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