/*

 * Copyright (c) 2016, 2019, 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/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1CollectionSet.hpp"

#include "gc/g1/g1CollectionSetCandidates.hpp"

#include "gc/g1/g1CollectorState.hpp"

#include "gc/g1/g1ParScanThreadState.hpp"

#include "gc/g1/g1Policy.hpp"

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

#include "gc/g1/heapRegionRemSet.hpp"

#include "gc/g1/heapRegionSet.hpp"

#include "logging/logStream.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

#include "utilities/quickSort.hpp"

G1CollectorState* G1CollectionSet::collector_state() {

  return _g1h->collector_state();

}

G1GCPhaseTimes* G1CollectionSet::phase_times() {

  return _policy->phase_times();

}

double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {

  return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase());

}

G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :

  _g1h(g1h),

  _policy(policy),

  _candidates(NULL),

  _eden_region_length(0),

  _survivor_region_length(0),

  _old_region_length(0),

  _collection_set_regions(NULL),

  _collection_set_cur_length(0),

  _collection_set_max_length(0),

  _num_optional_regions(0),

  _bytes_used_before(0),

  _recorded_rs_lengths(0),

  _inc_build_state(Inactive),

  _inc_part_start(0),

  _inc_bytes_used_before(0),

  _inc_recorded_rs_lengths(0),

  _inc_recorded_rs_lengths_diffs(0),

  _inc_predicted_elapsed_time_ms(0.0),

  _inc_predicted_elapsed_time_ms_diffs(0.0) {

}

G1CollectionSet::~G1CollectionSet() {

  if (_collection_set_regions != NULL) {

    FREE_C_HEAP_ARRAY(uint, _collection_set_regions);

  }

  free_optional_regions();

  clear_candidates();

}

void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,

                                          uint survivor_cset_region_length) {

  assert_at_safepoint_on_vm_thread();

  _eden_region_length     = eden_cset_region_length;

  _survivor_region_length = survivor_cset_region_length;

  assert((size_t) young_region_length() == _collection_set_cur_length,

         "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);

  _old_region_length = 0;

  free_optional_regions();

}

void G1CollectionSet::initialize(uint max_region_length) {

  guarantee(_collection_set_regions == NULL, "Must only initialize once.");

  _collection_set_max_length = max_region_length;

  _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);

}

void G1CollectionSet::free_optional_regions() {

  _num_optional_regions = 0;

}

void G1CollectionSet::clear_candidates() {

  delete _candidates;

  _candidates = NULL;

}

void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) {

  _recorded_rs_lengths = rs_lengths;

}

// Add the heap region at the head of the non-incremental collection set

void G1CollectionSet::add_old_region(HeapRegion* hr) {

  assert_at_safepoint_on_vm_thread();

  assert(_inc_build_state == Active,

         "Precondition, actively building cset or adding optional later on");

  assert(hr->is_old(), "the region should be old");

  assert(!hr->in_collection_set(), "should not already be in the collection set");

  _g1h->register_old_region_with_region_attr(hr);

  _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();

  assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");

  _bytes_used_before += hr->used();

  _recorded_rs_lengths += hr->rem_set()->occupied();

  _old_region_length++;

  _g1h->old_set_remove(hr);

}

void G1CollectionSet::add_optional_region(HeapRegion* hr) {

  assert(hr->is_old(), "the region should be old");

  assert(!hr->in_collection_set(), "should not already be in the CSet");

  _g1h->register_optional_region_with_region_attr(hr);

  hr->set_index_in_opt_cset(_num_optional_regions++);

}

void G1CollectionSet::start_incremental_building() {

  assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");

  assert(_inc_build_state == Inactive, "Precondition");

  _inc_bytes_used_before = 0;

  _inc_recorded_rs_lengths = 0;

  _inc_recorded_rs_lengths_diffs = 0;

  _inc_predicted_elapsed_time_ms = 0.0;

  _inc_predicted_elapsed_time_ms_diffs = 0.0;

  update_incremental_marker();

}

void G1CollectionSet::finalize_incremental_building() {

  assert(_inc_build_state == Active, "Precondition");

  assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");

  // The two "main" fields, _inc_recorded_rs_lengths and

  // _inc_predicted_elapsed_time_ms, are updated by the thread

  // that adds a new region to the CSet. Further updates by the

  // concurrent refinement thread that samples the young RSet lengths

  // are accumulated in the *_diffs fields. Here we add the diffs to

  // the "main" fields.

  if (_inc_recorded_rs_lengths_diffs >= 0) {

    _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs;

