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