1 /*
2 * Copyright (c) 2000, 2023, 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/gcLogPrecious.hpp"
29 #include "gc/shared/gc_globals.hpp"
30 #include "gc/shared/space.inline.hpp"
31 #include "logging/log.hpp"
32 #include "memory/virtualspace.hpp"
33 #include "runtime/java.hpp"
34 #include "runtime/os.hpp"
35 #include "services/memTracker.hpp"
36 #include "utilities/align.hpp"
37 #if INCLUDE_PARALLELGC
38 #include "gc/parallel/objectStartArray.hpp"
39 #endif
40
41 uint CardTable::_card_shift = 0;
42 uint CardTable::_card_size = 0;
43 uint CardTable::_card_size_in_words = 0;
44
45 void CardTable::initialize_card_size() {
46 assert(UseG1GC || UseParallelGC || UseSerialGC,
47 "Initialize card size should only be called by card based collectors.");
48
49 _card_size = GCCardSizeInBytes;
50 _card_shift = log2i_exact(_card_size);
51 _card_size_in_words = _card_size / sizeof(HeapWord);
52
53 // Set blockOffsetTable size based on card table entry size
54 BOTConstants::initialize_bot_size(_card_shift);
55
56 #if INCLUDE_PARALLELGC
57 // Set ObjectStartArray block size based on card table entry size
58 ObjectStartArray::initialize_block_size(_card_shift);
59 #endif
60
61 log_info_p(gc, init)("CardTable entry size: " UINT32_FORMAT, _card_size);
62 }
63
64 size_t CardTable::compute_byte_map_size(size_t num_bytes) {
65 assert(_page_size != 0, "uninitialized, check declaration order");
66 const size_t granularity = os::vm_allocation_granularity();
67 return align_up(num_bytes, MAX2(_page_size, granularity));
68 }
69
70 CardTable::CardTable(MemRegion whole_heap) :
71 _whole_heap(whole_heap),
72 _page_size(os::vm_page_size()),
73 _byte_map_size(0),
74 _byte_map(nullptr),
75 _byte_map_base(nullptr),
76 _cur_covered_regions(0),
77 _covered(MemRegion::create_array(_max_covered_regions, mtGC)),
78 _committed(MemRegion::create_array(_max_covered_regions, mtGC)),
79 _guard_region()
80 {
81 assert((uintptr_t(_whole_heap.start()) & (_card_size - 1)) == 0, "heap must start at card boundary");
82 assert((uintptr_t(_whole_heap.end()) & (_card_size - 1)) == 0, "heap must end at card boundary");
83 }
84
85 CardTable::~CardTable() {
86 MemRegion::destroy_array(_covered, _max_covered_regions);
87 MemRegion::destroy_array(_committed, _max_covered_regions);
88 }
89
90 void CardTable::initialize() {
91 size_t num_cards = cards_required(_whole_heap.word_size());
92
93 // each card takes 1 byte; + 1 for the guard card
94 size_t num_bytes = num_cards + 1;
95 _byte_map_size = compute_byte_map_size(num_bytes);
96
97 HeapWord* low_bound = _whole_heap.start();
98 HeapWord* high_bound = _whole_heap.end();
99
100 _cur_covered_regions = 0;
101
102 const size_t rs_align = _page_size == os::vm_page_size() ? 0 :
103 MAX2(_page_size, os::vm_allocation_granularity());
104 ReservedSpace heap_rs(_byte_map_size, rs_align, _page_size);
105
106 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
107
108 os::trace_page_sizes("Card Table", num_bytes, num_bytes,
109 _page_size, heap_rs.base(), heap_rs.size());
110 if (!heap_rs.is_reserved()) {
111 vm_exit_during_initialization("Could not reserve enough space for the "
112 "card marking array");
113 }
114
115 // The assembler store_check code will do an unsigned shift of the oop,
116 // then add it to _byte_map_base, i.e.
