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