1/*
2 * Copyright (c) 2001, 2017, 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
41G1BlockOffsetTable::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
53bool 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
60void 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
77G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) :
78 _next_offset_threshold(NULL),
79 _next_offset_index(0),
80 DEBUG_ONLY(_object_can_span(false) COMMA)
81 _bot(array),
82 _space(gsp)
83{
84}
85
86// The arguments follow the normal convention of denoting
87// a right-open interval: [start, end)
88void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
89
90 if (start >= end) {
91 // The start address is equal to the end address (or to
92 // the right of the end address) so there are not cards
93 // that need to be updated..
94 return;
95 }
96
97 // Write the backskip value for each region.
98 //
99 // offset
100 // card 2nd 3rd
101 // | +- 1st | |
102 // v v v v
103 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
104 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
105 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
106 // 11 19 75
107 // 12
108 //
109 // offset card is the card that points to the start of an object
110 // x - offset value of offset card
111 // 1st - start of first logarithmic region
112 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
113 // 2nd - start of second logarithmic region
114 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
115 // 3rd - start of third logarithmic region
116 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
117 //
118 // integer below the block offset entry is an example of
119 // the index of the entry
120 //
121 // Given an address,
122 // Find the index for the address
123 // Find the block offset table entry
124 // Convert the entry to a back slide
125 // (e.g., with today's, offset = 0x81 =>
126 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
127 // Move back N (e.g., 8) entries and repeat with the
128 // value of the new entry
129 //
130 size_t start_card = _bot->index_for(start);
131 size_t end_card = _bot->index_for(end-1);
132 assert(start ==_bot->address_for_index(start_card), "Precondition");
133 assert(end ==_bot->address_for_index(end_card)+BOTConstants::N_words, "Precondition");
134 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
135}
136
137// Unlike the normal convention in this code, the argument here denotes
138// a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
139// above.
140void G1BlockOffsetTablePart::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 > _bot->index_for(_space->bottom()), "Cannot be first card");
145 assert(_bot->offset_array(start_card-1) <= BOTConstants::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 (uint i = 0; i < BOTConstants::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 + (BOTConstants::power_to_cards_back(i+1) - 1);
154 offset = BOTConstants::N_words + i;
155 if (reach >= end_card) {
156 _bot->set_offset_array(start_card_for_region, end_card, offset);
157 start_card_for_region = reach + 1;
158 break;
159 }
160 _bot->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.
170void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const {
171
172 if (end_card < start_card) {
173 return;
174 }
175 guarantee(_bot->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card");
176 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
177 u_char entry = _bot->offset_array(c);
178 if (c - start_card > BOTConstants::power_to_cards_back(1)) {
179 guarantee(entry > BOTConstants::N_words,
180 "Should be in logarithmic region - "
181 "entry: %u, "
182 "_array->offset_array(c): %u, "
183 "N_words: %u",
184 (uint)entry, (uint)_bot->offset_array(c), BOTConstants::N_words);
185 }
186 size_t backskip = BOTConstants::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(_bot->offset_array(landing_card) <= entry,
191 "Monotonicity - landing_card offset: %u, "
192 "entry: %u",
193 (uint)_bot->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(_bot->offset_array(landing_card) <= BOTConstants::N_words,
198 "landing card offset: %u, "
199 "N_words: %u",
200 (uint)_bot->offset_array(landing_card), (uint)BOTConstants::N_words);
201 }
202 }
203}
204
205HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q,
206 HeapWord* n,
207 const void* addr) {
208 // We're not in the normal case. We need to handle an important subcase
209 // here: LAB allocation. An allocation previously recorded in the
210 // offset table was actually a lab allocation, and was divided into
211 // several objects subsequently. Fix this situation as we answer the
212 // query, by updating entries as we cross them.
213
214 // If the fist object's end q is at the card boundary. Start refining
215 // with the corresponding card (the value of the entry will be basically
216 // set to 0). If the object crosses the boundary -- start from the next card.
