jdk8-mips64-public/hotspot: src/share/vm/memory/blockOffsetTable.cpp@52e32c8b317e (annotated)

src/share/vm/memory/blockOffsetTable.cpp@52e32c8b317e (annotated)

src/share/vm/memory/blockOffsetTable.cpp

Wed, 22 Oct 2008 14:48:08 -0400

author: acorn
date: Wed, 22 Oct 2008 14:48:08 -0400
changeset 843: 52e32c8b317e
parent 777: 37f87013dfd8
child 1844: cff162798819
permissions: -rw-r--r--

6761092: jvm crashes when CDS is enabled.
Summary: CDS hardcoded max c++ virtual method table increased
Reviewed-by: coleenp, xlu, jmasa

 /*
  * Copyright 2000-2006 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 # include "incls/_precompiled.incl"
 # include "incls/_blockOffsetTable.cpp.incl"
 //////////////////////////////////////////////////////////////////////
 // BlockOffsetSharedArray
 //////////////////////////////////////////////////////////////////////
 BlockOffsetSharedArray::BlockOffsetSharedArray(MemRegion reserved,
                                                size_t init_word_size):
   _reserved(reserved), _end(NULL)
 {
   size_t size = compute_size(reserved.word_size());
   ReservedSpace rs(size);
   if (!rs.is_reserved()) {
     vm_exit_during_initialization("Could not reserve enough space for heap offset array");
   }
   if (!_vs.initialize(rs, 0)) {
     vm_exit_during_initialization("Could not reserve enough space for heap offset array");
   }
   _offset_array = (u_char*)_vs.low_boundary();
   resize(init_word_size);
   if (TraceBlockOffsetTable) {
     gclog_or_tty->print_cr("BlockOffsetSharedArray::BlockOffsetSharedArray: ");
     gclog_or_tty->print_cr("  "
                   "  rs.base(): " INTPTR_FORMAT
                   "  rs.size(): " INTPTR_FORMAT
                   "  rs end(): " INTPTR_FORMAT,
                   rs.base(), rs.size(), rs.base() + rs.size());
     gclog_or_tty->print_cr("  "
                   "  _vs.low_boundary(): " INTPTR_FORMAT
                   "  _vs.high_boundary(): " INTPTR_FORMAT,
                   _vs.low_boundary(),
                   _vs.high_boundary());
   }
 }
 void BlockOffsetSharedArray::resize(size_t new_word_size) {
   assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved");
   size_t new_size = compute_size(new_word_size);
   size_t old_size = _vs.committed_size();
   size_t delta;
   char* high = _vs.high();
   _end = _reserved.start() + new_word_size;
   if (new_size > old_size) {
     delta = ReservedSpace::page_align_size_up(new_size - old_size);
     assert(delta > 0, "just checking");
     if (!_vs.expand_by(delta)) {
       // Do better than this for Merlin
       vm_exit_out_of_memory(delta, "offset table expansion");
     }
     assert(_vs.high() == high + delta, "invalid expansion");
   } else {
     delta = ReservedSpace::page_align_size_down(old_size - new_size);
     if (delta == 0) return;
     _vs.shrink_by(delta);
     assert(_vs.high() == high - delta, "invalid expansion");
   }
 }
 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
   assert(p >= _reserved.start(), "just checking");
   size_t delta = pointer_delta(p, _reserved.start());
   return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
 }
 void BlockOffsetSharedArray::serialize(SerializeOopClosure* soc,
                                        HeapWord* start, HeapWord* end) {
   assert(_offset_array[0] == 0, "objects can't cross covered areas");
   assert(start <= end, "bad address range");
   size_t start_index = index_for(start);
   size_t end_index = index_for(end-1)+1;
   soc->do_region(&_offset_array[start_index],
                  (end_index - start_index) * sizeof(_offset_array[0]));
 }
 //////////////////////////////////////////////////////////////////////
 // BlockOffsetArray
 //////////////////////////////////////////////////////////////////////
 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
                                    MemRegion mr, bool init_to_zero) :
   BlockOffsetTable(mr.start(), mr.end()),
   _array(array),
   _init_to_zero(init_to_zero)
 {
   assert(_bottom <= _end, "arguments out of order");
   if (!_init_to_zero) {
     // initialize cards to point back to mr.start()
     set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
     _array->set_offset_array(0, 0);  // set first card to 0
   }
 }
 // The arguments follow the normal convention of denoting
 // a right-open interval: [start, end)
 void
 BlockOffsetArray::
 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
   if (start >= end) {
     // The start address is equal to the end address (or to
     // the right of the end address) so there are not cards
     // that need to be updated..
     return;
   }
   // Write the backskip value for each region.
