1 /*
2 * Copyright (c) 2000, 2018, 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/cardTable.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "gc/shared/space.inline.hpp"
29 #include "logging/log.hpp"
30 #include "memory/virtualspace.hpp"
31 #include "runtime/java.hpp"
32 #include "runtime/os.hpp"
33 #include "services/memTracker.hpp"
34 #include "utilities/align.hpp"
35
36 size_t CardTable::compute_byte_map_size() {
37 assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
38 "uninitialized, check declaration order");
39 assert(_page_size != 0, "uninitialized, check declaration order");
40 const size_t granularity = os::vm_allocation_granularity();
41 return align_up(_guard_index + 1, MAX2(_page_size, granularity));
42 }
43
44 CardTable::CardTable(MemRegion whole_heap, bool conc_scan) :
45 _scanned_concurrently(conc_scan),
46 _whole_heap(whole_heap),
47 _guard_index(0),
48 _last_valid_index(0),
49 _page_size(os::vm_page_size()),
50 _byte_map_size(0),
51 _byte_map(NULL),
52 _byte_map_base(NULL),
53 _cur_covered_regions(0),
54 _covered(NULL),
55 _committed(NULL),
56 _guard_region()
57 {
58 assert((uintptr_t(_whole_heap.start()) & (card_size - 1)) == 0, "heap must start at card boundary");
59 assert((uintptr_t(_whole_heap.end()) & (card_size - 1)) == 0, "heap must end at card boundary");
60
61 assert(card_size <= 512, "card_size must be less than 512"); // why?
62
63 _covered = new MemRegion[_max_covered_regions];
64 }
65
66 CardTable::~CardTable() {
67 if (_covered) {
68 delete[] _covered;
69 _covered = NULL;
70 }
71 if (_committed) {
72 delete[] _committed;
73 _committed = NULL;
74 }
75 }
76
77 void CardTable::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
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 = (CardValue*) 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 CardValue* guard_card = &_byte_map[_guard_index];
112 HeapWord* guard_page = align_down((HeapWord*)guard_card, _page_size);
113 _guard_region = MemRegion(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 log_trace(gc, barrier)("CardTable::CardTable: ");
119 log_trace(gc, barrier)(" &_byte_map[0]: " INTPTR_FORMAT " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
120 p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
121 log_trace(gc, barrier)(" _byte_map_base: " INTPTR_FORMAT, p2i(_byte_map_base));
122 }
123
124 int CardTable::find_covering_region_by_base(HeapWord* base) {
125 int i;
126 for (i = 0; i < _cur_covered_regions; i++) {
127 if (_covered[i].start() == base) return i;
128 if (_covered[i].start() > base) break;
129 }
130 // If we didn't find it, create a new one.
131 assert(_cur_covered_regions < _max_covered_regions,
132 "too many covered regions");
133 // Move the ones above up, to maintain sorted order.
134 for (int j = _cur_covered_regions; j > i; j--) {
135 _covered[j] = _covered[j-1];
136 _committed[j] = _committed[j-1];
137 }
138 int res = i;
139 _cur_covered_regions++;
140 _covered[res].set_start(base);
141 _covered[res].set_word_size(0);
142 CardValue* ct_start = byte_for(base);
143 HeapWord* ct_start_aligned = align_down((HeapWord*)ct_start, _page_size);
144 _committed[res].set_start(ct_start_aligned);
145 _committed[res].set_word_size(0);
146 return res;
147 }
148
149 int CardTable::find_covering_region_containing(HeapWord* addr) {
150 for (int i = 0; i < _cur_covered_regions; i++) {
151 if (_covered[i].contains(addr)) {
152 return i;
153 }
154 }
155 assert(0, "address outside of heap?");
156 return -1;
157 }
158
159 HeapWord* CardTable::largest_prev_committed_end(int ind) const {
160 HeapWord* max_end = NULL;
161 for (int j = 0; j < ind; j++) {
162 HeapWord* this_end = _committed[j].end();
163 if (this_end > max_end) max_end = this_end;
164 }
165 return max_end;
166 }
167
168 MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const {
169 MemRegion result = mr;
170 for (int r = 0; r < _cur_covered_regions; r += 1) {
171 if (r != self) {
172 result = result.minus(_committed[r]);
173 }
174 }
175 // Never include the guard page.
