/*

 * Copyright (c) 2001, 2012, 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/shared/parGCAllocBuffer.hpp"

#include "memory/sharedHeap.hpp"

#include "oops/arrayOop.hpp"

#include "oops/oop.inline.hpp"

ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) :

  _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL),

  _end(NULL), _hard_end(NULL),

  _retained(false), _retained_filler(),

  _allocated(0), _wasted(0)

{

  assert (min_size() > AlignmentReserve, "Inconsistency!");

  // arrayOopDesc::header_size depends on command line initialization.

  FillerHeaderSize = align_object_size(arrayOopDesc::header_size(T_INT));

  AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0;

}

size_t ParGCAllocBuffer::FillerHeaderSize;

// If the minimum object size is greater than MinObjAlignment, we can

// end up with a shard at the end of the buffer that's smaller than

// the smallest object.  We can't allow that because the buffer must

// look like it's full of objects when we retire it, so we make

// sure we have enough space for a filler int array object.

size_t ParGCAllocBuffer::AlignmentReserve;

void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) {

  assert(!retain || end_of_gc, "Can only retain at GC end.");

  if (_retained) {

    // If the buffer had been retained shorten the previous filler object.

    assert(_retained_filler.end() <= _top, "INVARIANT");

    CollectedHeap::fill_with_object(_retained_filler);

    // Wasted space book-keeping, otherwise (normally) done in invalidate()

    _wasted += _retained_filler.word_size();

    _retained = false;

  }

  assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained.");

  if (_top < _hard_end) {

    CollectedHeap::fill_with_object(_top, _hard_end);

    if (!retain) {

      invalidate();

    } else {

      // Is there wasted space we'd like to retain for the next GC?

      if (pointer_delta(_end, _top) > FillerHeaderSize) {

        _retained = true;

        _retained_filler = MemRegion(_top, FillerHeaderSize);

        _top = _top + FillerHeaderSize;

      } else {

        invalidate();

      }

    }

  }

}

void ParGCAllocBuffer::flush_stats(PLABStats* stats) {

  assert(ResizePLAB, "Wasted work");

  stats->add_allocated(_allocated);

  stats->add_wasted(_wasted);

  stats->add_unused(pointer_delta(_end, _top));

}

// Compute desired plab size and latch result for later

// use. This should be called once at the end of parallel

// scavenge; it clears the sensor accumulators.

void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) {

  assert(ResizePLAB, "Not set");

  if (_allocated == 0) {

    assert(_unused == 0,

           err_msg("Inconsistency in PLAB stats: "

                   "_allocated: "SIZE_FORMAT", "

                   "_wasted: "SIZE_FORMAT", "

                   "_unused: "SIZE_FORMAT", "

                   "_used  : "SIZE_FORMAT,

                   _allocated, _wasted, _unused, _used));

    _allocated = 1;

  }

  double wasted_frac    = (double)_unused/(double)_allocated;

  size_t target_refills = (size_t)((wasted_frac*TargetSurvivorRatio)/

                                   TargetPLABWastePct);

  if (target_refills == 0) {

    target_refills = 1;

  }

  _used = _allocated - _wasted - _unused;

  size_t plab_sz = _used/(target_refills*no_of_gc_workers);

  if (PrintPLAB) gclog_or_tty->print(" (plab_sz = %d ", plab_sz);

  // Take historical weighted average

  _filter.sample(plab_sz);

  // Clip from above and below, and align to object boundary

  plab_sz = MAX2(min_size(), (size_t)_filter.average());

  plab_sz = MIN2(max_size(), plab_sz);

  plab_sz = align_object_size(plab_sz);

  // Latch the result

  if (PrintPLAB) gclog_or_tty->print(" desired_plab_sz = %d) ", plab_sz);

  _desired_plab_sz = plab_sz;

  // Now clear the accumulators for next round:

  // note this needs to be fixed in the case where we

  // are retaining across scavenges. FIX ME !!! XXX

  _allocated = 0;

  _wasted    = 0;

  _unused    = 0;

}

#ifndef PRODUCT

void ParGCAllocBuffer::print() {

  gclog_or_tty->print("parGCAllocBuffer: _bottom: %p  _top: %p  _end: %p  _hard_end: %p"

             "_retained: %c _retained_filler: [%p,%p)\n",

             _bottom, _top, _end, _hard_end,

             "FT"[_retained], _retained_filler.start(), _retained_filler.end());