117 //
118 // _byte_map = _byte_map_base + (uintptr_t(low_bound) >> card_shift)
119 _byte_map = (CardValue*) heap_rs.base();
120 _byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift);
121 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
122 assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map");
123
124 CardValue* guard_card = &_byte_map[num_cards];
125 assert(is_aligned(guard_card, _page_size), "must be on its own OS page");
126 _guard_region = MemRegion((HeapWord*)guard_card, _page_size);
127
128 log_trace(gc, barrier)("CardTable::CardTable: ");
129 log_trace(gc, barrier)(" &_byte_map[0]: " PTR_FORMAT " &_byte_map[last_valid_index()]: " PTR_FORMAT,
130 p2i(&_byte_map[0]), p2i(&_byte_map[last_valid_index()]));
131 log_trace(gc, barrier)(" _byte_map_base: " PTR_FORMAT, p2i(_byte_map_base));
132 }
133
134 int CardTable::find_covering_region_by_base(HeapWord* base) {
135 int i;
136 for (i = 0; i < _cur_covered_regions; i++) {
137 if (_covered[i].start() == base) return i;
138 if (_covered[i].start() > base) break;
139 }
140 // If we didn't find it, create a new one.
141 assert(_cur_covered_regions < _max_covered_regions,
142 "too many covered regions");
143 // Move the ones above up, to maintain sorted order.
144 for (int j = _cur_covered_regions; j > i; j--) {
145 _covered[j] = _covered[j-1];
146 _committed[j] = _committed[j-1];
147 }
148 int res = i;
149 _cur_covered_regions++;
150 _covered[res].set_start(base);
151 _covered[res].set_word_size(0);
152 CardValue* ct_start = byte_for(base);
153 HeapWord* ct_start_aligned = align_down((HeapWord*)ct_start, _page_size);
154 _committed[res].set_start(ct_start_aligned);
155 _committed[res].set_word_size(0);
156 return res;
157 }
158
159 HeapWord* CardTable::largest_prev_committed_end(int ind) const {
160 HeapWord* max_end = nullptr;
161 for (int j = 0; j < ind; j++) {
162 HeapWord* this_end = _committed[j].end();
163 if (this_end > max_end) max_end = this_end;
164 }
165 return max_end;
166 }
167
168 MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const {
169 assert(mr.intersection(_guard_region).is_empty(), "precondition");
170 MemRegion result = mr;
171 for (int r = 0; r < _cur_covered_regions; r += 1) {
172 if (r != self) {
173 result = result.minus(_committed[r]);
174 }
175 }
176 return result;
177 }
178
179 void CardTable::resize_covered_region(MemRegion new_region) {
180 // We don't change the start of a region, only the end.
181 assert(_whole_heap.contains(new_region),
182 "attempt to cover area not in reserved area");
183 // collided is true if the expansion would push into another committed region
184 debug_only(bool collided = false;)
185 int const ind = find_covering_region_by_base(new_region.start());
186 MemRegion const old_region = _covered[ind];
187 assert(old_region.start() == new_region.start(), "just checking");
188 if (new_region.word_size() != old_region.word_size()) {
189 // Commit new or uncommit old pages, if necessary.
190 MemRegion cur_committed = _committed[ind];
191 // Extend the end of this _committed region
192 // to cover the end of any lower _committed regions.
193 // This forms overlapping regions, but never interior regions.
194 HeapWord* const max_prev_end = largest_prev_committed_end(ind);
195 if (max_prev_end > cur_committed.end()) {
196 cur_committed.set_end(max_prev_end);
197 }
198 // Align the end up to a page size (starts are already aligned).
199 HeapWord* new_end = (HeapWord*) byte_after(new_region.last());
200 HeapWord* new_end_aligned = align_up(new_end, _page_size);
201 assert(new_end_aligned >= new_end, "align up, but less");
202 // Check the other regions (excludes "ind") to ensure that
203 // the new_end_aligned does not intrude onto the committed
204 // space of another region.
205 int ri = 0;
206 for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
207 if (new_end_aligned > _committed[ri].start()) {
208 assert(new_end_aligned <= _committed[ri].end(),
209 "An earlier committed region can't cover a later committed region");
210 // Any region containing the new end
211 // should start at or beyond the region found (ind)
212 // for the new end (committed regions are not expected to
213 // be proper subsets of other committed regions).