  } else {

    // This is defensive. The diff should in theory be always positive

    // as RSets can only grow between GCs. However, given that we

    // sample their size concurrently with other threads updating them

    // it's possible that we might get the wrong size back, which

    // could make the calculations somewhat inaccurate.

    size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs);

    if (_inc_recorded_rs_lengths >= diffs) {

      _inc_recorded_rs_lengths -= diffs;

    } else {

      _inc_recorded_rs_lengths = 0;

    }

  }

  _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs;

  _inc_recorded_rs_lengths_diffs = 0;

  _inc_predicted_elapsed_time_ms_diffs = 0.0;

}

void G1CollectionSet::clear() {

  assert_at_safepoint_on_vm_thread();

  _collection_set_cur_length = 0;

}

void G1CollectionSet::iterate(HeapRegionClosure* cl) const {

  size_t len = _collection_set_cur_length;

  OrderAccess::loadload();

  for (uint i = 0; i < len; i++) {

    HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);

    bool result = cl->do_heap_region(r);

    if (result) {

      cl->set_incomplete();

      return;

    }

  }

}

void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {

  assert_at_safepoint();

  for (uint i = 0; i < _num_optional_regions; i++) {

    HeapRegion* r = _candidates->at(i);

    bool result = cl->do_heap_region(r);

    guarantee(!result, "Must not cancel iteration");

  }

}

void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const {

  assert_at_safepoint();

  size_t len = _collection_set_cur_length - _inc_part_start;

  if (len == 0) {

    return;

  }

  size_t start_pos = (worker_id * len) / total_workers;

  size_t cur_pos = start_pos;

  do {

    HeapRegion* r = _g1h->region_at(_collection_set_regions[cur_pos + _inc_part_start]);

    bool result = cl->do_heap_region(r);

    guarantee(!result, "Must not cancel iteration");

    cur_pos++;

    if (cur_pos == len) {

      cur_pos = 0;

    }

  } while (cur_pos != start_pos);

}

void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,

                                                     size_t new_rs_length) {

  // Update the CSet information that is dependent on the new RS length

  assert(hr->is_young(), "Precondition");

  assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");

  // We could have updated _inc_recorded_rs_lengths and

  // _inc_predicted_elapsed_time_ms directly but we'd need to do

  // that atomically, as this code is executed by a concurrent

  // refinement thread, potentially concurrently with a mutator thread

  // allocating a new region and also updating the same fields. To

  // avoid the atomic operations we accumulate these updates on two

  // separate fields (*_diffs) and we'll just add them to the "main"

  // fields at the start of a GC.

  ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();

  ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;

  _inc_recorded_rs_lengths_diffs += rs_lengths_diff;

  double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();

  double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);

  double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;

  _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;

  hr->set_recorded_rs_length(new_rs_length);

  hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);

}

void G1CollectionSet::add_young_region_common(HeapRegion* hr) {

  assert(hr->is_young(), "invariant");

  assert(_inc_build_state == Active, "Precondition");

  size_t collection_set_length = _collection_set_cur_length;

  assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length);

  hr->set_young_index_in_cset((int)collection_set_length);

  _collection_set_regions[collection_set_length] = hr->hrm_index();

  // Concurrent readers must observe the store of the value in the array before an

  // update to the length field.

  OrderAccess::storestore();

  _collection_set_cur_length++;

  assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");

  // This routine is used when:

  // * adding survivor regions to the incremental cset at the end of an

  //   evacuation pause or

  // * adding the current allocation region to the incremental cset

  //   when it is retired.

  // Therefore this routine may be called at a safepoint by the

  // VM thread, or in-between safepoints by mutator threads (when

  // retiring the current allocation region)

  // We need to clear and set the cached recorded/cached collection set

  // information in the heap region here (before the region gets added

  // to the collection set). An individual heap region's cached values

  // are calculated, aggregated with the policy collection set info,

  // and cached in the heap region here (initially) and (subsequently)

  // by the Young List sampling code.

