1 /*
2 * Copyright (c) 2000, 2013, 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_interface/collectedHeap.inline.hpp"
27 #include "memory/blockOffsetTable.inline.hpp"
28 #include "memory/iterator.hpp"
29 #include "memory/space.inline.hpp"
30 #include "memory/universe.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/java.hpp"
33 #include "services/memTracker.hpp"
34
35 //////////////////////////////////////////////////////////////////////
36 // BlockOffsetSharedArray
37 //////////////////////////////////////////////////////////////////////
38
39 BlockOffsetSharedArray::BlockOffsetSharedArray(MemRegion reserved,
40 size_t init_word_size):
41 _reserved(reserved), _end(NULL)
42 {
43 size_t size = compute_size(reserved.word_size());
44 ReservedSpace rs(size);
45 if (!rs.is_reserved()) {
46 vm_exit_during_initialization("Could not reserve enough space for heap offset array");
47 }
48
49 NMTTrackOp op(NMTTrackOp::TypeOp);
50 op.execute_op((address)rs.base(), 0, mtGC);
51
52 if (!_vs.initialize(rs, 0)) {
53 vm_exit_during_initialization("Could not reserve enough space for heap offset array");
54 }
55 _offset_array = (u_char*)_vs.low_boundary();
56 resize(init_word_size);
57 if (TraceBlockOffsetTable) {
58 gclog_or_tty->print_cr("BlockOffsetSharedArray::BlockOffsetSharedArray: ");
59 gclog_or_tty->print_cr(" "
60 " rs.base(): " INTPTR_FORMAT
61 " rs.size(): " INTPTR_FORMAT
62 " rs end(): " INTPTR_FORMAT,
63 rs.base(), rs.size(), rs.base() + rs.size());
64 gclog_or_tty->print_cr(" "
65 " _vs.low_boundary(): " INTPTR_FORMAT
66 " _vs.high_boundary(): " INTPTR_FORMAT,
67 _vs.low_boundary(),
68 _vs.high_boundary());
69 }
70 }
71
72 void BlockOffsetSharedArray::resize(size_t new_word_size) {
73 assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved");
74 size_t new_size = compute_size(new_word_size);
75 size_t old_size = _vs.committed_size();
76 size_t delta;
77 char* high = _vs.high();
78 _end = _reserved.start() + new_word_size;
79 if (new_size > old_size) {
80 delta = ReservedSpace::page_align_size_up(new_size - old_size);
81 assert(delta > 0, "just checking");
82 if (!_vs.expand_by(delta)) {
83 // Do better than this for Merlin
84 vm_exit_out_of_memory(delta, OOM_MMAP_ERROR, "offset table expansion");
85 }
86 assert(_vs.high() == high + delta, "invalid expansion");
87 } else {
88 delta = ReservedSpace::page_align_size_down(old_size - new_size);
89 if (delta == 0) return;
90 _vs.shrink_by(delta);
91 assert(_vs.high() == high - delta, "invalid expansion");
92 }
93 }
94
95 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
96 assert(p >= _reserved.start(), "just checking");
97 size_t delta = pointer_delta(p, _reserved.start());
98 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
99 }
100
101
102 //////////////////////////////////////////////////////////////////////
103 // BlockOffsetArray
104 //////////////////////////////////////////////////////////////////////
105
106 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
107 MemRegion mr, bool init_to_zero_) :
108 BlockOffsetTable(mr.start(), mr.end()),
109 _array(array)
110 {
111 assert(_bottom <= _end, "arguments out of order");
112 set_init_to_zero(init_to_zero_);
113 if (!init_to_zero_) {
114 // initialize cards to point back to mr.start()
115 set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
116 _array->set_offset_array(0, 0); // set first card to 0
117 }
118 }
119
120
121 // The arguments follow the normal convention of denoting
122 // a right-open interval: [start, end)
123 void
124 BlockOffsetArray::
125 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) {
126
127 check_reducing_assertion(reducing);
128 if (start >= end) {
129 // The start address is equal to the end address (or to
130 // the right of the end address) so there are not cards
131 // that need to be updated..
