = reset_val;
463 }
464 }
465 return cur_cards;
466 }
467 }
468 }
469 }
470 return MemRegion(mr.end(), mr.end());
471 }
472
473 uintx CardTableModRefBS::ct_max_alignment_constraint() {
474 return card_size * os::vm_page_size();
475 }
476
477 void CardTableModRefBS::verify_guard() {
478 // For product build verification
479 guarantee(_byte_map[_guard_index] == last_card,
480 "card table guard has been modified");
481 }
482
483 void CardTableModRefBS::verify() {
484 verify_guard();
485 }
486
487 #ifndef PRODUCT
488 void CardTableModRefBS::verify_region(MemRegion mr,
489 jbyte val, bool val_equals) {
490 jbyte* start = byte_for(mr.start());
491 jbyte* end = byte_for(mr.last());
492 bool failures = false;
493 for (jbyte* curr = start; curr <= end; ++curr) {
494 jbyte curr_val = *curr;
495 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
496 if (failed) {
497 if (!failures) {
498 log_error(gc, verify)("== CT verification failed: [" INTPTR_FORMAT "," INTPTR_FORMAT "]", p2i(start), p2i(end));
499 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
500 failures = true;
501 }
502 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
503 p2i(curr), p2i(addr_for(curr)),
504 p2i((HeapWord*) (((size_t) addr_for(curr)) + card_size)),
505 (int) curr_val);
506 }
507 }
508 guarantee(!failures, "there should not have been any failures");
509 }
510
511 void CardTableModRefBS::verify_not_dirty_region(MemRegion mr) {
512 verify_region(mr, dirty_card, false /* val_equals */);
513 }
514
515 void CardTableModRefBS::verify_dirty_region(MemRegion mr) {
516 verify_region(mr, dirty_card, true /* val_equals */);
517 }
518 #endif
519
520 void CardTableModRefBS::print_on(outputStream* st) const {
521 st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] byte_map_base: " INTPTR_FORMAT,
522 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(byte_map_base));
523 }