/*

 * Copyright (c) 2018, 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.

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 */

#include "precompiled.hpp"

#include "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1ConcurrentRefine.hpp"

#include "gc/g1/heapRegion.hpp"

#include "gc/g1/heapRegionManager.inline.hpp"

#include "gc/g1/heapRegionSet.inline.hpp"

#include "gc/g1/heterogeneousHeapRegionManager.hpp"

#include "memory/allocation.hpp"

HeterogeneousHeapRegionManager* HeterogeneousHeapRegionManager::manager() {

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  assert(g1h != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");

  HeapRegionManager* hrm = g1h->hrm();

  assert(hrm != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");

  return (HeterogeneousHeapRegionManager*)hrm;

}

void HeterogeneousHeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,

                                                G1RegionToSpaceMapper* prev_bitmap,

                                                G1RegionToSpaceMapper* next_bitmap,

                                                G1RegionToSpaceMapper* bot,

                                                G1RegionToSpaceMapper* cardtable,

                                                G1RegionToSpaceMapper* card_counts) {

  HeapRegionManager::initialize(heap_storage, prev_bitmap, next_bitmap, bot, cardtable, card_counts);

  // We commit bitmap for all regions during initialization and mark the bitmap space as special.

  // This allows regions to be un-committed while concurrent-marking threads are accessing the bitmap concurrently.

  _prev_bitmap_mapper->commit_and_set_special();

  _next_bitmap_mapper->commit_and_set_special();

}

// expand_by() is called to grow the heap. We grow into nvdimm now.

// Dram regions are committed later as needed during mutator region allocation or

// when young list target length is determined after gc cycle.

uint HeterogeneousHeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {

  uint num_regions_possible = total_regions_committed() >= max_expandable_length() ? 0 : max_expandable_length() - total_regions_committed();

  uint num_expanded = expand_nvdimm(MIN2(num_regions, num_regions_possible), pretouch_workers);

  return num_expanded;

}

// Expands heap starting from 'start' index. The question is should we expand from one memory (e.g. nvdimm) to another (e.g. dram).

// Looking at the code, expand_at() is called for humongous allocation where 'start' is in nv-dimm.

// So we only allocate regions in the same kind of memory as 'start'.

uint HeterogeneousHeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {

  if (num_regions == 0) {

    return 0;

  }

  uint target_num_regions = MIN2(num_regions, max_expandable_length() - total_regions_committed());

  uint end = is_in_nvdimm(start) ? end_index_of_nvdimm() : end_index_of_dram();

  uint num_expanded = expand_in_range(start, end, target_num_regions, pretouch_workers);

  assert(total_regions_committed() <= max_expandable_length(), "must be");

  return num_expanded;

}

// This function ensures that there are 'expected_num_regions' committed regions in dram.

// If new regions are committed, it un-commits that many regions from nv-dimm.

// If there are already more regions committed in dram, extra regions are un-committed.

void HeterogeneousHeapRegionManager::adjust_dram_regions(uint expected_num_regions, WorkGang* pretouch_workers) {

  // Release back the extra regions allocated in evacuation failure scenario.

  if(_no_borrowed_regions > 0) {

    _no_borrowed_regions -= shrink_dram(_no_borrowed_regions);

    _no_borrowed_regions -= shrink_nvdimm(_no_borrowed_regions);

  }

  if(expected_num_regions > free_list_dram_length()) {

    // If we are going to expand DRAM, we expand a little more so that we can absorb small variations in Young gen sizing.

    uint targeted_dram_regions = expected_num_regions * (1 + (double)G1YoungExpansionBufferPercent / 100);

    uint to_be_made_available = targeted_dram_regions - free_list_dram_length();

#ifdef ASSERT

    uint total_committed_before = total_regions_committed();

#endif

    uint can_be_made_available = shrink_nvdimm(to_be_made_available);

    uint ret = expand_dram(can_be_made_available, pretouch_workers);

