/*

 * Copyright (c) 2001, 2013, 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.

 *

 */

#ifndef SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

#define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

#include "gc_interface/collectedHeap.hpp"

#include "memory/allocation.hpp"

#include "memory/blockOffsetTable.hpp"

#include "memory/threadLocalAllocBuffer.hpp"

#include "utilities/globalDefinitions.hpp"

// Forward decl.

class PLABStats;

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

class ParGCAllocBuffer: public CHeapObj<mtGC> {

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;

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

  // Should not be called directly

  void flush_stats(PLABStats* stats);

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);

  virtual ~ParGCAllocBuffer() {}

  static const size_t 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;

    if (pointer_delta(_end, _top) >= word_sz) {

      _top = _top + word_sz;

      return res;

    } else {

      return NULL;

    }

  }

  // Allocate the object aligned to "alignment_in_bytes".

  HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);

  // 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(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");

    assert(pointer_delta(_top, obj)     == word_sz, "Bad undo");

    _top = obj;

  }

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

  // unallocated 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()).

  virtual 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

  // and retire the current buffer.

  void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, 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);

      // Since we have flushed the stats we need to clear

      // the _allocated and _wasted fields. Not doing so

      // will artifically inflate the values in the stats

      // to which we add them.

      // The next time we flush these values, we will add

      // what we have just flushed in addition to the size

      // of the buffers allocated between now and then.

      _allocated = 0;

      _wasted = 0;

    }

    // Retire the last allocation buffer.

    retire(end_of_gc, 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.

  virtual 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)

  { }

  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(uint no_of_gc_workers);

                                 // 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);

  }

};

#endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP