--- /dev/null	2017-11-09 09:38:01.297999907 +0100
+++ new/src/hotspot/share/jfr/recorder/storage/jfrVirtualMemory.cpp	2018-04-09 15:18:07.312879493 +0200
@@ -0,0 +1,533 @@
+/*
+ * Copyright (c) 2017, 2018, 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 "jfr/recorder/storage/jfrVirtualMemory.hpp"
+#include "memory/virtualspace.hpp"
+#include "runtime/orderAccess.inline.hpp"
+#include "runtime/os.hpp"
+#include "services/memTracker.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+/*
+ * A memory segment represents a virtual memory reservation.
+ * It provides ways to commit and decommit physical storage
+ * onto its virtual memory reservation.
+ */
+
+class JfrVirtualMemorySegment : public JfrCHeapObj {
+  friend class JfrVirtualMemoryManager;
+ private:
+  JfrVirtualMemorySegment* _next;
+  char* _top;
+  ReservedSpace _rs;
+  VirtualSpace  _virtual_memory;
+
+  // Convenience functions to access the underlying virtual space metadata
+  const u1* committed_low()  const { return (const u1*)_virtual_memory.low(); }
+  const u1* committed_high() const { return (const u1*)_virtual_memory.high(); }
+  const u1* reserved_low() const { return (const u1*)_virtual_memory.low_boundary(); }
+  const u1* reserved_high() const { return (const u1*)_virtual_memory.high_boundary(); }
+  size_t reserved_words() const  { return _virtual_memory.reserved_size() / BytesPerWord; }
+  size_t committed_words() const { return _virtual_memory.actual_committed_size() / BytesPerWord; }
+  bool is_pre_committed() const { return _virtual_memory.special(); }
+  VirtualSpace& virtual_space() { return _virtual_memory; }
+
+  JfrVirtualMemorySegment();
+  ~JfrVirtualMemorySegment();
+
+  JfrVirtualMemorySegment* next() const { return _next; }
+  void set_next(JfrVirtualMemorySegment* v) { _next = v; }
+
+  // Returns true if requested size is available in the committed area
+  bool is_available(size_t block_size_request_words) {
+    return block_size_request_words <= pointer_delta(committed_high(), _top, sizeof(char*));
+  }
+
+  // allocation pointer committed memory
+  char* top() const { return _top; }
+  void inc_top(size_t size_in_words) {
+    assert(is_available(size_in_words), "invariant");
+    _top += size_in_words * BytesPerWord;
+    assert(_top <= _virtual_memory.high(), "invariant");
+  }
+
+  // initialization is the virtual memory reservation
+  bool initialize(size_t reservation_size_request_bytes);
+  void* take_from_committed(size_t block_size_request_words);
+
+  // Returns committed memory
+  void* commit(size_t block_size_request_words) {
+    return take_from_committed(block_size_request_words);
+  }
+
+  // Commit more memory in a reservation
+  bool expand_by(size_t block_size_request_words);
+
+  // Decommits all committed memory in this reservation segment.
+  void decommit();
+};
+
+JfrVirtualMemorySegment::JfrVirtualMemorySegment() :
+  _next(NULL),
+  _top(NULL),
+  _rs(),
+  _virtual_memory() {}
+
+JfrVirtualMemorySegment::~JfrVirtualMemorySegment() {
+  decommit();
+  _rs.release();
+}
+
+bool JfrVirtualMemorySegment::initialize(size_t reservation_size_request_bytes) {
+  assert(is_aligned(reservation_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  _rs = ReservedSpace(reservation_size_request_bytes,
+                      os::vm_allocation_granularity(),
+                      UseLargePages && os::can_commit_large_page_memory(),
+                      false);
+  if (!_rs.is_reserved()) {
+    return false;
+  }
+  assert(_rs.base() != NULL, "invariant");
+  assert(_rs.size() != 0, "invariant");
+  assert(is_aligned(_rs.base(), os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(_rs.size(), os::vm_allocation_granularity()), "invariant");
+  os::trace_page_sizes("Jfr", reservation_size_request_bytes,
+                              reservation_size_request_bytes,
+                              os::vm_page_size(),
+                              _rs.base(),
+                              _rs.size());
+  MemTracker::record_virtual_memory_type((address)_rs.base(), mtTracing);
+  assert(is_aligned(_rs.base(), os::vm_page_size()), "invariant");
+  assert(is_aligned(_rs.size(), os::vm_page_size()), "invariant");
+
+  // ReservedSpaces marked as special will have the entire memory
+  // pre-committed. Setting a committed size will make sure that
+  // committed_size and actual_committed_size agrees.
