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src/share/vm/memory/blockOffsetTable.cpp@f258c5828eb8
src/share/vm/memory/blockOffsetTable.cpp
Mon, 29 Apr 2013 16:13:57 -0400
- author
- hseigel
- date
- Mon, 29 Apr 2013 16:13:57 -0400
- changeset 4987
- f258c5828eb8
- parent 4037
- da91efe96a93
- child 4993
- 746b070f5022
- permissions
- -rw-r--r--
8011773: Some tests on Interned String crashed JVM with OOM
Summary: Instead of terminating the VM, throw OutOfMemoryError exceptions.
Reviewed-by: coleenp, dholmes
1 /*
2 * Copyright (c) 2000, 2012, 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 */
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"
35 //////////////////////////////////////////////////////////////////////
36 // BlockOffsetSharedArray
37 //////////////////////////////////////////////////////////////////////
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 }
49 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
51 if (!_vs.initialize(rs, 0)) {
52 vm_exit_during_initialization("Could not reserve enough space for heap offset array");
53 }
54 _offset_array = (u_char*)_vs.low_boundary();
55 resize(init_word_size);
56 if (TraceBlockOffsetTable) {
57 gclog_or_tty->print_cr("BlockOffsetSharedArray::BlockOffsetSharedArray: ");
58 gclog_or_tty->print_cr(" "
59 " rs.base(): " INTPTR_FORMAT
60 " rs.size(): " INTPTR_FORMAT
61 " rs end(): " INTPTR_FORMAT,
62 rs.base(), rs.size(), rs.base() + rs.size());
63 gclog_or_tty->print_cr(" "
64 " _vs.low_boundary(): " INTPTR_FORMAT
65 " _vs.high_boundary(): " INTPTR_FORMAT,
66 _vs.low_boundary(),
67 _vs.high_boundary());
68 }
69 }
71 void BlockOffsetSharedArray::resize(size_t new_word_size) {
72 assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved");
73 size_t new_size = compute_size(new_word_size);
74 size_t old_size = _vs.committed_size();
75 size_t delta;
76 char* high = _vs.high();
77 _end = _reserved.start() + new_word_size;
78 if (new_size > old_size) {
79 delta = ReservedSpace::page_align_size_up(new_size - old_size);
80 assert(delta > 0, "just checking");
81 if (!_vs.expand_by(delta)) {
82 // Do better than this for Merlin
83 vm_exit_out_of_memory(delta, "offset table expansion");
84 }
85 assert(_vs.high() == high + delta, "invalid expansion");
86 } else {
87 delta = ReservedSpace::page_align_size_down(old_size - new_size);
88 if (delta == 0) return;
89 _vs.shrink_by(delta);
90 assert(_vs.high() == high - delta, "invalid expansion");
91 }
92 }
94 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
95 assert(p >= _reserved.start(), "just checking");
96 size_t delta = pointer_delta(p, _reserved.start());
97 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
98 }
101 //////////////////////////////////////////////////////////////////////
102 // BlockOffsetArray
103 //////////////////////////////////////////////////////////////////////
105 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
106 MemRegion mr, bool init_to_zero_) :
107 BlockOffsetTable(mr.start(), mr.end()),
108 _array(array)
109 {
110 assert(_bottom <= _end, "arguments out of order");
111 set_init_to_zero(init_to_zero_);
112 if (!init_to_zero_) {
113 // initialize cards to point back to mr.start()
114 set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
115 _array->set_offset_array(0, 0); // set first card to 0
116 }
117 }
120 // The arguments follow the normal convention of denoting
121 // a right-open interval: [start, end)
122 void
123 BlockOffsetArray::
124 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) {
126 check_reducing_assertion(reducing);
127 if (start >= end) {
128 // The start address is equal to the end address (or to
129 // the right of the end address) so there are not cards
130 // that need to be updated..
131 return;
132 }
134 // Write the backskip value for each region.