176 result = result.minus(_guard_region);
177 return result;
178 }
179
180 void CardTable::resize_covered_region(MemRegion new_region) {
181 // We don't change the start of a region, only the end.
182 assert(_whole_heap.contains(new_region),
183 "attempt to cover area not in reserved area");
184 debug_only(verify_guard();)
185 // collided is true if the expansion would push into another committed region
186 debug_only(bool collided = false;)
187 int const ind = find_covering_region_by_base(new_region.start());
188 MemRegion const old_region = _covered[ind];
189 assert(old_region.start() == new_region.start(), "just checking");
190 if (new_region.word_size() != old_region.word_size()) {
191 // Commit new or uncommit old pages, if necessary.
192 MemRegion cur_committed = _committed[ind];
193 // Extend the end of this _committed region
194 // to cover the end of any lower _committed regions.
195 // This forms overlapping regions, but never interior regions.
196 HeapWord* const max_prev_end = largest_prev_committed_end(ind);
197 if (max_prev_end > cur_committed.end()) {
198 cur_committed.set_end(max_prev_end);
199 }
200 // Align the end up to a page size (starts are already aligned).
201 HeapWord* new_end = (HeapWord*) byte_after(new_region.last());
202 HeapWord* new_end_aligned = align_up(new_end, _page_size);
203 assert(new_end_aligned >= new_end, "align up, but less");
204 // Check the other regions (excludes "ind") to ensure that
205 // the new_end_aligned does not intrude onto the committed
206 // space of another region.
207 int ri = 0;
208 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
209 if (new_end_aligned > _committed[ri].start()) {
210 assert(new_end_aligned <= _committed[ri].end(),
211 "An earlier committed region can't cover a later committed region");
212 // Any region containing the new end
213 // should start at or beyond the region found (ind)
214 // for the new end (committed regions are not expected to
215 // be proper subsets of other committed regions).
216 assert(_committed[ri].start() >= _committed[ind].start(),
217 "New end of committed region is inconsistent");
218 new_end_aligned = _committed[ri].start();
219 // new_end_aligned can be equal to the start of its
220 // committed region (i.e., of "ind") if a second
221 // region following "ind" also start at the same location
222 // as "ind".
223 assert(new_end_aligned >= _committed[ind].start(),
224 "New end of committed region is before start");
225 debug_only(collided = true;)
226 // Should only collide with 1 region
227 break;
228 }
229 }
230 #ifdef ASSERT
231 for (++ri; ri < _cur_covered_regions; ri++) {
232 assert(!_committed[ri].contains(new_end_aligned),
233 "New end of committed region is in a second committed region");
234 }
235 #endif
236 // The guard page is always committed and should not be committed over.
237 // "guarded" is used for assertion checking below and recalls the fact
238 // that the would-be end of the new committed region would have
239 // penetrated the guard page.
240 HeapWord* new_end_for_commit = new_end_aligned;
241
242 DEBUG_ONLY(bool guarded = false;)
243 if (new_end_for_commit > _guard_region.start()) {
244 new_end_for_commit = _guard_region.start();
245 DEBUG_ONLY(guarded = true;)
246 }
247
248 if (new_end_for_commit > cur_committed.end()) {
249 // Must commit new pages.
250 MemRegion const new_committed =
251 MemRegion(cur_committed.end(), new_end_for_commit);
252
253 assert(!new_committed.is_empty(), "Region should not be empty here");
254 os::commit_memory_or_exit((char*)new_committed.start(),
255 new_committed.byte_size(), _page_size,
256 !ExecMem, "card table expansion");
257 // Use new_end_aligned (as opposed to new_end_for_commit) because
258 // the cur_committed region may include the guard region.
259 } else if (new_end_aligned < cur_committed.end()) {
260 // Must uncommit pages.
