--- a/src/hotspot/share/jfr/leakprofiler/chains/bfsClosure.cpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/jfr/leakprofiler/chains/bfsClosure.cpp	Thu Sep 05 08:26:44 2019 +0200
@@ -22,7 +22,7 @@
  *
  */
 #include "precompiled.hpp"
-#include "jfr/leakprofiler/chains/bitset.hpp"
+#include "jfr/leakprofiler/chains/bitset.inline.hpp"
 #include "jfr/leakprofiler/chains/bfsClosure.hpp"
 #include "jfr/leakprofiler/chains/dfsClosure.hpp"
 #include "jfr/leakprofiler/chains/edge.hpp"

--- a/src/hotspot/share/jfr/leakprofiler/chains/bitset.cpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/jfr/leakprofiler/chains/bitset.cpp	Thu Sep 05 08:26:44 2019 +0200
@@ -22,37 +22,25 @@
  *
  */
 #include "precompiled.hpp"
-#include "jfr/leakprofiler/chains/bitset.hpp"
-#include "jfr/recorder/storage/jfrVirtualMemory.hpp"
-#include "memory/memRegion.hpp"
+#include "jfr/leakprofiler/chains/bitset.inline.hpp"
 
-BitSet::BitSet(const MemRegion& covered_region) :
-  _vmm(NULL),
-  _region_start(covered_region.start()),
-  _region_size(covered_region.word_size()) {
+BitSet::BitMapFragment::BitMapFragment(uintptr_t granule, BitMapFragment* next) :
+    _bits(_bitmap_granularity_size >> LogMinObjAlignmentInBytes, mtTracing, true /* clear */),
+    _next(next) {
+}
+
+BitSet::BitSet() :
+    _bitmap_fragments(32),
+    _fragment_list(NULL),
+    _last_fragment_bits(NULL),
+    _last_fragment_granule(0) {
 }
 
 BitSet::~BitSet() {
-  delete _vmm;
-}
-
-bool BitSet::initialize() {
-  assert(_vmm == NULL, "invariant");
-  _vmm = new JfrVirtualMemory();
-  if (_vmm == NULL) {
-    return false;
+  BitMapFragment* current = _fragment_list;
+  while (current != NULL) {
+    BitMapFragment* next = current->next();
+    delete current;
+    current = next;
   }
-
-  const BitMap::idx_t bits = _region_size >> LogMinObjAlignment;
-  const size_t words = bits / BitsPerWord;
-  const size_t raw_bytes = words * sizeof(BitMap::idx_t);
-
-  // the virtual memory invocation will reserve and commit the entire space
-  BitMap::bm_word_t* map = (BitMap::bm_word_t*)_vmm->initialize(raw_bytes, raw_bytes);
-  if (map == NULL) {
-    return false;
-  }
-  _bits = BitMapView(map, bits);
-  return true;
 }
-

--- a/src/hotspot/share/jfr/leakprofiler/chains/bitset.hpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/jfr/leakprofiler/chains/bitset.hpp	Thu Sep 05 08:26:44 2019 +0200
@@ -26,53 +26,91 @@
 #define SHARE_JFR_LEAKPROFILER_CHAINS_BITSET_HPP
 
 #include "memory/allocation.hpp"
+#include "oops/oop.hpp"
 #include "oops/oopsHierarchy.hpp"
-#include "utilities/bitMap.inline.hpp"
+#include "utilities/bitMap.hpp"
+#include "utilities/hashtable.hpp"
 
 class JfrVirtualMemory;
 class MemRegion;
 
 class BitSet : public CHeapObj<mtTracing> {
- private:
-  JfrVirtualMemory* _vmm;
-  const HeapWord* const _region_start;
-  BitMapView _bits;
-  const size_t _region_size;
+  const static size_t _bitmap_granularity_shift = 26; // 64M
+  const static size_t _bitmap_granularity_size = (size_t)1 << _bitmap_granularity_shift;
+  const static size_t _bitmap_granularity_mask = _bitmap_granularity_size - 1;
+
+  class BitMapFragment;
+
+  class BitMapFragmentTable : public BasicHashtable<mtTracing> {
+    class Entry : public BasicHashtableEntry<mtTracing> {
+    public:
+      uintptr_t _key;
+      CHeapBitMap* _value;
+
+      Entry* next() {
+        return (Entry*)BasicHashtableEntry<mtTracing>::next();
+      }
+    };
+
+  protected:
+    Entry* bucket(int i) const;
+
+    Entry* new_entry(unsigned int hashValue, uintptr_t key, CHeapBitMap* value);
+
+    unsigned hash_segment(uintptr_t key) {
+      unsigned hash = (unsigned)key;
+      return hash ^ (hash >> 3);
+    }
+
+    unsigned hash_to_index(unsigned hash) {
+      return hash & (BasicHashtable<mtTracing>::table_size() - 1);
+    }
+
+  public:
+    BitMapFragmentTable(int table_size) : BasicHashtable<mtTracing>(table_size, sizeof(Entry)) {}
+    void add(uintptr_t key, CHeapBitMap* value);
+    CHeapBitMap** lookup(uintptr_t key);
+  };
+
+  CHeapBitMap* get_fragment_bits(uintptr_t addr);
+
+  BitMapFragmentTable _bitmap_fragments;
+  BitMapFragment* _fragment_list;
+  CHeapBitMap* _last_fragment_bits;
+  uintptr_t _last_fragment_granule;
 
  public:
-  BitSet(const MemRegion& covered_region);
+  BitSet();
   ~BitSet();
 
