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#ifndef SHARE_GC_G1_G1COLLECTIONSET_HPP

#define SHARE_GC_G1_G1COLLECTIONSET_HPP

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

class G1CollectedHeap;

class G1CollectionSetCandidates;

class G1CollectorState;

class G1GCPhaseTimes;

class G1ParScanThreadStateSet;

class G1Policy;

class G1SurvivorRegions;

class HeapRegion;

class HeapRegionClaimer;

class HeapRegionClosure;

// The collection set.

//

// The set of regions that are evacuated during an evacuation pause.

//

// At the end of a collection, before freeing the collection set, this set

// contains all regions that were evacuated during this collection:

//

// - survivor regions from the last collection (if any)

// - eden regions allocated by the mutator

// - old gen regions evacuated during mixed gc

//

// This set is built incrementally at mutator time as regions are retired, and

// if this had been a mixed gc, some additional (during gc) incrementally added

// old regions from the collection set candidates built during the concurrent

// cycle.

//

// A more detailed overview of how the collection set changes over time follows:

//

// 0) at the end of GC the survivor regions are added to this collection set.

// 1) the mutator incrementally adds eden regions as they retire

//

// ----- gc starts

//

// 2) prepare (finalize) young regions of the collection set for collection

//    - relabel the survivors as eden

//    - finish up the incremental building that happened at mutator time

//

// iff this is a young-only collection:

//

// a3) evacuate the current collection set in one "initial evacuation" phase

//

// iff this is a mixed collection:

//

// b3) calculate the set of old gen regions we may be able to collect in this

//     collection from the list of collection set candidates.

//     - one part is added to the current collection set

//     - the remainder regions are labeled as optional, and NOT yet added to the

//     collection set.

// b4) evacuate the current collection set in the "initial evacuation" phase

// b5) evacuate the optional regions in the "optional evacuation" phase. This is

//     done in increments (or rounds).

//     b5-1) add a few of the optional regions to the current collection set

//     b5-2) evacuate only these newly added optional regions. For this mechanism we

//     reuse the incremental collection set building infrastructure (used also at

//     mutator time).

//     b5-3) repeat from b5-1 until the policy determines we are done

//

// all collections

//

// 6) free the collection set (contains all regions now; empties collection set

//    afterwards)

// 7) add survivors to this collection set

//

// ----- gc ends

//

// goto 1)

//

// Examples of how the collection set might look over time:

//

// Legend:

// S = survivor, E = eden, O = old.

// |xxxx| = increment (with increment markers), containing four regions

//

// |SSSS|                         ... after step 0), with four survivor regions

// |SSSSEE|                       ... at step 1), after retiring two eden regions

// |SSSSEEEE|                     ... after step 1), after retiring four eden regions

// |EEEEEEEE|                     ... after step 2)

//

// iff this is a young-only collection

//

// EEEEEEEE||                      ... after step a3), after initial evacuation phase

// ||                              ... after step 6)

// |SS|                            ... after step 7), with two survivor regions

//

// iff this is a mixed collection

//

// |EEEEEEEEOOOO|                  ... after step b3), added four regions to be

//                                     evacuated in the "initial evacuation" phase

// EEEEEEEEOOOO||                  ... after step b4), incremental part is empty

//                                     after evacuation

// EEEEEEEEOOOO|OO|                ... after step b5.1), added two regions to be

//                                     evacuated in the first round of the

//                                     "optional evacuation" phase

// EEEEEEEEOOOOOO|O|               ... after step b5.1), added one region to be

//                                     evacuated in the second round of the

//                                     "optional evacuation" phase

// EEEEEEEEOOOOOOO||               ... after step b5), the complete collection set.

// ||                              ... after step b6)

// |SSS|                           ... after step 7), with three survivor regions

//

class G1CollectionSet {

  G1CollectedHeap* _g1h;

  G1Policy* _policy;

  // All old gen collection set candidate regions for the current mixed phase.

  G1CollectionSetCandidates* _candidates;

  uint _eden_region_length;

  uint _survivor_region_length;

  uint _old_region_length;

  // The actual collection set as a set of region indices.

  // All entries in _collection_set_regions below _collection_set_cur_length are

  // assumed to be part of the collection set.

  // We assume that at any time there is at most only one writer and (one or more)

  // concurrent readers. This means we are good with using storestore and loadload

  // barriers on the writer and reader respectively only.

  uint* _collection_set_regions;

  volatile size_t _collection_set_cur_length;

  size_t _collection_set_max_length;

  // When doing mixed collections we can add old regions to the collection set, which

  // will be collected only if there is enough time. We call these optional regions.

  // This member records the current number of regions that are of that type that

  // correspond to the first x entries in the collection set candidates.

  uint _num_optional_regions;

  // The number of bytes in the collection set before the pause. Set from

  // the incrementally built collection set at the start of an evacuation

  // pause, and updated as more regions are added to the collection set.

  size_t _bytes_used_before;

  // The number of cards in the remembered set in the collection set. Set from

  // the incrementally built collection set at the start of an evacuation

  // pause, and updated as more regions are added to the collection set.

  size_t _recorded_rs_lengths;

  enum CSetBuildType {

    Active,             // We are actively building the collection set

    Inactive            // We are not actively building the collection set

  };

  CSetBuildType _inc_build_state;

  size_t _inc_part_start;

  // The associated information that is maintained while the incremental

  // collection set is being built with *young* regions. Used to populate

  // the recorded info for the evacuation pause.

  // The number of bytes in the incrementally built collection set.