}

#endif // !PRODUCT

const size_t ParGCAllocBufferWithBOT::ChunkSizeInWords =

MIN2(CardTableModRefBS::par_chunk_heapword_alignment(),

     ((size_t)Generation::GenGrain)/HeapWordSize);

const size_t ParGCAllocBufferWithBOT::ChunkSizeInBytes =

MIN2(CardTableModRefBS::par_chunk_heapword_alignment() * HeapWordSize,

     (size_t)Generation::GenGrain);

ParGCAllocBufferWithBOT::ParGCAllocBufferWithBOT(size_t word_sz,

                                                 BlockOffsetSharedArray* bsa) :

  ParGCAllocBuffer(word_sz),

  _bsa(bsa),

  _bt(bsa, MemRegion(_bottom, _hard_end)),

  _true_end(_hard_end)

{}

// The buffer comes with its own BOT, with a shared (obviously) underlying

// BlockOffsetSharedArray. We manipulate this BOT in the normal way

// as we would for any contiguous space. However, on occasion we

// need to do some buffer surgery at the extremities before we

// start using the body of the buffer for allocations. Such surgery

// (as explained elsewhere) is to prevent allocation on a card that

// is in the process of being walked concurrently by another GC thread.

// When such surgery happens at a point that is far removed (to the

// right of the current allocation point, top), we use the "contig"

// parameter below to directly manipulate the shared array without

// modifying the _next_threshold state in the BOT.

void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr,

                                                     bool contig) {

  CollectedHeap::fill_with_object(mr);

  if (contig) {

    _bt.alloc_block(mr.start(), mr.end());

  } else {

    _bt.BlockOffsetArray::alloc_block(mr.start(), mr.end());

  }

}

HeapWord* ParGCAllocBufferWithBOT::allocate_slow(size_t word_sz) {

  HeapWord* res = NULL;

  if (_true_end > _hard_end) {

    assert((HeapWord*)align_size_down(intptr_t(_hard_end),

                                      ChunkSizeInBytes) == _hard_end,

           "or else _true_end should be equal to _hard_end");

    assert(_retained, "or else _true_end should be equal to _hard_end");

    assert(_retained_filler.end() <= _top, "INVARIANT");

    CollectedHeap::fill_with_object(_retained_filler);

    if (_top < _hard_end) {

      fill_region_with_block(MemRegion(_top, _hard_end), true);

    }

    HeapWord* next_hard_end = MIN2(_true_end, _hard_end + ChunkSizeInWords);

    _retained_filler = MemRegion(_hard_end, FillerHeaderSize);

    _bt.alloc_block(_retained_filler.start(), _retained_filler.word_size());

    _top      = _retained_filler.end();

    _hard_end = next_hard_end;

    _end      = _hard_end - AlignmentReserve;

    res       = ParGCAllocBuffer::allocate(word_sz);

    if (res != NULL) {

      _bt.alloc_block(res, word_sz);

    }

  }

  return res;

}

void

ParGCAllocBufferWithBOT::undo_allocation(HeapWord* obj, size_t word_sz) {

  ParGCAllocBuffer::undo_allocation(obj, word_sz);

  // This may back us up beyond the previous threshold, so reset.

  _bt.set_region(MemRegion(_top, _hard_end));

  _bt.initialize_threshold();

}

void ParGCAllocBufferWithBOT::retire(bool end_of_gc, bool retain) {

  assert(!retain || end_of_gc, "Can only retain at GC end.");

  if (_retained) {

    // We're about to make the retained_filler into a block.

    _bt.BlockOffsetArray::alloc_block(_retained_filler.start(),

                                      _retained_filler.end());

  }

  // Reset _hard_end to _true_end (and update _end)

  if (retain && _hard_end != NULL) {

    assert(_hard_end <= _true_end, "Invariant.");

    _hard_end = _true_end;

    _end      = MAX2(_top, _hard_end - AlignmentReserve);

    assert(_end <= _hard_end, "Invariant.");

  }

  _true_end = _hard_end;

  HeapWord* pre_top = _top;

  ParGCAllocBuffer::retire(end_of_gc, retain);

  // Now any old _retained_filler is cut back to size, the free part is

  // filled with a filler object, and top is past the header of that

  // object.

  if (retain && _top < _end) {

    assert(end_of_gc && retain, "Or else retain should be false.");

    // If the lab does not start on a card boundary, we don't want to

    // allocate onto that card, since that might lead to concurrent

    // allocation and card scanning, which we don't support.  So we fill

    // the first card with a garbage object.

    size_t first_card_index = _bsa->index_for(pre_top);

    HeapWord* first_card_start = _bsa->address_for_index(first_card_index);

    if (first_card_start < pre_top) {

      HeapWord* second_card_start =

        _bsa->inc_by_region_size(first_card_start);

      // Ensure enough room to fill with the smallest block

      second_card_start = MAX2(second_card_start, pre_top + AlignmentReserve);

      // If the end is already in the first card, don't go beyond it!