214 assert(_committed[ri].start() >= _committed[ind].start(),
215 "New end of committed region is inconsistent");
216 new_end_aligned = _committed[ri].start();
217 // new_end_aligned can be equal to the start of its
218 // committed region (i.e., of "ind") if a second
219 // region following "ind" also start at the same location
220 // as "ind".
221 assert(new_end_aligned >= _committed[ind].start(),
222 "New end of committed region is before start");
223 debug_only(collided = true;)
224 // Should only collide with 1 region
225 break;
226 }
227 }
228 #ifdef ASSERT
229 for (++ri; ri < _cur_covered_regions; ri++) {
230 assert(!_committed[ri].contains(new_end_aligned),
231 "New end of committed region is in a second committed region");
232 }
233 #endif
234 // The guard page is always committed and should not be committed over.
235 // "guarded" is used for assertion checking below and recalls the fact
236 // that the would-be end of the new committed region would have
237 // penetrated the guard page.
238 HeapWord* new_end_for_commit = new_end_aligned;
239
240 DEBUG_ONLY(bool guarded = false;)
241 if (new_end_for_commit > _guard_region.start()) {
242 new_end_for_commit = _guard_region.start();
243 DEBUG_ONLY(guarded = true;)
244 }
245
246 if (new_end_for_commit > cur_committed.end()) {
247 // Must commit new pages.
248 MemRegion const new_committed =
249 MemRegion(cur_committed.end(), new_end_for_commit);
250
251 assert(!new_committed.is_empty(), "Region should not be empty here");
252 os::commit_memory_or_exit((char*)new_committed.start(),
253 new_committed.byte_size(), _page_size,
254 !ExecMem, "card table expansion");
255 // Use new_end_aligned (as opposed to new_end_for_commit) because
256 // the cur_committed region may include the guard region.
257 } else if (new_end_aligned < cur_committed.end()) {
258 // Must uncommit pages.
259 MemRegion const uncommit_region =
260 committed_unique_to_self(ind, MemRegion(new_end_aligned,
261 cur_committed.end()));
262 if (!uncommit_region.is_empty()) {
263 if (!os::uncommit_memory((char*)uncommit_region.start(),
264 uncommit_region.byte_size())) {
265 assert(false, "Card table contraction failed");
266 // The call failed so don't change the end of the
267 // committed region. This is better than taking the
268 // VM down.
269 new_end_aligned = _committed[ind].end();
270 }
271 }
272 }
273 // In any case, we can reset the end of the current committed entry.
274 _committed[ind].set_end(new_end_aligned);
275
276 #ifdef ASSERT
277 // Check that the last card in the new region is committed according
278 // to the tables.
279 bool covered = false;
280 for (int cr = 0; cr < _cur_covered_regions; cr++) {
281 if (_committed[cr].contains(new_end - 1)) {
282 covered = true;
283 break;
284 }
285 }
286 assert(covered, "Card for end of new region not committed");
287 #endif
288
289 // The default of 0 is not necessarily clean cards.
290 CardValue* entry;
291 if (old_region.last() < _whole_heap.start()) {
292 entry = byte_for(_whole_heap.start());
293 } else {
294 entry = byte_after(old_region.last());
295 }
296 assert(index_for(new_region.last()) <= last_valid_index(),
297 "The guard card will be overwritten");
298 // This line commented out cleans the newly expanded region and
299 // not the aligned up expanded region.
300 // CardValue* const end = byte_after(new_region.last());
301 CardValue* const end = (CardValue*) new_end_for_commit;
302 assert((end >= byte_after(new_region.last())) || collided || guarded,
303 "Expect to be beyond new region unless impacting another region");
304 // do nothing if we resized downward.
305 #ifdef ASSERT
306 for (int ri = 0; ri < _cur_covered_regions; ri++) {
307 if (ri != ind) {
308 // The end of the new committed region should not
309 // be in any existing region unless it matches
310 // the start of the next region.
311 assert(!_committed[ri].contains(end) ||
312 (_committed[ri].start() == (HeapWord*) end),
313 "Overlapping committed regions");
314 }
315 }
316 #endif
317 if (entry < end) {
318 memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue)));
319 }
320 }
321 // In any case, the covered size changes.