+  const size_t pre_committed_size = _rs.special() ? _rs.size() : 0;
+  const bool result = virtual_space().initialize_with_granularity(_rs, pre_committed_size, os::vm_page_size());
+
+  if (result) {
+    assert(virtual_space().committed_size() == virtual_space().actual_committed_size(),
+      "Checking that the pre-committed memory was registered by the VirtualSpace");
+    _top = virtual_space().low();
+  }
+  return result;
+}
+
+bool JfrVirtualMemorySegment::expand_by(size_t block_size_request_words) {
+  size_t block_size_request_bytes = block_size_request_words * BytesPerWord;
+  const size_t uncommitted = virtual_space().reserved_size() - virtual_space().actual_committed_size();
+  if (uncommitted < block_size_request_bytes) {
+    // commit whatever is left in the reservation
+    block_size_request_bytes = uncommitted;
+  }
+  assert(is_aligned(block_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  // commit block in reserved memory
+  bool result = virtual_space().expand_by(block_size_request_bytes, false);
+  assert(result, "Failed to commit memory");
+  return result;
+}
+
+void JfrVirtualMemorySegment::decommit() {
+  assert(_virtual_memory.committed_size() == _virtual_memory.actual_committed_size(),
+    "The committed memory doesn't match the expanded memory.");
+
+  const size_t committed_size = virtual_space().actual_committed_size();
+  if (committed_size > 0) {
+    virtual_space().shrink_by(committed_size);
+  }
+
+  assert(_virtual_memory.actual_committed_size() == 0, "invariant");
+}
+
+// Attempt to get a committed block
+void* JfrVirtualMemorySegment::take_from_committed(size_t block_size_request_words) {
+  // The virtual spaces are always expanded by the
+  // commit granularity to enforce the following condition.
+  // Without this the is_available check will not work correctly.
+  assert(_virtual_memory.committed_size() == _virtual_memory.actual_committed_size(),
+    "The committed memory doesn't match the expanded memory.");
+  if (!is_available(block_size_request_words)) {
+    return NULL;
+  }
+  void* const block = top();
+  assert(block != NULL, "invariant");
+  inc_top(block_size_request_words);
+  return block;
+}
+
+class JfrVirtualMemoryManager : public JfrCHeapObj {
+ typedef JfrVirtualMemorySegment Segment;
+ private:
+  Segment* _segments;
+  Segment* _current_segment;
+  size_t _reservation_size_request_words;
+  size_t _reservation_size_request_limit_words; // total reservation limit
+
+  // Sum of reserved and committed memory in the segments
+  size_t _current_reserved_words;
+  size_t _current_committed_words;
+
+  void link(Segment* segment);
+  Segment* current();
+
+  void inc_reserved_words(size_t words);
+  void inc_committed_words(size_t words);
+
+  bool new_segment(size_t reservation_size_request_words);
+
+  bool expand_segment_by(Segment* segment, size_t block_size_request_words);
+
+  bool expand_by(size_t block_size_request_words, size_t reservation_size_request_words);
+  bool can_reserve() const;
+
+ public:
+  JfrVirtualMemoryManager();
+  ~JfrVirtualMemoryManager();
+
+  bool initialize(size_t reservation_size_request_words, size_t segment_count = 1);
+  void* commit(size_t requested_block_size_words);
+
+  bool is_full() const {
+    return reserved_high() == committed_high();
+  }
+
+  const u1* committed_low() const { return _current_segment->committed_low(); }
+  const u1* committed_high() const { return _current_segment->committed_high(); }
+  const u1* reserved_low() const { return _current_segment->reserved_low(); }
+  const u1* reserved_high() const { return _current_segment->reserved_high(); }
+};
+
+JfrVirtualMemoryManager::JfrVirtualMemoryManager() :
+  _segments(NULL),
+  _current_segment(NULL),
+  _reservation_size_request_words(0),
+  _reservation_size_request_limit_words(0),
+  _current_reserved_words(0),
+  _current_committed_words(0) {}
+
+JfrVirtualMemoryManager::~JfrVirtualMemoryManager() {
+  JfrVirtualMemorySegment* segment = _segments;
+  while (segment != NULL) {
+    JfrVirtualMemorySegment* next_segment = segment->next();
+    delete segment;
+    segment = next_segment;
+  }
+}
+
+// for now only allow a singleton segment per virtual memory client
+bool JfrVirtualMemoryManager::initialize(size_t reservation_size_request_words, size_t segment_count /* 1 */) {
+  assert(is_aligned(reservation_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  _reservation_size_request_words = reservation_size_request_words;
+  assert(segment_count > 0, "invariant");
+  _reservation_size_request_limit_words = reservation_size_request_words * segment_count;
+  assert(is_aligned(_reservation_size_request_limit_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  return new_segment(_reservation_size_request_words);
+}
+
+bool JfrVirtualMemoryManager::can_reserve() const  {
+  return _reservation_size_request_limit_words == 0 ? true : _current_reserved_words < _reservation_size_request_limit_words;
+}
+
+// Allocate another segment and add it to the list.