135 //
136 // offset
137 // card 2nd 3rd
138 // | +- 1st | |
139 // v v v v
140 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
141 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
142 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
143 // 11 19 75
144 // 12
145 //
146 // offset card is the card that points to the start of an object
147 // x - offset value of offset card
148 // 1st - start of first logarithmic region
149 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
150 // 2nd - start of second logarithmic region
151 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
152 // 3rd - start of third logarithmic region
153 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
154 //
155 // integer below the block offset entry is an example of
156 // the index of the entry
157 //
158 // Given an address,
159 // Find the index for the address
160 // Find the block offset table entry
161 // Convert the entry to a back slide
162 // (e.g., with today's, offset = 0x81 =>
163 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
164 // Move back N (e.g., 8) entries and repeat with the
165 // value of the new entry
166 //
167 size_t start_card = _array->index_for(start);
168 size_t end_card = _array->index_for(end-1);
169 assert(start ==_array->address_for_index(start_card), "Precondition");
170 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
171 set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval
172 }
175 // Unlike the normal convention in this code, the argument here denotes
176 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
177 // above.
178 void
179 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) {
181 check_reducing_assertion(reducing);
182 if (start_card > end_card) {
183 return;
184 }
185 assert(start_card > _array->index_for(_bottom), "Cannot be first card");
186 assert(_array->offset_array(start_card-1) <= N_words,
187 "Offset card has an unexpected value");
188 size_t start_card_for_region = start_card;
189 u_char offset = max_jubyte;
190 for (int i = 0; i < N_powers; i++) {
191 // -1 so that the the card with the actual offset is counted. Another -1
192 // so that the reach ends in this region and not at the start
193 // of the next.
194 size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1);
195 offset = N_words + i;
196 if (reach >= end_card) {
197 _array->set_offset_array(start_card_for_region, end_card, offset, reducing);
198 start_card_for_region = reach + 1;
199 break;
200 }
201 _array->set_offset_array(start_card_for_region, reach, offset, reducing);
202 start_card_for_region = reach + 1;
203 }
204 assert(start_card_for_region > end_card, "Sanity check");
205 DEBUG_ONLY(check_all_cards(start_card, end_card);)
206 }
208 // The card-interval [start_card, end_card] is a closed interval; this
209 // is an expensive check -- use with care and only under protection of
210 // suitable flag.
211 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
213 if (end_card < start_card) {
214 return;
215 }
216 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
217 u_char last_entry = N_words;
218 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
219 u_char entry = _array->offset_array(c);
220 guarantee(entry >= last_entry, "Monotonicity");
221 if (c - start_card > power_to_cards_back(1)) {
222 guarantee(entry > N_words, "Should be in logarithmic region");
223 }
224 size_t backskip = entry_to_cards_back(entry);
225 size_t landing_card = c - backskip;
226 guarantee(landing_card >= (start_card - 1), "Inv");
227 if (landing_card >= start_card) {
228 guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity");
229 } else {
230 guarantee(landing_card == (start_card - 1), "Tautology");
231 // Note that N_words is the maximum offset value
232 guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");
233 }
234 last_entry = entry; // remember for monotonicity test
235 }
236 }
239 void
240 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
241 assert(blk_start != NULL && blk_end > blk_start,
242 "phantom block");
243 single_block(blk_start, blk_end);
244 }
246 // Action_mark - update the BOT for the block [blk_start, blk_end).
247 // Current typical use is for splitting a block.
248 // Action_single - udpate the BOT for an allocation.
249 // Action_verify - BOT verification.
250 void
251 BlockOffsetArray::do_block_internal(HeapWord* blk_start,
252 HeapWord* blk_end,
253 Action action, bool reducing) {
254 assert(Universe::heap()->is_in_reserved(blk_start),
255 "reference must be into the heap");
256 assert(Universe::heap()->is_in_reserved(blk_end-1),
257 "limit must be within the heap");
258 // This is optimized to make the test fast, assuming we only rarely
259 // cross boundaries.