132 return;
133 }
134
135 // Write the backskip value for each region.
136 //
137 // offset
138 // card 2nd 3rd
139 // | +- 1st | |
140 // v v v v
141 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
142 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
143 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
144 // 11 19 75
145 // 12
146 //
147 // offset card is the card that points to the start of an object
148 // x - offset value of offset card
149 // 1st - start of first logarithmic region
150 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
151 // 2nd - start of second logarithmic region
152 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
153 // 3rd - start of third logarithmic region
154 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
155 //
156 // integer below the block offset entry is an example of
157 // the index of the entry
158 //
159 // Given an address,
160 // Find the index for the address
161 // Find the block offset table entry
162 // Convert the entry to a back slide
163 // (e.g., with today's, offset = 0x81 =>
164 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
165 // Move back N (e.g., 8) entries and repeat with the
166 // value of the new entry
167 //
168 size_t start_card = _array->index_for(start);
169 size_t end_card = _array->index_for(end-1);
170 assert(start ==_array->address_for_index(start_card), "Precondition");
171 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
172 set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval
173 }
174
175
176 // Unlike the normal convention in this code, the argument here denotes
177 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
178 // above.
179 void
180 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) {
181
182 check_reducing_assertion(reducing);
183 if (start_card > end_card) {
184 return;
185 }
186 assert(start_card > _array->index_for(_bottom), "Cannot be first card");
187 assert(_array->offset_array(start_card-1) <= N_words,
188 "Offset card has an unexpected value");
189 size_t start_card_for_region = start_card;
190 u_char offset = max_jubyte;
191 for (int i = 0; i < N_powers; i++) {
192 // -1 so that the the card with the actual offset is counted. Another -1
193 // so that the reach ends in this region and not at the start
194 // of the next.
195 size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1);
196 offset = N_words + i;
197 if (reach >= end_card) {
198 _array->set_offset_array(start_card_for_region, end_card, offset, reducing);
199 start_card_for_region = reach + 1;
200 break;
201 }
202 _array->set_offset_array(start_card_for_region, reach, offset, reducing);
203 start_card_for_region = reach + 1;
204 }
205 assert(start_card_for_region > end_card, "Sanity check");
206 DEBUG_ONLY(check_all_cards(start_card, end_card);)
207 }
208
209 // The card-interval [start_card, end_card] is a closed interval; this
210 // is an expensive check -- use with care and only under protection of
211 // suitable flag.
212 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
213
214 if (end_card < start_card) {
215 return;
216 }
217 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
218 u_char last_entry = N_words;
219 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
220 u_char entry = _array->offset_array(c);
221 guarantee(entry >= last_entry, "Monotonicity");
222 if (c - start_card > power_to_cards_back(1)) {
223 guarantee(entry > N_words, "Should be in logarithmic region");
224 }
225 size_t backskip = entry_to_cards_back(entry);
226 size_t landing_card = c - backskip;
227 guarantee(landing_card >= (start_card - 1), "Inv");
228 if (landing_card >= start_card) {
229 guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity");
230 } else {
231 guarantee(landing_card == (start_card - 1), "Tautology");
232 // Note that N_words is the maximum offset value
233 guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");
234 }
235 last_entry = entry; // remember for monotonicity test
236 }
237 }
238
239
240 void
241 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
242 assert(blk_start != NULL && blk_end > blk_start,
243 "phantom block");
244 single_block(blk_start, blk_end);
245 }
246
247 // Action_mark - update the BOT for the block [blk_start, blk_end).
248 // Current typical use is for splitting a block.
249 // Action_single - udpate the BOT for an allocation.
250 // Action_verify - BOT verification.
251 void
252 BlockOffsetArray::do_block_internal(HeapWord* blk_start,
253 HeapWord* blk_end,
254 Action action, bool reducing) {
255 assert(Universe::heap()->is_in_reserved(blk_start),
256 "reference must be into the heap");
257 assert(Universe::heap()->is_in_reserved(blk_end-1),
258 "limit must be within the heap");
259 // This is optimized to make the test fast, assuming we only rarely
260 // cross boundaries.
