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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

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  * published by the Free Software Foundation.

  *

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  * 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

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/heapRegion.hpp"

 #include "memory/allocation.hpp"

 #include "memory/cardTableModRefBS.hpp"

 #include "runtime/mutex.hpp"

 #include "utilities/globalDefinitions.hpp"

 // Sparse remembered set for a heap region (the "owning" region).  Maps

 // indices of other regions to short sequences of cards in the other region

 // that might contain pointers into the owner region.

 // These tables only expand while they are accessed in parallel --

 // deletions may be done in single-threaded code.  This allows us to allow

 // unsynchronized reads/iterations, as long as expansions caused by

 // insertions only enqueue old versions for deletions, but do not delete

 // old versions synchronously.

 class SparsePRTEntry: public CHeapObj {

 public:

   enum SomePublicConstants {

     NullEntry     = -1,

     UnrollFactor  =  4

   };

 private:

   RegionIdx_t _region_ind;

   int         _next_index;

   CardIdx_t   _cards[1];

   // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length.

   // It should always be the last data member.

 public:

   // Returns the size of the entry, used for entry allocation.

   static size_t size() { return sizeof(SparsePRTEntry) + sizeof(CardIdx_t) * (cards_num() - 1); }

   // Returns the size of the card array.

   static int cards_num() {

     // The number of cards should be a multiple of 4, because that's our current

     // unrolling factor.

     static const int s = MAX2<int>(G1RSetSparseRegionEntries & ~(UnrollFactor - 1), UnrollFactor);

     return s;

   }

   // Set the region_ind to the given value, and delete all cards.

   inline void init(RegionIdx_t region_ind);

   RegionIdx_t r_ind() const { return _region_ind; }

   bool valid_entry() const { return r_ind() >= 0; }

   void set_r_ind(RegionIdx_t rind) { _region_ind = rind; }

   int next_index() const { return _next_index; }

   int* next_index_addr() { return &_next_index; }

   void set_next_index(int ni) { _next_index = ni; }

   // Returns "true" iff the entry contains the given card index.

   inline bool contains_card(CardIdx_t card_index) const;

   // Returns the number of non-NULL card entries.

   inline int num_valid_cards() const;

   // Requires that the entry not contain the given card index.  If there is

   // space available, add the given card index to the entry and return

   // "true"; otherwise, return "false" to indicate that the entry is full.

   enum AddCardResult {

     overflow,

     found,

     added

   };

   inline AddCardResult add_card(CardIdx_t card_index);

   // Copy the current entry's cards into "cards".

   inline void copy_cards(CardIdx_t* cards) const;

   // Copy the current entry's cards into the "_card" array of "e."

   inline void copy_cards(SparsePRTEntry* e) const;

   inline CardIdx_t card(int i) const { return _cards[i]; }

 };

 class RSHashTable : public CHeapObj {

   friend class RSHashTableIter;

   enum SomePrivateConstants {

     NullEntry = -1

   };

   size_t _capacity;

   size_t _capacity_mask;

   size_t _occupied_entries;

   size_t _occupied_cards;

   SparsePRTEntry* _entries;

   int* _buckets;

   int  _free_region;

   int  _free_list;

   // Requires that the caller hold a lock preventing parallel modifying

   // operations, and that the the table be less than completely full.  If

   // an entry for "region_ind" is already in the table, finds it and

   // returns its address; otherwise returns "NULL."

   SparsePRTEntry* entry_for_region_ind(RegionIdx_t region_ind) const;

   // Requires that the caller hold a lock preventing parallel modifying

   // operations, and that the the table be less than completely full.  If

   // an entry for "region_ind" is already in the table, finds it and

   // returns its address; otherwise allocates, initializes, inserts and

   // returns a new entry for "region_ind".

   SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind);

   // Returns the index of the next free entry in "_entries".

   int alloc_entry();

   // Declares the entry "fi" to be free.  (It must have already been

   // deleted from any bucket lists.

   void free_entry(int fi);

 public:

   RSHashTable(size_t capacity);

   ~RSHashTable();

   // Attempts to ensure that the given card_index in the given region is in

   // the sparse table.  If successful (because the card was already

   // present, or because it was successfullly added) returns "true".

   // Otherwise, returns "false" to indicate that the addition would

   // overflow the entry for the region.  The caller must transfer these

   // entries to a larger-capacity representation.

   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);

   bool get_cards(RegionIdx_t region_id, CardIdx_t* cards);

   bool delete_entry(RegionIdx_t region_id);

   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const;

   void add_entry(SparsePRTEntry* e);

   SparsePRTEntry* get_entry(RegionIdx_t region_id);

   void clear();

   size_t capacity() const      { return _capacity;       }

   size_t capacity_mask() const { return _capacity_mask;  }

   size_t occupied_entries() const { return _occupied_entries; }

   size_t occupied_cards() const   { return _occupied_cards;   }

   size_t mem_size() const;

   SparsePRTEntry* entry(int i) const { return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); }

   void print();

 };

 // ValueObj because will be embedded in HRRS iterator.

 class RSHashTableIter VALUE_OBJ_CLASS_SPEC {

   int _tbl_ind;         // [-1, 0.._rsht->_capacity)

   int _bl_ind;          // [-1, 0.._rsht->_capacity)

   short _card_ind;      // [0..SparsePRTEntry::cards_num())

   RSHashTable* _rsht;

   // If the bucket list pointed to by _bl_ind contains a card, sets

   // _bl_ind to the index of that entry, and returns the card.

   // Otherwise, returns SparseEntry::NullEntry.

