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.
  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 "oops/oop.inline.hpp"
  31 #include "runtime/java.hpp"
  32 #include "services/memTracker.hpp"
  33 
  34 
  35 
  36 //////////////////////////////////////////////////////////////////////
  37 // G1BlockOffsetSharedArray
  38 //////////////////////////////////////////////////////////////////////
  39 
  40 G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage) :
  41   _reserved(), _end(NULL), _listener(), _offset_array(NULL) {
  42 
  43   _reserved = heap;
  44   _end = NULL;
  45 
  46   MemRegion bot_reserved = storage->reserved();
  47 
  48   _offset_array = (u_char*)bot_reserved.start();
  49   _end = _reserved.end();
  50 
  51   storage->set_mapping_changed_listener(&_listener);
  52 
  53   if (TraceBlockOffsetTable) {
  54     gclog_or_tty->print_cr("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: ");
  55     gclog_or_tty->print_cr("  "
  56                   "  rs.base(): " PTR_FORMAT
  57                   "  rs.size(): " SIZE_FORMAT
  58                   "  rs end(): " PTR_FORMAT,
  59                   p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end()));
  60   }
  61 }
  62 
  63 bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
  64   assert(p >= _reserved.start(), "just checking");
  65   size_t delta = pointer_delta(p, _reserved.start());
  66   return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
  67 }
  68 
  69 #ifdef ASSERT
  70 void G1BlockOffsetSharedArray::check_index(size_t index, const char* msg) const {
  71   assert((index) < (_reserved.word_size() >> LogN_words),
  72          "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
  73          msg, (index), (_reserved.word_size() >> LogN_words));
  74   assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)),
  75          "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT
  76          " (%u) is not in committed area.",
  77          (index),
  78          p2i(address_for_index_raw(index)),
  79          G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index)));
  80 }
  81 #endif // ASSERT
  82 
  83 //////////////////////////////////////////////////////////////////////
  84 // G1BlockOffsetArray
  85 //////////////////////////////////////////////////////////////////////
  86 
  87 G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
  88                                        MemRegion mr) :
  89   G1BlockOffsetTable(mr.start(), mr.end()),
  90   _unallocated_block(_bottom),
  91   _array(array), _gsp(NULL) {
  92   assert(_bottom <= _end, "arguments out of order");
  93 }
  94 
  95 void G1BlockOffsetArray::set_space(G1OffsetTableContigSpace* sp) {
  96   _gsp = sp;
  97 }
  98 
  99 // The arguments follow the normal convention of denoting
 100 // a right-open interval: [start, end)
 101 void
 102 G1BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
 103 
 104   if (start >= end) {
 105     // The start address is equal to the end address (or to
 106     // the right of the end address) so there are not cards
 107     // that need to be updated..
 108     return;
 109   }
 110 
 111   // Write the backskip value for each region.
 112   //
 113   //    offset
 114   //    card             2nd                       3rd
 115   //     | +- 1st        |                         |
 116   //     v v             v                         v
 117   //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
 118   //    |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
 119   //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
 120   //    11              19                        75
 121   //      12
 122   //
 123   //    offset card is the card that points to the start of an object
 124   //      x - offset value of offset card
 125   //    1st - start of first logarithmic region
 126   //      0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
 127   //    2nd - start of second logarithmic region
 128   //      1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
 129   //    3rd - start of third logarithmic region
 130   //      2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
 131   //
 132   //    integer below the block offset entry is an example of
 133   //    the index of the entry
 134   //
 135   //    Given an address,
 136   //      Find the index for the address
 137   //      Find the block offset table entry
 138   //      Convert the entry to a back slide
 139   //        (e.g., with today's, offset = 0x81 =>
 140   //          back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
 141   //      Move back N (e.g., 8) entries and repeat with the
 142   //        value of the new entry
 143   //
 144   size_t start_card = _array->index_for(start);
 145   size_t end_card = _array->index_for(end-1);
 146   assert(start ==_array->address_for_index(start_card), "Precondition");
 147   assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
 148   set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
 149 }
 150 
 151 // Unlike the normal convention in this code, the argument here denotes
 152 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
 153 // above.
 154 void
 155 G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
 156   if (start_card > end_card) {
 157     return;
 158   }
 159   assert(start_card > _array->index_for(_bottom), "Cannot be first card");
 160   assert(_array->offset_array(start_card-1) <= N_words,
 161          "Offset card has an unexpected value");
 162   size_t start_card_for_region = start_card;
 163   u_char offset = max_jubyte;
 164   for (int i = 0; i < BlockOffsetArray::N_powers; i++) {
 165     // -1 so that the the card with the actual offset is counted.  Another -1
 166     // so that the reach ends in this region and not at the start
 167     // of the next.
 168     size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1);
 169     offset = N_words + i;
 170     if (reach >= end_card) {
 171       _array->set_offset_array(start_card_for_region, end_card, offset);
 172       start_card_for_region = reach + 1;
 173       break;
 174     }
 175     _array->set_offset_array(start_card_for_region, reach, offset);
 176     start_card_for_region = reach + 1;
 177   }
 178   assert(start_card_for_region > end_card, "Sanity check");
 179   DEBUG_ONLY(check_all_cards(start_card, end_card);)
 180 }
 181 
 182 // The card-interval [start_card, end_card] is a closed interval; this
 183 // is an expensive check -- use with care and only under protection of
 184 // suitable flag.
 185 void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
 186 
 187   if (end_card < start_card) {
 188     return;
 189   }
 190   guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
 191   for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
 192     u_char entry = _array->offset_array(c);
 193     if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) {
 194       guarantee(entry > N_words,
 195                 "Should be in logarithmic region - "
 196                 "entry: %u, "
 197                 "_array->offset_array(c): %u, "
 198                 "N_words: %u",
 199                 (uint)entry, (uint)_array->offset_array(c), (uint)N_words);
 200     }
 201     size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
 202     size_t landing_card = c - backskip;
 203     guarantee(landing_card >= (start_card - 1), "Inv");
 204     if (landing_card >= start_card) {
 205       guarantee(_array->offset_array(landing_card) <= entry,
 206                 "Monotonicity - landing_card offset: %u, "
 207                 "entry: %u",
 208                 (uint)_array->offset_array(landing_card), (uint)entry);
 209     } else {
 210       guarantee(landing_card == start_card - 1, "Tautology");
 211       // Note that N_words is the maximum offset value
 212       guarantee(_array->offset_array(landing_card) <= N_words,
 213                 "landing card offset: %u, "
 214                 "N_words: %u",
 215                 (uint)_array->offset_array(landing_card), (uint)N_words);
 216     }
 217   }
 218 }
 219 
 220 HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {
 221   assert(_bottom <= addr && addr < _end,
 222          "addr must be covered by this Array");
 223   // Must read this exactly once because it can be modified by parallel
 224   // allocation.
 225   HeapWord* ub = _unallocated_block;
 226   if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
 227     assert(ub < _end, "tautology (see above)");
 228     return ub;
 229   }
 230   // Otherwise, find the block start using the table.
 231   HeapWord* q = block_at_or_preceding(addr, false, 0);
 232   return forward_to_block_containing_addr(q, addr);
 233 }
 234 
 235 // This duplicates a little code from the above: unavoidable.
 236 HeapWord*
 237 G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const {
 238   assert(_bottom <= addr && addr < _end,
 239          "addr must be covered by this Array");
 240   // Must read this exactly once because it can be modified by parallel
 241   // allocation.
 242   HeapWord* ub = _unallocated_block;
 243   if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
 244     assert(ub < _end, "tautology (see above)");
 245     return ub;
 246   }
 247   // Otherwise, find the block start using the table.
 248   HeapWord* q = block_at_or_preceding(addr, false, 0);
 249   HeapWord* n = q + block_size(q);
 250   return forward_to_block_containing_addr_const(q, n, addr);
 251 }
 252 
 253 
 254 HeapWord*
 255 G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,
 256                                                           HeapWord* n,
 257                                                           const void* addr) {
 258   // We're not in the normal case.  We need to handle an important subcase
 259   // here: LAB allocation.  An allocation previously recorded in the
 260   // offset table was actually a lab allocation, and was divided into
 261   // several objects subsequently.  Fix this situation as we answer the
 262   // query, by updating entries as we cross them.
 263 
 264   // If the fist object's end q is at the card boundary. Start refining
 265   // with the corresponding card (the value of the entry will be basically
 266   // set to 0). If the object crosses the boundary -- start from the next card.
 267   size_t n_index = _array->index_for(n);
 268   size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n);
 269   // Calculate a consistent next boundary.  If "n" is not at the boundary
 270   // already, step to the boundary.
 271   HeapWord* next_boundary = _array->address_for_index(n_index) +
 272                             (n_index == next_index ? 0 : N_words);
 273   assert(next_boundary <= _array->_end,
 274          "next_boundary is beyond the end of the covered region "
 275          " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
 276          p2i(next_boundary), p2i(_array->_end));
 277   if (addr >= gsp()->top()) return gsp()->top();
 278   while (next_boundary < addr) {
 279     while (n <= next_boundary) {
 280       q = n;
 281       oop obj = oop(q);
 282       if (obj->klass_or_null() == NULL) return q;
 283       n += block_size(q);
 284     }
 285     assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
 286     // [q, n) is the block that crosses the boundary.
