1 /*
2 * Copyright (c) 2000, 2015, 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/cardTableModRefBS.inline.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "gc/shared/genCollectedHeap.hpp"
29 #include "gc/shared/space.inline.hpp"
30 #include "memory/virtualspace.hpp"
31 #include "logging/log.hpp"
32 #include "services/memTracker.hpp"
33 #include "utilities/align.hpp"
34 #include "utilities/macros.hpp"
35
36 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
37 // enumerate ref fields that have been modified (since the last
38 // enumeration.)
39
40 size_t CardTableModRefBS::compute_byte_map_size()
41 {
42 assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
43 "uninitialized, check declaration order");
44 assert(_page_size != 0, "uninitialized, check declaration order");
45 const size_t granularity = os::vm_allocation_granularity();
46 return align_up(_guard_index + 1, MAX2(_page_size, granularity));
47 }
48
49 CardTableModRefBS::CardTableModRefBS(
50 MemRegion whole_heap,
51 const BarrierSet::FakeRtti& fake_rtti) :
52 ModRefBarrierSet(fake_rtti.add_tag(BarrierSet::CardTableModRef)),
53 _whole_heap(whole_heap),
54 _guard_index(0),
55 _guard_region(),
56 _last_valid_index(0),
57 _page_size(os::vm_page_size()),
58 _byte_map_size(0),
59 _covered(NULL),
60 _committed(NULL),
61 _cur_covered_regions(0),
62 _byte_map(NULL),
63 byte_map_base(NULL)
64 {
65 assert((uintptr_t(_whole_heap.start()) & (card_size - 1)) == 0, "heap must start at card boundary");
66 assert((uintptr_t(_whole_heap.end()) & (card_size - 1)) == 0, "heap must end at card boundary");
67
68 assert(card_size <= 512, "card_size must be less than 512"); // why?
69
70 _covered = new MemRegion[_max_covered_regions];
71 if (_covered == NULL) {
72 vm_exit_during_initialization("Could not allocate card table covered region set.");
73 }
74 }
75
76 void CardTableModRefBS::initialize() {
77 _guard_index = cards_required(_whole_heap.word_size()) - 1;
78 _last_valid_index = _guard_index - 1;
79
80 _byte_map_size = compute_byte_map_size();
81
82 HeapWord* low_bound = _whole_heap.start();
83 HeapWord* high_bound = _whole_heap.end();
84
85 _cur_covered_regions = 0;
86 _committed = new MemRegion[_max_covered_regions];
87 if (_committed == NULL) {
88 vm_exit_during_initialization("Could not allocate card table committed region set.");
89 }
90
91 const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
92 MAX2(_page_size, (size_t) os::vm_allocation_granularity());
93 ReservedSpace heap_rs(_byte_map_size, rs_align, false);
94
95 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
96
97 os::trace_page_sizes("Card Table", _guard_index + 1, _guard_index + 1,
98 _page_size, heap_rs.base(), heap_rs.size());
99 if (!heap_rs.is_reserved()) {
100 vm_exit_during_initialization("Could not reserve enough space for the "
101 "card marking array");
102 }
103
104 // The assembler store_check code will do an unsigned shift of the oop,
105 // then add it to byte_map_base, i.e.
106 //
107 // _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
108 _byte_map = (jbyte*) heap_rs.base();
109 byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
110 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
111 assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
112
113 jbyte* guard_card = &_byte_map[_guard_index];
114 uintptr_t guard_page = align_down((uintptr_t)guard_card, _page_size);
115 _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
116 os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
117 !ExecMem, "card table last card");
118 *guard_card = last_card;
119
120 log_trace(gc, barrier)("CardTableModRefBS::CardTableModRefBS: ");
121 log_trace(gc, barrier)(" &_byte_map[0]: " INTPTR_FORMAT " &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
122 p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
123 log_trace(gc, barrier)(" byte_map_base: " INTPTR_FORMAT, p2i(byte_map_base));
124 }
125
126 CardTableModRefBS::~CardTableModRefBS() {
127 if (_covered) {
128 delete[] _covered;
129 _covered = NULL;
130 }
131 if (_committed) {
132 delete[] _committed;
133 _committed = NULL;
134 }
135 }
136
137 int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
138 int i;
139 for (i = 0; i < _cur_covered_regions; i++) {
140 if (_covered[i].start() == base) return i;
141 if (_covered[i].start() > base) break;
142 }
143 // If we didn't find it, create a new one.
144 assert(_cur_covered_regions < _max_covered_regions,
145 "too many covered regions");
146 // Move the ones above up, to maintain sorted order.
