1 /*
2 * Copyright (c) 2001, 2014, 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_implementation/g1/g1CollectedHeap.hpp"
27 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
28 #include "gc_implementation/g1/heapRegion.hpp"
29 #include "memory/space.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/java.hpp"
32 #include "services/memTracker.hpp"
33
34
35
36 //////////////////////////////////////////////////////////////////////
37 // G1BlockOffsetSharedArray
38 //////////////////////////////////////////////////////////////////////
39
40 G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage) :
41 _reserved(), _end(NULL), _listener(), _offset_array(NULL) {
42
43 _reserved = heap;
44 _end = NULL;
45
46 MemRegion bot_reserved = storage->reserved();
47
48 _offset_array = (u_char*)bot_reserved.start();
49 _end = _reserved.end();
50
51 storage->set_mapping_changed_listener(&_listener);
52
53 if (TraceBlockOffsetTable) {
54 gclog_or_tty->print_cr("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: ");
55 gclog_or_tty->print_cr(" "
56 " rs.base(): " PTR_FORMAT
57 " rs.size(): " SIZE_FORMAT
58 " rs end(): " PTR_FORMAT,
59 p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end()));
60 }
61 }
62
63 bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
64 assert(p >= _reserved.start(), "just checking");
65 size_t delta = pointer_delta(p, _reserved.start());
66 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
67 }
68
69 //////////////////////////////////////////////////////////////////////
70 // G1BlockOffsetArray
71 //////////////////////////////////////////////////////////////////////
72
73 G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
74 MemRegion mr) :
75 G1BlockOffsetTable(mr.start(), mr.end()),
76 _unallocated_block(_bottom),
77 _array(array), _gsp(NULL) {
78 assert(_bottom <= _end, "arguments out of order");
79 }
80
81 void G1BlockOffsetArray::set_space(G1OffsetTableContigSpace* sp) {
82 _gsp = sp;
83 }
84
85 // The arguments follow the normal convention of denoting
86 // a right-open interval: [start, end)
87 void
88 G1BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
89
90 if (start >= end) {
91 // The start address is equal to the end address (or to
92 // the right of the end address) so there are not cards
93 // that need to be updated..
94 return;
95 }
96
97 // Write the backskip value for each region.
98 //
99 // offset
100 // card 2nd 3rd
101 // | +- 1st | |
102 // v v v v
103 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
104 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
105 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
106 // 11 19 75
107 // 12
108 //
109 // offset card is the card that points to the start of an object
110 // x - offset value of offset card
111 // 1st - start of first logarithmic region
112 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
113 // 2nd - start of second logarithmic region
114 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
115 // 3rd - start of third logarithmic region
116 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
117 //
118 // integer below the block offset entry is an example of
119 // the index of the entry
120 //
121 // Given an address,
122 // Find the index for the address
123 // Find the block offset table entry
124 // Convert the entry to a back slide
125 // (e.g., with today's, offset = 0x81 =>
126 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
127 // Move back N (e.g., 8) entries and repeat with the
128 // value of the new entry
129 //
130 size_t start_card = _array->index_for(start);
131 size_t end_card = _array->index_for(end-1);
132 assert(start ==_array->address_for_index(start_card), "Precondition");
133 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
134 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
135 }
136
137 // Unlike the normal convention in this code, the argument here denotes
138 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
139 // above.
140 void
141 G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
142 if (start_card > end_card) {
143 return;
144 }
145 assert(start_card > _array->index_for(_bottom), "Cannot be first card");
146 assert(_array->offset_array(start_card-1) <= N_words,
147 "Offset card has an unexpected value");
148 size_t start_card_for_region = start_card;
149 u_char offset = max_jubyte;
150 for (int i = 0; i < BlockOffsetArray::N_powers; i++) {
151 // -1 so that the the card with the actual offset is counted. Another -1
152 // so that the reach ends in this region and not at the start
153 // of the next.
154 size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1);
155 offset = N_words + i;
156 if (reach >= end_card) {
157 _array->set_offset_array(start_card_for_region, end_card, offset);
158 start_card_for_region = reach + 1;
159 break;
160 }
161 _array->set_offset_array(start_card_for_region, reach, offset);
162 start_card_for_region = reach + 1;
163 }
164 assert(start_card_for_region > end_card, "Sanity check");
165 DEBUG_ONLY(check_all_cards(start_card, end_card);)
166 }
167
168 // The card-interval [start_card, end_card] is a closed interval; this
169 // is an expensive check -- use with care and only under protection of
170 // suitable flag.