 287     alloc_block_work2(&next_boundary, &next_index, q, n);
 288   }
 289   return forward_to_block_containing_addr_const(q, n, addr);
 290 }
 291 
 292 // Note that the committed size of the covered space may have changed,
 293 // so the table size might also wish to change.
 294 void G1BlockOffsetArray::resize(size_t new_word_size) {
 295   HeapWord* new_end = _bottom + new_word_size;
 296   _end = new_end;  // update _end
 297 }
 298 
 299 //
 300 //              threshold_
 301 //              |   _index_
 302 //              v   v
 303 //      +-------+-------+-------+-------+-------+
 304 //      | i-1   |   i   | i+1   | i+2   | i+3   |
 305 //      +-------+-------+-------+-------+-------+
 306 //       ( ^    ]
 307 //         block-start
 308 //
 309 void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_,
 310                                            HeapWord* blk_start, HeapWord* blk_end) {
 311   // For efficiency, do copy-in/copy-out.
 312   HeapWord* threshold = *threshold_;
 313   size_t    index = *index_;
 314 
 315   assert(blk_start != NULL && blk_end > blk_start,
 316          "phantom block");
 317   assert(blk_end > threshold, "should be past threshold");
 318   assert(blk_start <= threshold, "blk_start should be at or before threshold");
 319   assert(pointer_delta(threshold, blk_start) <= N_words,
 320          "offset should be <= BlockOffsetSharedArray::N");
 321   assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
 322          "reference must be into the heap");
 323   assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
 324          "limit must be within the heap");
 325   assert(threshold == _array->_reserved.start() + index*N_words,
 326          "index must agree with threshold");
 327 
 328   DEBUG_ONLY(size_t orig_index = index;)
 329 
 330   // Mark the card that holds the offset into the block.  Note
 331   // that _next_offset_index and _next_offset_threshold are not
 332   // updated until the end of this method.
 333   _array->set_offset_array(index, threshold, blk_start);
 334 
 335   // We need to now mark the subsequent cards that this blk spans.
 336 
 337   // Index of card on which blk ends.
 338   size_t end_index   = _array->index_for(blk_end - 1);
 339 
 340   // Are there more cards left to be updated?
 341   if (index + 1 <= end_index) {
 342     HeapWord* rem_st  = _array->address_for_index(index + 1);
 343     // Calculate rem_end this way because end_index
 344     // may be the last valid index in the covered region.
 345     HeapWord* rem_end = _array->address_for_index(end_index) +  N_words;
 346     set_remainder_to_point_to_start(rem_st, rem_end);
 347   }
 348 
 349   index = end_index + 1;
 350   // Calculate threshold_ this way because end_index
 351   // may be the last valid index in the covered region.
 352   threshold = _array->address_for_index(end_index) + N_words;
 353   assert(threshold >= blk_end, "Incorrect offset threshold");
 354 
 355   // index_ and threshold_ updated here.
 356   *threshold_ = threshold;
 357   *index_ = index;
 358 
 359 #ifdef ASSERT
 360   // The offset can be 0 if the block starts on a boundary.  That
 361   // is checked by an assertion above.
 362   size_t start_index = _array->index_for(blk_start);
 363   HeapWord* boundary = _array->address_for_index(start_index);
 364   assert((_array->offset_array(orig_index) == 0 &&
 365           blk_start == boundary) ||
 366           (_array->offset_array(orig_index) > 0 &&
 367          _array->offset_array(orig_index) <= N_words),
 368          "offset array should have been set - "
 369          "orig_index offset: %u, "
 370          "blk_start: " PTR_FORMAT ", "
 371          "boundary: " PTR_FORMAT,
 372          (uint)_array->offset_array(orig_index),
 373          p2i(blk_start), p2i(boundary));
 374   for (size_t j = orig_index + 1; j <= end_index; j++) {
 375     assert(_array->offset_array(j) > 0 &&
 376            _array->offset_array(j) <=
 377              (u_char) (N_words+BlockOffsetArray::N_powers-1),
 378            "offset array should have been set - "
 379            "%u not > 0 OR %u not <= %u",
 380            (uint) _array->offset_array(j),
 381            (uint) _array->offset_array(j),
 382            (uint) (N_words+BlockOffsetArray::N_powers-1));
 383   }
 384 #endif
 385 }
 386 
 387 void G1BlockOffsetArray::verify() const {
 388   assert(gsp()->bottom() < gsp()->top(), "Only non-empty regions should be verified.");
 389   size_t start_card = _array->index_for(gsp()->bottom());
 390   size_t end_card = _array->index_for(gsp()->top() - 1);
 391 
 392   for (size_t current_card = start_card; current_card < end_card; current_card++) {
 393     u_char entry = _array->offset_array(current_card);
 394     if (entry < N_words) {
 395       // The entry should point to an object before the current card. Verify that
 396       // it is possible to walk from that object in to the current card by just
 397       // iterating over the objects following it.