260 uintptr_t end_ui = (uintptr_t)(blk_end - 1);
261 uintptr_t start_ui = (uintptr_t)blk_start;
262 // Calculate the last card boundary preceding end of blk
263 intptr_t boundary_before_end = (intptr_t)end_ui;
264 clear_bits(boundary_before_end, right_n_bits(LogN));
265 if (start_ui <= (uintptr_t)boundary_before_end) {
266 // blk starts at or crosses a boundary
267 // Calculate index of card on which blk begins
268 size_t start_index = _array->index_for(blk_start);
269 // Index of card on which blk ends
270 size_t end_index = _array->index_for(blk_end - 1);
271 // Start address of card on which blk begins
272 HeapWord* boundary = _array->address_for_index(start_index);
273 assert(boundary <= blk_start, "blk should start at or after boundary");
274 if (blk_start != boundary) {
275 // blk starts strictly after boundary
276 // adjust card boundary and start_index forward to next card
277 boundary += N_words;
278 start_index++;
279 }
280 assert(start_index <= end_index, "monotonicity of index_for()");
281 assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
282 switch (action) {
283 case Action_mark: {
284 if (init_to_zero()) {
285 _array->set_offset_array(start_index, boundary, blk_start, reducing);
286 break;
287 } // Else fall through to the next case
288 }
289 case Action_single: {
290 _array->set_offset_array(start_index, boundary, blk_start, reducing);
291 // We have finished marking the "offset card". We need to now
292 // mark the subsequent cards that this blk spans.
293 if (start_index < end_index) {
294 HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
295 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
296 set_remainder_to_point_to_start(rem_st, rem_end, reducing);
297 }
298 break;
299 }
300 case Action_check: {
301 _array->check_offset_array(start_index, boundary, blk_start);
302 // We have finished checking the "offset card". We need to now
303 // check the subsequent cards that this blk spans.
304 check_all_cards(start_index + 1, end_index);
305 break;
306 }
307 default:
308 ShouldNotReachHere();
309 }
310 }
311 }
313 // The range [blk_start, blk_end) represents a single contiguous block
314 // of storage; modify the block offset table to represent this
315 // information; Right-open interval: [blk_start, blk_end)
316 // NOTE: this method does _not_ adjust _unallocated_block.
317 void
318 BlockOffsetArray::single_block(HeapWord* blk_start,
319 HeapWord* blk_end) {
320 do_block_internal(blk_start, blk_end, Action_single);
321 }
323 void BlockOffsetArray::verify() const {
324 // For each entry in the block offset table, verify that
325 // the entry correctly finds the start of an object at the
326 // first address covered by the block or to the left of that
327 // first address.
329 size_t next_index = 1;
330 size_t last_index = last_active_index();
332 // Use for debugging. Initialize to NULL to distinguish the
333 // first iteration through the while loop.
334 HeapWord* last_p = NULL;
335 HeapWord* last_start = NULL;
336 oop last_o = NULL;
338 while (next_index <= last_index) {
339 // Use an address past the start of the address for
340 // the entry.
341 HeapWord* p = _array->address_for_index(next_index) + 1;
342 if (p >= _end) {
343 // That's all of the allocated block table.
344 return;
345 }
346 // block_start() asserts that start <= p.
347 HeapWord* start = block_start(p);
348 // First check if the start is an allocated block and only
349 // then if it is a valid object.
350 oop o = oop(start);
351 assert(!Universe::is_fully_initialized() ||
352 _sp->is_free_block(start) ||
353 o->is_oop_or_null(), "Bad object was found");
354 next_index++;
355 last_p = p;
356 last_start = start;
357 last_o = o;
358 }
359 }
361 //////////////////////////////////////////////////////////////////////
362 // BlockOffsetArrayNonContigSpace
363 //////////////////////////////////////////////////////////////////////
365 // The block [blk_start, blk_end) has been allocated;
366 // adjust the block offset table to represent this information;
367 // NOTE: Clients of BlockOffsetArrayNonContigSpace: consider using
368 // the somewhat more lightweight split_block() or
369 // (when init_to_zero()) mark_block() wherever possible.