#ifdef ASSERT

    assert(ret == can_be_made_available, "should be equal");

    assert(total_committed_before == total_regions_committed(), "invariant not met");

#endif

  } else {

    uint to_be_released = free_list_dram_length() - expected_num_regions;

    // if number of extra DRAM regions is small, do not shrink.

    if (to_be_released < expected_num_regions * G1YoungExpansionBufferPercent / 100) {

      return;

    }

#ifdef ASSERT

    uint total_committed_before = total_regions_committed();

#endif

    uint ret = shrink_dram(to_be_released);

    assert(ret == to_be_released, "Should be able to shrink by given amount");

    ret = expand_nvdimm(to_be_released, pretouch_workers);

#ifdef ASSERT

    assert(ret == to_be_released, "Should be able to expand by given amount");

    assert(total_committed_before == total_regions_committed(), "invariant not met");

#endif

  }

}

uint HeterogeneousHeapRegionManager::total_regions_committed() const {

  return num_committed_dram() + num_committed_nvdimm();

}

uint HeterogeneousHeapRegionManager::num_committed_dram() const {

  // This class does not keep count of committed regions in dram and nv-dimm.

  // G1RegionToHeteroSpaceMapper keeps this information.

  return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_dram();

}

uint HeterogeneousHeapRegionManager::num_committed_nvdimm() const {

  // See comment for num_committed_dram()

  return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_nvdimm();

}

// Return maximum number of regions that heap can expand to.

uint HeterogeneousHeapRegionManager::max_expandable_length() const {

  return _max_regions;

}

uint HeterogeneousHeapRegionManager::find_unavailable_in_range(uint start_idx, uint end_idx, uint* res_idx) const {

  guarantee(res_idx != NULL, "checking");

  guarantee(start_idx <= (max_length() + 1), "checking");

  uint num_regions = 0;

  uint cur = start_idx;

  while (cur <= end_idx && is_available(cur)) {

    cur++;

  }

  if (cur == end_idx + 1) {

    return num_regions;

  }

  *res_idx = cur;

  while (cur <= end_idx && !is_available(cur)) {

    cur++;

  }

  num_regions = cur - *res_idx;

#ifdef ASSERT

  for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {

    assert(!is_available(i), "just checking");

  }

  assert(cur == end_idx + 1 || num_regions == 0 || is_available(cur),

    "The region at the current position %u must be available or at the end", cur);

#endif

  return num_regions;

}

uint HeterogeneousHeapRegionManager::expand_dram(uint num_regions, WorkGang* pretouch_workers) {

  return expand_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, pretouch_workers);

}

uint HeterogeneousHeapRegionManager::expand_nvdimm(uint num_regions, WorkGang* pretouch_workers) {

  return expand_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, pretouch_workers);

}

// Follows same logic as expand_at() form HeapRegionManager.

uint HeterogeneousHeapRegionManager::expand_in_range(uint start, uint end, uint num_regions, WorkGang* pretouch_gang) {

  uint so_far = 0;

  uint chunk_start = 0;

  uint num_last_found = 0;

  while (so_far < num_regions &&

         (num_last_found = find_unavailable_in_range(start, end, &chunk_start)) > 0) {

    uint to_commit = MIN2(num_regions - so_far, num_last_found);

    make_regions_available(chunk_start, to_commit, pretouch_gang);

    so_far += to_commit;

    start = chunk_start + to_commit + 1;

  }

  return so_far;

}

// Shrink in the range of indexes which are reserved for dram.

uint HeterogeneousHeapRegionManager::shrink_dram(uint num_regions, bool update_free_list) {

  return shrink_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, update_free_list);

}

// Shrink in the range of indexes which are reserved for nv-dimm.

uint HeterogeneousHeapRegionManager::shrink_nvdimm(uint num_regions, bool update_free_list) {

  return shrink_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, update_free_list);

}

// Find empty regions in given range, un-commit them and return the count.

