/*

 * Copyright (c) 2001, 2017, 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

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 */

#include "precompiled.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "gc/shared/plab.inline.hpp"

#include "gc/shared/threadLocalAllocBuffer.hpp"

#include "logging/log.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,

         "Minimum PLAB size " SIZE_FORMAT " must be larger than alignment reserve " SIZE_FORMAT " "

         "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);

  }

}

void PLABStats::log_plab_allocation() {

  log_debug(gc, plab)("%s PLAB allocation: "

                      "allocated: " SIZE_FORMAT "B, "

                      "wasted: " SIZE_FORMAT "B, "

                      "unused: " SIZE_FORMAT "B, "

                      "used: " SIZE_FORMAT "B, "

                      "undo waste: " SIZE_FORMAT "B, ",

                      _description,

                      _allocated * HeapWordSize,

                      _wasted * HeapWordSize,

                      _unused * HeapWordSize,

                      used() * HeapWordSize,

                      _undo_wasted * HeapWordSize);

}

void PLABStats::log_sizing(size_t calculated_words, size_t net_desired_words) {

  log_debug(gc, plab)("%s sizing: "

                      "calculated: " SIZE_FORMAT "B, "

                      "actual: " SIZE_FORMAT "B",

                      _description,

                      calculated_words * HeapWordSize,

                      net_desired_words * HeapWordSize);

}

// Calculates plab size for current number of gc worker threads.

size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) {

  return align_object_size(MIN2(MAX2(min_size(), _desired_net_plab_sz / no_of_gc_workers), max_size()));

}

// Compute desired plab size for one gc worker thread 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() {

  log_plab_allocation();

  if (!ResizePLAB) {

    // Clear accumulators for next round.

    reset();

    return;

  }

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

         "PLAB clipping computation may be incorrect");

  assert(_allocated != 0 || _unused == 0,

         "Inconsistency in PLAB stats: "

         "_allocated: " SIZE_FORMAT ", "

         "_wasted: " SIZE_FORMAT ", "

         "_unused: " SIZE_FORMAT ", "

         "_undo_wasted: " SIZE_FORMAT,

         _allocated, _wasted, _unused, _undo_wasted);

  size_t plab_sz = compute_desired_plab_sz();

  // Take historical weighted average

  _filter.sample(plab_sz);

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

  log_sizing(plab_sz, _desired_net_plab_sz);

  // Clear accumulators for next round

  reset();

}

size_t PLABStats::compute_desired_plab_sz() {

  size_t allocated      = MAX2(_allocated, size_t(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;

  // Assumed to have 1 gc worker thread

  size_t recent_plab_sz = used / target_refills;

  return recent_plab_sz;

}