   //
   //    offset
   //    card             2nd                       3rd
   //     | +- 1st        |                         |
   //     v v             v                         v
   //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
   //    |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
   //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
   //    11              19                        75
   //      12
   //
   //    offset card is the card that points to the start of an object
   //      x - offset value of offset card
   //    1st - start of first logarithmic region
   //      0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
   //    2nd - start of second logarithmic region
   //      1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
   //    3rd - start of third logarithmic region
   //      2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
   //
   //    integer below the block offset entry is an example of
   //    the index of the entry
   //
   //    Given an address,
   //      Find the index for the address
   //      Find the block offset table entry
   //      Convert the entry to a back slide
   //        (e.g., with today's, offset = 0x81 =>
   //          back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
   //      Move back N (e.g., 8) entries and repeat with the
   //        value of the new entry
   //
   size_t start_card = _array->index_for(start);
   size_t end_card = _array->index_for(end-1);
   assert(start ==_array->address_for_index(start_card), "Precondition");
   assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
   set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
 }
 // Unlike the normal convention in this code, the argument here denotes
 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
 // above.
 void
 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
   if (start_card > end_card) {
     return;
   }
   assert(start_card > _array->index_for(_bottom), "Cannot be first card");
   assert(_array->offset_array(start_card-1) <= N_words,
     "Offset card has an unexpected value");
   size_t start_card_for_region = start_card;
   u_char offset = max_jubyte;
   for (int i = 0; i < N_powers; i++) {
     // -1 so that the the card with the actual offset is counted.  Another -1
     // so that the reach ends in this region and not at the start
     // of the next.
     size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1);
     offset = N_words + i;
     if (reach >= end_card) {
       _array->set_offset_array(start_card_for_region, end_card, offset);
       start_card_for_region = reach + 1;
       break;
     }
     _array->set_offset_array(start_card_for_region, reach, offset);
     start_card_for_region = reach + 1;
   }
   assert(start_card_for_region > end_card, "Sanity check");
   DEBUG_ONLY(check_all_cards(start_card, end_card);)
 }
 // The card-interval [start_card, end_card] is a closed interval; this
 // is an expensive check -- use with care and only under protection of
 // suitable flag.
 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
   if (end_card < start_card) {
     return;
   }
   guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
   for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
     u_char entry = _array->offset_array(c);
     if (c - start_card > power_to_cards_back(1)) {
       guarantee(entry > N_words, "Should be in logarithmic region");
     }
     size_t backskip = entry_to_cards_back(entry);
     size_t landing_card = c - backskip;
     guarantee(landing_card >= (start_card - 1), "Inv");
     if (landing_card >= start_card) {
       guarantee(_array->offset_array(landing_card) <= entry, "monotonicity");
     } else {
       guarantee(landing_card == start_card - 1, "Tautology");
       guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");
     }
   }
 }
 void
 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
   assert(blk_start != NULL && blk_end > blk_start,
          "phantom block");
   single_block(blk_start, blk_end);
 }
 // Action_mark - update the BOT for the block [blk_start, blk_end).
 //               Current typical use is for splitting a block.
 // Action_single - udpate the BOT for an allocation.
 // Action_verify - BOT verification.
 void
 BlockOffsetArray::do_block_internal(HeapWord* blk_start,
                                     HeapWord* blk_end,
                                     Action action) {
   assert(Universe::heap()->is_in_reserved(blk_start),
          "reference must be into the heap");
   assert(Universe::heap()->is_in_reserved(blk_end-1),
          "limit must be within the heap");
   // This is optimized to make the test fast, assuming we only rarely
   // cross boundaries.
