1 /*
2 * Copyright (c) 2001, 2015, 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.
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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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/heapRegion.hpp"
29 #include "gc/shared/space.hpp"
30 #include "logging/log.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/java.hpp"
33 #include "services/memTracker.hpp"
34
35
36
37 //////////////////////////////////////////////////////////////////////
38 // G1BlockOffsetTable
39 //////////////////////////////////////////////////////////////////////
40
41 G1BlockOffsetTable::G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage) :
42 _reserved(heap), _offset_array(NULL) {
43
44 MemRegion bot_reserved = storage->reserved();
45
46 _offset_array = (u_char*)bot_reserved.start();
47
48 log_trace(gc, bot)("G1BlockOffsetTable::G1BlockOffsetTable: ");
49 log_trace(gc, bot)(" rs.base(): " PTR_FORMAT " rs.size(): " SIZE_FORMAT " rs end(): " PTR_FORMAT,
50 p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end()));
51 }
52
53 bool G1BlockOffsetTable::is_card_boundary(HeapWord* p) const {
54 assert(p >= _reserved.start(), "just checking");
55 size_t delta = pointer_delta(p, _reserved.start());
56 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
57 }
58
59 #ifdef ASSERT
60 void G1BlockOffsetTable::check_index(size_t index, const char* msg) const {
61 assert((index) < (_reserved.word_size() >> LogN_words),
62 "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
63 msg, (index), (_reserved.word_size() >> LogN_words));
64 assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)),
65 "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT
66 " (%u) is not in committed area.",
67 (index),
68 p2i(address_for_index_raw(index)),
69 G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index)));
70 }
71 #endif // ASSERT
72
73 //////////////////////////////////////////////////////////////////////
74 // G1BlockOffsetTablePart
75 //////////////////////////////////////////////////////////////////////
76
77 G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) :
78 _bot(array),
79 _space(gsp),
80 _next_offset_threshold(NULL),
81 _next_offset_index(0)
82 { }
83
84 // The arguments follow the normal convention of denoting
85 // a right-open interval: [start, end)
86 void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
87
88 if (start >= end) {
89 // The start address is equal to the end address (or to
90 // the right of the end address) so there are not cards
91 // that need to be updated..
92 return;
93 }
94
95 // Write the backskip value for each region.
96 //
97 // offset
98 // card 2nd 3rd
99 // | +- 1st | |
100 // v v v v
101 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
102 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
103 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
104 // 11 19 75
105 // 12
106 //
107 // offset card is the card that points to the start of an object
108 // x - offset value of offset card
109 // 1st - start of first logarithmic region
110 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
111 // 2nd - start of second logarithmic region
112 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
113 // 3rd - start of third logarithmic region
114 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
115 //
116 // integer below the block offset entry is an example of
117 // the index of the entry
118 //
119 // Given an address,
120 // Find the index for the address
121 // Find the block offset table entry
122 // Convert the entry to a back slide
123 // (e.g., with today's, offset = 0x81 =>
124 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
125 // Move back N (e.g., 8) entries and repeat with the
126 // value of the new entry
127 //
128 size_t start_card = _bot->index_for(start);
129 size_t end_card = _bot->index_for(end-1);
130 assert(start ==_bot->address_for_index(start_card), "Precondition");
131 assert(end ==_bot->address_for_index(end_card)+N_words, "Precondition");
132 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
133 }
134
135 // Unlike the normal convention in this code, the argument here denotes
136 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
137 // above.
138 void G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
139 if (start_card > end_card) {
140 return;
141 }
142 assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card");
143 assert(_bot->offset_array(start_card-1) <= N_words,
144 "Offset card has an unexpected value");
145 size_t start_card_for_region = start_card;
146 u_char offset = max_jubyte;
147 for (int i = 0; i < BlockOffsetArray::N_powers; i++) {
148 // -1 so that the the card with the actual offset is counted. Another -1
149 // so that the reach ends in this region and not at the start
150 // of the next.
151 size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1);
152 offset = N_words + i;
153 if (reach >= end_card) {
154 _bot->set_offset_array(start_card_for_region, end_card, offset);
155 start_card_for_region = reach + 1;
156 break;
157 }
158 _bot->set_offset_array(start_card_for_region, reach, offset);
159 start_card_for_region = reach + 1;
160 }
161 assert(start_card_for_region > end_card, "Sanity check");
162 DEBUG_ONLY(check_all_cards(start_card, end_card);)
163 }
164
165 // The card-interval [start_card, end_card] is a closed interval; this
166 // is an expensive check -- use with care and only under protection of
167 // suitable flag.