171 void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
172
173 if (end_card < start_card) {
174 return;
175 }
176 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
177 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
178 u_char entry = _array->offset_array(c);
179 if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) {
180 guarantee(entry > N_words,
181 err_msg("Should be in logarithmic region - "
182 "entry: %u, "
183 "_array->offset_array(c): %u, "
184 "N_words: %u",
185 (uint)entry, (uint)_array->offset_array(c), (uint)N_words));
186 }
187 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
188 size_t landing_card = c - backskip;
189 guarantee(landing_card >= (start_card - 1), "Inv");
190 if (landing_card >= start_card) {
191 guarantee(_array->offset_array(landing_card) <= entry,
192 err_msg("Monotonicity - landing_card offset: %u, "
193 "entry: %u",
194 (uint)_array->offset_array(landing_card), (uint)entry));
195 } else {
196 guarantee(landing_card == start_card - 1, "Tautology");
197 // Note that N_words is the maximum offset value
198 guarantee(_array->offset_array(landing_card) <= N_words,
199 err_msg("landing card offset: %u, "
200 "N_words: %u",
201 (uint)_array->offset_array(landing_card), (uint)N_words));
202 }
203 }
204 }
205
206 HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {
207 assert(_bottom <= addr && addr < _end,
208 "addr must be covered by this Array");
209 // Must read this exactly once because it can be modified by parallel
210 // allocation.
211 HeapWord* ub = _unallocated_block;
212 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
213 assert(ub < _end, "tautology (see above)");
214 return ub;
215 }
216 // Otherwise, find the block start using the table.
217 HeapWord* q = block_at_or_preceding(addr, false, 0);
218 return forward_to_block_containing_addr(q, addr);
219 }
220
221 // This duplicates a little code from the above: unavoidable.
222 HeapWord*
223 G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const {
224 assert(_bottom <= addr && addr < _end,
225 "addr must be covered by this Array");
226 // Must read this exactly once because it can be modified by parallel
227 // allocation.
228 HeapWord* ub = _unallocated_block;
229 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
230 assert(ub < _end, "tautology (see above)");
231 return ub;
232 }
233 // Otherwise, find the block start using the table.
234 HeapWord* q = block_at_or_preceding(addr, false, 0);
235 HeapWord* n = q + block_size(q);
236 return forward_to_block_containing_addr_const(q, n, addr);
237 }
238
239
240 HeapWord*
241 G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,
242 HeapWord* n,
243 const void* addr) {
244 // We're not in the normal case. We need to handle an important subcase
245 // here: LAB allocation. An allocation previously recorded in the
246 // offset table was actually a lab allocation, and was divided into
247 // several objects subsequently. Fix this situation as we answer the
248 // query, by updating entries as we cross them.
249
250 // If the fist object's end q is at the card boundary. Start refining
251 // with the corresponding card (the value of the entry will be basically
252 // set to 0). If the object crosses the boundary -- start from the next card.
253 size_t n_index = _array->index_for(n);
254 size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n);
255 // Calculate a consistent next boundary. If "n" is not at the boundary
256 // already, step to the boundary.
257 HeapWord* next_boundary = _array->address_for_index(n_index) +
258 (n_index == next_index ? 0 : N_words);
259 assert(next_boundary <= _array->_end,
260 err_msg("next_boundary is beyond the end of the covered region "
261 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
262 p2i(next_boundary), p2i(_array->_end)));
263 if (addr >= gsp()->top()) return gsp()->top();
264 while (next_boundary < addr) {
265 while (n <= next_boundary) {
266 q = n;
267 oop obj = oop(q);
268 if (obj->klass_or_null() == NULL) return q;
269 n += block_size(q);
270 }
271 assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
272 // [q, n) is the block that crosses the boundary.
273 alloc_block_work2(&next_boundary, &next_index, q, n);
274 }
275 return forward_to_block_containing_addr_const(q, n, addr);
276 }
277
278 // Note that the committed size of the covered space may have changed,
279 // so the table size might also wish to change.
