hotspot/src/share/vm/gc/g1/g1CollectionSet.cpp - platform/libcore - Gitiles

 /*
  * 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/g1CollectorPolicy.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());
 }


 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h) :
   _g1(g1h),
   _policy(NULL),
   _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);
 }
	/*
	* 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/g1CollectorPolicy.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());
	}


	G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h) :
	_g1(g1h),
	_policy(NULL),
	_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);
	}