   uintptr_t end_ui = (uintptr_t)(blk_end - 1);
   uintptr_t start_ui = (uintptr_t)blk_start;
   // Calculate the last card boundary preceding end of blk
   intptr_t boundary_before_end = (intptr_t)end_ui;
   clear_bits(boundary_before_end, right_n_bits(LogN));
   if (start_ui <= (uintptr_t)boundary_before_end) {
     // blk starts at or crosses a boundary
     // Calculate index of card on which blk begins
     size_t    start_index = _array->index_for(blk_start);
     // Index of card on which blk ends
     size_t    end_index   = _array->index_for(blk_end - 1);
     // Start address of card on which blk begins
     HeapWord* boundary    = _array->address_for_index(start_index);
     assert(boundary <= blk_start, "blk should start at or after boundary");
     if (blk_start != boundary) {
       // blk starts strictly after boundary
       // adjust card boundary and start_index forward to next card
       boundary += N_words;
       start_index++;
     }
     assert(start_index <= end_index, "monotonicity of index_for()");
     assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
     switch (action) {
       case Action_mark: {
         if (init_to_zero()) {
           _array->set_offset_array(start_index, boundary, blk_start);
           break;
         } // Else fall through to the next case
       }
       case Action_single: {
         _array->set_offset_array(start_index, boundary, blk_start);
         // We have finished marking the "offset card". We need to now
         // mark the subsequent cards that this blk spans.
         if (start_index < end_index) {
           HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
           HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
           set_remainder_to_point_to_start(rem_st, rem_end);
         }
         break;
       }
       case Action_check: {
         _array->check_offset_array(start_index, boundary, blk_start);
         // We have finished checking the "offset card". We need to now
         // check the subsequent cards that this blk spans.
         check_all_cards(start_index + 1, end_index);
         break;
       }
       default:
         ShouldNotReachHere();
     }
   }
 }
 // The range [blk_start, blk_end) represents a single contiguous block
 // of storage; modify the block offset table to represent this
 // information; Right-open interval: [blk_start, blk_end)
 // NOTE: this method does _not_ adjust _unallocated_block.
 void
 BlockOffsetArray::single_block(HeapWord* blk_start,
                                HeapWord* blk_end) {
   do_block_internal(blk_start, blk_end, Action_single);
 }
 void BlockOffsetArray::verify() const {
   // For each entry in the block offset table, verify that
   // the entry correctly finds the start of an object at the
   // first address covered by the block or to the left of that
   // first address.
   size_t next_index = 1;
   size_t last_index = last_active_index();
   // Use for debugging.  Initialize to NULL to distinguish the
   // first iteration through the while loop.
   HeapWord* last_p = NULL;
   HeapWord* last_start = NULL;
   oop last_o = NULL;
   while (next_index <= last_index) {
     // Use an address past the start of the address for
     // the entry.
     HeapWord* p = _array->address_for_index(next_index) + 1;
     if (p >= _end) {
       // That's all of the allocated block table.
       return;
     }
     // block_start() asserts that start <= p.
     HeapWord* start = block_start(p);
     // First check if the start is an allocated block and only
     // then if it is a valid object.
     oop o = oop(start);
     assert(!Universe::is_fully_initialized() ||
            _sp->is_free_block(start) ||
            o->is_oop_or_null(), "Bad object was found");
     next_index++;
     last_p = p;
     last_start = start;
     last_o = o;
   }
 }
 //////////////////////////////////////////////////////////////////////
 // BlockOffsetArrayNonContigSpace
 //////////////////////////////////////////////////////////////////////
 // The block [blk_start, blk_end) has been allocated;
 // adjust the block offset table to represent this information;
 // NOTE: Clients of BlockOffsetArrayNonContigSpace: consider using
 // the somewhat more lightweight split_block() or
 // (when init_to_zero()) mark_block() wherever possible.
 // right-open interval: [blk_start, blk_end)
 void
 BlockOffsetArrayNonContigSpace::alloc_block(HeapWord* blk_start,
                                             HeapWord* blk_end) {
   assert(blk_start != NULL && blk_end > blk_start,
          "phantom block");
   single_block(blk_start, blk_end);
   allocated(blk_start, blk_end);
 }
 // Adjust BOT to show that a previously whole block has been split
 // into two.  We verify the BOT for the first part (prefix) and
 // update the  BOT for the second part (suffix).
 //      blk is the start of the block
 //      blk_size is the size of the original block
 //      left_blk_size is the size of the first part of the split
 void BlockOffsetArrayNonContigSpace::split_block(HeapWord* blk,
                                                  size_t blk_size,
                                                  size_t left_blk_size) {
   // Verify that the BOT shows [blk, blk + blk_size) to be one block.
   verify_single_block(blk, blk_size);
   // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size)
   // is one single block.
   assert(blk_size > 0, "Should be positive");
   assert(left_blk_size > 0, "Should be positive");
   assert(left_blk_size < blk_size, "Not a split");
   // Start addresses of prefix block and suffix block.