280 void G1BlockOffsetArray::resize(size_t new_word_size) {
281 HeapWord* new_end = _bottom + new_word_size;
282 _end = new_end; // update _end
283 }
284
285 //
286 // threshold_
287 // | _index_
288 // v v
289 // +-------+-------+-------+-------+-------+
290 // | i-1 | i | i+1 | i+2 | i+3 |
291 // +-------+-------+-------+-------+-------+
292 // ( ^ ]
293 // block-start
294 //
295 void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_,
296 HeapWord* blk_start, HeapWord* blk_end) {
297 // For efficiency, do copy-in/copy-out.
298 HeapWord* threshold = *threshold_;
299 size_t index = *index_;
300
301 assert(blk_start != NULL && blk_end > blk_start,
302 "phantom block");
303 assert(blk_end > threshold, "should be past threshold");
304 assert(blk_start <= threshold, "blk_start should be at or before threshold");
305 assert(pointer_delta(threshold, blk_start) <= N_words,
306 "offset should be <= BlockOffsetSharedArray::N");
307 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
308 "reference must be into the heap");
309 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
310 "limit must be within the heap");
311 assert(threshold == _array->_reserved.start() + index*N_words,
312 "index must agree with threshold");
313
314 DEBUG_ONLY(size_t orig_index = index;)
315
316 // Mark the card that holds the offset into the block. Note
317 // that _next_offset_index and _next_offset_threshold are not
318 // updated until the end of this method.
319 _array->set_offset_array(index, threshold, blk_start);
320
321 // We need to now mark the subsequent cards that this blk spans.
322
323 // Index of card on which blk ends.
324 size_t end_index = _array->index_for(blk_end - 1);
325
326 // Are there more cards left to be updated?
327 if (index + 1 <= end_index) {
328 HeapWord* rem_st = _array->address_for_index(index + 1);
329 // Calculate rem_end this way because end_index
330 // may be the last valid index in the covered region.
331 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
332 set_remainder_to_point_to_start(rem_st, rem_end);
333 }
334
335 index = end_index + 1;
336 // Calculate threshold_ this way because end_index
337 // may be the last valid index in the covered region.
338 threshold = _array->address_for_index(end_index) + N_words;
339 assert(threshold >= blk_end, "Incorrect offset threshold");
340
341 // index_ and threshold_ updated here.
342 *threshold_ = threshold;
343 *index_ = index;
344
345 #ifdef ASSERT
346 // The offset can be 0 if the block starts on a boundary. That
347 // is checked by an assertion above.
348 size_t start_index = _array->index_for(blk_start);
349 HeapWord* boundary = _array->address_for_index(start_index);
350 assert((_array->offset_array(orig_index) == 0 &&
351 blk_start == boundary) ||
352 (_array->offset_array(orig_index) > 0 &&
353 _array->offset_array(orig_index) <= N_words),
354 err_msg("offset array should have been set - "
355 "orig_index offset: %u, "
356 "blk_start: " PTR_FORMAT ", "
357 "boundary: " PTR_FORMAT,
358 (uint)_array->offset_array(orig_index),
359 p2i(blk_start), p2i(boundary)));
360 for (size_t j = orig_index + 1; j <= end_index; j++) {
361 assert(_array->offset_array(j) > 0 &&
362 _array->offset_array(j) <=
363 (u_char) (N_words+BlockOffsetArray::N_powers-1),
364 err_msg("offset array should have been set - "
365 "%u not > 0 OR %u not <= %u",
366 (uint) _array->offset_array(j),
367 (uint) _array->offset_array(j),
368 (uint) (N_words+BlockOffsetArray::N_powers-1)));
369 }
370 #endif
371 }
372
373 void G1BlockOffsetArray::verify() const {
374 assert(gsp()->bottom() < gsp()->top(), "Only non-empty regions should be verified.");
375 size_t start_card = _array->index_for(gsp()->bottom());
376 size_t end_card = _array->index_for(gsp()->top() - 1);
377
378 for (size_t current_card = start_card; current_card < end_card; current_card++) {
379 u_char entry = _array->offset_array(current_card);
380 if (entry < N_words) {
381 // The entry should point to an object before the current card. Verify that
382 // it is possible to walk from that object in to the current card by just
383 // iterating over the objects following it.