217 size_t n_index = _bot->index_for(n);
218 size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n);
219 // Calculate a consistent next boundary. If "n" is not at the boundary
220 // already, step to the boundary.
221 HeapWord* next_boundary = _bot->address_for_index(n_index) +
222 (n_index == next_index ? 0 : BOTConstants::N_words);
223 assert(next_boundary <= _bot->_reserved.end(),
224 "next_boundary is beyond the end of the covered region "
225 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
226 p2i(next_boundary), p2i(_bot->_reserved.end()));
227 if (addr >= _space->top()) return _space->top();
228 while (next_boundary < addr) {
229 while (n <= next_boundary) {
230 q = n;
231 oop obj = oop(q);
232 if (obj->klass_or_null_acquire() == NULL) return q;
233 n += block_size(q);
234 }
235 assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
236 // [q, n) is the block that crosses the boundary.
237 alloc_block_work(&next_boundary, &next_index, q, n);
238 }
239 return forward_to_block_containing_addr_const(q, n, addr);
240}
241
242//
243// threshold_
244// | _index_
245// v v
246// +-------+-------+-------+-------+-------+
247// | i-1 | i | i+1 | i+2 | i+3 |
248// +-------+-------+-------+-------+-------+
249// ( ^ ]
250// block-start
251//
252void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_,
253 HeapWord* blk_start, HeapWord* blk_end) {
254 // For efficiency, do copy-in/copy-out.
255 HeapWord* threshold = *threshold_;
256 size_t index = *index_;
257
258 assert(blk_start != NULL && blk_end > blk_start,
259 "phantom block");
260 assert(blk_end > threshold, "should be past threshold");
261 assert(blk_start <= threshold, "blk_start should be at or before threshold");
262 assert(pointer_delta(threshold, blk_start) <= BOTConstants::N_words,
263 "offset should be <= BlockOffsetSharedArray::N");
264 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
265 "reference must be into the heap");
266 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
267 "limit must be within the heap");
268 assert(threshold == _bot->_reserved.start() + index*BOTConstants::N_words,
269 "index must agree with threshold");
270
271 DEBUG_ONLY(size_t orig_index = index;)
272
273 // Mark the card that holds the offset into the block. Note
274 // that _next_offset_index and _next_offset_threshold are not
275 // updated until the end of this method.
276 _bot->set_offset_array(index, threshold, blk_start);
277
278 // We need to now mark the subsequent cards that this blk spans.
279
280 // Index of card on which blk ends.
281 size_t end_index = _bot->index_for(blk_end - 1);
282
283 // Are there more cards left to be updated?
284 if (index + 1 <= end_index) {
285 HeapWord* rem_st = _bot->address_for_index(index + 1);
286 // Calculate rem_end this way because end_index
287 // may be the last valid index in the covered region.
288 HeapWord* rem_end = _bot->address_for_index(end_index) + BOTConstants::N_words;
289 set_remainder_to_point_to_start(rem_st, rem_end);
290 }
291
292 index = end_index + 1;
293 // Calculate threshold_ this way because end_index
294 // may be the last valid index in the covered region.
295 threshold = _bot->address_for_index(end_index) + BOTConstants::N_words;
296 assert(threshold >= blk_end, "Incorrect offset threshold");
297
298 // index_ and threshold_ updated here.
299 *threshold_ = threshold;
300 *index_ = index;
301
302#ifdef ASSERT
303 // The offset can be 0 if the block starts on a boundary. That
304 // is checked by an assertion above.