   CardIdx_t find_first_card_in_list();

   // Computes the proper card index for the card whose offset in the

   // current region (as indicated by _bl_ind) is "ci".

   // This is subject to errors when there is iteration concurrent with

   // modification, but these errors should be benign.

   size_t compute_card_ind(CardIdx_t ci);

 public:

   RSHashTableIter() :

     _tbl_ind(RSHashTable::NullEntry),

     _bl_ind(RSHashTable::NullEntry),

     _card_ind((SparsePRTEntry::cards_num() - 1)),

     _rsht(NULL) {}

   void init(RSHashTable* rsht) {

     _rsht = rsht;

     _tbl_ind = -1; // So that first increment gets to 0.

     _bl_ind = RSHashTable::NullEntry;

     _card_ind = (SparsePRTEntry::cards_num() - 1);

   }

   bool has_next(size_t& card_index);

 };

 // Concurrent accesss to a SparsePRT must be serialized by some external

 // mutex.

 class SparsePRTIter;

 class SparsePRTCleanupTask;

 class SparsePRT VALUE_OBJ_CLASS_SPEC {

   friend class SparsePRTCleanupTask;

   //  Iterations are done on the _cur hash table, since they only need to

   //  see entries visible at the start of a collection pause.

   //  All other operations are done using the _next hash table.

   RSHashTable* _cur;

   RSHashTable* _next;

   HeapRegion* _hr;

   enum SomeAdditionalPrivateConstants {

     InitialCapacity = 16

   };

   void expand();

   bool _expanded;

   bool expanded() { return _expanded; }

   void set_expanded(bool b) { _expanded = b; }

   SparsePRT* _next_expanded;

   SparsePRT* next_expanded() { return _next_expanded; }

   void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; }

   bool should_be_on_expanded_list();

   static SparsePRT* _head_expanded_list;

 public:

   SparsePRT(HeapRegion* hr);

   ~SparsePRT();

   size_t occupied() const { return _next->occupied_cards(); }

   size_t mem_size() const;

   // Attempts to ensure that the given card_index in the given region is in

   // the sparse table.  If successful (because the card was already

   // present, or because it was successfullly added) returns "true".

   // Otherwise, returns "false" to indicate that the addition would

   // overflow the entry for the region.  The caller must transfer these

   // entries to a larger-capacity representation.

   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);

   // If the table hold an entry for "region_ind",  Copies its

   // cards into "cards", which must be an array of length at least

   // "SparePRTEntry::cards_num()", and returns "true"; otherwise,

   // returns "false".

   bool get_cards(RegionIdx_t region_ind, CardIdx_t* cards);

   // Return the pointer to the entry associated with the given region.

   SparsePRTEntry* get_entry(RegionIdx_t region_ind);

   // If there is an entry for "region_ind", removes it and return "true";

   // otherwise returns "false."

   bool delete_entry(RegionIdx_t region_ind);

   // Clear the table, and reinitialize to initial capacity.

   void clear();

   // Ensure that "_cur" and "_next" point to the same table.

   void cleanup();

   // Clean up all tables on the expanded list.  Called single threaded.

   static void cleanup_all();

   RSHashTable* cur() const { return _cur; }

   void init_iterator(SparsePRTIter* sprt_iter);

   static void add_to_expanded_list(SparsePRT* sprt);

   static SparsePRT* get_from_expanded_list();

   // The purpose of these three methods is to help the GC workers

   // during the cleanup pause to recreate the expanded list, purging

   // any tables from it that belong to regions that are freed during

   // cleanup (if we don't purge those tables, there is a race that

   // causes various crashes; see CR 7014261).

   //

   // We chose to recreate the expanded list, instead of purging

   // entries from it by iterating over it, to avoid this serial phase

   // at the end of the cleanup pause.

   //

   // The three methods below work as follows:

   // * reset_for_cleanup_tasks() : Nulls the expanded list head at the

   //   start of the cleanup pause.

   // * do_cleanup_work() : Called by the cleanup workers for every

   //   region that is not free / is being freed by the cleanup

   //   pause. It creates a list of expanded tables whose head / tail

   //   are on the thread-local SparsePRTCleanupTask object.

   // * finish_cleanup_task() : Called by the cleanup workers after

   //   they complete their cleanup task. It adds the local list into

   //   the global expanded list. It assumes that the

   //   ParGCRareEvent_lock is being held to ensure MT-safety.

   static void reset_for_cleanup_tasks();

   void do_cleanup_work(SparsePRTCleanupTask* sprt_cleanup_task);

   static void finish_cleanup_task(SparsePRTCleanupTask* sprt_cleanup_task);

   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const {

     return _next->contains_card(region_id, card_index);

   }

 };

 class SparsePRTIter: public RSHashTableIter {

 public:

   void init(const SparsePRT* sprt) {

     RSHashTableIter::init(sprt->cur());

   }

   bool has_next(size_t& card_index) {

     return RSHashTableIter::has_next(card_index);

   }

 };

 // This allows each worker during a cleanup pause to create a

 // thread-local list of sparse tables that have been expanded and need

 // to be processed at the beginning of the next GC pause. This lists

 // are concatenated into the single expanded list at the end of the

 // cleanup pause.

 class SparsePRTCleanupTask VALUE_OBJ_CLASS_SPEC {

 private:

   SparsePRT* _head;

   SparsePRT* _tail;

 public:

   SparsePRTCleanupTask() : _head(NULL), _tail(NULL) { }

   void add(SparsePRT* sprt);

   SparsePRT* head() { return _head; }

   SparsePRT* tail() { return _tail; }

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP