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 
  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   _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)
  88 void 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.
 140 void 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.
 170 void 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 
 205 HeapWord* 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 //
 252 void 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 
 328 void 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
 370 void G1BlockOffsetTablePart::set_object_can_span(bool can_span) {
 371   _object_can_span = can_span;
 372 }
 373 #endif
 374 
 375 #ifndef PRODUCT
 376 void
 377 G1BlockOffsetTablePart::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 
 393 HeapWord* 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 
 401 void 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 
 408 HeapWord* 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 
 416 void 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 }