  // Used to set _collection_set_bytes_used_before at the start of

  // an evacuation pause.

  size_t _inc_bytes_used_before;

  // The RSet lengths recorded for regions in the CSet. It is updated

  // by the thread that adds a new region to the CSet. We assume that

  // only one thread can be allocating a new CSet region (currently,

  // it does so after taking the Heap_lock) hence no need to

  // synchronize updates to this field.

  size_t _inc_recorded_rs_lengths;

  // A concurrent refinement thread periodically samples the young

  // region RSets and needs to update _inc_recorded_rs_lengths as

  // the RSets grow. Instead of having to synchronize updates to that

  // field we accumulate them in this field and add it to

  // _inc_recorded_rs_lengths_diffs at the start of a GC.

  ssize_t _inc_recorded_rs_lengths_diffs;

  // The predicted elapsed time it will take to collect the regions in

  // the CSet. This is updated by the thread that adds a new region to

  // the CSet. See the comment for _inc_recorded_rs_lengths about

  // MT-safety assumptions.

  double _inc_predicted_elapsed_time_ms;

  // See the comment for _inc_recorded_rs_lengths_diffs.

  double _inc_predicted_elapsed_time_ms_diffs;

  void set_recorded_rs_lengths(size_t rs_lengths);

  G1CollectorState* collector_state();

  G1GCPhaseTimes* phase_times();

  void verify_young_cset_indices() const NOT_DEBUG_RETURN;

  double predict_region_elapsed_time_ms(HeapRegion* hr);

  // Update the incremental collection set information when adding a region.

  void add_young_region_common(HeapRegion* hr);

  // Add old region "hr" to the collection set.

  void add_old_region(HeapRegion* hr);

  void free_optional_regions();

  // Add old region "hr" to optional collection set.

  void add_optional_region(HeapRegion* hr);

  void move_candidates_to_collection_set(uint num_regions);

  // Finalize the young part of the initial collection set. Relabel survivor regions

  // as Eden and calculate a prediction on how long the evacuation of all young regions

  // will take.

  double finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors);

  // Perform any final calculations on the incremental collection set fields before we

  // can use them.

  void finalize_incremental_building();

  // Select the old regions of the initial collection set and determine how many optional

  // regions we might be able to evacuate in this pause.

  void finalize_old_part(double time_remaining_ms);

public:

  G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy);

  ~G1CollectionSet();

  // Initializes the collection set giving the maximum possible length of the collection set.

  void initialize(uint max_region_length);

  void clear_candidates();

  void set_candidates(G1CollectionSetCandidates* candidates) {

    assert(_candidates == NULL, "Trying to replace collection set candidates.");

    _candidates = candidates;

  }

  G1CollectionSetCandidates* candidates() { return _candidates; }

  void init_region_lengths(uint eden_cset_region_length,

                           uint survivor_cset_region_length);

  uint region_length() const       { return young_region_length() +

                                            old_region_length(); }

  uint young_region_length() const { return eden_region_length() +

                                            survivor_region_length(); }

  uint eden_region_length() const     { return _eden_region_length;     }

  uint survivor_region_length() const { return _survivor_region_length; }

  uint old_region_length() const      { return _old_region_length;      }

  uint optional_region_length() const { return _num_optional_regions; }

  // Reset the contents of the collection set.

  void clear();

  // Incremental collection set support

  // Initialize incremental collection set info.

  void start_incremental_building();

  // Start a new collection set increment.

  void update_incremental_marker() { _inc_build_state = Active; _inc_part_start = _collection_set_cur_length; }

  // Stop adding regions to the current collection set increment.

  void stop_incremental_building() { _inc_build_state = Inactive; }

  // Iterate over the current collection set increment applying the given HeapRegionClosure

  // from a starting position determined by the given worker id.

  void iterate_incremental_part_from(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id, uint total_workers) const;

  // Returns the length of the current increment in number of regions.

  size_t increment_length() const { return _collection_set_cur_length - _inc_part_start; }

  // Returns the length of the whole current collection set in number of regions

  size_t cur_length() const { return _collection_set_cur_length; }

  // Iterate over the entire collection set (all increments calculated so far), applying

  // the given HeapRegionClosure on all of them.

  void iterate(HeapRegionClosure* cl) const;

  void iterate_optional(HeapRegionClosure* cl) const;

  size_t recorded_rs_lengths() { return _recorded_rs_lengths; }

  size_t bytes_used_before() const {

    return _bytes_used_before;

  }

  void reset_bytes_used_before() {

    _bytes_used_before = 0;

  }

  // Finalize the initial collection set consisting of all young regions potentially a

  // few old gen regions.

  void finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor);

  // Finalize the next collection set from the set of available optional old gen regions.

  bool finalize_optional_for_evacuation(double remaining_pause_time);

  // Abandon (clean up) optional collection set regions that were not evacuated in this

  // pause.

  void abandon_optional_collection_set(G1ParScanThreadStateSet* pss);

  // Update information about hr in the aggregated information for

  // the incrementally built collection set.

  void update_young_region_prediction(HeapRegion* hr, size_t new_rs_length);

  // Add eden region to the collection set.

  void add_eden_region(HeapRegion* hr);

  // Add survivor region to the collection set.

  void add_survivor_regions(HeapRegion* hr);

#ifndef PRODUCT

  bool verify_young_ages();

  void print(outputStream* st);

#endif // !PRODUCT

};

#endif // SHARE_GC_G1_G1COLLECTIONSET_HPP