261 MemRegion const uncommit_region =
262 committed_unique_to_self(ind, MemRegion(new_end_aligned,
263 cur_committed.end()));
264 if (!uncommit_region.is_empty()) {
265 // It is not safe to uncommit cards if the boundary between
266 // the generations is moving. A shrink can uncommit cards
267 // owned by generation A but being used by generation B.
268 if (!UseAdaptiveGCBoundary) {
269 if (!os::uncommit_memory((char*)uncommit_region.start(),
270 uncommit_region.byte_size())) {
271 assert(false, "Card table contraction failed");
272 // The call failed so don't change the end of the
273 // committed region. This is better than taking the
274 // VM down.
275 new_end_aligned = _committed[ind].end();
276 }
277 } else {
278 new_end_aligned = _committed[ind].end();
279 }
280 }
281 }
282 // In any case, we can reset the end of the current committed entry.
283 _committed[ind].set_end(new_end_aligned);
284
285 #ifdef ASSERT
286 // Check that the last card in the new region is committed according
287 // to the tables.
288 bool covered = false;
289 for (int cr = 0; cr < _cur_covered_regions; cr++) {
290 if (_committed[cr].contains(new_end - 1)) {
291 covered = true;
292 break;
293 }
294 }
295 assert(covered, "Card for end of new region not committed");
296 #endif
297
298 // The default of 0 is not necessarily clean cards.
299 CardValue* entry;
300 if (old_region.last() < _whole_heap.start()) {
301 entry = byte_for(_whole_heap.start());
302 } else {
303 entry = byte_after(old_region.last());
304 }
305 assert(index_for(new_region.last()) < _guard_index,
306 "The guard card will be overwritten");
307 // This line commented out cleans the newly expanded region and
308 // not the aligned up expanded region.
309 // CardValue* const end = byte_after(new_region.last());
310 CardValue* const end = (CardValue*) new_end_for_commit;
311 assert((end >= byte_after(new_region.last())) || collided || guarded,
312 "Expect to be beyond new region unless impacting another region");
313 // do nothing if we resized downward.
314 #ifdef ASSERT
315 for (int ri = 0; ri < _cur_covered_regions; ri++) {
316 if (ri != ind) {
317 // The end of the new committed region should not
318 // be in any existing region unless it matches
319 // the start of the next region.
320 assert(!_committed[ri].contains(end) ||
321 (_committed[ri].start() == (HeapWord*) end),
322 "Overlapping committed regions");
323 }
324 }
325 #endif
326 if (entry < end) {
327 memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue)));
328 }
329 }
330 // In any case, the covered size changes.
331 _covered[ind].set_word_size(new_region.word_size());
332
333 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
334 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
335 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
336 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
337 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
338 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
339 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
340 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
341 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
342
343 // Touch the last card of the covered region to show that it
344 // is committed (or SEGV).
345 debug_only((void) (*byte_for(_covered[ind].last()));)
346 debug_only(verify_guard();)
347 }
348
349 // Note that these versions are precise! The scanning code has to handle the
350 // fact that the write barrier may be either precise or imprecise.
351 void CardTable::dirty_MemRegion(MemRegion mr) {
352 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
353 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
354 CardValue* cur = byte_for(mr.start());
355 CardValue* last = byte_after(mr.last());
356 while (cur < last) {
357 *cur = dirty_card;
358 cur++;
359 }
360 }
361
362 void CardTable::clear_MemRegion(MemRegion mr) {
363 // Be conservative: only clean cards entirely contained within the
364 // region.
365 CardValue* cur;
366 if (mr.start() == _whole_heap.start()) {
367 cur = byte_for(mr.start());
368 } else {
369 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
370 cur = byte_after(mr.start() - 1);
371 }
372 CardValue* last = byte_after(mr.last());
373 memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue)));
374 }
375
376 void CardTable::clear(MemRegion mr) {
377 for (int i = 0; i < _cur_covered_regions; i++) {
378 MemRegion mri = mr.intersection(_covered[i]);
379 if (!mri.is_empty()) clear_MemRegion(mri);
380 }
381 }
382
383 void CardTable::dirty(MemRegion mr) {
384 CardValue* first = byte_for(mr.start());
385 CardValue* last = byte_after(mr.last());
386 memset(first, dirty_card, last-first);
387 }
388
389 // Unlike several other card table methods, dirty_card_iterate()
390 // iterates over dirty cards ranges in increasing address order.