uint HeterogeneousHeapRegionManager::shrink_in_range(uint start, uint end, uint num_regions, bool update_free_list) {

  if (num_regions == 0) {

    return 0;

  }

  uint so_far = 0;

  uint idx_last_found = 0;

  uint num_last_found;

  while (so_far < num_regions &&

         (num_last_found = find_empty_in_range_reverse(start, end, &idx_last_found)) > 0) {

    uint to_uncommit = MIN2(num_regions - so_far, num_last_found);

    if(update_free_list) {

      _free_list.remove_starting_at(at(idx_last_found + num_last_found - to_uncommit), to_uncommit);

    }

    uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);

    so_far += to_uncommit;

    end = idx_last_found;

  }

  return so_far;

}

uint HeterogeneousHeapRegionManager::find_empty_in_range_reverse(uint start_idx, uint end_idx, uint* res_idx) {

  guarantee(res_idx != NULL, "checking");

  guarantee(start_idx < max_length(), "checking");

  guarantee(end_idx < max_length(), "checking");

  if(start_idx > end_idx) {

    return 0;

  }

  uint num_regions_found = 0;

  jlong cur = end_idx;

  while (cur >= start_idx && !(is_available(cur) && at(cur)->is_empty())) {

    cur--;

  }

  if (cur == start_idx - 1) {

    return num_regions_found;

  }

  jlong old_cur = cur;

  // cur indexes the first empty region

  while (cur >= start_idx && is_available(cur) && at(cur)->is_empty()) {

    cur--;

  }

  *res_idx = cur + 1;

  num_regions_found = old_cur - cur;

#ifdef ASSERT

  for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {

    assert(at(i)->is_empty(), "just checking");

  }

#endif

  return num_regions_found;

}

HeapRegion* HeterogeneousHeapRegionManager::allocate_free_region(HeapRegionType type) {

  // We want to prevent mutators from proceeding when we have borrowed regions from the last collection. This

  // will force a full collection to remedy the situation.

  // Free region requests from GC threads can proceed.

  if(type.is_eden() || type.is_humongous()) {

    if(has_borrowed_regions()) {

      return NULL;

    }

  }

  // old and humongous regions are allocated from nv-dimm; eden and survivor regions are allocated from dram

  // assumption: dram regions take higher indexes

  bool from_nvdimm = (type.is_old() || type.is_humongous()) ? true : false;

  bool from_head = from_nvdimm;

  HeapRegion* hr = _free_list.remove_region(from_head);

  if (hr != NULL && ( (from_nvdimm && !is_in_nvdimm(hr->hrm_index())) || (!from_nvdimm && !is_in_dram(hr->hrm_index())) ) ) {

    _free_list.add_ordered(hr);

    hr = NULL;

  }

#ifdef ASSERT

  uint total_committed_before = total_regions_committed();

#endif

  if (hr == NULL) {

    if (!from_nvdimm) {

      uint ret = shrink_nvdimm(1);

      if (ret == 1) {

        ret = expand_dram(1, NULL);

        assert(ret == 1, "We should be able to commit one region");

        hr = _free_list.remove_region(from_head);

      }

    }

    else { /*is_old*/

      uint ret = shrink_dram(1);

      if (ret == 1) {

        ret = expand_nvdimm(1, NULL);

        assert(ret == 1, "We should be able to commit one region");

        hr = _free_list.remove_region(from_head);

      }

    }

  }

#ifdef ASSERT

  assert(total_committed_before == total_regions_committed(), "invariant not met");

#endif

  // When an old region is requested (which happens during collection pause) and we can't find any empty region

  // in the set of available regions (which is an evacuation failure scenario), we borrow (or pre-allocate) an unavailable region

  // from nv-dimm. This region is used to evacuate surviving objects from eden, survivor or old.

  if(hr == NULL && type.is_old()) {

    hr = borrow_old_region_for_gc();

