/*

 * Copyright (c) 2000, 2015, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "gc/shared/blockOffsetTable.inline.hpp"

#include "gc/shared/collectedHeap.inline.hpp"

#include "gc/shared/space.inline.hpp"

#include "memory/iterator.hpp"

#include "memory/universe.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/java.hpp"

#include "services/memTracker.hpp"

//////////////////////////////////////////////////////////////////////

// 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");

  }

  MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);

  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,

                  p2i(rs.base()), rs.size(), p2i(rs.base() + rs.size()));

    gclog_or_tty->print_cr("  "

                  "  _vs.low_boundary(): " INTPTR_FORMAT

                  "  _vs.high_boundary(): " INTPTR_FORMAT,

                  p2i(_vs.low_boundary()),

                  p2i(_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, OOM_MMAP_ERROR, "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;

}

//////////////////////////////////////////////////////////////////////

// BlockOffsetArray

//////////////////////////////////////////////////////////////////////

BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,

                                   MemRegion mr, bool init_to_zero_) :

  BlockOffsetTable(mr.start(), mr.end()),

  _array(array)

{

  assert(_bottom <= _end, "arguments out of order");

  set_init_to_zero(init_to_zero_);

  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, bool reducing) {

  check_reducing_assertion(reducing);

  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, reducing); // 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, bool reducing) {

  check_reducing_assertion(reducing);

  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, reducing);

      start_card_for_region = reach + 1;

      break;

    }

    _array->set_offset_array(start_card_for_region, reach, offset, reducing);

    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");

  u_char last_entry = N_words;

  for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {

    u_char entry = _array->offset_array(c);

    guarantee(entry >= last_entry, "Monotonicity");

    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");

      // Note that N_words is the maximum offset value

      guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");

    }

    last_entry = entry;  // remember for monotonicity test

  }

}

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, bool reducing) {

  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, reducing);

          break;

        } // Else fall through to the next case

      }

      case Action_single: {

        _array->set_offset_array(start_index, boundary, blk_start, reducing);

        // 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, reducing);

        }

        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 does 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, true /* reducing */);

    // 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, true /* reducing */);

      } 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, true /* reducing */);

        // 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, true /* reducing */);

            } 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, true /* reducing */);

          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, bool reducing) {

  do_block_internal(blk_start, blk_end, Action_mark, reducing);

}

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