147 for (int j = _cur_covered_regions; j > i; j--) {
148 _covered[j] = _covered[j-1];
149 _committed[j] = _committed[j-1];
150 }
151 int res = i;
152 _cur_covered_regions++;
153 _covered[res].set_start(base);
154 _covered[res].set_word_size(0);
155 jbyte* ct_start = byte_for(base);
156 uintptr_t ct_start_aligned = align_down((uintptr_t)ct_start, _page_size);
157 _committed[res].set_start((HeapWord*)ct_start_aligned);
158 _committed[res].set_word_size(0);
159 return res;
160 }
161
162 int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
163 for (int i = 0; i < _cur_covered_regions; i++) {
164 if (_covered[i].contains(addr)) {
165 return i;
166 }
167 }
168 assert(0, "address outside of heap?");
169 return -1;
170 }
171
172 HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
173 HeapWord* max_end = NULL;
174 for (int j = 0; j < ind; j++) {
175 HeapWord* this_end = _committed[j].end();
176 if (this_end > max_end) max_end = this_end;
177 }
178 return max_end;
179 }
180
181 MemRegion CardTableModRefBS::committed_unique_to_self(int self,
182 MemRegion mr) const {
183 MemRegion result = mr;
184 for (int r = 0; r < _cur_covered_regions; r += 1) {
185 if (r != self) {
186 result = result.minus(_committed[r]);
187 }
188 }
189 // Never include the guard page.
190 result = result.minus(_guard_region);
191 return result;
192 }
193
194 void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
195 // We don't change the start of a region, only the end.
196 assert(_whole_heap.contains(new_region),
197 "attempt to cover area not in reserved area");
198 debug_only(verify_guard();)
199 // collided is true if the expansion would push into another committed region
200 debug_only(bool collided = false;)
201 int const ind = find_covering_region_by_base(new_region.start());
202 MemRegion const old_region = _covered[ind];
203 assert(old_region.start() == new_region.start(), "just checking");
204 if (new_region.word_size() != old_region.word_size()) {
205 // Commit new or uncommit old pages, if necessary.
206 MemRegion cur_committed = _committed[ind];
207 // Extend the end of this _committed region
208 // to cover the end of any lower _committed regions.
209 // This forms overlapping regions, but never interior regions.
210 HeapWord* const max_prev_end = largest_prev_committed_end(ind);
211 if (max_prev_end > cur_committed.end()) {
212 cur_committed.set_end(max_prev_end);
213 }
214 // Align the end up to a page size (starts are already aligned).
215 jbyte* const new_end = byte_after(new_region.last());
216 HeapWord* new_end_aligned = (HeapWord*) align_up(new_end, _page_size);
217 assert((void*)new_end_aligned >= (void*) new_end, "align up, but less");
218 // Check the other regions (excludes "ind") to ensure that
219 // the new_end_aligned does not intrude onto the committed
220 // space of another region.
221 int ri = 0;
222 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
223 if (new_end_aligned > _committed[ri].start()) {
224 assert(new_end_aligned <= _committed[ri].end(),
225 "An earlier committed region can't cover a later committed region");
226 // Any region containing the new end
227 // should start at or beyond the region found (ind)
228 // for the new end (committed regions are not expected to
229 // be proper subsets of other committed regions).
230 assert(_committed[ri].start() >= _committed[ind].start(),
231 "New end of committed region is inconsistent");
232 new_end_aligned = _committed[ri].start();
233 // new_end_aligned can be equal to the start of its
234 // committed region (i.e., of "ind") if a second
235 // region following "ind" also start at the same location
236 // as "ind".
237 assert(new_end_aligned >= _committed[ind].start(),
238 "New end of committed region is before start");
239 debug_only(collided = true;)
240 // Should only collide with 1 region
241 break;
242 }
243 }
244 #ifdef ASSERT
245 for (++ri; ri < _cur_covered_regions; ri++) {
246 assert(!_committed[ri].contains(new_end_aligned),
247 "New end of committed region is in a second committed region");
248 }
249 #endif
250 // The guard page is always committed and should not be committed over.
251 // "guarded" is used for assertion checking below and recalls the fact
252 // that the would-be end of the new committed region would have
253 // penetrated the guard page.
254 HeapWord* new_end_for_commit = new_end_aligned;
255
256 DEBUG_ONLY(bool guarded = false;)
257 if (new_end_for_commit > _guard_region.start()) {
258 new_end_for_commit = _guard_region.start();
259 DEBUG_ONLY(guarded = true;)
260 }
261
262 if (new_end_for_commit > cur_committed.end()) {
263 // Must commit new pages.