   HeapWord* pref_addr = blk;
   HeapWord* suff_addr = blk + left_blk_size;
   HeapWord* end_addr  = blk + blk_size;
   // Indices for starts of prefix block and suffix block.
   size_t pref_index = _array->index_for(pref_addr);
   if (_array->address_for_index(pref_index) != pref_addr) {
     // pref_addr deos not begin pref_index
     pref_index++;
   }
   size_t suff_index = _array->index_for(suff_addr);
   if (_array->address_for_index(suff_index) != suff_addr) {
     // suff_addr does not begin suff_index
     suff_index++;
   }
   // Definition: A block B, denoted [B_start, B_end) __starts__
   //     a card C, denoted [C_start, C_end), where C_start and C_end
   //     are the heap addresses that card C covers, iff
   //     B_start <= C_start < B_end.
   //
   //     We say that a card C "is started by" a block B, iff
   //     B "starts" C.
   //
   //     Note that the cardinality of the set of cards {C}
   //     started by a block B can be 0, 1, or more.
   //
   // Below, pref_index and suff_index are, respectively, the
   // first (least) card indices that the prefix and suffix of
   // the split start; end_index is one more than the index of
   // the last (greatest) card that blk starts.
   size_t end_index  = _array->index_for(end_addr - 1) + 1;
   // Calculate the # cards that the prefix and suffix affect.
   size_t num_pref_cards = suff_index - pref_index;
   size_t num_suff_cards = end_index  - suff_index;
   // Change the cards that need changing
   if (num_suff_cards > 0) {
     HeapWord* boundary = _array->address_for_index(suff_index);
     // Set the offset card for suffix block
     _array->set_offset_array(suff_index, boundary, suff_addr);
     // Change any further cards that need changing in the suffix
     if (num_pref_cards > 0) {
       if (num_pref_cards >= num_suff_cards) {
         // Unilaterally fix all of the suffix cards: closed card
         // index interval in args below.
         set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1);
       } else {
         // Unilaterally fix the first (num_pref_cards - 1) following
         // the "offset card" in the suffix block.
         set_remainder_to_point_to_start_incl(suff_index + 1,
           suff_index + num_pref_cards - 1);
         // Fix the appropriate cards in the remainder of the
         // suffix block -- these are the last num_pref_cards
         // cards in each power block of the "new" range plumbed
         // from suff_addr.
         bool more = true;
         uint i = 1;
         while (more && (i < N_powers)) {
           size_t back_by = power_to_cards_back(i);
           size_t right_index = suff_index + back_by - 1;
           size_t left_index  = right_index - num_pref_cards + 1;
           if (right_index >= end_index - 1) { // last iteration
             right_index = end_index - 1;
             more = false;
           }
           if (back_by > num_pref_cards) {
             // Fill in the remainder of this "power block", if it
             // is non-null.
             if (left_index <= right_index) {
               _array->set_offset_array(left_index, right_index,
                                      N_words + i - 1);
             } else {
               more = false; // we are done
             }
             i++;
             break;
           }
           i++;
         }
         while (more && (i < N_powers)) {
           size_t back_by = power_to_cards_back(i);
           size_t right_index = suff_index + back_by - 1;
           size_t left_index  = right_index - num_pref_cards + 1;
           if (right_index >= end_index - 1) { // last iteration
             right_index = end_index - 1;
             if (left_index > right_index) {
               break;
             }
             more  = false;
           }
           assert(left_index <= right_index, "Error");
           _array->set_offset_array(left_index, right_index, N_words + i - 1);
           i++;
         }
       }
     } // else no more cards to fix in suffix
   } // else nothing needs to be done
   // Verify that we did the right thing
   verify_single_block(pref_addr, left_blk_size);
   verify_single_block(suff_addr, blk_size - left_blk_size);
 }
 // Mark the BOT such that if [blk_start, blk_end) straddles a card
 // boundary, the card following the first such boundary is marked
 // with the appropriate offset.
 // NOTE: this method does _not_ adjust _unallocated_block or
 // any cards subsequent to the first one.
 void
 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start,
                                            HeapWord* blk_end) {
   do_block_internal(blk_start, blk_end, Action_mark);
 }
 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe(
   const void* addr) const {
   assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
   assert(_bottom <= addr && addr < _end,
          "addr must be covered by this Array");
   // Must read this exactly once because it can be modified by parallel
   // allocation.
