1 /*
2 * Copyright (c) 2001, 2016, 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/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((int)BOTConstants::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() >> BOTConstants::LogN_words),
62 "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
63 msg, (index), (_reserved.word_size() >> BOTConstants::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 _object_can_span(false)
83 { }
84
85 // The arguments follow the normal convention of denoting
86 // a right-open interval: [start, end)
87 void G1BlockOffsetTablePart:: 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 = _bot->index_for(start);
130 size_t end_card = _bot->index_for(end-1);
131 assert(start ==_bot->address_for_index(start_card), "Precondition");
132 assert(end ==_bot->address_for_index(end_card)+BOTConstants::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 G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
140 if (start_card > end_card) {
141 return;
142 }
143 assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card");
144 assert(_bot->offset_array(start_card-1) <= BOTConstants::N_words,
145 "Offset card has an unexpected value");
146 size_t start_card_for_region = start_card;
147 u_char offset = max_jubyte;
148 for (uint i = 0; i < BOTConstants::N_powers; i++) {
149 // -1 so that the the card with the actual offset is counted. Another -1
150 // so that the reach ends in this region and not at the start
151 // of the next.
152 size_t reach = start_card - 1 + (BOTConstants::power_to_cards_back(i+1) - 1);
153 offset = BOTConstants::N_words + i;
154 if (reach >= end_card) {
155 _bot->set_offset_array(start_card_for_region, end_card, offset);
156 start_card_for_region = reach + 1;
157 break;
158 }
159 _bot->set_offset_array(start_card_for_region, reach, offset);
160 start_card_for_region = reach + 1;
161 }
162 assert(start_card_for_region > end_card, "Sanity check");
163 DEBUG_ONLY(check_all_cards(start_card, end_card);)
164 }
165
166 // The card-interval [start_card, end_card] is a closed interval; this
167 // is an expensive check -- use with care and only under protection of
168 // suitable flag.
169 void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const {
170
171 if (end_card < start_card) {
172 return;
173 }
174 guarantee(_bot->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card");
175 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
176 u_char entry = _bot->offset_array(c);
177 if (c - start_card > BOTConstants::power_to_cards_back(1)) {
178 guarantee(entry > BOTConstants::N_words,
179 "Should be in logarithmic region - "
180 "entry: %u, "
181 "_array->offset_array(c): %u, "
182 "N_words: %u",
183 (uint)entry, (uint)_bot->offset_array(c), BOTConstants::N_words);
184 }
185 size_t backskip = BOTConstants::entry_to_cards_back(entry);
186 size_t landing_card = c - backskip;
187 guarantee(landing_card >= (start_card - 1), "Inv");
188 if (landing_card >= start_card) {
189 guarantee(_bot->offset_array(landing_card) <= entry,
190 "Monotonicity - landing_card offset: %u, "
191 "entry: %u",
192 (uint)_bot->offset_array(landing_card), (uint)entry);
193 } else {
194 guarantee(landing_card == start_card - 1, "Tautology");
195 // Note that N_words is the maximum offset value
196 guarantee(_bot->offset_array(landing_card) <= BOTConstants::N_words,
197 "landing card offset: %u, "
198 "N_words: %u",
199 (uint)_bot->offset_array(landing_card), (uint)BOTConstants::N_words);
200 }
201 }
202 }
203
204 HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q,
205 HeapWord* n,
206 const void* addr) {
207 // We're not in the normal case. We need to handle an important subcase
208 // here: LAB allocation. An allocation previously recorded in the
209 // offset table was actually a lab allocation, and was divided into
210 // several objects subsequently. Fix this situation as we answer the
211 // query, by updating entries as we cross them.
212
213 // If the fist object's end q is at the card boundary. Start refining
214 // with the corresponding card (the value of the entry will be basically
215 // set to 0). If the object crosses the boundary -- start from the next card.
216 size_t n_index = _bot->index_for(n);
217 size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n);
218 // Calculate a consistent next boundary. If "n" is not at the boundary
219 // already, step to the boundary.