      // Or if the remainder is too small for a filler object, gobble it up.

      if (_hard_end < second_card_start ||

          pointer_delta(_hard_end, second_card_start) < AlignmentReserve) {

        second_card_start = _hard_end;

      }

      if (pre_top < second_card_start) {

        MemRegion first_card_suffix(pre_top, second_card_start);

        fill_region_with_block(first_card_suffix, true);

      }

      pre_top = second_card_start;

      _top = pre_top;

      _end = MAX2(_top, _hard_end - AlignmentReserve);

    }

    // If the lab does not end on a card boundary, we don't want to

    // allocate onto that card, since that might lead to concurrent

    // allocation and card scanning, which we don't support.  So we fill

    // the last card with a garbage object.

    size_t last_card_index = _bsa->index_for(_hard_end);

    HeapWord* last_card_start = _bsa->address_for_index(last_card_index);

    if (last_card_start < _hard_end) {

      // Ensure enough room to fill with the smallest block

      last_card_start = MIN2(last_card_start, _hard_end - AlignmentReserve);

      // If the top is already in the last card, don't go back beyond it!

      // Or if the remainder is too small for a filler object, gobble it up.

      if (_top > last_card_start ||

          pointer_delta(last_card_start, _top) < AlignmentReserve) {

        last_card_start = _top;

      }

      if (last_card_start < _hard_end) {

        MemRegion last_card_prefix(last_card_start, _hard_end);

        fill_region_with_block(last_card_prefix, false);

      }

      _hard_end = last_card_start;

      _end      = MAX2(_top, _hard_end - AlignmentReserve);

      _true_end = _hard_end;

      assert(_end <= _hard_end, "Invariant.");

    }

    // At this point:

    //   1) we had a filler object from the original top to hard_end.

    //   2) We've filled in any partial cards at the front and back.

    if (pre_top < _hard_end) {

      // Now we can reset the _bt to do allocation in the given area.

      MemRegion new_filler(pre_top, _hard_end);

      fill_region_with_block(new_filler, false);

      _top = pre_top + ParGCAllocBuffer::FillerHeaderSize;

      // If there's no space left, don't retain.

      if (_top >= _end) {

        _retained = false;

        invalidate();

        return;

      }

      _retained_filler = MemRegion(pre_top, _top);

      _bt.set_region(MemRegion(_top, _hard_end));

      _bt.initialize_threshold();

      assert(_bt.threshold() > _top, "initialize_threshold failed!");

      // There may be other reasons for queries into the middle of the

      // filler object.  When such queries are done in parallel with

      // allocation, bad things can happen, if the query involves object

      // iteration.  So we ensure that such queries do not involve object

      // iteration, by putting another filler object on the boundaries of

      // such queries.  One such is the object spanning a parallel card

      // chunk boundary.

      // "chunk_boundary" is the address of the first chunk boundary less

      // than "hard_end".

      HeapWord* chunk_boundary =

        (HeapWord*)align_size_down(intptr_t(_hard_end-1), ChunkSizeInBytes);

      assert(chunk_boundary < _hard_end, "Or else above did not work.");

      assert(pointer_delta(_true_end, chunk_boundary) >= AlignmentReserve,

             "Consequence of last card handling above.");

      if (_top <= chunk_boundary) {

        assert(_true_end == _hard_end, "Invariant.");

        while (_top <= chunk_boundary) {

          assert(pointer_delta(_hard_end, chunk_boundary) >= AlignmentReserve,

                 "Consequence of last card handling above.");

          _bt.BlockOffsetArray::alloc_block(chunk_boundary, _hard_end);

          CollectedHeap::fill_with_object(chunk_boundary, _hard_end);

          _hard_end = chunk_boundary;

          chunk_boundary -= ChunkSizeInWords;

        }

        _end = _hard_end - AlignmentReserve;

        assert(_top <= _end, "Invariant.");

        // Now reset the initial filler chunk so it doesn't overlap with

        // the one(s) inserted above.

        MemRegion new_filler(pre_top, _hard_end);

        fill_region_with_block(new_filler, false);

      }

    } else {

      _retained = false;

      invalidate();

    }

  } else {

    assert(!end_of_gc ||

           (!_retained && _true_end == _hard_end), "Checking.");

  }

  assert(_end <= _hard_end, "Invariant.");

  assert(_top < _end || _top == _hard_end, "Invariant");

}