   HeapWord* ub = _unallocated_block;
   if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
     assert(ub < _end, "tautology (see above)");
     return ub;
   }
   // Otherwise, find the block start using the table.
   size_t index = _array->index_for(addr);
   HeapWord* q = _array->address_for_index(index);
   uint offset = _array->offset_array(index);    // Extend u_char to uint.
   while (offset >= N_words) {
     // The excess of the offset from N_words indicates a power of Base
     // to go back by.
     size_t n_cards_back = entry_to_cards_back(offset);
     q -= (N_words * n_cards_back);
     assert(q >= _sp->bottom(), "Went below bottom!");
     index -= n_cards_back;
     offset = _array->offset_array(index);
   }
   assert(offset < N_words, "offset too large");
   index--;
   q -= offset;
   HeapWord* n = q;
   while (n <= addr) {
     debug_only(HeapWord* last = q);   // for debugging
     q = n;
     n += _sp->block_size(n);
   }
   assert(q <= addr, "wrong order for current and arg");
   assert(addr <= n, "wrong order for arg and next");
   return q;
 }
 HeapWord* BlockOffsetArrayNonContigSpace::block_start_careful(
   const void* addr) const {
   assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
   assert(_bottom <= addr && addr < _end,
          "addr must be covered by this Array");
   // Must read this exactly once because it can be modified by parallel
   // allocation.
   HeapWord* ub = _unallocated_block;
   if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
     assert(ub < _end, "tautology (see above)");
     return ub;
   }
   // Otherwise, find the block start using the table, but taking
   // care (cf block_start_unsafe() above) not to parse any objects/blocks
   // on the cards themsleves.
   size_t index = _array->index_for(addr);
   assert(_array->address_for_index(index) == addr,
          "arg should be start of card");
   HeapWord* q = (HeapWord*)addr;
   uint offset;
   do {
     offset = _array->offset_array(index);
     if (offset < N_words) {
       q -= offset;
     } else {
       size_t n_cards_back = entry_to_cards_back(offset);
       q -= (n_cards_back * N_words);
       index -= n_cards_back;
     }
   } while (offset >= N_words);
   assert(q <= addr, "block start should be to left of arg");
   return q;
 }
 #ifndef PRODUCT
 // Verification & debugging - ensure that the offset table reflects the fact
 // that the block [blk_start, blk_end) or [blk, blk + size) is a
 // single block of storage. NOTE: can't const this because of
 // call to non-const do_block_internal() below.
 void BlockOffsetArrayNonContigSpace::verify_single_block(
   HeapWord* blk_start, HeapWord* blk_end) {
   if (VerifyBlockOffsetArray) {
     do_block_internal(blk_start, blk_end, Action_check);
   }
 }
 void BlockOffsetArrayNonContigSpace::verify_single_block(
   HeapWord* blk, size_t size) {
   verify_single_block(blk, blk + size);
 }
 // Verify that the given block is before _unallocated_block
 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
   HeapWord* blk_start, HeapWord* blk_end) const {
   if (BlockOffsetArrayUseUnallocatedBlock) {
     assert(blk_start < blk_end, "Block inconsistency?");
     assert(blk_end <= _unallocated_block, "_unallocated_block problem");
   }
 }
 void BlockOffsetArrayNonContigSpace::verify_not_unallocated(
   HeapWord* blk, size_t size) const {
   verify_not_unallocated(blk, blk + size);
 }
 #endif // PRODUCT
 size_t BlockOffsetArrayNonContigSpace::last_active_index() const {
   if (_unallocated_block == _bottom) {
     return 0;
   } else {
     return _array->index_for(_unallocated_block - 1);
   }
 }
 //////////////////////////////////////////////////////////////////////
 // BlockOffsetArrayContigSpace
 //////////////////////////////////////////////////////////////////////
 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const {
   assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
   // Otherwise, find the block start using the table.
   assert(_bottom <= addr && addr < _end,
          "addr must be covered by this Array");
   size_t index = _array->index_for(addr);
   // We must make sure that the offset table entry we use is valid.  If
   // "addr" is past the end, start at the last known one and go forward.
   index = MIN2(index, _next_offset_index-1);
   HeapWord* q = _array->address_for_index(index);
   uint offset = _array->offset_array(index);    // Extend u_char to uint.
   while (offset > N_words) {
     // The excess of the offset from N_words indicates a power of Base
     // to go back by.