168 void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const {
169
170 if (end_card < start_card) {
171 return;
172 }
173 guarantee(_bot->offset_array(start_card) == N_words, "Wrong value in second card");
174 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
175 u_char entry = _bot->offset_array(c);
176 if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) {
177 guarantee(entry > N_words,
178 "Should be in logarithmic region - "
179 "entry: %u, "
180 "_array->offset_array(c): %u, "
181 "N_words: %u",
182 (uint)entry, (uint)_bot->offset_array(c), (uint)N_words);
183 }
184 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
185 size_t landing_card = c - backskip;
186 guarantee(landing_card >= (start_card - 1), "Inv");
187 if (landing_card >= start_card) {
188 guarantee(_bot->offset_array(landing_card) <= entry,
189 "Monotonicity - landing_card offset: %u, "
190 "entry: %u",
191 (uint)_bot->offset_array(landing_card), (uint)entry);
192 } else {
193 guarantee(landing_card == start_card - 1, "Tautology");
194 // Note that N_words is the maximum offset value
195 guarantee(_bot->offset_array(landing_card) <= N_words,
196 "landing card offset: %u, "
197 "N_words: %u",
198 (uint)_bot->offset_array(landing_card), (uint)N_words);
199 }
200 }
201 }
202
203 HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q,
204 HeapWord* n,
205 const void* addr) {
206 // We're not in the normal case. We need to handle an important subcase
207 // here: LAB allocation. An allocation previously recorded in the
208 // offset table was actually a lab allocation, and was divided into
209 // several objects subsequently. Fix this situation as we answer the
210 // query, by updating entries as we cross them.
211
212 // If the fist object's end q is at the card boundary. Start refining
213 // with the corresponding card (the value of the entry will be basically
214 // set to 0). If the object crosses the boundary -- start from the next card.
215 size_t n_index = _bot->index_for(n);
216 size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n);
217 // Calculate a consistent next boundary. If "n" is not at the boundary
218 // already, step to the boundary.
219 HeapWord* next_boundary = _bot->address_for_index(n_index) +
220 (n_index == next_index ? 0 : N_words);
221 assert(next_boundary <= _bot->_reserved.end(),
222 "next_boundary is beyond the end of the covered region "
223 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
224 p2i(next_boundary), p2i(_bot->_reserved.end()));
225 if (addr >= _space->top()) return _space->top();
226 while (next_boundary < addr) {
227 while (n <= next_boundary) {
228 q = n;
229 oop obj = oop(q);
230 if (obj->klass_or_null() == NULL) return q;
231 n += block_size(q);
232 }
233 assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
234 // [q, n) is the block that crosses the boundary.
235 alloc_block_work(&next_boundary, &next_index, q, n);
236 }
237 return forward_to_block_containing_addr_const(q, n, addr);
238 }
239
240 //
241 // threshold_
242 // | _index_
243 // v v
244 // +-------+-------+-------+-------+-------+
245 // | i-1 | i | i+1 | i+2 | i+3 |
246 // +-------+-------+-------+-------+-------+
247 // ( ^ ]
248 // block-start
249 //
250 void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_,
251 HeapWord* blk_start, HeapWord* blk_end) {
252 // For efficiency, do copy-in/copy-out.
253 HeapWord* threshold = *threshold_;
254 size_t index = *index_;
255
256 assert(blk_start != NULL && blk_end > blk_start,
257 "phantom block");
258 assert(blk_end > threshold, "should be past threshold");
259 assert(blk_start <= threshold, "blk_start should be at or before threshold");
260 assert(pointer_delta(threshold, blk_start) <= N_words,
261 "offset should be <= BlockOffsetSharedArray::N");
262 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
263 "reference must be into the heap");
264 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
265 "limit must be within the heap");
266 assert(threshold == _bot->_reserved.start() + index*N_words,
267 "index must agree with threshold");
268
269 DEBUG_ONLY(size_t orig_index = index;)
270
271 // Mark the card that holds the offset into the block. Note
272 // that _next_offset_index and _next_offset_threshold are not
273 // updated until the end of this method.
274 _bot->set_offset_array(index, threshold, blk_start);
275
276 // We need to now mark the subsequent cards that this blk spans.
277
278 // Index of card on which blk ends.
279 size_t end_index = _bot->index_for(blk_end - 1);
280
281 // Are there more cards left to be updated?
282 if (index + 1 <= end_index) {
283 HeapWord* rem_st = _bot->address_for_index(index + 1);
284 // Calculate rem_end this way because end_index
285 // may be the last valid index in the covered region.
286 HeapWord* rem_end = _bot->address_for_index(end_index) + N_words;
287 set_remainder_to_point_to_start(rem_st, rem_end);
288 }
289
290 index = end_index + 1;
291 // Calculate threshold_ this way because end_index
292 // may be the last valid index in the covered region.