370 // right-open interval: [blk_start, blk_end)
371 void
372 BlockOffsetArrayNonContigSpace::alloc_block(HeapWord* blk_start,
373 HeapWord* blk_end) {
374 assert(blk_start != NULL && blk_end > blk_start,
375 "phantom block");
376 single_block(blk_start, blk_end);
377 allocated(blk_start, blk_end);
378 }
380 // Adjust BOT to show that a previously whole block has been split
381 // into two. We verify the BOT for the first part (prefix) and
382 // update the BOT for the second part (suffix).
383 // blk is the start of the block
384 // blk_size is the size of the original block
385 // left_blk_size is the size of the first part of the split
386 void BlockOffsetArrayNonContigSpace::split_block(HeapWord* blk,
387 size_t blk_size,
388 size_t left_blk_size) {
389 // Verify that the BOT shows [blk, blk + blk_size) to be one block.
390 verify_single_block(blk, blk_size);
391 // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size)
392 // is one single block.
393 assert(blk_size > 0, "Should be positive");
394 assert(left_blk_size > 0, "Should be positive");
395 assert(left_blk_size < blk_size, "Not a split");
397 // Start addresses of prefix block and suffix block.
398 HeapWord* pref_addr = blk;
399 HeapWord* suff_addr = blk + left_blk_size;
400 HeapWord* end_addr = blk + blk_size;
402 // Indices for starts of prefix block and suffix block.
403 size_t pref_index = _array->index_for(pref_addr);
404 if (_array->address_for_index(pref_index) != pref_addr) {
405 // pref_addr does not begin pref_index
406 pref_index++;
407 }
409 size_t suff_index = _array->index_for(suff_addr);
410 if (_array->address_for_index(suff_index) != suff_addr) {
411 // suff_addr does not begin suff_index
412 suff_index++;
413 }
415 // Definition: A block B, denoted [B_start, B_end) __starts__
416 // a card C, denoted [C_start, C_end), where C_start and C_end
417 // are the heap addresses that card C covers, iff
418 // B_start <= C_start < B_end.
419 //
420 // We say that a card C "is started by" a block B, iff
421 // B "starts" C.
422 //
423 // Note that the cardinality of the set of cards {C}
424 // started by a block B can be 0, 1, or more.
425 //
426 // Below, pref_index and suff_index are, respectively, the
427 // first (least) card indices that the prefix and suffix of
428 // the split start; end_index is one more than the index of
429 // the last (greatest) card that blk starts.
430 size_t end_index = _array->index_for(end_addr - 1) + 1;
432 // Calculate the # cards that the prefix and suffix affect.
433 size_t num_pref_cards = suff_index - pref_index;
435 size_t num_suff_cards = end_index - suff_index;
436 // Change the cards that need changing
437 if (num_suff_cards > 0) {
438 HeapWord* boundary = _array->address_for_index(suff_index);
439 // Set the offset card for suffix block
440 _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */);
441 // Change any further cards that need changing in the suffix
442 if (num_pref_cards > 0) {
443 if (num_pref_cards >= num_suff_cards) {
444 // Unilaterally fix all of the suffix cards: closed card
445 // index interval in args below.
446 set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */);
447 } else {
448 // Unilaterally fix the first (num_pref_cards - 1) following
449 // the "offset card" in the suffix block.
450 set_remainder_to_point_to_start_incl(suff_index + 1,
451 suff_index + num_pref_cards - 1, true /* reducing */);
452 // Fix the appropriate cards in the remainder of the
453 // suffix block -- these are the last num_pref_cards
454 // cards in each power block of the "new" range plumbed
455 // from suff_addr.