-  bool initialize();
+  BitMap::idx_t addr_to_bit(uintptr_t addr) const;
 
-  BitMap::idx_t mark_obj(const HeapWord* addr) {
-    const BitMap::idx_t bit = addr_to_bit(addr);
-    _bits.set_bit(bit);
-    return bit;
+  void mark_obj(uintptr_t addr);
+
+  void mark_obj(oop obj) {
+    return mark_obj(cast_from_oop<uintptr_t>(obj));
   }
 
-  BitMap::idx_t mark_obj(oop obj) {
-    return mark_obj((HeapWord*)obj);
+  bool is_marked(uintptr_t addr);
+
+  bool is_marked(oop obj) {
+    return is_marked(cast_from_oop<uintptr_t>(obj));
   }
+};
 
-  bool is_marked(const HeapWord* addr) const {
-    return is_marked(addr_to_bit(addr));
+class BitSet::BitMapFragment : public CHeapObj<mtTracing> {
+  CHeapBitMap _bits;
+  BitMapFragment* _next;
+
+public:
+  BitMapFragment(uintptr_t granule, BitMapFragment* next);
+
+  BitMapFragment* next() const {
+    return _next;
   }
 
-  bool is_marked(oop obj) const {
-    return is_marked((HeapWord*)obj);
-  }
-
-  BitMap::idx_t size() const {
-    return _bits.size();
-  }
-
-  BitMap::idx_t addr_to_bit(const HeapWord* addr) const {
-    return pointer_delta(addr, _region_start) >> LogMinObjAlignment;
-  }
-
-  bool is_marked(const BitMap::idx_t bit) const {
-    return _bits.at(bit);
+  CHeapBitMap* bits() {
+    return &_bits;
   }
 };
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/leakprofiler/chains/bitset.inline.hpp	Thu Sep 05 08:26:44 2019 +0200
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2019, 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_JFR_LEAKPROFILER_CHAINS_BITSET_INLINE_HPP
+#define SHARE_JFR_LEAKPROFILER_CHAINS_BITSET_INLINE_HPP
+
+#include "jfr/leakprofiler/chains/bitset.hpp"
+#include "jfr/recorder/storage/jfrVirtualMemory.hpp"
+#include "memory/memRegion.hpp"
+#include "utilities/bitMap.inline.hpp"
+#include "utilities/hashtable.inline.hpp"
+
+inline BitSet::BitMapFragmentTable::Entry* BitSet::BitMapFragmentTable::bucket(int i) const {
+  return (Entry*)BasicHashtable<mtTracing>::bucket(i);
+}
+
+inline BitSet::BitMapFragmentTable::Entry* BitSet::BitMapFragmentTable::new_entry(unsigned int hash,
+                                                                                  uintptr_t key,
+                                                                                  CHeapBitMap* value) {
+  Entry* entry = (Entry*)BasicHashtable<mtTracing>::new_entry(hash);
+  entry->_key = key;
+  entry->_value = value;
+  return entry;
+}
+
+inline void BitSet::BitMapFragmentTable::add(uintptr_t key, CHeapBitMap* value) {
+  unsigned hash = hash_segment(key);
+  Entry* entry = new_entry(hash, key, value);
+  BasicHashtable<mtTracing>::add_entry(hash_to_index(hash), entry);
+}
+
+inline CHeapBitMap** BitSet::BitMapFragmentTable::lookup(uintptr_t key) {
+  unsigned hash = hash_segment(key);
+  int index = hash_to_index(hash);
+  for (Entry* e = bucket(index); e != NULL; e = e->next()) {
+    if (e->hash() == hash && e->_key == key) {
+      return &(e->_value);
+    }
+  }
+  return NULL;
+}
+
+inline BitMap::idx_t BitSet::addr_to_bit(uintptr_t addr) const {
+  return (addr & _bitmap_granularity_mask) >> LogMinObjAlignmentInBytes;
+}
+
+inline CHeapBitMap* BitSet::get_fragment_bits(uintptr_t addr) {
+  uintptr_t granule = addr >> _bitmap_granularity_shift;
+  if (granule == _last_fragment_granule) {
+    return _last_fragment_bits;
+  }
+  CHeapBitMap* bits = NULL;
+
+  CHeapBitMap** found = _bitmap_fragments.lookup(granule);
+  if (found != NULL) {
+    bits = *found;
+  } else {
+    BitMapFragment* fragment = new BitMapFragment(granule, _fragment_list);
+    bits = fragment->bits();
+    _fragment_list = fragment;
+    if (_bitmap_fragments.number_of_entries() * 100 / _bitmap_fragments.table_size() > 25) {
+      _bitmap_fragments.resize(_bitmap_fragments.table_size() * 2);
+    }
+    _bitmap_fragments.add(granule, bits);
+  }
+
+  _last_fragment_bits = bits;
+  _last_fragment_granule = granule;
+
+  return bits;
+}
+
+inline void BitSet::mark_obj(uintptr_t addr) {
+  CHeapBitMap* bits = get_fragment_bits(addr);
+  const BitMap::idx_t bit = addr_to_bit(addr);
+  bits->set_bit(bit);
+}
+
+inline bool BitSet::is_marked(uintptr_t addr) {
+  CHeapBitMap* bits = get_fragment_bits(addr);
+  const BitMap::idx_t bit = addr_to_bit(addr);
+  return bits->at(bit);
+}
+
+#endif // SHARE_JFR_LEAKPROFILER_CHAINS_BITSET_INLINE_HPP

