1 /*
2 * Copyright (c) 2000, 2020, 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(MemRegion::create_array(_max_covered_regions, mtGC)),
55 _committed(MemRegion::create_array(_max_covered_regions, mtGC)),
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
64 CardTable::~CardTable() {
65 MemRegion::destroy_array(_covered, _max_covered_regions);
66 MemRegion::destroy_array(_committed, _max_covered_regions);
67 }
68
69 void CardTable::initialize() {
70 _guard_index = cards_required(_whole_heap.word_size()) - 1;
71 _last_valid_index = _guard_index - 1;
72
73 _byte_map_size = compute_byte_map_size();
74
75 HeapWord* low_bound = _whole_heap.start();
76 HeapWord* high_bound = _whole_heap.end();
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);
83
84 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
85
86 os::trace_page_sizes("Card Table", _guard_index + 1, _guard_index + 1,
87 _page_size, heap_rs.base(), heap_rs.size());
88 if (!heap_rs.is_reserved()) {
89 vm_exit_during_initialization("Could not reserve enough space for the "
90 "card marking array");
91 }
92
93 // The assembler store_check code will do an unsigned shift of the oop,
94 // then add it to _byte_map_base, i.e.
95 //
96 // _byte_map = _byte_map_base + (uintptr_t(low_bound) >> card_shift)
97 _byte_map = (CardValue*) heap_rs.base();
98 _byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
99 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
100 assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
101
102 CardValue* guard_card = &_byte_map[_guard_index];
103 HeapWord* guard_page = align_down((HeapWord*)guard_card, _page_size);
104 _guard_region = MemRegion(guard_page, _page_size);
105 os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
106 !ExecMem, "card table last card");
107 *guard_card = last_card;
108
109 log_trace(gc, barrier)("CardTable::CardTable: ");
110 log_trace(gc, barrier)(" &_byte_map[0]: " INTPTR_FORMAT " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
111 p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
112 log_trace(gc, barrier)(" _byte_map_base: " INTPTR_FORMAT, p2i(_byte_map_base));
113 }
114
115 int CardTable::find_covering_region_by_base(HeapWord* base) {
116 int i;
117 for (i = 0; i < _cur_covered_regions; i++) {
118 if (_covered[i].start() == base) return i;
119 if (_covered[i].start() > base) break;
120 }
121 // If we didn't find it, create a new one.
122 assert(_cur_covered_regions < _max_covered_regions,
123 "too many covered regions");
124 // Move the ones above up, to maintain sorted order.
125 for (int j = _cur_covered_regions; j > i; j--) {
126 _covered[j] = _covered[j-1];
127 _committed[j] = _committed[j-1];
128 }
129 int res = i;
130 _cur_covered_regions++;
131 _covered[res].set_start(base);
132 _covered[res].set_word_size(0);
133 CardValue* ct_start = byte_for(base);
134 HeapWord* ct_start_aligned = align_down((HeapWord*)ct_start, _page_size);
135 _committed[res].set_start(ct_start_aligned);
136 _committed[res].set_word_size(0);
137 return res;
138 }
139
140 int CardTable::find_covering_region_containing(HeapWord* addr) {
141 for (int i = 0; i < _cur_covered_regions; i++) {
142 if (_covered[i].contains(addr)) {
143 return i;
144 }
145 }
146 assert(0, "address outside of heap?");
147 return -1;
148 }
149
150 HeapWord* CardTable::largest_prev_committed_end(int ind) const {
151 HeapWord* max_end = NULL;
152 for (int j = 0; j < ind; j++) {
153 HeapWord* this_end = _committed[j].end();
154 if (this_end > max_end) max_end = this_end;
155 }
156 return max_end;
157 }
158
159 MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const {
160 MemRegion result = mr;
161 for (int r = 0; r < _cur_covered_regions; r += 1) {
162 if (r != self) {
163 result = result.minus(_committed[r]);
164 }
165 }
166 // Never include the guard page.