  }

  if (hr != NULL) {

    assert(hr->next() == NULL, "Single region should not have next");

    assert(is_available(hr->hrm_index()), "Must be committed");

  }

  return hr;

}

uint HeterogeneousHeapRegionManager::find_contiguous_only_empty(size_t num) {

  if (has_borrowed_regions()) {

      return G1_NO_HRM_INDEX;

  }

  return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, true);

}

uint HeterogeneousHeapRegionManager::find_contiguous_empty_or_unavailable(size_t num) {

  if (has_borrowed_regions()) {

    return G1_NO_HRM_INDEX;

  }

  return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, false);

}

uint HeterogeneousHeapRegionManager::find_contiguous(size_t start, size_t end, size_t num, bool empty_only) {

  uint found = 0;

  size_t length_found = 0;

  uint cur = (uint)start;

  uint length_unavailable = 0;

  while (length_found < num && cur <= end) {

    HeapRegion* hr = _regions.get_by_index(cur);

    if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {

      // This region is a potential candidate for allocation into.

      if (!is_available(cur)) {

        if(shrink_dram(1) == 1) {

          uint ret = expand_in_range(cur, cur, 1, NULL);

          assert(ret == 1, "We should be able to expand at this index");

        } else {

          length_unavailable++;

        }

      }

      length_found++;

    }

    else {

      // This region is not a candidate. The next region is the next possible one.

      found = cur + 1;

      length_found = 0;

    }

    cur++;

  }

  if (length_found == num) {

    for (uint i = found; i < (found + num); i++) {

      HeapRegion* hr = _regions.get_by_index(i);

      // sanity check

      guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),

                "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT

                " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));

    }

    if (!empty_only && length_unavailable > (max_expandable_length() - total_regions_committed())) {

      // if 'length_unavailable' number of regions will be made available, we will exceed max regions.

      return G1_NO_HRM_INDEX;

    }

    return found;

  }

  else {

    return G1_NO_HRM_INDEX;

  }

}

uint HeterogeneousHeapRegionManager::find_highest_free(bool* expanded) {

  // Loop downwards from the highest dram region index, looking for an

  // entry which is either free or not yet committed.  If not yet

  // committed, expand_at that index.

  uint curr = end_index_of_dram();

  while (true) {

    HeapRegion *hr = _regions.get_by_index(curr);

    if (hr == NULL && !(total_regions_committed() < _max_regions)) {

      uint res = shrink_nvdimm(1);

      if (res == 1) {

        res = expand_in_range(curr, curr, 1, NULL);

        assert(res == 1, "We should be able to expand since shrink was successful");

        *expanded = true;

        return curr;

      }

    }

    else {

      if (hr->is_free()) {

        *expanded = false;

        return curr;

      }

    }

    if (curr == start_index_of_dram()) {

      return G1_NO_HRM_INDEX;

    }

    curr--;

  }

}

// We need to override this since region 0 which serves are dummy region in base class may not be available here.

// This is a corner condition when either number of regions is small. When adaptive sizing is used, initial heap size

// could be just one region.  This region is commited in dram to be used for young generation, leaving region 0 (which is in nvdimm)

// unavailable.

HeapRegion* HeterogeneousHeapRegionManager::get_dummy_region() {

  uint curr = 0;

  while (curr < _regions.length()) {

    if (is_available(curr)) {

      return new_heap_region(curr);

    }

    curr++;

  }

  assert(false, "We should always find a region available for dummy region");

  return NULL;

}

// First shrink in dram, then in nv-dimm.

uint HeterogeneousHeapRegionManager::shrink_by(uint num_regions) {

  // This call is made at end of full collection. Before making this call the region sets are tore down (tear_down_region_sets()).

