/*

 * Copyright (c) 2001, 2011, 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_implementation/g1/g1BlockOffsetTable.inline.hpp"

#include "memory/space.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/java.hpp"

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

// G1BlockOffsetSharedArray

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

G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion reserved,

                                                   size_t init_word_size) :

  _reserved(reserved), _end(NULL)

{

  size_t size = compute_size(reserved.word_size());

  ReservedSpace rs(ReservedSpace::allocation_align_size_up(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("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: ");

    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 G1BlockOffsetSharedArray::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");

    // Initialization of the contents is left to the

    // G1BlockOffsetArray that uses it.

  } 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 G1BlockOffsetSharedArray::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;

}

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

// G1BlockOffsetArray

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

G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,

                                       MemRegion mr, bool init_to_zero) :

  G1BlockOffsetTable(mr.start(), mr.end()),

  _unallocated_block(_bottom),

  _array(array), _csp(NULL),

  _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

  }

}

void G1BlockOffsetArray::set_space(Space* sp) {

  _sp = sp;

  _csp = sp->toContiguousSpace();

}

// The arguments follow the normal convention of denoting

// a right-open interval: [start, end)

void

G1BlockOffsetArray:: 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

G1BlockOffsetArray::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 < BlockOffsetArray::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 + (BlockOffsetArray::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 block [blk_start, blk_end) has been allocated;

// adjust the block offset table to represent this information;

// right-open interval: [blk_start, blk_end)

void

G1BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {

  mark_block(blk_start, blk_end);

  allocated(blk_start, blk_end);

}

// Adjust BOT to show that a previously whole block has been split

// into two.

void G1BlockOffsetArray::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.

  mark_block(blk + left_blk_size, blk + blk_size);

}

// Action_mark - update the BOT for the block [blk_start, blk_end).

//               Current typical use is for splitting a block.

// Action_single - update the BOT for an allocation.

// Action_verify - BOT verification.

void G1BlockOffsetArray::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 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 G1BlockOffsetArray::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 > BlockOffsetArray::power_to_cards_back(1)) {

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

    }

    size_t backskip = BlockOffsetArray::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");

    }

  }

}

// 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

G1BlockOffsetArray::single_block(HeapWord* blk_start, HeapWord* blk_end) {

  do_block_internal(blk_start, blk_end, Action_single);

}

// 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

G1BlockOffsetArray::mark_block(HeapWord* blk_start, HeapWord* blk_end) {

  do_block_internal(blk_start, blk_end, Action_mark);

}

HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {

  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.

  HeapWord* q = block_at_or_preceding(addr, false, 0);

  return forward_to_block_containing_addr(q, addr);

}

// This duplicates a little code from the above: unavoidable.

HeapWord*

G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const {

  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.

  HeapWord* q = block_at_or_preceding(addr, false, 0);

  HeapWord* n = q + _sp->block_size(q);

  return forward_to_block_containing_addr_const(q, n, addr);

}

HeapWord*

G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,

                                                          HeapWord* n,

                                                          const void* addr) {

  // We're not in the normal case.  We need to handle an important subcase

  // here: LAB allocation.  An allocation previously recorded in the

  // offset table was actually a lab allocation, and was divided into

  // several objects subsequently.  Fix this situation as we answer the

  // query, by updating entries as we cross them.

  // If the fist object's end q is at the card boundary. Start refining

  // with the corresponding card (the value of the entry will be basically

  // set to 0). If the object crosses the boundary -- start from the next card.

  size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n);

  HeapWord* next_boundary = _array->address_for_index(next_index);

  if (csp() != NULL) {

    if (addr >= csp()->top()) return csp()->top();

    while (next_boundary < addr) {

      while (n <= next_boundary) {

        q = n;

        oop obj = oop(q);

        if (obj->klass_or_null() == NULL) return q;

        n += obj->size();

      }

      assert(q <= next_boundary && n > next_boundary, "Consequence of loop");

      // [q, n) is the block that crosses the boundary.

      alloc_block_work2(&next_boundary, &next_index, q, n);

    }

  } else {

    while (next_boundary < addr) {

      while (n <= next_boundary) {

        q = n;

        oop obj = oop(q);

        if (obj->klass_or_null() == NULL) return q;

        n += _sp->block_size(q);

      }

      assert(q <= next_boundary && n > next_boundary, "Consequence of loop");

      // [q, n) is the block that crosses the boundary.

      alloc_block_work2(&next_boundary, &next_index, q, n);

    }

  }

  return forward_to_block_containing_addr_const(q, n, addr);

}

HeapWord* G1BlockOffsetArray::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--);

    q -= offset;

  } while (offset == N_words);

  assert(q <= addr, "block start should be to left of arg");

  return q;

}

// Note that the committed size of the covered space may have changed,

// so the table size might also wish to change.

void G1BlockOffsetArray::resize(size_t new_word_size) {

  HeapWord* new_end = _bottom + new_word_size;

  if (_end < new_end && !init_to_zero()) {

    // verify that the old and new boundaries are also card boundaries

    assert(_array->is_card_boundary(_end),

           "_end not a card boundary");

    assert(_array->is_card_boundary(new_end),

           "new _end would not be a card boundary");

    // set all the newly added cards

    _array->set_offset_array(_end, new_end, N_words);

  }

  _end = new_end;  // update _end

}

void G1BlockOffsetArray::set_region(MemRegion mr) {

  _bottom = mr.start();

  _end = mr.end();

}

//

//              threshold_

//              |   _index_

//              v   v

//      +-------+-------+-------+-------+-------+

//      | i-1   |   i   | i+1   | i+2   | i+3   |

//      +-------+-------+-------+-------+-------+

//       ( ^    ]

//         block-start

//

void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_,

                                           HeapWord* blk_start, HeapWord* blk_end) {

  // For efficiency, do copy-in/copy-out.

  HeapWord* threshold = *threshold_;

  size_t    index = *index_;

  assert(blk_start != NULL && blk_end > blk_start,

         "phantom block");

  assert(blk_end > threshold, "should be past threshold");

  assert(blk_start <= threshold, "blk_start should be at or before threshold");

  assert(pointer_delta(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(threshold == _array->_reserved.start() + index*N_words,

         "index must agree with threshold");

  DEBUG_ONLY(size_t orig_index = 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(index, 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 (index + 1 <= end_index) {

    HeapWord* rem_st  = _array->address_for_index(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);

  }

  index = end_index + 1;

  // Calculate threshold_ this way because end_index

  // may be the last valid index in the covered region.

  threshold = _array->address_for_index(end_index) + N_words;

  assert(threshold >= blk_end, "Incorrect offset threshold");

  // index_ and threshold_ updated here.

  *threshold_ = threshold;

  *index_ = index;

#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);