167 result = result.minus(_guard_region);
168 return result;
169 }
170
171 void CardTable::resize_covered_region(MemRegion new_region) {
172 // We don't change the start of a region, only the end.
173 assert(_whole_heap.contains(new_region),
174 "attempt to cover area not in reserved area");
175 debug_only(verify_guard();)
176 // collided is true if the expansion would push into another committed region
177 debug_only(bool collided = false;)
178 int const ind = find_covering_region_by_base(new_region.start());
179 MemRegion const old_region = _covered[ind];
180 assert(old_region.start() == new_region.start(), "just checking");
181 if (new_region.word_size() != old_region.word_size()) {
182 // Commit new or uncommit old pages, if necessary.
183 MemRegion cur_committed = _committed[ind];
184 // Extend the end of this _committed region
185 // to cover the end of any lower _committed regions.
186 // This forms overlapping regions, but never interior regions.
187 HeapWord* const max_prev_end = largest_prev_committed_end(ind);
188 if (max_prev_end > cur_committed.end()) {
189 cur_committed.set_end(max_prev_end);
190 }
191 // Align the end up to a page size (starts are already aligned).
192 HeapWord* new_end = (HeapWord*) byte_after(new_region.last());
193 HeapWord* new_end_aligned = align_up(new_end, _page_size);
194 assert(new_end_aligned >= new_end, "align up, but less");
195 // Check the other regions (excludes "ind") to ensure that
196 // the new_end_aligned does not intrude onto the committed
197 // space of another region.
198 int ri = 0;
199 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
200 if (new_end_aligned > _committed[ri].start()) {
201 assert(new_end_aligned <= _committed[ri].end(),
202 "An earlier committed region can't cover a later committed region");
203 // Any region containing the new end
204 // should start at or beyond the region found (ind)
205 // for the new end (committed regions are not expected to
206 // be proper subsets of other committed regions).
207 assert(_committed[ri].start() >= _committed[ind].start(),
208 "New end of committed region is inconsistent");
209 new_end_aligned = _committed[ri].start();
210 // new_end_aligned can be equal to the start of its
211 // committed region (i.e., of "ind") if a second
212 // region following "ind" also start at the same location
213 // as "ind".
214 assert(new_end_aligned >= _committed[ind].start(),
215 "New end of committed region is before start");
216 debug_only(collided = true;)
217 // Should only collide with 1 region
218 break;
219 }
220 }
221 #ifdef ASSERT
222 for (++ri; ri < _cur_covered_regions; ri++) {
223 assert(!_committed[ri].contains(new_end_aligned),
224 "New end of committed region is in a second committed region");
225 }
226 #endif
227 // The guard page is always committed and should not be committed over.
228 // "guarded" is used for assertion checking below and recalls the fact
229 // that the would-be end of the new committed region would have
230 // penetrated the guard page.
231 HeapWord* new_end_for_commit = new_end_aligned;
232
233 DEBUG_ONLY(bool guarded = false;)
234 if (new_end_for_commit > _guard_region.start()) {
235 new_end_for_commit = _guard_region.start();
236 DEBUG_ONLY(guarded = true;)
237 }
238
239 if (new_end_for_commit > cur_committed.end()) {
240 // Must commit new pages.
241 MemRegion const new_committed =
242 MemRegion(cur_committed.end(), new_end_for_commit);
243
244 assert(!new_committed.is_empty(), "Region should not be empty here");
245 os::commit_memory_or_exit((char*)new_committed.start(),
246 new_committed.byte_size(), _page_size,
247 !ExecMem, "card table expansion");
248 // Use new_end_aligned (as opposed to new_end_for_commit) because
249 // the cur_committed region may include the guard region.
250 } else if (new_end_aligned < cur_committed.end()) {
251 // Must uncommit pages.
252 MemRegion const uncommit_region =
253 committed_unique_to_self(ind, MemRegion(new_end_aligned,
254 cur_committed.end()));
255 if (!uncommit_region.is_empty()) {
256 if (!os::uncommit_memory((char*)uncommit_region.start(),
257 uncommit_region.byte_size())) {
258 assert(false, "Card table contraction failed");
259 // The call failed so don't change the end of the
260 // committed region. This is better than taking the
261 // VM down.