391 void CardTable::dirty_card_iterate(MemRegion mr, MemRegionClosure* cl) {
392 for (int i = 0; i < _cur_covered_regions; i++) {
393 MemRegion mri = mr.intersection(_covered[i]);
394 if (!mri.is_empty()) {
395 CardValue *cur_entry, *next_entry, *limit;
396 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
397 cur_entry <= limit;
398 cur_entry = next_entry) {
399 next_entry = cur_entry + 1;
400 if (*cur_entry == dirty_card) {
401 size_t dirty_cards;
402 // Accumulate maximal dirty card range, starting at cur_entry
403 for (dirty_cards = 1;
404 next_entry <= limit && *next_entry == dirty_card;
405 dirty_cards++, next_entry++);
406 MemRegion cur_cards(addr_for(cur_entry),
407 dirty_cards*card_size_in_words);
408 cl->do_MemRegion(cur_cards);
409 }
410 }
411 }
412 }
413 }
414
415 MemRegion CardTable::dirty_card_range_after_reset(MemRegion mr,
416 bool reset,
417 int reset_val) {
418 for (int i = 0; i < _cur_covered_regions; i++) {
419 MemRegion mri = mr.intersection(_covered[i]);
420 if (!mri.is_empty()) {
421 CardValue* 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 if (reset) {
435 for (size_t i = 0; i < dirty_cards; i++) {
436 cur_entry[i] = reset_val;
437 }
438 }
439 return cur_cards;
440 }
441 }
442 }
443 }
444 return MemRegion(mr.end(), mr.end());
445 }
446
447 uintx CardTable::ct_max_alignment_constraint() {
448 return card_size * os::vm_page_size();
449 }
450
451 void CardTable::verify_guard() {
452 // For product build verification
453 guarantee(_byte_map[_guard_index] == last_card,
454 "card table guard has been modified");
455 }
456
457 void CardTable::invalidate(MemRegion mr) {
458 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
459 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
460 for (int i = 0; i < _cur_covered_regions; i++) {
461 MemRegion mri = mr.intersection(_covered[i]);
462 if (!mri.is_empty()) dirty_MemRegion(mri);
463 }
464 }
465
466 void CardTable::verify() {
467 verify_guard();
468 }
469
470 #ifndef PRODUCT
471 void CardTable::verify_region(MemRegion mr, CardValue val, bool val_equals) {
472 CardValue* start = byte_for(mr.start());
473 CardValue* end = byte_for(mr.last());
474 bool failures = false;
475 for (CardValue* curr = start; curr <= end; ++curr) {
476 CardValue curr_val = *curr;
477 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
478 if (failed) {
479 if (!failures) {
480 log_error(gc, verify)("== CT verification failed: [" INTPTR_FORMAT "," INTPTR_FORMAT "]", p2i(start), p2i(end));
481 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
482 failures = true;
483 }
484 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
485 p2i(curr), p2i(addr_for(curr)),
486 p2i((HeapWord*) (((size_t) addr_for(curr)) + card_size)),
487 (int) curr_val);
488 }
489 }
490 guarantee(!failures, "there should not have been any failures");
491 }
492
493 void CardTable::verify_not_dirty_region(MemRegion mr) {
494 verify_region(mr, dirty_card, false /* val_equals */);
495 }
496
497 void CardTable::verify_dirty_region(MemRegion mr) {
498 verify_region(mr, dirty_card, true /* val_equals */);
499 }
500 #endif
501
502 void CardTable::print_on(outputStream* st) const {
503 st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] _byte_map_base: " INTPTR_FORMAT,
504 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(_byte_map_base));
505 }