/*

 * Copyright (c) 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#include "precompiled.hpp"

#include "gc/z/zArray.inline.hpp"

#include "gc/z/zPage.inline.hpp"

#include "gc/z/zRelocationSet.hpp"

#include "gc/z/zRelocationSetSelector.hpp"

#include "logging/log.hpp"

#include "runtime/globals.hpp"

#include "utilities/debug.hpp"

ZRelocationSetSelectorGroup::ZRelocationSetSelectorGroup(const char* name,

                                                         size_t page_size,

                                                         size_t object_size_limit) :

    _name(name),

    _page_size(page_size),

    _object_size_limit(object_size_limit),

    _fragmentation_limit(page_size * (ZFragmentationLimit / 100)),

    _registered_pages(),

    _sorted_pages(NULL),

    _nselected(0),

    _relocating(0),

    _fragmentation(0) {}

ZRelocationSetSelectorGroup::~ZRelocationSetSelectorGroup() {

  FREE_C_HEAP_ARRAY(const ZPage*, _sorted_pages);

}

void ZRelocationSetSelectorGroup::register_live_page(const ZPage* page, size_t garbage) {

  if (garbage > _fragmentation_limit) {

    _registered_pages.add(page);

  } else {

    _fragmentation += garbage;

  }

}

void ZRelocationSetSelectorGroup::semi_sort() {

  // Semi-sort registered pages by live bytes in ascending order

  const size_t npartitions_shift = 11;

  const size_t npartitions = (size_t)1 << npartitions_shift;

  const size_t partition_size = _page_size >> npartitions_shift;

  const size_t partition_size_shift = exact_log2(partition_size);

  const size_t npages = _registered_pages.size();

  size_t partition_slots[npartitions];

  size_t partition_finger[npartitions];

  // Allocate destination array

  _sorted_pages = REALLOC_C_HEAP_ARRAY(const ZPage*, _sorted_pages, npages, mtGC);

  debug_only(memset(_sorted_pages, 0, npages * sizeof(ZPage*)));

  // Calculate partition slots

  memset(partition_slots, 0, sizeof(partition_slots));

  ZArrayIterator<const ZPage*> iter1(&_registered_pages);

  for (const ZPage* page; iter1.next(&page);) {

    const size_t index = page->live_bytes() >> partition_size_shift;

    partition_slots[index]++;

  }

  // Calculate accumulated partition slots and fingers

  size_t prev_partition_slots = 0;

  for (size_t i = 0; i < npartitions; i++) {

    partition_slots[i] += prev_partition_slots;

    partition_finger[i] = prev_partition_slots;

    prev_partition_slots = partition_slots[i];

  }

  // Sort pages into partitions

  ZArrayIterator<const ZPage*> iter2(&_registered_pages);

  for (const ZPage* page; iter2.next(&page);) {

    const size_t index = page->live_bytes() >> partition_size_shift;

    const size_t finger = partition_finger[index]++;

    assert(_sorted_pages[finger] == NULL, "Invalid finger");

    _sorted_pages[finger] = page;

  }

}

void ZRelocationSetSelectorGroup::select() {

  // Calculate the number of pages to relocate by successively including pages in

  // a candidate relocation set and calculate the maximum space requirement for

  // their live objects.

  const size_t npages = _registered_pages.size();

  size_t selected_from = 0;

  size_t selected_to = 0;

  size_t from_size = 0;

  semi_sort();

  for (size_t from = 1; from <= npages; from++) {

    // Add page to the candidate relocation set

    from_size += _sorted_pages[from - 1]->live_bytes();

    // Calculate the maximum number of pages needed by the candidate relocation set.

    // By subtracting the object size limit from the pages size we get the maximum

    // number of pages that the relocation set is guaranteed to fit in, regardless

    // of in which order the objects are relocated.

    const size_t to = ceil((double)(from_size) / (double)(_page_size - _object_size_limit));

    // Calculate the relative difference in reclaimable space compared to our

    // currently selected final relocation set. If this number is larger than the

    // acceptable fragmentation limit, then the current candidate relocation set

    // becomes our new final relocation set.

    const size_t diff_from = from - selected_from;

    const size_t diff_to = to - selected_to;

    const double diff_reclaimable = 100 - percent_of(diff_to, diff_from);

    if (diff_reclaimable > ZFragmentationLimit) {

      selected_from = from;

      selected_to = to;

    }

    log_trace(gc, reloc)("Candidate Relocation Set (%s Pages): "

                         SIZE_FORMAT "->" SIZE_FORMAT ", %.1f%% relative defragmentation, %s",

                         _name, from, to, diff_reclaimable, (selected_from == from) ? "Selected" : "Rejected");

  }

  // Finalize selection

  _nselected = selected_from;

  // Update statistics

  _relocating = from_size;

  for (size_t i = _nselected; i < npages; i++) {

    const ZPage* const page = _sorted_pages[i];

    _fragmentation += page->size() - page->live_bytes();

  }

  log_debug(gc, reloc)("Relocation Set (%s Pages): " SIZE_FORMAT "->" SIZE_FORMAT ", " SIZE_FORMAT " skipped",

                       _name, selected_from, selected_to, npages - _nselected);

}

const ZPage* const* ZRelocationSetSelectorGroup::selected() const {

  return _sorted_pages;

}

size_t ZRelocationSetSelectorGroup::nselected() const {

  return _nselected;

}

size_t ZRelocationSetSelectorGroup::relocating() const {

  return _relocating;

}

size_t ZRelocationSetSelectorGroup::fragmentation() const {

  return _fragmentation;

}

ZRelocationSetSelector::ZRelocationSetSelector() :

    _small("Small", ZPageSizeSmall, ZObjectSizeLimitSmall),

    _medium("Medium", ZPageSizeMedium, ZObjectSizeLimitMedium),

    _live(0),

    _garbage(0),

    _fragmentation(0) {}

void ZRelocationSetSelector::register_live_page(const ZPage* page) {

  const uint8_t type = page->type();

  const size_t live = page->live_bytes();

  const size_t garbage = page->size() - live;

  if (type == ZPageTypeSmall) {

    _small.register_live_page(page, garbage);

  } else if (type == ZPageTypeMedium) {

    _medium.register_live_page(page, garbage);

  } else {

    _fragmentation += garbage;

  }

  _live += live;

  _garbage += garbage;

}

void ZRelocationSetSelector::register_garbage_page(const ZPage* page) {

  _garbage += page->size();

}

void ZRelocationSetSelector::select(ZRelocationSet* relocation_set) {

  // Select pages to relocate. The resulting relocation set will be

  // sorted such that medium pages comes first, followed by small

  // pages. Pages within each page group will be semi-sorted by live

  // bytes in ascending order. Relocating pages in this order allows

  // us to start reclaiming memory more quickly.

  // Select pages from each group

  _medium.select();

  _small.select();

  // Populate relocation set

  relocation_set->populate(_medium.selected(), _medium.nselected(),

                           _small.selected(), _small.nselected());

}

size_t ZRelocationSetSelector::live() const {

  return _live;

}

size_t ZRelocationSetSelector::garbage() const {

  return _garbage;

}

size_t ZRelocationSetSelector::relocating() const {

  return _small.relocating() + _medium.relocating();

}

size_t ZRelocationSetSelector::fragmentation() const {

  return _fragmentation + _small.fragmentation() + _medium.fragmentation();

}