305 size_t start_index = _bot->index_for(blk_start);
306 HeapWord* boundary = _bot->address_for_index(start_index);
307 assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) ||
308 (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= BOTConstants::N_words),
309 "offset array should have been set - "
310 "orig_index offset: %u, "
311 "blk_start: " PTR_FORMAT ", "
312 "boundary: " PTR_FORMAT,
313 (uint)_bot->offset_array(orig_index),
314 p2i(blk_start), p2i(boundary));
315 for (size_t j = orig_index + 1; j <= end_index; j++) {
316 assert(_bot->offset_array(j) > 0 &&
317 _bot->offset_array(j) <=
318 (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1),
319 "offset array should have been set - "
320 "%u not > 0 OR %u not <= %u",
321 (uint) _bot->offset_array(j),
322 (uint) _bot->offset_array(j),
323 (uint) (BOTConstants::N_words+BOTConstants::N_powers-1));
324 }
325#endif
326}
327
328void G1BlockOffsetTablePart::verify() const {
329 assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified.");
330 size_t start_card = _bot->index_for(_space->bottom());
331 size_t end_card = _bot->index_for(_space->top() - 1);
332
333 for (size_t current_card = start_card; current_card < end_card; current_card++) {
334 u_char entry = _bot->offset_array(current_card);
335 if (entry < BOTConstants::N_words) {
336 // The entry should point to an object before the current card. Verify that
337 // it is possible to walk from that object in to the current card by just
338 // iterating over the objects following it.
339 HeapWord* card_address = _bot->address_for_index(current_card);
340 HeapWord* obj_end = card_address - entry;
341 while (obj_end < card_address) {
342 HeapWord* obj = obj_end;
343 size_t obj_size = block_size(obj);
344 obj_end = obj + obj_size;
345 guarantee(obj_end > obj && obj_end <= _space->top(),
346 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
347 p2i(obj), obj_size, p2i(obj_end), p2i(_space->top()));
348 }
349 } else {
350 // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
351 // We need to make sure that we are going backwards and that we don't pass the start of the
352 // corresponding heap region. But that is about all we can verify.
353 size_t backskip = BOTConstants::entry_to_cards_back(entry);
354 guarantee(backskip >= 1, "Must be going back at least one card.");
355
356 size_t max_backskip = current_card - start_card;
357 guarantee(backskip <= max_backskip,
358 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
359 start_card, current_card, backskip);
360
361 HeapWord* backskip_address = _bot->address_for_index(current_card - backskip);
362 guarantee(backskip_address >= _space->bottom(),
363 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
364 p2i(_space->bottom()), p2i(backskip_address));
365 }
366 }
367}
368
369#ifdef ASSERT
370void G1BlockOffsetTablePart::set_object_can_span(bool can_span) {
371 _object_can_span = can_span;
372}
373#endif
374
375#ifndef PRODUCT
376void
377G1BlockOffsetTablePart::print_on(outputStream* out) {
378 size_t from_index = _bot->index_for(_space->bottom());
379 size_t to_index = _bot->index_for(_space->end());
380 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
381 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
382 p2i(_space->bottom()), p2i(_space->end()), from_index, to_index);
383 for (size_t i = from_index; i < to_index; ++i) {
384 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
385 i, p2i(_bot->address_for_index(i)),
386 (uint) _bot->offset_array(i));
387 }
388 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
389 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index);
390}
391#endif // !PRODUCT
392
393HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
394 _next_offset_index = _bot->index_for_raw(_space->bottom());
395 _next_offset_index++;
396 _next_offset_threshold =
397 _bot->address_for_index_raw(_next_offset_index);
398 return _next_offset_threshold;
399}
400
401void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
402 size_t bottom_index = _bot->index_for_raw(_space->bottom());
403 assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
404 "Precondition of call");
405 _bot->set_offset_array_raw(bottom_index, 0);
406}
407
408HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
409 _next_offset_index = _bot->index_for(_space->bottom());
410 _next_offset_index++;
411 _next_offset_threshold =
412 _bot->address_for_index(_next_offset_index);
413 return _next_offset_threshold;
414}
415
416void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
417 // The first BOT entry should have offset 0.
418 reset_bot();
419 alloc_block(_space->bottom(), obj_top);
420 if (fill_size > 0) {
421 alloc_block(obj_top, fill_size);
422 }
423}
424