220 HeapWord* next_boundary = _bot->address_for_index(n_index) +
221 (n_index == next_index ? 0 : BOTConstants::N_words);
222 assert(next_boundary <= _bot->_reserved.end(),
223 "next_boundary is beyond the end of the covered region "
224 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
225 p2i(next_boundary), p2i(_bot->_reserved.end()));
226 if (addr >= _space->top()) return _space->top();
227 while (next_boundary < addr) {
228 while (n <= next_boundary) {
229 q = n;
230 oop obj = oop(q);
231 if (obj->klass_or_null_acquire() == NULL) return q;
232 n += block_size(q);
233 }
234 assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
235 // [q, n) is the block that crosses the boundary.
236 alloc_block_work(&next_boundary, &next_index, q, n);
237 }
238 return forward_to_block_containing_addr_const(q, n, addr);
239 }
240
241 //
242 // threshold_
243 // | _index_
244 // v v
245 // +-------+-------+-------+-------+-------+
246 // | i-1 | i | i+1 | i+2 | i+3 |
247 // +-------+-------+-------+-------+-------+
248 // ( ^ ]
249 // block-start
250 //
251 void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_,
252 HeapWord* blk_start, HeapWord* blk_end) {
253 // For efficiency, do copy-in/copy-out.
254 HeapWord* threshold = *threshold_;
255 size_t index = *index_;
256
257 assert(blk_start != NULL && blk_end > blk_start,
258 "phantom block");
259 assert(blk_end > threshold, "should be past threshold");
260 assert(blk_start <= threshold, "blk_start should be at or before threshold");
261 assert(pointer_delta(threshold, blk_start) <= BOTConstants::N_words,
262 "offset should be <= BlockOffsetSharedArray::N");
263 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
264 "reference must be into the heap");
265 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
266 "limit must be within the heap");
267 assert(threshold == _bot->_reserved.start() + index*BOTConstants::N_words,
268 "index must agree with threshold");
269
270 DEBUG_ONLY(size_t orig_index = index;)
271
272 // Mark the card that holds the offset into the block. Note
273 // that _next_offset_index and _next_offset_threshold are not
274 // updated until the end of this method.
275 _bot->set_offset_array(index, threshold, blk_start);
276
277 // We need to now mark the subsequent cards that this blk spans.
278
279 // Index of card on which blk ends.
280 size_t end_index = _bot->index_for(blk_end - 1);
281
282 // Are there more cards left to be updated?
283 if (index + 1 <= end_index) {
284 HeapWord* rem_st = _bot->address_for_index(index + 1);
285 // Calculate rem_end this way because end_index
286 // may be the last valid index in the covered region.
287 HeapWord* rem_end = _bot->address_for_index(end_index) + BOTConstants::N_words;
288 set_remainder_to_point_to_start(rem_st, rem_end);
289 }
290
291 index = end_index + 1;
292 // Calculate threshold_ this way because end_index
293 // may be the last valid index in the covered region.
294 threshold = _bot->address_for_index(end_index) + BOTConstants::N_words;
295 assert(threshold >= blk_end, "Incorrect offset threshold");
296
297 // index_ and threshold_ updated here.
298 *threshold_ = threshold;
299 *index_ = index;
300
301 #ifdef ASSERT
302 // The offset can be 0 if the block starts on a boundary. That
303 // is checked by an assertion above.