+bool JfrVirtualMemoryManager::new_segment(size_t reservation_size_request_words) {
+  assert(reservation_size_request_words > 0, "invariant");
+  assert(is_aligned(reservation_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  Segment* segment = new Segment();
+  if (NULL == segment) {
+    return false;
+  }
+  if (!segment->initialize(reservation_size_request_words * BytesPerWord)) {
+    delete segment;
+    return false;
+  }
+  assert(segment->reserved_words() == reservation_size_request_words,
+    "Actual reserved memory size differs from requested reservation memory size");
+  link(segment);
+  return true;
+}
+
+bool JfrVirtualMemoryManager::expand_segment_by(JfrVirtualMemorySegment* segment, size_t block_size_request_words) {
+  assert(segment != NULL, "invariant");
+  const size_t before = segment->committed_words();
+  const bool result = segment->expand_by(block_size_request_words);
+  const size_t after = segment->committed_words();
+  // after and before can be the same if the memory was pre-committed.
+  assert(after >= before, "Inconsistency");
+  inc_committed_words(after - before);
+  return result;
+}
+
+void JfrVirtualMemoryManager::inc_reserved_words(size_t words) {
+  _current_reserved_words += words;
+}
+
+JfrVirtualMemorySegment* JfrVirtualMemoryManager::current() {
+  return _current_segment;
+}
+
+void JfrVirtualMemoryManager::inc_committed_words(size_t words) {
+  _current_committed_words += words;
+}
+
+bool JfrVirtualMemoryManager::expand_by(size_t block_size_request_words, size_t reservation_size_request_words) {
+  assert(is_aligned(block_size_request_words * BytesPerWord, os::vm_page_size()), "invariant");
+  assert(is_aligned(block_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(reservation_size_request_words * BytesPerWord, os::vm_page_size()), "invariant");
+  assert(is_aligned(reservation_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  assert(block_size_request_words <= reservation_size_request_words, "invariant");
+  // Attempt to commit more memory from the the current virtual space reservation.
+  if (expand_segment_by(current(), block_size_request_words)) {
+    return true;
+  }
+
+  // reached limit of what is allowed to be reserved?
+  if (!can_reserve()) {
+    return false;
+  }
+
+  // Get another segment.
+  if (!new_segment(reservation_size_request_words)) {
+    return false;
+  }
+
+  if (current()->is_pre_committed()) {
+    // The memory was pre-committed, so we are done here.