293 threshold = _bot->address_for_index(end_index) + N_words;
294 assert(threshold >= blk_end, "Incorrect offset threshold");
295
296 // index_ and threshold_ updated here.
297 *threshold_ = threshold;
298 *index_ = index;
299
300 #ifdef ASSERT
301 // The offset can be 0 if the block starts on a boundary. That
302 // is checked by an assertion above.
303 size_t start_index = _bot->index_for(blk_start);
304 HeapWord* boundary = _bot->address_for_index(start_index);
305 assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) ||
306 (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= N_words),
307 "offset array should have been set - "
308 "orig_index offset: %u, "
309 "blk_start: " PTR_FORMAT ", "
310 "boundary: " PTR_FORMAT,
311 (uint)_bot->offset_array(orig_index),
312 p2i(blk_start), p2i(boundary));
313 for (size_t j = orig_index + 1; j <= end_index; j++) {
314 assert(_bot->offset_array(j) > 0 &&
315 _bot->offset_array(j) <=
316 (u_char) (N_words+BlockOffsetArray::N_powers-1),
317 "offset array should have been set - "
318 "%u not > 0 OR %u not <= %u",
319 (uint) _bot->offset_array(j),
320 (uint) _bot->offset_array(j),
321 (uint) (N_words+BlockOffsetArray::N_powers-1));
322 }
323 #endif
324 }
325
326 void G1BlockOffsetTablePart::verify() const {
327 assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified.");
328 size_t start_card = _bot->index_for(_space->bottom());
329 size_t end_card = _bot->index_for(_space->top() - 1);
330
331 for (size_t current_card = start_card; current_card < end_card; current_card++) {
332 u_char entry = _bot->offset_array(current_card);
333 if (entry < N_words) {
334 // The entry should point to an object before the current card. Verify that
335 // it is possible to walk from that object in to the current card by just
336 // iterating over the objects following it.
337 HeapWord* card_address = _bot->address_for_index(current_card);
338 HeapWord* obj_end = card_address - entry;
339 while (obj_end < card_address) {
340 HeapWord* obj = obj_end;
341 size_t obj_size = block_size(obj);
342 obj_end = obj + obj_size;
343 guarantee(obj_end > obj && obj_end <= _space->top(),
344 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
345 p2i(obj), obj_size, p2i(obj_end), p2i(_space->top()));
346 }
347 } else {
348 // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
349 // We need to make sure that we are going backwards and that we don't pass the start of the
350 // corresponding heap region. But that is about all we can verify.
351 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
352 guarantee(backskip >= 1, "Must be going back at least one card.");
353
354 size_t max_backskip = current_card - start_card;
355 guarantee(backskip <= max_backskip,
356 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
357 start_card, current_card, backskip);
358
359 HeapWord* backskip_address = _bot->address_for_index(current_card - backskip);
360 guarantee(backskip_address >= _space->bottom(),
361 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
362 p2i(_space->bottom()), p2i(backskip_address));
363 }
364 }
365 }
366
367 #ifndef PRODUCT
368 void
369 G1BlockOffsetTablePart::print_on(outputStream* out) {
370 size_t from_index = _bot->index_for(_space->bottom());
371 size_t to_index = _bot->index_for(_space->end());
372 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
373 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
374 p2i(_space->bottom()), p2i(_space->end()), from_index, to_index);
375 for (size_t i = from_index; i < to_index; ++i) {
376 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
377 i, p2i(_bot->address_for_index(i)),
378 (uint) _bot->offset_array(i));
379 }
380 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
381 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index);
382 }
383 #endif // !PRODUCT
384
385 HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
386 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
387 "just checking");
388 _next_offset_index = _bot->index_for_raw(_space->bottom());
389 _next_offset_index++;
390 _next_offset_threshold =
391 _bot->address_for_index_raw(_next_offset_index);
392 return _next_offset_threshold;
393 }
394
395 void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
396 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
397 "just checking");
398 size_t bottom_index = _bot->index_for_raw(_space->bottom());
399 assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
400 "Precondition of call");
401 _bot->set_offset_array_raw(bottom_index, 0);
402 }
403
404 HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
405 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
406 "just checking");
407 _next_offset_index = _bot->index_for(_space->bottom());
408 _next_offset_index++;
409 _next_offset_threshold =
410 _bot->address_for_index(_next_offset_index);
411 return _next_offset_threshold;
412 }
413
414 void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
415 // The first BOT entry should have offset 0.
416 reset_bot();
417 alloc_block(_space->bottom(), obj_top);
418 if (fill_size > 0) {
419 alloc_block(obj_top, fill_size);
420 }
421 }