456 bool more = true;
457 uint i = 1;
458 while (more && (i < N_powers)) {
459 size_t back_by = power_to_cards_back(i);
460 size_t right_index = suff_index + back_by - 1;
461 size_t left_index = right_index - num_pref_cards + 1;
462 if (right_index >= end_index - 1) { // last iteration
463 right_index = end_index - 1;
464 more = false;
465 }
466 if (back_by > num_pref_cards) {
467 // Fill in the remainder of this "power block", if it
468 // is non-null.
469 if (left_index <= right_index) {
470 _array->set_offset_array(left_index, right_index,
471 N_words + i - 1, true /* reducing */);
472 } else {
473 more = false; // we are done
474 }
475 i++;
476 break;
477 }
478 i++;
479 }
480 while (more && (i < N_powers)) {
481 size_t back_by = power_to_cards_back(i);
482 size_t right_index = suff_index + back_by - 1;
483 size_t left_index = right_index - num_pref_cards + 1;
484 if (right_index >= end_index - 1) { // last iteration
485 right_index = end_index - 1;
486 if (left_index > right_index) {
487 break;
488 }
489 more = false;
490 }
491 assert(left_index <= right_index, "Error");
492 _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */);
493 i++;
494 }
495 }
496 } // else no more cards to fix in suffix
497 } // else nothing needs to be done
498 // Verify that we did the right thing
499 verify_single_block(pref_addr, left_blk_size);
500 verify_single_block(suff_addr, blk_size - left_blk_size);
501 }
504 // Mark the BOT such that if [blk_start, blk_end) straddles a card
505 // boundary, the card following the first such boundary is marked
506 // with the appropriate offset.
507 // NOTE: this method does _not_ adjust _unallocated_block or
508 // any cards subsequent to the first one.
509 void
510 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start,
511 HeapWord* blk_end, bool reducing) {
512 do_block_internal(blk_start, blk_end, Action_mark, reducing);
513 }
515 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe(
516 const void* addr) const {
517 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
518 assert(_bottom <= addr && addr < _end,
519 "addr must be covered by this Array");
520 // Must read this exactly once because it can be modified by parallel
521 // allocation.
522 HeapWord* ub = _unallocated_block;
523 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
524 assert(ub < _end, "tautology (see above)");
525 return ub;
526 }
528 // Otherwise, find the block start using the table.
529 size_t index = _array->index_for(addr);
530 HeapWord* q = _array->address_for_index(index);
532 uint offset = _array->offset_array(index); // Extend u_char to uint.
533 while (offset >= N_words) {
534 // The excess of the offset from N_words indicates a power of Base
535 // to go back by.
536 size_t n_cards_back = entry_to_cards_back(offset);
537 q -= (N_words * n_cards_back);
538 assert(q >= _sp->bottom(),
539 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
540 q, _sp->bottom()));
541 assert(q < _sp->end(),
542 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
543 q, _sp->end()));
544 index -= n_cards_back;
545 offset = _array->offset_array(index);
546 }
547 assert(offset < N_words, "offset too large");
548 index--;
549 q -= offset;
550 assert(q >= _sp->bottom(),
551 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
552 q, _sp->bottom()));
553 assert(q < _sp->end(),
554 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
555 q, _sp->end()));
556 HeapWord* n = q;
558 while (n <= addr) {
559 debug_only(HeapWord* last = q); // for debugging
560 q = n;
561 n += _sp->block_size(n);
562 assert(n > q,
563 err_msg("Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT","
564 " while querying blk_start(" PTR_FORMAT ")"
565 " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")",
566 n, last, addr, _sp->bottom(), _sp->end()));
567 }
568 assert(q <= addr,
569 err_msg("wrong order for current (" INTPTR_FORMAT ")" " <= arg (" INTPTR_FORMAT ")",
570 q, addr));
571 assert(addr <= n,
572 err_msg("wrong order for arg (" INTPTR_FORMAT ") <= next (" INTPTR_FORMAT ")",
573 addr, n));
574 return q;
575 }
577 HeapWord* BlockOffsetArrayNonContigSpace::block_start_careful(
578 const void* addr) const {
579 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
581 assert(_bottom <= addr && addr < _end,
582 "addr must be covered by this Array");
583 // Must read this exactly once because it can be modified by parallel
584 // allocation.