+    assert(block_size_request_words <= current()->committed_words(),
+           "The new VirtualSpace was pre-committed, so it"
+           "should be large enough to fit the alloc request.");
+    return true;
+  }
+  return expand_segment_by(current(), block_size_request_words);
+}
+
+void JfrVirtualMemoryManager::link(JfrVirtualMemorySegment* segment) {
+  assert(segment != NULL, "invariant");
+  if (_segments == NULL) {
+    _segments = segment;
+  } else {
+    assert(_current_segment != NULL, "invariant");
+    assert(_segments == _current_segment, "invariant");
+    _current_segment->set_next(segment);
+  }
+  _current_segment = segment;
+  inc_reserved_words(segment->reserved_words());
+  inc_committed_words(segment->committed_words());
+}
+
+void* JfrVirtualMemoryManager::commit(size_t block_size_request_words) {
+  assert(is_aligned(block_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  void* block = current()->commit(block_size_request_words);
+  if (block != NULL) {
+    return block;
+  }
+  assert(block == NULL, "invariant");
+  if (is_full()) {
+    return NULL;
+  }
+  assert(block_size_request_words <= _reservation_size_request_words, "invariant");
+  if (expand_by(block_size_request_words, _reservation_size_request_words)) {
+    block = current()->commit(block_size_request_words);
+    assert(block != NULL, "The allocation was expected to succeed after the expansion");
+  }
+  return block;
+}
+
+JfrVirtualMemory::JfrVirtualMemory() :
+  _vmm(NULL),
+  _reserved_low(),
+  _reserved_high(),
+  _top(NULL),
+  _commit_point(NULL),
+  _physical_commit_size_request_words(0),
+  _aligned_datum_size_bytes(0) {}
+
+JfrVirtualMemory::~JfrVirtualMemory() {
+  assert(_vmm != NULL, "invariant");
+  delete _vmm;
+}
+
+size_t JfrVirtualMemory::aligned_datum_size_bytes() const {
+  return _aligned_datum_size_bytes;
+}
+
+static void adjust_allocation_ratio(size_t* const reservation_size_bytes, size_t* const commit_size_bytes) {
+  assert(reservation_size_bytes != NULL, "invariant");
+  assert(*reservation_size_bytes > 0, "invariant");
+  assert(commit_size_bytes != NULL, "invariant");
+  assert(*commit_size_bytes > 0, "invariant");
+  assert(*reservation_size_bytes >= *commit_size_bytes, "invariant");
+  assert(is_aligned(*reservation_size_bytes, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(*commit_size_bytes, os::vm_allocation_granularity()), "invariant");
+
+  size_t reservation_size_units = *reservation_size_bytes / os::vm_allocation_granularity();
+  size_t commit_size_units = *commit_size_bytes / os::vm_allocation_granularity();
+  assert(reservation_size_units > 0, "invariant");
+  assert(commit_size_units > 0, "invariant");
+
+  size_t original_ratio_units = reservation_size_units / commit_size_units;
+  size_t rem = reservation_size_units % commit_size_units;
+  assert(original_ratio_units > 0, "invariant");
+
+  if (rem > 0) {
+    reservation_size_units -= rem % original_ratio_units;
+    commit_size_units += rem / original_ratio_units;
+  }
+
+  assert(commit_size_units > 0, "invariant");
+  assert(reservation_size_units % original_ratio_units == 0, "invariant");
+  assert(original_ratio_units * commit_size_units == reservation_size_units , "invariant");
+  assert(original_ratio_units == reservation_size_units / commit_size_units, "invariant");
+  *reservation_size_bytes = reservation_size_units * os::vm_allocation_granularity();
+  *commit_size_bytes = commit_size_units * os::vm_allocation_granularity();
+  assert((*reservation_size_bytes % *commit_size_bytes) == 0, "invariant");
+}
+
+
+void* JfrVirtualMemory::initialize(size_t reservation_size_request_bytes,
+                                   size_t block_size_request_bytes,
+                                   size_t datum_size_bytes /* 1 */) {
+  assert(_vmm == NULL, "invariant");
+  _vmm = new JfrVirtualMemoryManager();
+
+  if (_vmm == NULL) {
+    return NULL;
+  }
+
+  assert(reservation_size_request_bytes > 0, "invariant");
+  _aligned_datum_size_bytes = align_up(datum_size_bytes, BytesPerWord);
+  assert(is_aligned(_aligned_datum_size_bytes, BytesPerWord), "invariant");
+
+  reservation_size_request_bytes = ReservedSpace::allocation_align_size_up(reservation_size_request_bytes);