     size_t n_cards_back = entry_to_cards_back(offset);
     q -= (N_words * n_cards_back);
     assert(q >= _sp->bottom(), "Went below bottom!");
     index -= n_cards_back;
     offset = _array->offset_array(index);
   }
   while (offset == N_words) {
     assert(q >= _sp->bottom(), "Went below bottom!");
     q -= N_words;
     index--;
     offset = _array->offset_array(index);
   }
   assert(offset < N_words, "offset too large");
   q -= offset;
   HeapWord* n = q;
   while (n <= addr) {
     debug_only(HeapWord* last = q);   // for debugging
     q = n;
     n += _sp->block_size(n);
   }
   assert(q <= addr, "wrong order for current and arg");
   assert(addr <= n, "wrong order for arg and next");
   return q;
 }
 //
 //              _next_offset_threshold
 //              |   _next_offset_index
 //              v   v
 //      +-------+-------+-------+-------+-------+
 //      | i-1   |   i   | i+1   | i+2   | i+3   |
 //      +-------+-------+-------+-------+-------+
 //       ( ^    ]
 //         block-start
 //
 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start,
                                         HeapWord* blk_end) {
   assert(blk_start != NULL && blk_end > blk_start,
          "phantom block");
   assert(blk_end > _next_offset_threshold,
          "should be past threshold");
   assert(blk_start <= _next_offset_threshold,
          "blk_start should be at or before threshold")
   assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words,
          "offset should be <= BlockOffsetSharedArray::N");
   assert(Universe::heap()->is_in_reserved(blk_start),
          "reference must be into the heap");
   assert(Universe::heap()->is_in_reserved(blk_end-1),
          "limit must be within the heap");
   assert(_next_offset_threshold ==
          _array->_reserved.start() + _next_offset_index*N_words,
          "index must agree with threshold");
   debug_only(size_t orig_next_offset_index = _next_offset_index;)
   // Mark the card that holds the offset into the block.  Note
   // that _next_offset_index and _next_offset_threshold are not
   // updated until the end of this method.
   _array->set_offset_array(_next_offset_index,
                            _next_offset_threshold,
                            blk_start);
   // We need to now mark the subsequent cards that this blk spans.
   // Index of card on which blk ends.
   size_t end_index   = _array->index_for(blk_end - 1);
   // Are there more cards left to be updated?
   if (_next_offset_index + 1 <= end_index) {
     HeapWord* rem_st  = _array->address_for_index(_next_offset_index + 1);
     // Calculate rem_end this way because end_index
     // may be the last valid index in the covered region.
     HeapWord* rem_end = _array->address_for_index(end_index) +  N_words;
     set_remainder_to_point_to_start(rem_st, rem_end);
   }
   // _next_offset_index and _next_offset_threshold updated here.
   _next_offset_index = end_index + 1;
   // Calculate _next_offset_threshold this way because end_index
   // may be the last valid index in the covered region.
   _next_offset_threshold = _array->address_for_index(end_index) +
     N_words;
   assert(_next_offset_threshold >= blk_end, "Incorrent offset threshold");
 #ifdef ASSERT
   // The offset can be 0 if the block starts on a boundary.  That
   // is checked by an assertion above.
   size_t start_index = _array->index_for(blk_start);
   HeapWord* boundary    = _array->address_for_index(start_index);
   assert((_array->offset_array(orig_next_offset_index) == 0 &&
           blk_start == boundary) ||
           (_array->offset_array(orig_next_offset_index) > 0 &&
          _array->offset_array(orig_next_offset_index) <= N_words),
          "offset array should have been set");
   for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) {
     assert(_array->offset_array(j) > 0 &&
            _array->offset_array(j) <= (u_char) (N_words+N_powers-1),
            "offset array should have been set");
   }
 #endif
 }
 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {
   assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
          "just checking");
   _next_offset_index = _array->index_for(_bottom);
   _next_offset_index++;
   _next_offset_threshold =
     _array->address_for_index(_next_offset_index);
   return _next_offset_threshold;
 }
 void BlockOffsetArrayContigSpace::zero_bottom_entry() {
   assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
          "just checking");
   size_t bottom_index = _array->index_for(_bottom);
   _array->set_offset_array(bottom_index, 0);
 }
 void BlockOffsetArrayContigSpace::serialize(SerializeOopClosure* soc) {
   if (soc->reading()) {
     // Null these values so that the serializer won't object to updating them.
     _next_offset_threshold = NULL;
     _next_offset_index = 0;
   }
   soc->do_ptr(&_next_offset_threshold);
   soc->do_size_t(&_next_offset_index);
 }
 size_t BlockOffsetArrayContigSpace::last_active_index() const {
   size_t result = _next_offset_index - 1;
   return result >= 0 ? result : 0;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/blockOffsetTable.cpp@52e32c8b317e (annotated)

src/share/vm/memory/blockOffsetTable.cpp