262 new_end_aligned = _committed[ind].end();
263 }
264 }
265 }
266 // In any case, we can reset the end of the current committed entry.
267 _committed[ind].set_end(new_end_aligned);
268
269 #ifdef ASSERT
270 // Check that the last card in the new region is committed according
271 // to the tables.
272 bool covered = false;
273 for (int cr = 0; cr < _cur_covered_regions; cr++) {
274 if (_committed[cr].contains(new_end - 1)) {
275 covered = true;
276 break;
277 }
278 }
279 assert(covered, "Card for end of new region not committed");
280 #endif
281
282 // The default of 0 is not necessarily clean cards.
283 CardValue* entry;
284 if (old_region.last() < _whole_heap.start()) {
285 entry = byte_for(_whole_heap.start());
286 } else {
287 entry = byte_after(old_region.last());
288 }
289 assert(index_for(new_region.last()) < _guard_index,
290 "The guard card will be overwritten");
291 // This line commented out cleans the newly expanded region and
292 // not the aligned up expanded region.
293 // CardValue* const end = byte_after(new_region.last());
294 CardValue* const end = (CardValue*) new_end_for_commit;
295 assert((end >= byte_after(new_region.last())) || collided || guarded,
296 "Expect to be beyond new region unless impacting another region");
297 // do nothing if we resized downward.
298 #ifdef ASSERT
299 for (int ri = 0; ri < _cur_covered_regions; ri++) {
300 if (ri != ind) {
301 // The end of the new committed region should not
302 // be in any existing region unless it matches
303 // the start of the next region.
304 assert(!_committed[ri].contains(end) ||
305 (_committed[ri].start() == (HeapWord*) end),
306 "Overlapping committed regions");
307 }
308 }
309 #endif
310 if (entry < end) {
311 memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue)));
312 }
313 }
314 // In any case, the covered size changes.
315 _covered[ind].set_word_size(new_region.word_size());
316
317 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
318 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
319 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
320 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
321 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
322 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
323 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
324 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
325 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
326
327 // Touch the last card of the covered region to show that it
328 // is committed (or SEGV).
329 debug_only((void) (*byte_for(_covered[ind].last()));)
330 debug_only(verify_guard();)
331 }
332
333 // Note that these versions are precise! The scanning code has to handle the
334 // fact that the write barrier may be either precise or imprecise.
335 void CardTable::dirty_MemRegion(MemRegion mr) {
336 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
337 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
338 CardValue* cur = byte_for(mr.start());
339 CardValue* last = byte_after(mr.last());
340 while (cur < last) {
341 *cur = dirty_card;
342 cur++;
343 }
344 }
345
346 void CardTable::clear_MemRegion(MemRegion mr) {
347 // Be conservative: only clean cards entirely contained within the
348 // region.
349 CardValue* cur;
350 if (mr.start() == _whole_heap.start()) {
351 cur = byte_for(mr.start());
352 } else {
353 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
354 cur = byte_after(mr.start() - 1);
355 }
356 CardValue* last = byte_after(mr.last());
357 memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue)));
358 }
359
360 void CardTable::clear(MemRegion mr) {
361 for (int i = 0; i < _cur_covered_regions; i++) {
362 MemRegion mri = mr.intersection(_covered[i]);
363 if (!mri.is_empty()) clear_MemRegion(mri);
364 }
365 }
366
367 void CardTable::dirty(MemRegion mr) {
368 CardValue* first = byte_for(mr.start());
369 CardValue* last = byte_after(mr.last());
370 memset(first, dirty_card, last-first);
371 }
372
373 // Unlike several other card table methods, dirty_card_iterate()
374 // iterates over dirty cards ranges in increasing address order.