--- a/src/hotspot/share/jfr/leakprofiler/chains/dfsClosure.cpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/jfr/leakprofiler/chains/dfsClosure.cpp	Thu Sep 05 08:26:44 2019 +0200
@@ -23,7 +23,7 @@
  */
 
 #include "precompiled.hpp"
-#include "jfr/leakprofiler/chains/bitset.hpp"
+#include "jfr/leakprofiler/chains/bitset.inline.hpp"
 #include "jfr/leakprofiler/chains/dfsClosure.hpp"
 #include "jfr/leakprofiler/chains/edge.hpp"
 #include "jfr/leakprofiler/chains/edgeStore.hpp"

--- a/src/hotspot/share/jfr/leakprofiler/chains/pathToGcRootsOperation.cpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/jfr/leakprofiler/chains/pathToGcRootsOperation.cpp	Thu Sep 05 08:26:44 2019 +0200
@@ -26,7 +26,7 @@
 #include "gc/shared/collectedHeap.hpp"
 #include "jfr/leakprofiler/leakProfiler.hpp"
 #include "jfr/leakprofiler/chains/bfsClosure.hpp"
-#include "jfr/leakprofiler/chains/bitset.hpp"
+#include "jfr/leakprofiler/chains/bitset.inline.hpp"
 #include "jfr/leakprofiler/chains/dfsClosure.hpp"
 #include "jfr/leakprofiler/chains/edge.hpp"
 #include "jfr/leakprofiler/chains/edgeQueue.hpp"
@@ -57,8 +57,8 @@
  * Initial memory reservation: 5% of the heap OR at least 32 Mb
  * Commit ratio: 1 : 10 (subject to allocation granularties)
  */
-static size_t edge_queue_memory_reservation(const MemRegion& heap_region) {
-  const size_t memory_reservation_bytes = MAX2(heap_region.byte_size() / 20, 32*M);
+static size_t edge_queue_memory_reservation() {
+  const size_t memory_reservation_bytes = MAX2(MaxHeapSize / 20, 32*M);
   assert(memory_reservation_bytes >= (size_t)32*M, "invariant");
   return memory_reservation_bytes;
 }
@@ -84,17 +84,16 @@
   assert(_cutoff_ticks > 0, "invariant");
 
   // The bitset used for marking is dimensioned as a function of the heap size
-  const MemRegion heap_region = Universe::heap()->reserved_region();
-  BitSet mark_bits(heap_region);
+  BitSet mark_bits;
 
   // The edge queue is dimensioned as a fraction of the heap size
-  const size_t edge_queue_reservation_size = edge_queue_memory_reservation(heap_region);
+  const size_t edge_queue_reservation_size = edge_queue_memory_reservation();
   EdgeQueue edge_queue(edge_queue_reservation_size, edge_queue_memory_commit_size(edge_queue_reservation_size));
 
   // The initialize() routines will attempt to reserve and allocate backing storage memory.
   // Failure to accommodate will render root chain processing impossible.
   // As a fallback on failure, just write out the existing samples, flat, without chains.
-  if (!(mark_bits.initialize() && edge_queue.initialize())) {
+  if (!edge_queue.initialize()) {
     log_warning(jfr)("Unable to allocate memory for root chain processing");
     return;
   }

--- a/src/hotspot/share/utilities/hashtable.cpp	Thu Sep 05 14:55:21 2019 +0800
+++ b/src/hotspot/share/utilities/hashtable.cpp	Thu Sep 05 08:26:44 2019 +0200
@@ -306,6 +306,7 @@
 template class BasicHashtable<mtInternal>;
 template class BasicHashtable<mtModule>;
 template class BasicHashtable<mtCompiler>;
+template class BasicHashtable<mtTracing>;
 
 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);