322 _covered[ind].set_word_size(new_region.word_size());
323
324 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
325 log_trace(gc, barrier)(" _covered[%d].start(): " PTR_FORMAT " _covered[%d].last(): " PTR_FORMAT,
326 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
327 log_trace(gc, barrier)(" _committed[%d].start(): " PTR_FORMAT " _committed[%d].last(): " PTR_FORMAT,
328 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
329 log_trace(gc, barrier)(" byte_for(start): " PTR_FORMAT " byte_for(last): " PTR_FORMAT,
330 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
331 log_trace(gc, barrier)(" addr_for(start): " PTR_FORMAT " addr_for(last): " PTR_FORMAT,
332 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
333
334 // Touch the last card of the covered region to show that it
335 // is committed (or SEGV).
336 debug_only((void) (*byte_for(_covered[ind].last()));)
337 }
338
339 // Note that these versions are precise! The scanning code has to handle the
340 // fact that the write barrier may be either precise or imprecise.
341 void CardTable::dirty_MemRegion(MemRegion mr) {
342 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
343 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
344 CardValue* cur = byte_for(mr.start());
345 CardValue* last = byte_after(mr.last());
346 while (cur < last) {
347 *cur = dirty_card;
348 cur++;
349 }
350 }
351
352 void CardTable::clear_MemRegion(MemRegion mr) {
353 // Be conservative: only clean cards entirely contained within the
354 // region.
355 CardValue* cur;
356 if (mr.start() == _whole_heap.start()) {
357 cur = byte_for(mr.start());
358 } else {
359 assert(mr.start() > _whole_heap.start(), "mr is not covered.");
360 cur = byte_after(mr.start() - 1);
361 }
362 CardValue* last = byte_after(mr.last());
363 memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue)));
364 }
365
366 void CardTable::clear(MemRegion mr) {
367 for (int i = 0; i < _cur_covered_regions; i++) {
368 MemRegion mri = mr.intersection(_covered[i]);
369 if (!mri.is_empty()) clear_MemRegion(mri);
370 }
371 }
372
373 uintx CardTable::ct_max_alignment_constraint() {
374 // Calculate maximum alignment using GCCardSizeInBytes as card_size hasn't been set yet
375 return GCCardSizeInBytes * os::vm_page_size();
376 }
377
378 void CardTable::invalidate(MemRegion mr) {
379 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
380 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
381 for (int i = 0; i < _cur_covered_regions; i++) {
382 MemRegion mri = mr.intersection(_covered[i]);
383 if (!mri.is_empty()) dirty_MemRegion(mri);
384 }
385 }
386
387 #ifndef PRODUCT
388 void CardTable::verify_region(MemRegion mr, CardValue val, bool val_equals) {
389 CardValue* start = byte_for(mr.start());
390 CardValue* end = byte_for(mr.last());
391 bool failures = false;
392 for (CardValue* curr = start; curr <= end; ++curr) {
393 CardValue curr_val = *curr;
394 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
395 if (failed) {
396 if (!failures) {
397 log_error(gc, verify)("== CT verification failed: [" PTR_FORMAT "," PTR_FORMAT "]", p2i(start), p2i(end));
398 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
399 failures = true;
400 }
401 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
402 p2i(curr), p2i(addr_for(curr)),
403 p2i((HeapWord*) (((size_t) addr_for(curr)) + _card_size)),
404 (int) curr_val);
405 }
406 }
407 guarantee(!failures, "there should not have been any failures");
408 }
409
410 void CardTable::verify_not_dirty_region(MemRegion mr) {
411 verify_region(mr, dirty_card, false /* val_equals */);
412 }
413
414 void CardTable::verify_dirty_region(MemRegion mr) {
415 verify_region(mr, dirty_card, true /* val_equals */);
416 }
417 #endif
418
419 void CardTable::print_on(outputStream* st) const {
420 st->print_cr("Card table byte_map: [" PTR_FORMAT "," PTR_FORMAT "] _byte_map_base: " PTR_FORMAT,
421 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(_byte_map_base));
422 }