264 MemRegion const new_committed =
265 MemRegion(cur_committed.end(), new_end_for_commit);
266
267 assert(!new_committed.is_empty(), "Region should not be empty here");
268 os::commit_memory_or_exit((char*)new_committed.start(),
269 new_committed.byte_size(), _page_size,
270 !ExecMem, "card table expansion");
271 // Use new_end_aligned (as opposed to new_end_for_commit) because
272 // the cur_committed region may include the guard region.
273 } else if (new_end_aligned < cur_committed.end()) {
274 // Must uncommit pages.
275 MemRegion const uncommit_region =
276 committed_unique_to_self(ind, MemRegion(new_end_aligned,
277 cur_committed.end()));
278 if (!uncommit_region.is_empty()) {
279 // It is not safe to uncommit cards if the boundary between
280 // the generations is moving. A shrink can uncommit cards
281 // owned by generation A but being used by generation B.
282 if (!UseAdaptiveGCBoundary) {
283 if (!os::uncommit_memory((char*)uncommit_region.start(),
284 uncommit_region.byte_size())) {
285 assert(false, "Card table contraction failed");
286 // The call failed so don't change the end of the
287 // committed region. This is better than taking the
288 // VM down.
289 new_end_aligned = _committed[ind].end();
290 }
291 } else {
292 new_end_aligned = _committed[ind].end();
293 }
294 }
295 }
296 // In any case, we can reset the end of the current committed entry.
297 _committed[ind].set_end(new_end_aligned);
298
299 #ifdef ASSERT
300 // Check that the last card in the new region is committed according
301 // to the tables.
302 bool covered = false;
303 for (int cr = 0; cr < _cur_covered_regions; cr++) {
304 if (_committed[cr].contains(new_end - 1)) {
305 covered = true;
306 break;
307 }
308 }
309 assert(covered, "Card for end of new region not committed");
310 #endif
311
312 // The default of 0 is not necessarily clean cards.
313 jbyte* entry;
314 if (old_region.last() < _whole_heap.start()) {
315 entry = byte_for(_whole_heap.start());
316 } else {
317 entry = byte_after(old_region.last());
318 }
319 assert(index_for(new_region.last()) < _guard_index,
320 "The guard card will be overwritten");
321 // This line commented out cleans the newly expanded region and
322 // not the aligned up expanded region.
323 // jbyte* const end = byte_after(new_region.last());
324 jbyte* const end = (jbyte*) new_end_for_commit;
325 assert((end >= byte_after(new_region.last())) || collided || guarded,
326 "Expect to be beyond new region unless impacting another region");
327 // do nothing if we resized downward.
328 #ifdef ASSERT
329 for (int ri = 0; ri < _cur_covered_regions; ri++) {
330 if (ri != ind) {
331 // The end of the new committed region should not
332 // be in any existing region unless it matches
333 // the start of the next region.
334 assert(!_committed[ri].contains(end) ||
335 (_committed[ri].start() == (HeapWord*) end),
336 "Overlapping committed regions");
337 }
338 }
339 #endif
340 if (entry < end) {
341 memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
342 }
343 }
344 // In any case, the covered size changes.
345 _covered[ind].set_word_size(new_region.word_size());
346
347 log_trace(gc, barrier)("CardTableModRefBS::resize_covered_region: ");
348 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
349 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
350 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
351 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
352 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
353 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
354 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
355 p2i(addr_for((jbyte*) _committed[ind].start())), p2i(addr_for((jbyte*) _committed[ind].last())));
356
357 // Touch the last card of the covered region to show that it
358 // is committed (or SEGV).
359 debug_only((void) (*byte_for(_covered[ind].last()));)
360 debug_only(verify_guard();)
361 }
362
363 // Note that these versions are precise! The scanning code has to handle the
364 // fact that the write barrier may be either precise or imprecise.
365
366 void CardTableModRefBS::write_ref_field_work(void* field, oop newVal, bool release) {
367 inline_write_ref_field(field, newVal, release);
368 }
369
370
371 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
372 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
373 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
374 jbyte* cur = byte_for(mr.start());
375 jbyte* last = byte_after(mr.last());
376 while (cur < last) {
377 *cur = dirty_card;
378 cur++;
379 }
380 }
381
382 void CardTableModRefBS::invalidate(MemRegion mr) {
383 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
384 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
385 for (int i = 0; i < _cur_covered_regions; i++) {
386 MemRegion mri = mr.intersection(_covered[i]);
387 if (!mri.is_empty()) dirty_MemRegion(mri);
388 }
389 }
390
391 void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
392 // Be conservative: only clean cards entirely contained within the
393 // region.
394 jbyte* cur;
395 if (mr.start() == _whole_heap.start()) {
396 cur = byte_for(mr.start());
397 } else {
398 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
399 cur = byte_after(mr.start() - 1);
400 }
401 jbyte* last = byte_after(mr.last());
402 memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
403 }
404
405 void CardTableModRefBS::clear(MemRegion mr) {
406 for (int i = 0; i < _cur_covered_regions; i++) {
407 MemRegion mri = mr.intersection(_covered[i]);
408 if (!mri.is_empty()) clear_MemRegion(mri);
409 }
410 }
411
412 void CardTableModRefBS::dirty(MemRegion mr) {
413 jbyte* first = byte_for(mr.start());
414 jbyte* last = byte_after(mr.last());
415 memset(first, dirty_card, last-first);
416 }
417
418 // Unlike several other card table methods, dirty_card_iterate()
419 // iterates over dirty cards ranges in increasing address order.
420 void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
421 MemRegionClosure* cl) {
422 for (int i = 0; i < _cur_covered_regions; i++) {
423 MemRegion mri = mr.intersection(_covered[i]);
424 if (!mri.is_empty()) {
425 jbyte *cur_entry, *next_entry, *limit;
426 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
427 cur_entry <= limit;
428 cur_entry = next_entry) {
429 next_entry = cur_entry + 1;
430 if (*cur_entry == dirty_card) {
431 size_t dirty_cards;
432 // Accumulate maximal dirty card range, starting at cur_entry
433 for (dirty_cards = 1;
434 next_entry <= limit && *next_entry == dirty_card;
435 dirty_cards++, next_entry++);
436 MemRegion cur_cards(addr_for(cur_entry),
437 dirty_cards*card_size_in_words);
438 cl->do_MemRegion(cur_cards);
439 }
440 }
441 }
442 }
443 }
444
445 MemRegion CardTableModRefBS::dirty_card_range_after_reset(MemRegion mr,
446 bool reset,
447 int reset_val) {
448 for (int i = 0; i < _cur_covered_regions; i++) {
449 MemRegion mri = mr.intersection(_covered[i]);
450 if (!mri.is_empty()) {
451 jbyte* cur_entry, *next_entry, *limit;
452 for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
453 cur_entry <= limit;
454 cur_entry = next_entry) {
455 next_entry = cur_entry + 1;
456 if (*cur_entry == dirty_card) {
457 size_t dirty_cards;
458 // Accumulate maximal dirty card range, starting at cur_entry
459 for (dirty_cards = 1;
460 next_entry <= limit && *next_entry == dirty_card;
461 dirty_cards++, next_entry++);
462 MemRegion cur_cards(addr_for(cur_entry),
463 dirty_cards*card_size_in_words);
464 if (reset) {
465 for (size_t i = 0; i < dirty_cards; i++) {
466 cur_entry[i] = reset_val;
467 }
468 }
469 return cur_cards;
470 }
471 }
472 }
473 }
474 return MemRegion(mr.end(), mr.end());
475 }
476
477 uintx CardTableModRefBS::ct_max_alignment_constraint() {
478 return card_size * os::vm_page_size();
479 }
480
481 void CardTableModRefBS::verify_guard() {
482 // For product build verification
483 guarantee(_byte_map[_guard_index] == last_card,
484 "card table guard has been modified");
485 }
486
487 void CardTableModRefBS::verify() {
488 verify_guard();
489 }
490
491 #ifndef PRODUCT
492 void CardTableModRefBS::verify_region(MemRegion mr,
493 jbyte val, bool val_equals) {
494 jbyte* start = byte_for(mr.start());
495 jbyte* end = byte_for(mr.last());
496 bool failures = false;
497 for (jbyte* curr = start; curr <= end; ++curr) {
498 jbyte curr_val = *curr;
499 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
500 if (failed) {
501 if (!failures) {
502 log_error(gc, verify)("== CT verification failed: [" INTPTR_FORMAT "," INTPTR_FORMAT "]", p2i(start), p2i(end));
503 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
504 failures = true;
505 }
506 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
507 p2i(curr), p2i(addr_for(curr)),
508 p2i((HeapWord*) (((size_t) addr_for(curr)) + card_size)),
509 (int) curr_val);
510 }
511 }
512 guarantee(!failures, "there should not have been any failures");
513 }
514
515 void CardTableModRefBS::verify_not_dirty_region(MemRegion mr) {
516 verify_region(mr, dirty_card, false /* val_equals */);
517 }
518
519 void CardTableModRefBS::verify_dirty_region(MemRegion mr) {
520 verify_region(mr, dirty_card, true /* val_equals */);
521 }
522 #endif
523
524 void CardTableModRefBS::print_on(outputStream* st) const {
525 st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] byte_map_base: " INTPTR_FORMAT,
526 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(byte_map_base));
527 }
528