src/hotspot/share/gc/g1/g1CollectionSet.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2016, 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.
  *
  */

 #include "precompiled.hpp"
 #include "gc/g1/g1CollectedHeap.hpp"
 #include "gc/g1/g1CollectionSet.hpp"
 #include "gc/g1/g1CollectorState.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/quickSort.hpp"

 G1CollectorState* G1CollectionSet::collector_state() {
   return _g1h->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()->in_young_only_phase());
 }

 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
   _g1h(g1h),
   _policy(policy),
   _cset_chooser(new CollectionSetChooser()),
   _eden_region_length(0),
   _survivor_region_length(0),
   _old_region_length(0),
   _bytes_used_before(0),
   _recorded_rs_lengths(0),
   _collection_set_regions(NULL),
   _collection_set_cur_length(0),
   _collection_set_max_length(0),
   // Incremental CSet attributes
   _inc_build_state(Inactive),
   _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);
   }
   delete _cset_chooser;
 }

 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;
 }

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

   assert(!hr->in_collection_set(), "should not already be in the CSet");
   _g1h->register_old_region_with_cset(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();
   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(_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;
   _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::clear() {
   assert_at_safepoint_on_vm_thread();
   _collection_set_cur_length = 0;
 }

 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
   iterate_from(cl, 0, 1);
 }

 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const {
   size_t len = _collection_set_cur_length;
   OrderAccess::loadload();
   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]);
     bool result = cl->do_heap_region(r);
     if (result) {
       cl->set_incomplete();
       return;
     }
     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_cset(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();
   double predicted_old_time_ms = 0.0;

   if (collector_state()->in_mixed_phase()) {
     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_percent = _policy->reclaimable_bytes_percent(reclaimable_bytes);
       double threshold = (double) G1HeapWastePercent;
       if (reclaimable_percent <= 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_percent, 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()
       _g1h->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);

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

 #ifdef ASSERT
 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
 private:
   size_t _young_length;
   int* _heap_region_indices;
 public:
   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
     _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC);
     for (size_t i = 0; i < young_length; i++) {
       _heap_region_indices[i] = -1;
     }
   }
   ~G1VerifyYoungCSetIndicesClosure() {
     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
   }

   virtual bool do_heap_region(HeapRegion* r) {
     const int idx = r->young_index_in_cset();

     assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
     assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index());

     assert(_heap_region_indices[idx] == -1,
            "Index %d used by multiple regions, first use by region %u, second by region %u",
            idx, _heap_region_indices[idx], r->hrm_index());

     _heap_region_indices[idx] = r->hrm_index();

     return false;
   }
 };

 void G1CollectionSet::verify_young_cset_indices() const {
   assert_at_safepoint_on_vm_thread();

   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
   iterate(&cl);
 }
 #endif
	/*
	* Copyright (c) 2016, 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.
	*
	*/

	#include "precompiled.hpp"
	#include "gc/g1/g1CollectedHeap.hpp"
	#include "gc/g1/g1CollectionSet.hpp"
	#include "gc/g1/g1CollectorState.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/quickSort.hpp"

	G1CollectorState* G1CollectionSet::collector_state() {
	return _g1h->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()->in_young_only_phase());
	}

	G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
	_g1h(g1h),
	_policy(policy),
	_cset_chooser(new CollectionSetChooser()),
	_eden_region_length(0),
	_survivor_region_length(0),
	_old_region_length(0),
	_bytes_used_before(0),
	_recorded_rs_lengths(0),
	_collection_set_regions(NULL),
	_collection_set_cur_length(0),
	_collection_set_max_length(0),
	// Incremental CSet attributes
	_inc_build_state(Inactive),
	_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);
	}
	delete _cset_chooser;
	}

	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;
	}

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

	assert(!hr->in_collection_set(), "should not already be in the CSet");
	_g1h->register_old_region_with_cset(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();
	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(_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;
	_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::clear() {
	assert_at_safepoint_on_vm_thread();
	_collection_set_cur_length = 0;
	}

	void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
	iterate_from(cl, 0, 1);
	}

	void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const {
	size_t len = _collection_set_cur_length;
	OrderAccess::loadload();
	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]);
	bool result = cl->do_heap_region(r);
	if (result) {
	cl->set_incomplete();
	return;
	}
	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_cset(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();
	double predicted_old_time_ms = 0.0;

	if (collector_state()->in_mixed_phase()) {
	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_percent = _policy->reclaimable_bytes_percent(reclaimable_bytes);
	double threshold = (double) G1HeapWastePercent;
	if (reclaimable_percent <= 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_percent, 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()
	_g1h->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);

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

	#ifdef ASSERT
	class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
	private:
	size_t _young_length;
	int* _heap_region_indices;
	public:
	G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
	_heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC);
	for (size_t i = 0; i < young_length; i++) {
	_heap_region_indices[i] = -1;
	}
	}
	~G1VerifyYoungCSetIndicesClosure() {
	FREE_C_HEAP_ARRAY(int, _heap_region_indices);
	}

	virtual bool do_heap_region(HeapRegion* r) {
	const int idx = r->young_index_in_cset();

	assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
	assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index());

	assert(_heap_region_indices[idx] == -1,
	"Index %d used by multiple regions, first use by region %u, second by region %u",
	idx, _heap_region_indices[idx], r->hrm_index());

	_heap_region_indices[idx] = r->hrm_index();

	return false;
	}
	};

	void G1CollectionSet::verify_young_cset_indices() const {
	assert_at_safepoint_on_vm_thread();

	G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
	iterate(&cl);
	}
	#endif