diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/gc/g1/sparsePRT.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/sparsePRT.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,350 @@
+/*
+ * Copyright (c) 2001, 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.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_SPARSEPRT_HPP
+#define SHARE_VM_GC_G1_SPARSEPRT_HPP
+
+#include "gc/g1/g1CollectedHeap.hpp"
+#include "gc/g1/heapRegion.hpp"
+#include "gc/shared/cardTableModRefBS.hpp"
+#include "memory/allocation.hpp"
+#include "runtime/mutex.hpp"
+#include "utilities/align.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<mtGC> {
+private:
+  // The type of a card entry.
+  typedef uint16_t card_elem_t;
+
+  // We need to make sizeof(SparsePRTEntry) an even multiple of maximum member size,
+  // in order to force correct alignment that could otherwise cause SIGBUS errors
+  // when reading the member variables. This calculates the minimum number of card
+  // array elements required to get that alignment.
+  static const size_t card_array_alignment = sizeof(int) / sizeof(card_elem_t);
+
+  RegionIdx_t _region_ind;
+  int         _next_index;
+  int         _next_null;
+  // The actual cards stored in this array.
+  // 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.
+  card_elem_t _cards[card_array_alignment];
+
+  // Copy the current entry's cards into "cards".
+  inline void copy_cards(card_elem_t* cards) const;
+public:
+  // Returns the size of the entry, used for entry allocation.
+  static size_t size() { return sizeof(SparsePRTEntry) + sizeof(card_elem_t) * (cards_num() - card_array_alignment); }
+  // Returns the size of the card array.
+  static int cards_num() {
+    return align_up((int)G1RSetSparseRegionEntries, (int)card_array_alignment);
+  }
+
+  // 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 { return _next_null; }
+
+  // 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 the "_card" array of "e."
+  inline void copy_cards(SparsePRTEntry* e) const;
+
+  inline CardIdx_t card(int i) const {
+    assert(i >= 0, "must be nonnegative");
+    assert(i < cards_num(), "range checking");
+    return (CardIdx_t)_cards[i];
+  }
+};
+
+class RSHashTable : public CHeapObj<mtGC> {
+
+  friend class RSHashTableIter;
+
+
+  // Inverse maximum hash table occupancy used.
+  static float TableOccupancyFactor;
+
+  size_t _num_entries;
+
+  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 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();
+
+  static const int NullEntry = -1;
+
+  bool should_expand() const { return _occupied_entries == _num_entries; }
+
+  // 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 successfully 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) const;
+
+  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;
+  // The number of SparsePRTEntry instances available.
+  size_t num_entries() const { return _num_entries; }
+
+  SparsePRTEntry* entry(int i) const {
+    assert(i >= 0 && (size_t)i < _num_entries, "precondition");
+    return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i);
+  }
+
+  void print();
+};
+
+// ValueObj because will be embedded in HRRS iterator.
+class RSHashTableIter VALUE_OBJ_CLASS_SPEC {
+  // Return value indicating "invalid/no card".
+  static const int NoCardFound = -1;
+
+  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,
+  // Returns the card found if there is, otherwise returns InvalidCard.
+  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(RSHashTable* rsht) :
+    _tbl_ind(RSHashTable::NullEntry), // So that first increment gets to 0.
+    _bl_ind(RSHashTable::NullEntry),
+    _card_ind((SparsePRTEntry::cards_num() - 1)),
+    _rsht(rsht) {}
+
+  bool has_next(size_t& card_index);
+};
+
+// Concurrent access 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* volatile _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 successfully 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);
+
+  // 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; }
+
+  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:
+  SparsePRTIter(const SparsePRT* sprt) :
+    RSHashTableIter(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_G1_SPARSEPRT_HPP