585 HeapWord* ub = _unallocated_block;
586 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
587 assert(ub < _end, "tautology (see above)");
588 return ub;
589 }
591 // Otherwise, find the block start using the table, but taking
592 // care (cf block_start_unsafe() above) not to parse any objects/blocks
593 // on the cards themsleves.
594 size_t index = _array->index_for(addr);
595 assert(_array->address_for_index(index) == addr,
596 "arg should be start of card");
598 HeapWord* q = (HeapWord*)addr;
599 uint offset;
600 do {
601 offset = _array->offset_array(index);
602 if (offset < N_words) {
603 q -= offset;
604 } else {
605 size_t n_cards_back = entry_to_cards_back(offset);
606 q -= (n_cards_back * N_words);
607 index -= n_cards_back;
608 }
609 } while (offset >= N_words);
610 assert(q <= addr, "block start should be to left of arg");
611 return q;
612 }
614 #ifndef PRODUCT
615 // Verification & debugging - ensure that the offset table reflects the fact
616 // that the block [blk_start, blk_end) or [blk, blk + size) is a
617 // single block of storage. NOTE: can't const this because of
618 // call to non-const do_block_internal() below.
619 void BlockOffsetArrayNonContigSpace::verify_single_block(
620 HeapWord* blk_start, HeapWord* blk_end) {
621 if (VerifyBlockOffsetArray) {
622 do_block_internal(blk_start, blk_end, Action_check);
623 }
624 }
626 void BlockOffsetArrayNonContigSpace::verify_single_block(
627 HeapWord* blk, size_t size) {
628 verify_single_block(blk, blk + size);
629 }
631 // Verify that the given block is before _unallocated_block
632 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
633 HeapWord* blk_start, HeapWord* blk_end) const {
634 if (BlockOffsetArrayUseUnallocatedBlock) {
635 assert(blk_start < blk_end, "Block inconsistency?");
636 assert(blk_end <= _unallocated_block, "_unallocated_block problem");
637 }
638 }
640 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
641 HeapWord* blk, size_t size) const {
642 verify_not_unallocated(blk, blk + size);
643 }
644 #endif // PRODUCT
646 size_t BlockOffsetArrayNonContigSpace::last_active_index() const {
647 if (_unallocated_block == _bottom) {
648 return 0;
649 } else {
650 return _array->index_for(_unallocated_block - 1);
651 }
652 }
654 //////////////////////////////////////////////////////////////////////
655 // BlockOffsetArrayContigSpace
656 //////////////////////////////////////////////////////////////////////
658 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const {
659 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
661 // Otherwise, find the block start using the table.
662 assert(_bottom <= addr && addr < _end,
663 "addr must be covered by this Array");
664 size_t index = _array->index_for(addr);
665 // We must make sure that the offset table entry we use is valid. If
666 // "addr" is past the end, start at the last known one and go forward.
667 index = MIN2(index, _next_offset_index-1);
668 HeapWord* q = _array->address_for_index(index);
670 uint offset = _array->offset_array(index); // Extend u_char to uint.
671 while (offset > N_words) {
672 // The excess of the offset from N_words indicates a power of Base
673 // to go back by.