 398       HeapWord* card_address = _array->address_for_index(current_card);
 399       HeapWord* obj_end = card_address - entry;
 400       while (obj_end < card_address) {
 401         HeapWord* obj = obj_end;
 402         size_t obj_size = block_size(obj);
 403         obj_end = obj + obj_size;
 404         guarantee(obj_end > obj && obj_end <= gsp()->top(),
 405                   "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
 406                   p2i(obj), obj_size, p2i(obj_end), p2i(gsp()->top()));
 407       }
 408     } else {
 409       // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
 410       // We need to make sure that we are going backwards and that we don't pass the start of the
 411       // corresponding heap region. But that is about all we can verify.
 412       size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
 413       guarantee(backskip >= 1, "Must be going back at least one card.");
 414 
 415       size_t max_backskip = current_card - start_card;
 416       guarantee(backskip <= max_backskip,
 417                 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
 418                 start_card, current_card, backskip);
 419 
 420       HeapWord* backskip_address = _array->address_for_index(current_card - backskip);
 421       guarantee(backskip_address >= gsp()->bottom(),
 422                 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
 423                 p2i(gsp()->bottom()), p2i(backskip_address));
 424     }
 425   }
 426 }
 427 
 428 #ifndef PRODUCT
 429 void
 430 G1BlockOffsetArray::print_on(outputStream* out) {
 431   size_t from_index = _array->index_for(_bottom);
 432   size_t to_index = _array->index_for(_end);
 433   out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
 434                 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
 435                 p2i(_bottom), p2i(_end), from_index, to_index);
 436   for (size_t i = from_index; i < to_index; ++i) {
 437     out->print_cr("  entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
 438                   i, p2i(_array->address_for_index(i)),
 439                   (uint) _array->offset_array(i));
 440   }
 441 }
 442 #endif // !PRODUCT
 443 
 444 //////////////////////////////////////////////////////////////////////
 445 // G1BlockOffsetArrayContigSpace
 446 //////////////////////////////////////////////////////////////////////
 447 
 448 HeapWord*
 449 G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) {
 450   assert(_bottom <= addr && addr < _end,
 451          "addr must be covered by this Array");
 452   HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
 453   return forward_to_block_containing_addr(q, addr);
 454 }
 455 
 456 HeapWord*
 457 G1BlockOffsetArrayContigSpace::
 458 block_start_unsafe_const(const void* addr) const {
 459   assert(_bottom <= addr && addr < _end,
 460          "addr must be covered by this Array");
 461   HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
 462   HeapWord* n = q + block_size(q);
 463   return forward_to_block_containing_addr_const(q, n, addr);
 464 }
 465 
 466 G1BlockOffsetArrayContigSpace::
 467 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
 468                               MemRegion mr) :
 469   G1BlockOffsetArray(array, mr)
 470 {
 471   _next_offset_threshold = NULL;
 472   _next_offset_index = 0;
 473 }
 474 
 475 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold_raw() {
 476   assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
 477          "just checking");
 478   _next_offset_index = _array->index_for_raw(_bottom);
 479   _next_offset_index++;
 480   _next_offset_threshold =
 481     _array->address_for_index_raw(_next_offset_index);
 482   return _next_offset_threshold;
 483 }
 484 
 485 void G1BlockOffsetArrayContigSpace::zero_bottom_entry_raw() {
 486   assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
 487          "just checking");
 488   size_t bottom_index = _array->index_for_raw(_bottom);
 489   assert(_array->address_for_index_raw(bottom_index) == _bottom,
 490          "Precondition of call");
 491   _array->set_offset_array_raw(bottom_index, 0);
 492 }
 493 
 494 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
 495   assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
 496          "just checking");
 497   _next_offset_index = _array->index_for(_bottom);
 498   _next_offset_index++;
 499   _next_offset_threshold =
 500     _array->address_for_index(_next_offset_index);
 501   return _next_offset_threshold;
 502 }
 503 
 504 void
 505 G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* new_top) {
 506   assert(new_top <= _end, "_end should have already been updated");
 507 
 508   // The first BOT entry should have offset 0.
 509   reset_bot();
 510   alloc_block(_bottom, new_top);
 511  }
 512 
 513 #ifndef PRODUCT
 514 void
 515 G1BlockOffsetArrayContigSpace::print_on(outputStream* out) {
 516   G1BlockOffsetArray::print_on(out);
 517   out->print_cr("  next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
 518   out->print_cr("  next offset index:     " SIZE_FORMAT, _next_offset_index);
 519 }
 520 #endif // !PRODUCT