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 bool
 373 G1BlockOffsetArray::verify_for_object(HeapWord* obj_start,
 374                                       size_t word_size) const {
 375   size_t first_card = _array->index_for(obj_start);
 376   size_t last_card = _array->index_for(obj_start + word_size - 1);
 377   if (!_array->is_card_boundary(obj_start)) {
 378     // If the object is not on a card boundary the BOT entry of the
 379     // first card should point to another object so we should not
 380     // check that one.
 381     first_card += 1;
 382   }
 383   for (size_t card = first_card; card <= last_card; card += 1) {
 384     HeapWord* card_addr = _array->address_for_index(card);
 385     HeapWord* block_start = block_start_const(card_addr);
 386     if (block_start != obj_start) {
 387       gclog_or_tty->print_cr("block start: "PTR_FORMAT" is incorrect - "
 388                              "card index: "SIZE_FORMAT" "
 389                              "card addr: "PTR_FORMAT" BOT entry: %u "
 390                              "obj: "PTR_FORMAT" word size: "SIZE_FORMAT" "
 391                              "cards: ["SIZE_FORMAT","SIZE_FORMAT"]",
 392                              p2i(block_start), card, p2i(card_addr),
 393                              _array->offset_array(card),
 394                              p2i(obj_start), word_size, first_card, last_card);
 395       return false;
 396     }
 397   }
 398   return true;
 399 }
 400 
 401 #ifndef PRODUCT
 402 void
 403 G1BlockOffsetArray::print_on(outputStream* out) {
 404   size_t from_index = _array->index_for(_bottom);
 405   size_t to_index = _array->index_for(_end);
 406   out->print_cr(">> BOT for area ["PTR_FORMAT","PTR_FORMAT") "
 407                 "cards ["SIZE_FORMAT","SIZE_FORMAT")",
 408                 p2i(_bottom), p2i(_end), from_index, to_index);
 409   for (size_t i = from_index; i < to_index; ++i) {
 410     out->print_cr("  entry "SIZE_FORMAT_W(8)" | "PTR_FORMAT" : %3u",
 411                   i, p2i(_array->address_for_index(i)),
 412                   (uint) _array->offset_array(i));
 413   }
 414 }
 415 #endif // !PRODUCT
 416 
 417 //////////////////////////////////////////////////////////////////////
 418 // G1BlockOffsetArrayContigSpace
 419 //////////////////////////////////////////////////////////////////////
 420 
 421 HeapWord*
 422 G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) {
 423   assert(_bottom <= addr && addr < _end,
 424          "addr must be covered by this Array");
 425   HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
 426   return forward_to_block_containing_addr(q, addr);
 427 }
 428 
 429 HeapWord*
 430 G1BlockOffsetArrayContigSpace::
 431 block_start_unsafe_const(const void* addr) const {
 432   assert(_bottom <= addr && addr < _end,
 433          "addr must be covered by this Array");
 434   HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
 435   HeapWord* n = q + block_size(q);
 436   return forward_to_block_containing_addr_const(q, n, addr);
 437 }
 438 
 439 G1BlockOffsetArrayContigSpace::
 440 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
 441                               MemRegion mr) :
 442   G1BlockOffsetArray(array, mr)
 443 {
 444   _next_offset_threshold = NULL;
 445   _next_offset_index = 0;
 446 }
 447 
 448 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold_raw() {
 449   assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
 450          "just checking");
 451   _next_offset_index = _array->index_for_raw(_bottom);
 452   _next_offset_index++;
 453   _next_offset_threshold =
 454     _array->address_for_index_raw(_next_offset_index);
 455   return _next_offset_threshold;
 456 }
 457 
 458 void G1BlockOffsetArrayContigSpace::zero_bottom_entry_raw() {
 459   assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
 460          "just checking");
 461   size_t bottom_index = _array->index_for_raw(_bottom);
 462   assert(_array->address_for_index_raw(bottom_index) == _bottom,
 463          "Precondition of call");
 464   _array->set_offset_array_raw(bottom_index, 0);
 465 }
 466 
 467 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
 468   assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
 469          "just checking");
 470   _next_offset_index = _array->index_for(_bottom);
 471   _next_offset_index++;
 472   _next_offset_threshold =
 473     _array->address_for_index(_next_offset_index);
 474   return _next_offset_threshold;
 475 }
 476 
 477 void
 478 G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* new_top) {
 479   assert(new_top <= _end, "_end should have already been updated");
 480 
 481   // The first BOT entry should have offset 0.
 482   reset_bot();
 483   alloc_block(_bottom, new_top);
 484  }
 485 
 486 #ifndef PRODUCT
 487 void
 488 G1BlockOffsetArrayContigSpace::print_on(outputStream* out) {
 489   G1BlockOffsetArray::print_on(out);
 490   out->print_cr("  next offset threshold: "PTR_FORMAT, p2i(_next_offset_threshold));
 491   out->print_cr("  next offset index:     "SIZE_FORMAT, _next_offset_index);
 492 }
 493 #endif // !PRODUCT