/*

 * Copyright 2001-2008 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.

 *

 */

// Forward decl.

class PLABStats;

// A per-thread allocation buffer used during GC.

class ParGCAllocBuffer: public CHeapObj {

protected:

  char head[32];

  size_t _word_sz;          // in HeapWord units

  HeapWord* _bottom;

  HeapWord* _top;

  HeapWord* _end;       // last allocatable address + 1

  HeapWord* _hard_end;  // _end + AlignmentReserve

  bool      _retained;  // whether we hold a _retained_filler

  MemRegion _retained_filler;

  // In support of ergonomic sizing of PLAB's

  size_t    _allocated;     // in HeapWord units

  size_t    _wasted;        // in HeapWord units

  char tail[32];

  static size_t FillerHeaderSize;

  static size_t AlignmentReserve;

public:

  // Initializes the buffer to be empty, but with the given "word_sz".

  // Must get initialized with "set_buf" for an allocation to succeed.

  ParGCAllocBuffer(size_t word_sz);

  static const size_t min_size() {

    return ThreadLocalAllocBuffer::min_size();

  }

  static const size_t max_size() {

    return ThreadLocalAllocBuffer::max_size();

  }

  // If an allocation of the given "word_sz" can be satisfied within the

  // buffer, do the allocation, returning a pointer to the start of the

  // allocated block.  If the allocation request cannot be satisfied,

  // return NULL.

  HeapWord* allocate(size_t word_sz) {

    HeapWord* res = _top;

    HeapWord* new_top = _top + word_sz;

    if (new_top <= _end) {

      _top = new_top;

      return res;

    } else {

      return NULL;

    }

  }

  // Undo the last allocation in the buffer, which is required to be of the

  // "obj" of the given "word_sz".

  void undo_allocation(HeapWord* obj, size_t word_sz) {

    assert(_top - word_sz >= _bottom

           && _top - word_sz == obj,

           "Bad undo_allocation");

    _top = _top - word_sz;

  }

  // The total (word) size of the buffer, including both allocated and

  // unallocted space.

  size_t word_sz() { return _word_sz; }

  // Should only be done if we are about to reset with a new buffer of the

  // given size.

  void set_word_size(size_t new_word_sz) {

    assert(new_word_sz > AlignmentReserve, "Too small");

    _word_sz = new_word_sz;

  }

  // The number of words of unallocated space remaining in the buffer.

  size_t words_remaining() {

    assert(_end >= _top, "Negative buffer");

    return pointer_delta(_end, _top, HeapWordSize);

  }

  bool contains(void* addr) {

    return (void*)_bottom <= addr && addr < (void*)_hard_end;

  }

  // Sets the space of the buffer to be [buf, space+word_sz()).

  void set_buf(HeapWord* buf) {

    _bottom   = buf;

    _top      = _bottom;

    _hard_end = _bottom + word_sz();

    _end      = _hard_end - AlignmentReserve;

    assert(_end >= _top, "Negative buffer");

    // In support of ergonomic sizing

    _allocated += word_sz();

  }

  // Flush the stats supporting ergonomic sizing of PLAB's

  void flush_stats(PLABStats* stats);

  void flush_stats_and_retire(PLABStats* stats, bool retain) {

    // We flush the stats first in order to get a reading of

    // unused space in the last buffer.

    if (ResizePLAB) {

      flush_stats(stats);

    }

    // Retire the last allocation buffer.

    retire(true, retain);

  }

  // Force future allocations to fail and queries for contains()

  // to return false

  void invalidate() {

    assert(!_retained, "Shouldn't retain an invalidated buffer.");

    _end    = _hard_end;

    _wasted += pointer_delta(_end, _top);  // unused  space

    _top    = _end;      // force future allocations to fail

    _bottom = _end;      // force future contains() queries to return false

  }

  // Fills in the unallocated portion of the buffer with a garbage object.

  // If "end_of_gc" is TRUE, is after the last use in the GC.  IF "retain"

  // is true, attempt to re-use the unused portion in the next GC.

  void retire(bool end_of_gc, bool retain);

  void print() PRODUCT_RETURN;

};

// PLAB stats book-keeping

class PLABStats VALUE_OBJ_CLASS_SPEC {

  size_t _allocated;      // total allocated

  size_t _wasted;         // of which wasted (internal fragmentation)

  size_t _unused;         // Unused in last buffer

  size_t _used;           // derived = allocated - wasted - unused

  size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized

  AdaptiveWeightedAverage

         _filter;         // integrator with decay

 public:

  PLABStats(size_t desired_plab_sz_, unsigned wt) :

    _allocated(0),

    _wasted(0),

    _unused(0),

    _used(0),

    _desired_plab_sz(desired_plab_sz_),

    _filter(wt)

  {

    size_t min_sz = min_size();

    size_t max_sz = max_size();

    size_t aligned_min_sz = align_object_size(min_sz);

    size_t aligned_max_sz = align_object_size(max_sz);

    assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&

           min_sz <= max_sz,

           "PLAB clipping computation in adjust_desired_plab_sz()"

           " may be incorrect");

  }

  static const size_t min_size() {

    return ParGCAllocBuffer::min_size();

  }

  static const size_t max_size() {

    return ParGCAllocBuffer::max_size();

  }

  size_t desired_plab_sz() {

    return _desired_plab_sz;

  }

  void adjust_desired_plab_sz(); // filter computation, latches output to

                                 // _desired_plab_sz, clears sensor accumulators

  void add_allocated(size_t v) {

    Atomic::add_ptr(v, &_allocated);

  }

  void add_unused(size_t v) {

    Atomic::add_ptr(v, &_unused);

  }

  void add_wasted(size_t v) {

    Atomic::add_ptr(v, &_wasted);

  }

};

class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {

  BlockOffsetArrayContigSpace _bt;

  BlockOffsetSharedArray*     _bsa;

  HeapWord*                   _true_end;  // end of the whole ParGCAllocBuffer

  static const size_t ChunkSizeInWords;

  static const size_t ChunkSizeInBytes;

  HeapWord* allocate_slow(size_t word_sz);

  void fill_region_with_block(MemRegion mr, bool contig);

public:

  ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);

  HeapWord* allocate(size_t word_sz) {

    HeapWord* res = ParGCAllocBuffer::allocate(word_sz);

    if (res != NULL) {

      _bt.alloc_block(res, word_sz);

    } else {

      res = allocate_slow(word_sz);

    }

    return res;

  }

  void undo_allocation(HeapWord* obj, size_t word_sz);

  void set_buf(HeapWord* buf_start) {

    ParGCAllocBuffer::set_buf(buf_start);

    _true_end = _hard_end;

    _bt.set_region(MemRegion(buf_start, word_sz()));

    _bt.initialize_threshold();

  }

  void retire(bool end_of_gc, bool retain);

  MemRegion range() {

    return MemRegion(_top, _true_end);

  }

};