674 size_t n_cards_back = entry_to_cards_back(offset);
675 q -= (N_words * n_cards_back);
676 assert(q >= _sp->bottom(), "Went below bottom!");
677 index -= n_cards_back;
678 offset = _array->offset_array(index);
679 }
680 while (offset == N_words) {
681 assert(q >= _sp->bottom(), "Went below bottom!");
682 q -= N_words;
683 index--;
684 offset = _array->offset_array(index);
685 }
686 assert(offset < N_words, "offset too large");
687 q -= offset;
688 HeapWord* n = q;
690 while (n <= addr) {
691 debug_only(HeapWord* last = q); // for debugging
692 q = n;
693 n += _sp->block_size(n);
694 }
695 assert(q <= addr, "wrong order for current and arg");
696 assert(addr <= n, "wrong order for arg and next");
697 return q;
698 }
700 //
701 // _next_offset_threshold
702 // | _next_offset_index
703 // v v
704 // +-------+-------+-------+-------+-------+
705 // | i-1 | i | i+1 | i+2 | i+3 |
706 // +-------+-------+-------+-------+-------+
707 // ( ^ ]
708 // block-start
709 //
711 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start,
712 HeapWord* blk_end) {
713 assert(blk_start != NULL && blk_end > blk_start,
714 "phantom block");
715 assert(blk_end > _next_offset_threshold,
716 "should be past threshold");
717 assert(blk_start <= _next_offset_threshold,
718 "blk_start should be at or before threshold");
719 assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words,
720 "offset should be <= BlockOffsetSharedArray::N");
721 assert(Universe::heap()->is_in_reserved(blk_start),
722 "reference must be into the heap");
723 assert(Universe::heap()->is_in_reserved(blk_end-1),
724 "limit must be within the heap");
725 assert(_next_offset_threshold ==
726 _array->_reserved.start() + _next_offset_index*N_words,
727 "index must agree with threshold");
729 debug_only(size_t orig_next_offset_index = _next_offset_index;)
731 // Mark the card that holds the offset into the block. Note
732 // that _next_offset_index and _next_offset_threshold are not
733 // updated until the end of this method.
734 _array->set_offset_array(_next_offset_index,
735 _next_offset_threshold,
736 blk_start);
738 // We need to now mark the subsequent cards that this blk spans.
740 // Index of card on which blk ends.
741 size_t end_index = _array->index_for(blk_end - 1);
743 // Are there more cards left to be updated?
744 if (_next_offset_index + 1 <= end_index) {
745 HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1);
746 // Calculate rem_end this way because end_index
747 // may be the last valid index in the covered region.
748 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
749 set_remainder_to_point_to_start(rem_st, rem_end);
750 }
752 // _next_offset_index and _next_offset_threshold updated here.
753 _next_offset_index = end_index + 1;
754 // Calculate _next_offset_threshold this way because end_index
755 // may be the last valid index in the covered region.
756 _next_offset_threshold = _array->address_for_index(end_index) + N_words;
757 assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold");
759 #ifdef ASSERT
760 // The offset can be 0 if the block starts on a boundary. That
761 // is checked by an assertion above.
762 size_t start_index = _array->index_for(blk_start);
763 HeapWord* boundary = _array->address_for_index(start_index);
764 assert((_array->offset_array(orig_next_offset_index) == 0 &&
765 blk_start == boundary) ||
766 (_array->offset_array(orig_next_offset_index) > 0 &&
767 _array->offset_array(orig_next_offset_index) <= N_words),
768 "offset array should have been set");
769 for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) {
770 assert(_array->offset_array(j) > 0 &&
771 _array->offset_array(j) <= (u_char) (N_words+N_powers-1),
772 "offset array should have been set");
773 }
774 #endif
775 }
777 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {
778 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
779 "just checking");
780 _next_offset_index = _array->index_for(_bottom);
781 _next_offset_index++;
782 _next_offset_threshold =
783 _array->address_for_index(_next_offset_index);
784 return _next_offset_threshold;
785 }
787 void BlockOffsetArrayContigSpace::zero_bottom_entry() {
788 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
789 "just checking");
790 size_t bottom_index = _array->index_for(_bottom);
791 _array->set_offset_array(bottom_index, 0);
792 }
794 size_t BlockOffsetArrayContigSpace::last_active_index() const {
795 size_t result = _next_offset_index - 1;
796 return result >= 0 ? result : 0;
797 }
