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