261 uintptr_t end_ui = (uintptr_t)(blk_end - 1);
262 uintptr_t start_ui = (uintptr_t)blk_start;
263 // Calculate the last card boundary preceding end of blk
264 intptr_t boundary_before_end = (intptr_t)end_ui;
265 clear_bits(boundary_before_end, right_n_bits(LogN));
266 if (start_ui <= (uintptr_t)boundary_before_end) {
267 // blk starts at or crosses a boundary
268 // Calculate index of card on which blk begins
269 size_t start_index = _array->index_for(blk_start);
270 // Index of card on which blk ends
271 size_t end_index = _array->index_for(blk_end - 1);
272 // Start address of card on which blk begins
273 HeapWord* boundary = _array->address_for_index(start_index);
274 assert(boundary <= blk_start, "blk should start at or after boundary");
275 if (blk_start != boundary) {
276 // blk starts strictly after boundary
277 // adjust card boundary and start_index forward to next card
278 boundary += N_words;
279 start_index++;
280 }
281 assert(start_index <= end_index, "monotonicity of index_for()");
282 assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
283 switch (action) {
284 case Action_mark: {
285 if (init_to_zero()) {
286 _array->set_offset_array(start_index, boundary, blk_start, reducing);
287 break;
288 } // Else fall through to the next case
289 }
290 case Action_single: {
291 _array->set_offset_array(start_index, boundary, blk_start, reducing);
292 // We have finished marking the "offset card". We need to now
293 // mark the subsequent cards that this blk spans.
294 if (start_index < end_index) {
295 HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
296 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
297 set_remainder_to_point_to_start(rem_st, rem_end, reducing);
298 }
299 break;
300 }
301 case Action_check: {
302 _array->check_offset_array(start_index, boundary, blk_start);
303 // We have finished checking the "offset card". We need to now
304 // check the subsequent cards that this blk spans.
305 check_all_cards(start_index + 1, end_index);
306 break;
307 }
308 default:
309 ShouldNotReachHere();
310 }
311 }
312 }
313
314 // The range [blk_start, blk_end) represents a single contiguous block
315 // of storage; modify the block offset table to represent this
316 // information; Right-open interval: [blk_start, blk_end)
317 // NOTE: this method does _not_ adjust _unallocated_block.
318 void
319 BlockOffsetArray::single_block(HeapWord* blk_start,
320 HeapWord* blk_end) {
321 do_block_internal(blk_start, blk_end, Action_single);
322 }
323
324 void BlockOffsetArray::verify() const {
325 // For each entry in the block offset table, verify that
326 // the entry correctly finds the start of an object at the
327 // first address covered by the block or to the left of that
328 // first address.
329
330 size_t next_index = 1;
331 size_t last_index = last_active_index();
332
333 // Use for debugging. Initialize to NULL to distinguish the
334 // first iteration through the while loop.
335 HeapWord* last_p = NULL;
336 HeapWord* last_start = NULL;
337 oop last_o = NULL;
338
339 while (next_index <= last_index) {
340 // Use an address past the start of the address for
341 // the entry.
342 HeapWord* p = _array->address_for_index(next_index) + 1;
343 if (p >= _end) {
344 // That's all of the allocated block table.
345 return;
346 }
347 // block_start() asserts that start <= p.
348 HeapWord* start = block_start(p);
349 // First check if the start is an allocated block and only
350 // then if it is a valid object.
351 oop o = oop(start);
352 assert(!Universe::is_fully_initialized() ||
353 _sp->is_free_block(start) ||
354 o->is_oop_or_null(), "Bad object was found");
355 next_index++;
356 last_p = p;
357 last_start = start;
358 last_o = o;
359 }
360 }
361
362 //////////////////////////////////////////////////////////////////////
363 // BlockOffsetArrayNonContigSpace
364 //////////////////////////////////////////////////////////////////////
365
366 // The block [blk_start, blk_end) has been allocated;
367 // adjust the block offset table to represent this information;
368 // NOTE: Clients of BlockOffsetArrayNonContigSpace: consider using
369 // the somewhat more lightweight split_block() or
370 // (when init_to_zero()) mark_block() wherever possible.