375 void CardTable::dirty_card_iterate(MemRegion mr, MemRegionClosure* cl) {
376 for (int i = 0; i < _cur_covered_regions; i++) {
377 MemRegion mri = mr.intersection(_covered[i]);
378 if (!mri.is_empty()) {
379 CardValue *cur_entry, *next_entry, *limit;
380 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
381 cur_entry <= limit;
382 cur_entry = next_entry) {
383 next_entry = cur_entry + 1;
384 if (*cur_entry == dirty_card) {
385 size_t dirty_cards;
386 // Accumulate maximal dirty card range, starting at cur_entry
387 for (dirty_cards = 1;
388 next_entry <= limit && *next_entry == dirty_card;
389 dirty_cards++, next_entry++);
390 MemRegion cur_cards(addr_for(cur_entry),
391 dirty_cards*card_size_in_words);
392 cl->do_MemRegion(cur_cards);
393 }
394 }
395 }
396 }
397 }
398
399 MemRegion CardTable::dirty_card_range_after_reset(MemRegion mr,
400 bool reset,
401 int reset_val) {
402 for (int i = 0; i < _cur_covered_regions; i++) {
403 MemRegion mri = mr.intersection(_covered[i]);
404 if (!mri.is_empty()) {
405 CardValue* cur_entry, *next_entry, *limit;
406 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
407 cur_entry <= limit;
408 cur_entry = next_entry) {
409 next_entry = cur_entry + 1;
410 if (*cur_entry == dirty_card) {
411 size_t dirty_cards;
412 // Accumulate maximal dirty card range, starting at cur_entry
413 for (dirty_cards = 1;
414 next_entry <= limit && *next_entry == dirty_card;
415 dirty_cards++, next_entry++);
416 MemRegion cur_cards(addr_for(cur_entry),
417 dirty_cards*card_size_in_words);
418 if (reset) {
419 for (size_t i = 0; i < dirty_cards; i++) {
420 cur_entry[i] = reset_val;
421 }
422 }
423 return cur_cards;
424 }
425 }
426 }
427 }
428 return MemRegion(mr.end(), mr.end());
429 }
430
431 uintx CardTable::ct_max_alignment_constraint() {
432 return card_size * os::vm_page_size();
433 }
434
435 void CardTable::verify_guard() {
436 // For product build verification
437 guarantee(_byte_map[_guard_index] == last_card,
438 "card table guard has been modified");
439 }
440
441 void CardTable::invalidate(MemRegion mr) {
442 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
443 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
444 for (int i = 0; i < _cur_covered_regions; i++) {
445 MemRegion mri = mr.intersection(_covered[i]);
446 if (!mri.is_empty()) dirty_MemRegion(mri);
447 }
448 }
449
450 void CardTable::verify() {
451 verify_guard();
452 }
453
454 #ifndef PRODUCT
455 void CardTable::verify_region(MemRegion mr, CardValue val, bool val_equals) {
456 CardValue* start = byte_for(mr.start());
457 CardValue* end = byte_for(mr.last());
458 bool failures = false;
459 for (CardValue* curr = start; curr <= end; ++curr) {
460 CardValue curr_val = *curr;
461 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
462 if (failed) {
463 if (!failures) {
464 log_error(gc, verify)("== CT verification failed: [" INTPTR_FORMAT "," INTPTR_FORMAT "]", p2i(start), p2i(end));
465 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
466 failures = true;
467 }
468 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
469 p2i(curr), p2i(addr_for(curr)),
470 p2i((HeapWord*) (((size_t) addr_for(curr)) + card_size)),
471 (int) curr_val);
472 }
473 }
474 guarantee(!failures, "there should not have been any failures");
475 }
476
477 void CardTable::verify_not_dirty_region(MemRegion mr) {
478 verify_region(mr, dirty_card, false /* val_equals */);
479 }
480
481 void CardTable::verify_dirty_region(MemRegion mr) {
482 verify_region(mr, dirty_card, true /* val_equals */);
483 }
484 #endif
485
486 void CardTable::print_on(outputStream* st) const {
487 st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] _byte_map_base: " INTPTR_FORMAT,
488 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(_byte_map_base));
489 }