304 size_t start_index = _bot->index_for(blk_start);
305 HeapWord* boundary = _bot->address_for_index(start_index);
306 assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) ||
307 (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= BOTConstants::N_words),
308 "offset array should have been set - "
309 "orig_index offset: %u, "
310 "blk_start: " PTR_FORMAT ", "
311 "boundary: " PTR_FORMAT,
312 (uint)_bot->offset_array(orig_index),
313 p2i(blk_start), p2i(boundary));
314 for (size_t j = orig_index + 1; j <= end_index; j++) {
315 assert(_bot->offset_array(j) > 0 &&
316 _bot->offset_array(j) <=
317 (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1),
318 "offset array should have been set - "
319 "%u not > 0 OR %u not <= %u",
320 (uint) _bot->offset_array(j),
321 (uint) _bot->offset_array(j),
322 (uint) (BOTConstants::N_words+BOTConstants::N_powers-1));
323 }
324 #endif
325 }
326
327 void G1BlockOffsetTablePart::verify() const {
328 assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified.");
329 size_t start_card = _bot->index_for(_space->bottom());
330 size_t end_card = _bot->index_for(_space->top() - 1);
331
332 for (size_t current_card = start_card; current_card < end_card; current_card++) {
333 u_char entry = _bot->offset_array(current_card);
334 if (entry < BOTConstants::N_words) {
335 // The entry should point to an object before the current card. Verify that
336 // it is possible to walk from that object in to the current card by just
337 // iterating over the objects following it.
338 HeapWord* card_address = _bot->address_for_index(current_card);
339 HeapWord* obj_end = card_address - entry;
340 while (obj_end < card_address) {
341 HeapWord* obj = obj_end;
342 size_t obj_size = block_size(obj);
343 obj_end = obj + obj_size;
344 guarantee(obj_end > obj && obj_end <= _space->top(),
345 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
346 p2i(obj), obj_size, p2i(obj_end), p2i(_space->top()));
347 }
348 } else {
349 // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
350 // We need to make sure that we are going backwards and that we don't pass the start of the
351 // corresponding heap region. But that is about all we can verify.
352 size_t backskip = BOTConstants::entry_to_cards_back(entry);
353 guarantee(backskip >= 1, "Must be going back at least one card.");
354
355 size_t max_backskip = current_card - start_card;
356 guarantee(backskip <= max_backskip,
357 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
358 start_card, current_card, backskip);
359
360 HeapWord* backskip_address = _bot->address_for_index(current_card - backskip);
361 guarantee(backskip_address >= _space->bottom(),
362 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
363 p2i(_space->bottom()), p2i(backskip_address));
364 }
365 }
366 }
367
368 #ifndef PRODUCT
369 void
370 G1BlockOffsetTablePart::print_on(outputStream* out) {
371 size_t from_index = _bot->index_for(_space->bottom());
372 size_t to_index = _bot->index_for(_space->end());
373 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
374 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
375 p2i(_space->bottom()), p2i(_space->end()), from_index, to_index);
376 for (size_t i = from_index; i < to_index; ++i) {
377 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
378 i, p2i(_bot->address_for_index(i)),
379 (uint) _bot->offset_array(i));
380 }
381 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
382 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index);
383 }
384 #endif // !PRODUCT
385
386 HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
387 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
388 "just checking");
389 _next_offset_index = _bot->index_for_raw(_space->bottom());
390 _next_offset_index++;
391 _next_offset_threshold =
392 _bot->address_for_index_raw(_next_offset_index);
393 return _next_offset_threshold;
394 }
395
396 void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
397 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
398 "just checking");
399 size_t bottom_index = _bot->index_for_raw(_space->bottom());
400 assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
401 "Precondition of call");
402 _bot->set_offset_array_raw(bottom_index, 0);
403 }
404
405 HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
406 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
407 "just checking");
408 _next_offset_index = _bot->index_for(_space->bottom());
409 _next_offset_index++;
410 _next_offset_threshold =
411 _bot->address_for_index(_next_offset_index);
412 return _next_offset_threshold;
413 }
414
415 void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
416 // The first BOT entry should have offset 0.
417 reset_bot();
418 alloc_block(_space->bottom(), obj_top);
419 if (fill_size > 0) {
420 alloc_block(obj_top, fill_size);
421 }
422 }
423
424 void G1BlockOffsetTablePart::set_continues_humongous(bool is_humongous) {
425 _object_can_span = is_humongous;
426 }