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 * This code is free software; you can redistribute it and/or modify it

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 * published by the Free Software Foundation.

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 * 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

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 */

#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 "logging/log.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);

  log_trace(gc, bot)("BlockOffsetSharedArray::BlockOffsetSharedArray: ");

  log_trace(gc, bot)("   rs.base(): " INTPTR_FORMAT " rs.size(): " INTPTR_FORMAT " rs end(): " INTPTR_FORMAT,

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

  log_trace(gc, bot)("   _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((int)BOTConstants::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() + BOTConstants::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)+BOTConstants::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) <= BOTConstants::N_words,

    "Offset card has an unexpected value");

  size_t start_card_for_region = start_card;

  u_char offset = max_jubyte;

  for (uint i = 0; i < BOTConstants::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 + (BOTConstants::power_to_cards_back(i+1) - 1);

    offset = BOTConstants::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) == BOTConstants::N_words, "Wrong value in second card");

  u_char last_entry = BOTConstants::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 > BOTConstants::power_to_cards_back(1)) {

      guarantee(entry > BOTConstants::N_words, "Should be in logarithmic region");

    }

    size_t backskip = BOTConstants::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) <= BOTConstants::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(_sp->is_in_reserved(blk_start),

         "reference must be into the space");

  assert(_sp->is_in_reserved(blk_end-1),

         "limit must be within the space");

  // 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((int)BOTConstants::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 += BOTConstants::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) + BOTConstants::N_words;

          HeapWord* rem_end = _array->address_for_index(end_index) + BOTConstants::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) ||

           oopDesc::is_oop_or_null(o), "Bad object was found");

    next_index++;

    last_p = p;

    last_start = start;

    last_o = o;

  }

}

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

// 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 > BOTConstants::N_words) {

    // The excess of the offset from N_words indicates a power of Base

    // to go back by.

    size_t n_cards_back = BOTConstants::entry_to_cards_back(offset);

    q -= (BOTConstants::N_words * n_cards_back);

    assert(q >= _sp->bottom(), "Went below bottom!");

    index -= n_cards_back;

    offset = _array->offset_array(index);

  }

  while (offset == BOTConstants::N_words) {

    assert(q >= _sp->bottom(), "Went below bottom!");

    q -= BOTConstants::N_words;

    index--;

    offset = _array->offset_array(index);

  }

  assert(offset < BOTConstants::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) <= BOTConstants::N_words,

         "offset should be <= BlockOffsetSharedArray::N");

  assert(_sp->is_in_reserved(blk_start),

         "reference must be into the space");

  assert(_sp->is_in_reserved(blk_end-1),

         "limit must be within the space");

  assert(_next_offset_threshold ==

         _array->_reserved.start() + _next_offset_index*BOTConstants::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) +  BOTConstants::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) + BOTConstants::N_words;

  assert(_next_offset_threshold >= blk_end, "Incorrect 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) <= BOTConstants::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) (BOTConstants::N_words+BOTConstants::N_powers-1),

           "offset array should have been set");

  }

#endif

}

HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {

  _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() {

  size_t bottom_index = _array->index_for(_bottom);

  _array->set_offset_array(bottom_index, 0);

}

size_t BlockOffsetArrayContigSpace::last_active_index() const {

  return _next_offset_index == 0 ? 0 : _next_offset_index - 1;

}