371 // right-open interval: [blk_start, blk_end)
372 void
373 BlockOffsetArrayNonContigSpace::alloc_block(HeapWord* blk_start,
374 HeapWord* blk_end) {
375 assert(blk_start != NULL && blk_end > blk_start,
376 "phantom block");
377 single_block(blk_start, blk_end);
378 allocated(blk_start, blk_end);
379 }
380
381 // Adjust BOT to show that a previously whole block has been split
382 // into two. We verify the BOT for the first part (prefix) and
383 // update the BOT for the second part (suffix).
384 // blk is the start of the block
385 // blk_size is the size of the original block
386 // left_blk_size is the size of the first part of the split
387 void BlockOffsetArrayNonContigSpace::split_block(HeapWord* blk,
388 size_t blk_size,
389 size_t left_blk_size) {
390 // Verify that the BOT shows [blk, blk + blk_size) to be one block.
391 verify_single_block(blk, blk_size);
392 // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size)
393 // is one single block.
394 assert(blk_size > 0, "Should be positive");
395 assert(left_blk_size > 0, "Should be positive");
396 assert(left_blk_size < blk_size, "Not a split");
397
398 // Start addresses of prefix block and suffix block.
399 HeapWord* pref_addr = blk;
400 HeapWord* suff_addr = blk + left_blk_size;
401 HeapWord* end_addr = blk + blk_size;
402
403 // Indices for starts of prefix block and suffix block.
404 size_t pref_index = _array->index_for(pref_addr);
405 if (_array->address_for_index(pref_index) != pref_addr) {
406 // pref_addr does not begin pref_index
407 pref_index++;
408 }
409
410 size_t suff_index = _array->index_for(suff_addr);
411 if (_array->address_for_index(suff_index) != suff_addr) {
412 // suff_addr does not begin suff_index
413 suff_index++;
414 }
415
416 // Definition: A block B, denoted [B_start, B_end) __starts__
417 // a card C, denoted [C_start, C_end), where C_start and C_end
418 // are the heap addresses that card C covers, iff
419 // B_start <= C_start < B_end.
420 //
421 // We say that a card C "is started by" a block B, iff
422 // B "starts" C.
423 //
424 // Note that the cardinality of the set of cards {C}
425 // started by a block B can be 0, 1, or more.
426 //
427 // Below, pref_index and suff_index are, respectively, the
428 // first (least) card indices that the prefix and suffix of
429 // the split start; end_index is one more than the index of
430 // the last (greatest) card that blk starts.
431 size_t end_index = _array->index_for(end_addr - 1) + 1;
432
433 // Calculate the # cards that the prefix and suffix affect.
434 size_t num_pref_cards = suff_index - pref_index;
435
436 size_t num_suff_cards = end_index - suff_index;
437 // Change the cards that need changing
438 if (num_suff_cards > 0) {
439 HeapWord* boundary = _array->address_for_index(suff_index);
440 // Set the offset card for suffix block
441 _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */);
442 // Change any further cards that need changing in the suffix
443 if (num_pref_cards > 0) {
444 if (num_pref_cards >= num_suff_cards) {
445 // Unilaterally fix all of the suffix cards: closed card
446 // index interval in args below.
447 set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */);
448 } else {
449 // Unilaterally fix the first (num_pref_cards - 1) following
450 // the "offset card" in the suffix block.
451 set_remainder_to_point_to_start_incl(suff_index + 1,
452 suff_index + num_pref_cards - 1, true /* reducing */);
453 // Fix the appropriate cards in the remainder of the
454 // suffix block -- these are the last num_pref_cards
455 // cards in each power block of the "new" range plumbed
456 // from suff_addr.