  // So shrink() calls below do not need to remove uncomitted regions from free list.

  uint ret = shrink_dram(num_regions, false /* update_free_list */);

  ret += shrink_nvdimm(num_regions - ret, false /* update_free_list */);

  return ret;

}

void HeterogeneousHeapRegionManager::verify() {

  HeapRegionManager::verify();

}

uint HeterogeneousHeapRegionManager::free_list_dram_length() const {

  return _free_list.num_of_regions_in_range(start_index_of_dram(), end_index_of_dram());

}

uint HeterogeneousHeapRegionManager::free_list_nvdimm_length() const {

  return _free_list.num_of_regions_in_range(start_index_of_nvdimm(), end_index_of_nvdimm());

}

bool HeterogeneousHeapRegionManager::is_in_nvdimm(uint index) const {

  return index >= start_index_of_nvdimm() && index <= end_index_of_nvdimm();

}

bool HeterogeneousHeapRegionManager::is_in_dram(uint index) const {

  return index >= start_index_of_dram() && index <= end_index_of_dram();

}

// We have to make sure full collection copies all surviving objects to NV-DIMM.

// We might not have enough regions in nvdimm_set, so we need to make more regions on NV-DIMM available for full collection.

// Note: by doing this we are breaking the in-variant that total number of committed regions is equal to current heap size.

// After full collection ends, we will re-establish this in-variant by freeing DRAM regions.

void HeterogeneousHeapRegionManager::prepare_for_full_collection_start() {

  _total_commited_before_full_gc = total_regions_committed() - _no_borrowed_regions;

  _no_borrowed_regions = 0;

  expand_nvdimm(num_committed_dram(), NULL);

  remove_all_free_regions();

}

// We need to bring back the total committed regions to before full collection start.

// Unless we are close to OOM, all regular (not pinned) regions in DRAM should be free.

// We shrink all free regions in DRAM and if needed from NV-DIMM (when there are pinned DRAM regions)

// If we can't bring back committed regions count to _total_commited_before_full_gc, we keep the extra count in _no_borrowed_regions.

// When this GC finishes, new regions won't be allocated since has_borrowed_regions() is true. VM will be forced to re-try GC

// with clear soft references followed by OOM error in worst case.

void HeterogeneousHeapRegionManager::prepare_for_full_collection_end() {

  uint shrink_size = total_regions_committed() - _total_commited_before_full_gc;

  uint so_far = 0;

  uint idx_last_found = 0;

  uint num_last_found;

  uint end = (uint)_regions.length() - 1;

  while (so_far < shrink_size &&

         (num_last_found = find_empty_in_range_reverse(0, end, &idx_last_found)) > 0) {

    uint to_uncommit = MIN2(shrink_size - so_far, num_last_found);

    uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);

    so_far += to_uncommit;

    end = idx_last_found;

  }

  // See comment above the function.

  _no_borrowed_regions = shrink_size - so_far;

}

uint HeterogeneousHeapRegionManager::start_index_of_dram() const { return _max_regions;}

uint HeterogeneousHeapRegionManager::end_index_of_dram() const { return 2*_max_regions - 1; }

uint HeterogeneousHeapRegionManager::start_index_of_nvdimm() const { return 0; }

uint HeterogeneousHeapRegionManager::end_index_of_nvdimm() const { return _max_regions - 1; }

// This function is called when there are no free nv-dimm regions.

// It borrows a region from the set of unavailable regions in nv-dimm for GC purpose.

HeapRegion* HeterogeneousHeapRegionManager::borrow_old_region_for_gc() {

  assert(free_list_nvdimm_length() == 0, "this function should be called only when there are no nv-dimm regions in free list");

  uint ret = expand_nvdimm(1, NULL);

  if(ret != 1) {

    return NULL;

  }

  HeapRegion* hr = _free_list.remove_region(true /*from_head*/);

  assert(is_in_nvdimm(hr->hrm_index()), "allocated region should be in nv-dimm");

  _no_borrowed_regions++;

  return hr;

}

bool HeterogeneousHeapRegionManager::has_borrowed_regions() const {

  return _no_borrowed_regions > 0;

}