  // Ignore calls to this due to retirement during full gc.

  if (!_g1h->collector_state()->in_full_gc()) {

    size_t rs_length = hr->rem_set()->occupied();

    double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);

    // Cache the values we have added to the aggregated information

    // in the heap region in case we have to remove this region from

    // the incremental collection set, or it is updated by the

    // rset sampling code

    hr->set_recorded_rs_length(rs_length);

    hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);

    _inc_recorded_rs_lengths += rs_length;

    _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;

    _inc_bytes_used_before += hr->used();

  }

  assert(!hr->in_collection_set(), "invariant");

  _g1h->register_young_region_with_region_attr(hr);

}

void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {

  assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());

  add_young_region_common(hr);

}

void G1CollectionSet::add_eden_region(HeapRegion* hr) {

  assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());

  add_young_region_common(hr);

}

#ifndef PRODUCT

class G1VerifyYoungAgesClosure : public HeapRegionClosure {

public:

  bool _valid;

public:

  G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }

  virtual bool do_heap_region(HeapRegion* r) {

    guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());

    SurvRateGroup* group = r->surv_rate_group();

    if (group == NULL) {

      log_error(gc, verify)("## encountered NULL surv_rate_group in young region");

      _valid = false;

    }

    if (r->age_in_surv_rate_group() < 0) {

      log_error(gc, verify)("## encountered negative age in young region");

      _valid = false;

    }

    return false;

  }

  bool valid() const { return _valid; }

};

bool G1CollectionSet::verify_young_ages() {

  assert_at_safepoint_on_vm_thread();

  G1VerifyYoungAgesClosure cl;

  iterate(&cl);

  if (!cl.valid()) {

    LogStreamHandle(Error, gc, verify) log;

    print(&log);

  }

  return cl.valid();

}

class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {

  outputStream* _st;

public:

  G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }

  virtual bool do_heap_region(HeapRegion* r) {

    assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());

    _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",

                  HR_FORMAT_PARAMS(r),

                  p2i(r->prev_top_at_mark_start()),

                  p2i(r->next_top_at_mark_start()),

                  r->age_in_surv_rate_group_cond());

    return false;

  }

};

void G1CollectionSet::print(outputStream* st) {

  st->print_cr("\nCollection_set:");

  G1PrintCollectionSetDetailClosure cl(st);

  iterate(&cl);

}

#endif // !PRODUCT

double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {

  double young_start_time_sec = os::elapsedTime();

  finalize_incremental_building();

  guarantee(target_pause_time_ms > 0.0,

            "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);

  size_t pending_cards = _policy->pending_cards();

  double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);

  double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);

  log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",

                            pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);

  // The young list is laid with the survivor regions from the previous

  // pause are appended to the RHS of the young list, i.e.

  //   [Newly Young Regions ++ Survivors from last pause].

  uint survivor_region_length = survivors->length();

  uint eden_region_length = _g1h->eden_regions_count();

  init_region_lengths(eden_region_length, survivor_region_length);

  verify_young_cset_indices();

  // Clear the fields that point to the survivor list - they are all young now.

  survivors->convert_to_eden();

  _bytes_used_before = _inc_bytes_used_before;

  time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);

  log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",

                            eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);

  // The number of recorded young regions is the incremental

  // collection set's current size

  set_recorded_rs_lengths(_inc_recorded_rs_lengths);

  double young_end_time_sec = os::elapsedTime();

  phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);

  return time_remaining_ms;

}

static int compare_region_idx(const uint a, const uint b) {

  if (a > b) {

    return 1;

  } else if (a == b) {

    return 0;

  } else {

    return -1;

  }

}

void G1CollectionSet::finalize_old_part(double time_remaining_ms) {

  double non_young_start_time_sec = os::elapsedTime();

  if (collector_state()->in_mixed_phase()) {

    candidates()->verify();

    uint num_initial_old_regions;

    uint num_optional_old_regions;

    _policy->calculate_old_collection_set_regions(candidates(),

                                                  time_remaining_ms,

                                                  num_initial_old_regions,

                                                  num_optional_old_regions);

    // Prepare initial old regions.

    move_candidates_to_collection_set(num_initial_old_regions);

    // Prepare optional old regions for evacuation.

    uint candidate_idx = candidates()->cur_idx();

    for (uint i = 0; i < num_optional_old_regions; i++) {

      add_optional_region(candidates()->at(candidate_idx + i));

    }

    candidates()->verify();

  }

  stop_incremental_building();

  double non_young_end_time_sec = os::elapsedTime();

  phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);

  QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);

}

void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {

  if (num_old_candidate_regions == 0) {

    return;

  }

  uint candidate_idx = candidates()->cur_idx();

  for (uint i = 0; i < num_old_candidate_regions; i++) {

    HeapRegion* r = candidates()->at(candidate_idx + i);

    // This potentially optional candidate region is going to be an actual collection

    // set region. Clear cset marker.

    _g1h->clear_region_attr(r);

    add_old_region(r);

  }

  candidates()->remove(num_old_candidate_regions);

  candidates()->verify();

}