457 bool more = true;
458 uint i = 1;
459 while (more && (i < N_powers)) {
460 size_t back_by = power_to_cards_back(i);
461 size_t right_index = suff_index + back_by - 1;
462 size_t left_index = right_index - num_pref_cards + 1;
463 if (right_index >= end_index - 1) { // last iteration
464 right_index = end_index - 1;
465 more = false;
466 }
467 if (back_by > num_pref_cards) {
468 // Fill in the remainder of this "power block", if it
469 // is non-null.
470 if (left_index <= right_index) {
471 _array->set_offset_array(left_index, right_index,
472 N_words + i - 1, true /* reducing */);
473 } else {
474 more = false; // we are done
475 }
476 i++;
477 break;
478 }
479 i++;
480 }
481 while (more && (i < N_powers)) {
482 size_t back_by = power_to_cards_back(i);
483 size_t right_index = suff_index + back_by - 1;
484 size_t left_index = right_index - num_pref_cards + 1;
485 if (right_index >= end_index - 1) { // last iteration
486 right_index = end_index - 1;
487 if (left_index > right_index) {
488 break;
489 }
490 more = false;
491 }
492 assert(left_index <= right_index, "Error");
493 _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */);
494 i++;
495 }
496 }
497 } // else no more cards to fix in suffix
498 } // else nothing needs to be done
499 // Verify that we did the right thing
500 verify_single_block(pref_addr, left_blk_size);
501 verify_single_block(suff_addr, blk_size - left_blk_size);
502 }
503
504
505 // Mark the BOT such that if [blk_start, blk_end) straddles a card
506 // boundary, the card following the first such boundary is marked
507 // with the appropriate offset.
508 // NOTE: this method does _not_ adjust _unallocated_block or
509 // any cards subsequent to the first one.
510 void
511 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start,
512 HeapWord* blk_end, bool reducing) {
513 do_block_internal(blk_start, blk_end, Action_mark, reducing);
514 }
515
516 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe(
517 const void* addr) const {
518 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
519 assert(_bottom <= addr && addr < _end,
520 "addr must be covered by this Array");
521 // Must read this exactly once because it can be modified by parallel
522 // allocation.
523 HeapWord* ub = _unallocated_block;
524 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
525 assert(ub < _end, "tautology (see above)");
526 return ub;
527 }
528
529 // Otherwise, find the block start using the table.
530 size_t index = _array->index_for(addr);
531 HeapWord* q = _array->address_for_index(index);
532
533 uint offset = _array->offset_array(index); // Extend u_char to uint.
534 while (offset >= N_words) {
535 // The excess of the offset from N_words indicates a power of Base
536 // to go back by.
537 size_t n_cards_back = entry_to_cards_back(offset);
538 q -= (N_words * n_cards_back);
539 assert(q >= _sp->bottom(),
540 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
541 q, _sp->bottom()));
542 assert(q < _sp->end(),
543 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
544 q, _sp->end()));
545 index -= n_cards_back;
546 offset = _array->offset_array(index);
547 }
548 assert(offset < N_words, "offset too large");
549 index--;
550 q -= offset;
551 assert(q >= _sp->bottom(),
552 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
553 q, _sp->bottom()));
554 assert(q < _sp->end(),
555 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
556 q, _sp->end()));
557 HeapWord* n = q;
558
559 while (n <= addr) {
560 debug_only(HeapWord* last = q); // for debugging
561 q = n;
562 n += _sp->block_size(n);
563 assert(n > q,
564 err_msg("Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT","
565 " while querying blk_start(" PTR_FORMAT ")"
566 " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")",
567 n, last, addr, _sp->bottom(), _sp->end()));
568 }
569 assert(q <= addr,
570 err_msg("wrong order for current (" INTPTR_FORMAT ")" " <= arg (" INTPTR_FORMAT ")",
571 q, addr));
572 assert(addr <= n,
573 err_msg("wrong order for arg (" INTPTR_FORMAT ") <= next (" INTPTR_FORMAT ")",
574 addr, n));
575 return q;
576 }
577
578 HeapWord* BlockOffsetArrayNonContigSpace::block_start_careful(
579 const void* addr) const {
580 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
581
582 assert(_bottom <= addr && addr < _end,
583 "addr must be covered by this Array");
584 // Must read this exactly once because it can be modified by parallel
585 // allocation.
