/*

 * Copyright (c) 2001, 2015, 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/shared/collectedHeap.hpp"

#include "gc/shared/plab.hpp"

#include "gc/shared/threadLocalAllocBuffer.hpp"

#include "oops/arrayOop.hpp"

#include "oops/oop.inline.hpp"

size_t PLAB::min_size() {

  // Make sure that we return something that is larger than AlignmentReserve

  return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve;

}

size_t PLAB::max_size() {

  return ThreadLocalAllocBuffer::max_size();

}

PLAB::PLAB(size_t desired_plab_sz_) :

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

  _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0), _undo_wasted(0)

{

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

  AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? align_object_size(arrayOopDesc::header_size(T_INT)) : 0;

  assert(min_size() > AlignmentReserve,

                 "to be able to contain objects", min_size(), AlignmentReserve));

}

// 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 PLAB::AlignmentReserve;

void PLAB::flush_and_retire_stats(PLABStats* stats) {

  // Retire the last allocation buffer.

  size_t unused = retire_internal();

  // Now flush the statistics.

  stats->add_allocated(_allocated);

  stats->add_wasted(_wasted);

  stats->add_undo_wasted(_undo_wasted);

  stats->add_unused(unused);

  // Since we have flushed the stats we need to clear  the _allocated and _wasted

  // fields in case somebody retains an instance of this over GCs. Not doing so

  // will artifically inflate the values in the statistics.

  _allocated   = 0;

  _wasted      = 0;

  _undo_wasted = 0;

}

void PLAB::retire() {

  _wasted += retire_internal();

}

size_t PLAB::retire_internal() {

  size_t result = 0;

  if (_top < _hard_end) {

    CollectedHeap::fill_with_object(_top, _hard_end);

    result += invalidate();

  }

  return result;

}

void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) {

  CollectedHeap::fill_with_object(obj, word_sz);

  _undo_wasted += word_sz;

}

void PLAB::undo_last_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;

}

void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) {

  // Is the alloc in the current alloc buffer?

  if (contains(obj)) {

    assert(contains(obj + word_sz - 1),

      "should contain whole object");

    undo_last_allocation(obj, word_sz);

  } else {

    add_undo_waste(obj, word_sz);

  }

}

// 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");

  assert(is_object_aligned(max_size()) && min_size() <= max_size(),

         "PLAB clipping computation may be incorrect");

  if (_allocated == 0) {

    assert(_unused == 0,

           err_msg("Inconsistency in PLAB stats: "

                   _allocated, _wasted, _unused, _undo_wasted));

    _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;

  }

  size_t used = _allocated - _wasted - _unused;

  size_t recent_plab_sz = used / (target_refills * no_of_gc_workers);

  // Take historical weighted average

  _filter.sample(recent_plab_sz);

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

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

  new_plab_sz = MIN2(max_size(), new_plab_sz);

  new_plab_sz = align_object_size(new_plab_sz);

  // Latch the result

  if (PrintPLAB) {

  }

  _desired_plab_sz = new_plab_sz;

  reset();

}

#ifndef PRODUCT

void PLAB::print() {

  gclog_or_tty->print_cr("PLAB: _bottom: " PTR_FORMAT "  _top: " PTR_FORMAT

    "  _end: " PTR_FORMAT "  _hard_end: " PTR_FORMAT ")",

    p2i(_bottom), p2i(_top), p2i(_end), p2i(_hard_end));

}

#endif // !PRODUCT