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