586 HeapWord* ub = _unallocated_block;
587 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
588 assert(ub < _end, "tautology (see above)");
589 return ub;
590 }
591
592 // Otherwise, find the block start using the table, but taking
593 // care (cf block_start_unsafe() above) not to parse any objects/blocks
594 // on the cards themsleves.
595 size_t index = _array->index_for(addr);
596 assert(_array->address_for_index(index) == addr,
597 "arg should be start of card");
598
599 HeapWord* q = (HeapWord*)addr;
600 uint offset;
601 do {
602 offset = _array->offset_array(index);
603 if (offset < N_words) {
604 q -= offset;
605 } else {
606 size_t n_cards_back = entry_to_cards_back(offset);
607 q -= (n_cards_back * N_words);
608 index -= n_cards_back;
609 }
610 } while (offset >= N_words);
611 assert(q <= addr, "block start should be to left of arg");
612 return q;
613 }
614
615 #ifndef PRODUCT
616 // Verification & debugging - ensure that the offset table reflects the fact
617 // that the block [blk_start, blk_end) or [blk, blk + size) is a
618 // single block of storage. NOTE: can't const this because of
619 // call to non-const do_block_internal() below.
620 void BlockOffsetArrayNonContigSpace::verify_single_block(
621 HeapWord* blk_start, HeapWord* blk_end) {
622 if (VerifyBlockOffsetArray) {
623 do_block_internal(blk_start, blk_end, Action_check);
624 }
625 }
626
627 void BlockOffsetArrayNonContigSpace::verify_single_block(
628 HeapWord* blk, size_t size) {
629 verify_single_block(blk, blk + size);
630 }
631
632 // Verify that the given block is before _unallocated_block
633 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
634 HeapWord* blk_start, HeapWord* blk_end) const {
635 if (BlockOffsetArrayUseUnallocatedBlock) {
636 assert(blk_start < blk_end, "Block inconsistency?");
637 assert(blk_end <= _unallocated_block, "_unallocated_block problem");
638 }
639 }
640
641 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
642 HeapWord* blk, size_t size) const {
643 verify_not_unallocated(blk, blk + size);
644 }
645 #endif // PRODUCT
646
647 size_t BlockOffsetArrayNonContigSpace::last_active_index() const {
648 if (_unallocated_block == _bottom) {
649 return 0;
650 } else {
651 return _array->index_for(_unallocated_block - 1);
652 }
653 }
654
655 //////////////////////////////////////////////////////////////////////
656 // BlockOffsetArrayContigSpace
657 //////////////////////////////////////////////////////////////////////
658
659 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const {
660 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
661
662 // Otherwise, find the block start using the table.
663 assert(_bottom <= addr && addr < _end,
664 "addr must be covered by this Array");
665 size_t index = _array->index_for(addr);
666 // We must make sure that the offset table entry we use is valid. If
667 // "addr" is past the end, start at the last known one and go forward.
668 index = MIN2(index, _next_offset_index-1);
669 HeapWord* q = _array->address_for_index(index);
670
671 uint offset = _array->offset_array(index); // Extend u_char to uint.
672 while (offset > N_words) {
673 // The excess of the offset from N_words indicates a power of Base
674 // to go back by.