384 HeapWord* card_address = _array->address_for_index(current_card);
385 HeapWord* obj_end = card_address - entry;
386 while (obj_end < card_address) {
387 HeapWord* obj = obj_end;
388 size_t obj_size = block_size(obj);
389 obj_end = obj + obj_size;
390 guarantee(obj_end > obj && obj_end <= gsp()->top(),
391 err_msg("Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
392 p2i(obj), obj_size, p2i(obj_end), p2i(gsp()->top())));
393 }
394 } else {
395 // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
396 // We need to make sure that we are going backwards and that we don't pass the start of the
397 // corresponding heap region. But that is about all we can verify.
398 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
399 guarantee(backskip >= 1, "Must be going back at least one card.");
400
401 size_t max_backskip = current_card - start_card;
402 guarantee(backskip <= max_backskip,
403 err_msg("Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
404 start_card, current_card, backskip));
405
406 HeapWord* backskip_address = _array->address_for_index(current_card - backskip);
407 guarantee(backskip_address >= gsp()->bottom(),
408 err_msg("Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
409 p2i(gsp()->bottom()), p2i(backskip_address)));
410 }
411 }
412 }
413
414 #ifndef PRODUCT
415 void
416 G1BlockOffsetArray::print_on(outputStream* out) {
417 size_t from_index = _array->index_for(_bottom);
418 size_t to_index = _array->index_for(_end);
419 out->print_cr(">> BOT for area ["PTR_FORMAT","PTR_FORMAT") "
420 "cards ["SIZE_FORMAT","SIZE_FORMAT")",
421 p2i(_bottom), p2i(_end), from_index, to_index);
422 for (size_t i = from_index; i < to_index; ++i) {
423 out->print_cr(" entry "SIZE_FORMAT_W(8)" | "PTR_FORMAT" : %3u",
424 i, p2i(_array->address_for_index(i)),
425 (uint) _array->offset_array(i));
426 }
427 }
428 #endif // !PRODUCT
429
430 //////////////////////////////////////////////////////////////////////
431 // G1BlockOffsetArrayContigSpace
432 //////////////////////////////////////////////////////////////////////
433
434 HeapWord*
435 G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) {
436 assert(_bottom <= addr && addr < _end,
437 "addr must be covered by this Array");
438 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
439 return forward_to_block_containing_addr(q, addr);
440 }
441
442 HeapWord*
443 G1BlockOffsetArrayContigSpace::
444 block_start_unsafe_const(const void* addr) const {
445 assert(_bottom <= addr && addr < _end,
446 "addr must be covered by this Array");
447 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
448 HeapWord* n = q + block_size(q);
449 return forward_to_block_containing_addr_const(q, n, addr);
450 }
451
452 G1BlockOffsetArrayContigSpace::
453 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
454 MemRegion mr) :
455 G1BlockOffsetArray(array, mr)
456 {
457 _next_offset_threshold = NULL;
458 _next_offset_index = 0;
459 }
460
461 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold_raw() {
462 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
463 "just checking");
464 _next_offset_index = _array->index_for_raw(_bottom);
465 _next_offset_index++;
466 _next_offset_threshold =
467 _array->address_for_index_raw(_next_offset_index);
468 return _next_offset_threshold;
469 }
470
471 void G1BlockOffsetArrayContigSpace::zero_bottom_entry_raw() {
472 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
473 "just checking");
474 size_t bottom_index = _array->index_for_raw(_bottom);
475 assert(_array->address_for_index_raw(bottom_index) == _bottom,
476 "Precondition of call");
477 _array->set_offset_array_raw(bottom_index, 0);
478 }
479
480 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
481 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
482 "just checking");
483 _next_offset_index = _array->index_for(_bottom);
484 _next_offset_index++;
485 _next_offset_threshold =
486 _array->address_for_index(_next_offset_index);
487 return _next_offset_threshold;
488 }
489
490 void
491 G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* new_top) {
492 assert(new_top <= _end, "_end should have already been updated");
493
494 // The first BOT entry should have offset 0.
495 reset_bot();
496 alloc_block(_bottom, new_top);
497 }
498
499 #ifndef PRODUCT
500 void
501 G1BlockOffsetArrayContigSpace::print_on(outputStream* out) {
502 G1BlockOffsetArray::print_on(out);
503 out->print_cr(" next offset threshold: "PTR_FORMAT, p2i(_next_offset_threshold));
504 out->print_cr(" next offset index: "SIZE_FORMAT, _next_offset_index);
505 }
506 #endif // !PRODUCT