/*

 * Copyright (c) 2016, 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.hpp"

#include "gc/g1/g1CollectionSet.hpp"

#include "gc/g1/g1CollectorState.hpp"

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

#include "gc/g1/heapRegionRemSet.hpp"

#include "gc/g1/heapRegionSet.hpp"

#include "utilities/debug.hpp"

G1CollectorState* G1CollectionSet::collector_state() {

  return _g1->collector_state();

}

G1GCPhaseTimes* G1CollectionSet::phase_times() {

  return _policy->phase_times();

}

CollectionSetChooser* G1CollectionSet::cset_chooser() {

  return _cset_chooser;

}

double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {

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

}

  _g1(g1h),

  _cset_chooser(new CollectionSetChooser()),

  _eden_region_length(0),

  _survivor_region_length(0),

  _old_region_length(0),

  _head(NULL),

  _bytes_used_before(0),

  _recorded_rs_lengths(0),

  // Incremental CSet attributes

  _inc_build_state(Inactive),

  _inc_head(NULL),

  _inc_tail(NULL),

  _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() {

  delete _cset_chooser;

}

void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,

                                          uint survivor_cset_region_length) {

  _eden_region_length     = eden_cset_region_length;

  _survivor_region_length = survivor_cset_region_length;

  _old_region_length      = 0;

}

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(_inc_build_state == Active, "Precondition");

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

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

  _g1->register_old_region_with_cset(hr);

  hr->set_next_in_collection_set(_head);

  _head = hr;

  _bytes_used_before += hr->used();

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

  _recorded_rs_lengths += rs_length;

  _old_region_length += 1;

}

// Initialize the per-collection-set information

void G1CollectionSet::start_incremental_building() {

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

  _inc_head = NULL;

  _inc_tail = NULL;

  _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;

  _inc_build_state = Active;

}

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::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(hr->young_index_in_cset() > -1, "should have already been set");

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

  // 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.

  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);

  size_t used_bytes = hr->used();

  _inc_recorded_rs_lengths += rs_length;

  _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;

  _inc_bytes_used_before += used_bytes;

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

  _g1->register_young_region_with_cset(hr);

  assert(hr->next_in_collection_set() == NULL, "invariant");

}

// Add the region at the RHS of the incremental cset

void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {

  // We should only ever be appending survivors at the end of a pause

  assert(hr->is_survivor(), "Logic");

  // Do the 'common' stuff

  add_young_region_common(hr);

  // Now add the region at the right hand side

  if (_inc_tail == NULL) {

    assert(_inc_head == NULL, "invariant");

    _inc_head = hr;

  } else {

    _inc_tail->set_next_in_collection_set(hr);

  }

  _inc_tail = hr;

}

// Add the region to the LHS of the incremental cset

void G1CollectionSet::add_eden_region(HeapRegion* hr) {

  // Survivors should be added to the RHS at the end of a pause

  assert(hr->is_eden(), "Logic");

  // Do the 'common' stuff

  add_young_region_common(hr);

  // Add the region at the left hand side

  hr->set_next_in_collection_set(_inc_head);

  if (_inc_head == NULL) {

    assert(_inc_tail == NULL, "Invariant");

    _inc_tail = hr;

  }

  _inc_head = hr;

}

#ifndef PRODUCT

void G1CollectionSet::print(HeapRegion* list_head, outputStream* st) {

  assert(list_head == inc_head() || list_head == head(), "must be");

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

  HeapRegion* csr = list_head;

  while (csr != NULL) {

    HeapRegion* next = csr->next_in_collection_set();

    assert(csr->in_collection_set(), "bad CS");

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

                 HR_FORMAT_PARAMS(csr),

                 p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),

                 csr->age_in_surv_rate_group_cond());

    csr = next;

  }

}

#endif // !PRODUCT

double G1CollectionSet::finalize_young_part(double target_pause_time_ms) {

  double young_start_time_sec = os::elapsedTime();

  YoungList* young_list = _g1->young_list();

  finalize_incremental_building();

  guarantee(target_pause_time_ms > 0.0,

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

  guarantee(_head == NULL, "Precondition");

  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);

  collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());

  // 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 = young_list->survivor_length();

  uint eden_region_length = young_list->eden_length();

  init_region_lengths(eden_region_length, survivor_region_length);

  HeapRegion* hr = young_list->first_survivor_region();

  while (hr != NULL) {

    assert(hr->is_survivor(), "badly formed young list");

    // There is a convention that all the young regions in the CSet

    // are tagged as "eden", so we do this for the survivors here. We

    // use the special set_eden_pre_gc() as it doesn't check that the

    // region is free (which is not the case here).

    hr->set_eden_pre_gc();

    hr = hr->get_next_young_region();

  }

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

  young_list->clear_survivors();

  _head = _inc_head;

  _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;

}

void G1CollectionSet::finalize_old_part(double time_remaining_ms) {

  double non_young_start_time_sec = os::elapsedTime();

  double predicted_old_time_ms = 0.0;

  if (!collector_state()->gcs_are_young()) {

    cset_chooser()->verify();

    const uint min_old_cset_length = _policy->calc_min_old_cset_length();

    const uint max_old_cset_length = _policy->calc_max_old_cset_length();

    uint expensive_region_num = 0;

    bool check_time_remaining = _policy->adaptive_young_list_length();

    HeapRegion* hr = cset_chooser()->peek();

    while (hr != NULL) {

      if (old_region_length() >= max_old_cset_length) {

        // Added maximum number of old regions to the CSet.

        log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",

                                  old_region_length(), max_old_cset_length);

        break;

      }

      // Stop adding regions if the remaining reclaimable space is

      // not above G1HeapWastePercent.

      size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();

      double reclaimable_perc = _policy->reclaimable_bytes_perc(reclaimable_bytes);

      double threshold = (double) G1HeapWastePercent;

      if (reclaimable_perc <= threshold) {

        // We've added enough old regions that the amount of uncollected

        // reclaimable space is at or below the waste threshold. Stop

        // adding old regions to the CSet.

        log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "

                                  "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",

                                  old_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);

        break;

      }

      double predicted_time_ms = predict_region_elapsed_time_ms(hr);

      if (check_time_remaining) {

        if (predicted_time_ms > time_remaining_ms) {

          // Too expensive for the current CSet.

          if (old_region_length() >= min_old_cset_length) {

            // We have added the minimum number of old regions to the CSet,

            // we are done with this CSet.

            log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "

                                      "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",

                                      predicted_time_ms, time_remaining_ms, old_region_length(), min_old_cset_length);

            break;

          }

          // We'll add it anyway given that we haven't reached the

          // minimum number of old regions.

          expensive_region_num += 1;

        }

      } else {

        if (old_region_length() >= min_old_cset_length) {

          // In the non-auto-tuning case, we'll finish adding regions

          // to the CSet if we reach the minimum.

          log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",

                                    old_region_length(), min_old_cset_length);

          break;

        }

      }

      // We will add this region to the CSet.

      time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);

      predicted_old_time_ms += predicted_time_ms;

      cset_chooser()->pop(); // already have region via peek()

      _g1->old_set_remove(hr);

      add_old_region(hr);

      hr = cset_chooser()->peek();

    }

    if (hr == NULL) {

      log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");

    }

    if (expensive_region_num > 0) {

      // We print the information once here at the end, predicated on

      // whether we added any apparently expensive regions or not, to

      // avoid generating output per region.

      log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."

                                "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",

                                old_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);

    }

    cset_chooser()->verify();

  }

  stop_incremental_building();

  log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",

                            old_region_length(), predicted_old_time_ms, time_remaining_ms);

  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);

}