675 size_t n_cards_back = entry_to_cards_back(offset);
676 q -= (N_words * n_cards_back);
677 assert(q >= _sp->bottom(), "Went below bottom!");
678 index -= n_cards_back;
679 offset = _array->offset_array(index);
680 }
681 while (offset == N_words) {
682 assert(q >= _sp->bottom(), "Went below bottom!");
683 q -= N_words;
684 index--;
685 offset = _array->offset_array(index);
686 }
687 assert(offset < N_words, "offset too large");
688 q -= offset;
689 HeapWord* n = q;
690
691 while (n <= addr) {
692 debug_only(HeapWord* last = q); // for debugging
693 q = n;
694 n += _sp->block_size(n);
695 }
696 assert(q <= addr, "wrong order for current and arg");
697 assert(addr <= n, "wrong order for arg and next");
698 return q;
699 }
700
701 //
702 // _next_offset_threshold
703 // | _next_offset_index
704 // v v
705 // +-------+-------+-------+-------+-------+
706 // | i-1 | i | i+1 | i+2 | i+3 |
707 // +-------+-------+-------+-------+-------+
708 // ( ^ ]
709 // block-start
710 //
711
712 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start,
713 HeapWord* blk_end) {
714 assert(blk_start != NULL && blk_end > blk_start,
715 "phantom block");
716 assert(blk_end > _next_offset_threshold,
717 "should be past threshold");
718 assert(blk_start <= _next_offset_threshold,
719 "blk_start should be at or before threshold");
720 assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words,
721 "offset should be <= BlockOffsetSharedArray::N");
722 assert(Universe::heap()->is_in_reserved(blk_start),
723 "reference must be into the heap");
724 assert(Universe::heap()->is_in_reserved(blk_end-1),
725 "limit must be within the heap");
726 assert(_next_offset_threshold ==
727 _array->_reserved.start() + _next_offset_index*N_words,
728 "index must agree with threshold");
729
730 debug_only(size_t orig_next_offset_index = _next_offset_index;)
731
732 // Mark the card that holds the offset into the block. Note
733 // that _next_offset_index and _next_offset_threshold are not
734 // updated until the end of this method.
735 _array->set_offset_array(_next_offset_index,
736 _next_offset_threshold,
737 blk_start);
738
739 // We need to now mark the subsequent cards that this blk spans.
740
741 // Index of card on which blk ends.
742 size_t end_index = _array->index_for(blk_end - 1);
743
744 // Are there more cards left to be updated?
745 if (_next_offset_index + 1 <= end_index) {
746 HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1);
747 // Calculate rem_end this way because end_index
748 // may be the last valid index in the covered region.
749 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
750 set_remainder_to_point_to_start(rem_st, rem_end);
751 }
752
753 // _next_offset_index and _next_offset_threshold updated here.
754 _next_offset_index = end_index + 1;
755 // Calculate _next_offset_threshold this way because end_index
756 // may be the last valid index in the covered region.
757 _next_offset_threshold = _array->address_for_index(end_index) + N_words;
758 assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold");
759
760 #ifdef ASSERT
761 // The offset can be 0 if the block starts on a boundary. That
762 // is checked by an assertion above.
763 size_t start_index = _array->index_for(blk_start);
764 HeapWord* boundary = _array->address_for_index(start_index);
765 assert((_array->offset_array(orig_next_offset_index) == 0 &&
766 blk_start == boundary) ||
767 (_array->offset_array(orig_next_offset_index) > 0 &&
768 _array->offset_array(orig_next_offset_index) <= N_words),
769 "offset array should have been set");
770 for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) {
771 assert(_array->offset_array(j) > 0 &&
772 _array->offset_array(j) <= (u_char) (N_words+N_powers-1),
773 "offset array should have been set");
774 }
775 #endif
776 }
777
778 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {
779 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
780 "just checking");
781 _next_offset_index = _array->index_for(_bottom);
782 _next_offset_index++;
783 _next_offset_threshold =
784 _array->address_for_index(_next_offset_index);
785 return _next_offset_threshold;
786 }
787
788 void BlockOffsetArrayContigSpace::zero_bottom_entry() {
789 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
790 "just checking");
791 size_t bottom_index = _array->index_for(_bottom);
792 _array->set_offset_array(bottom_index, 0);
793 }
794
795 size_t BlockOffsetArrayContigSpace::last_active_index() const {
796 size_t result = _next_offset_index - 1;
797 return result >= 0 ? result : 0;
798 }