+  assert(is_aligned(reservation_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(reservation_size_request_bytes, _aligned_datum_size_bytes), "invariant");
+  block_size_request_bytes = MAX2(block_size_request_bytes, (size_t)os::vm_allocation_granularity());
+  block_size_request_bytes = ReservedSpace::allocation_align_size_up(block_size_request_bytes);
+  assert(is_aligned(block_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(block_size_request_bytes, _aligned_datum_size_bytes), "invariant");
+  // adjustment to valid ratio in units of vm_allocation_granularity
+  adjust_allocation_ratio(&reservation_size_request_bytes, &block_size_request_bytes);
+  assert(is_aligned(reservation_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(reservation_size_request_bytes, _aligned_datum_size_bytes), "invariant");
+  assert(is_aligned(block_size_request_bytes, os::vm_allocation_granularity()), "invariant");
+  assert(is_aligned(block_size_request_bytes, _aligned_datum_size_bytes), "invariant");
+  assert((reservation_size_request_bytes % block_size_request_bytes) == 0, "invariant");
+  const size_t reservation_size_request_words = reservation_size_request_bytes / BytesPerWord;
+  _physical_commit_size_request_words = block_size_request_bytes / BytesPerWord;
+  // virtual memory reservation
+  if (!_vmm->initialize(reservation_size_request_words)) {
+    // is implicitly "full" if reservation fails
+    assert(is_full(), "invariant");
+    return NULL;
+  }
+  _reserved_low = (const u1*)_vmm->reserved_low();
+  _reserved_high = (const u1*)_vmm->reserved_high();
+  // reservation complete
+  _top = (u1*)_vmm->committed_high();
+  _commit_point = _top;
+  assert(_reserved_low == _top, "invariant"); // initial empty state
+  assert((size_t)(_reserved_high - _reserved_low) == reservation_size_request_bytes, "invariant");
+  // initial commit
+  commit_memory_block();
+  return _top;
+}
+
+void* JfrVirtualMemory::commit(size_t block_size_request_words) {
+  assert(_vmm != NULL, "invariant");
+  assert(is_aligned(block_size_request_words * BytesPerWord, os::vm_allocation_granularity()), "invariant");
+  return _vmm->commit(block_size_request_words);
+}
+
+bool JfrVirtualMemory::is_full() const {
+  return _top == _reserved_high;
+}
+
+bool JfrVirtualMemory::is_empty() const {
+  return _top == _reserved_low;
+}
+
+bool JfrVirtualMemory::commit_memory_block() {
+  assert(_vmm != NULL, "invariant");
+  assert(!is_full(), "invariant");
+  assert(_top == _commit_point, "invariant");
+
+  void* const block = _vmm->commit(_physical_commit_size_request_words);
+  if (block != NULL) {
+    _commit_point = _vmm->committed_high();
+    return true;
+  }
+  // all reserved virtual memory is committed
+  assert(block == NULL, "invariant");
+  assert(_vmm->reserved_high() == _vmm->committed_high(), "invariant");
+  return false;
+}
+
+void* JfrVirtualMemory::new_datum() {
+  assert(_vmm != NULL, "invariant");
+  assert(!is_full(), "invariant");
+  if (_top == _commit_point) {
+    if (!commit_memory_block()) {
+      assert(is_full(), "invariant");
+      return NULL;
+    }
+  }
+  assert(_top + _aligned_datum_size_bytes <= _commit_point, "invariant");
+  u1* allocation = _top;
+  _top += _aligned_datum_size_bytes;
+  assert(is_aligned(allocation, _aligned_datum_size_bytes), "invariant");
+  return allocation;
+}
+
+void* JfrVirtualMemory::index_ptr(size_t index) {
+  assert((index * _aligned_datum_size_bytes) + _reserved_low < _commit_point, "invariant");
+  return (void*)((index * _aligned_datum_size_bytes) + _reserved_low);
+}
+
+void* JfrVirtualMemory::get(size_t index) {
+  return index_ptr(index);
+}
+
+size_t JfrVirtualMemory::count() const {
+  return (_top - _reserved_low) / _aligned_datum_size_bytes;
+}
+
+size_t JfrVirtualMemory::live_set() const {
+  return _top - _reserved_low;
+}
+
+size_t JfrVirtualMemory::reserved_size() const {
+  return _reserved_high - _reserved_low;
+}
+
+bool JfrVirtualMemory::compact(size_t index) {
+  assert(index > 0, "invariant");
+  assert(index <= reserved_size(), "invariant");
+  const u1* low = static_cast<u1*>(index_ptr(index));
+  const size_t block_size = _top - low;
+  memcpy(const_cast<u1*>(_reserved_low), low, block_size);
+  _top = const_cast<u1*>(_reserved_low) + block_size;
+  assert(live_set() == block_size, "invariant");
+  return true;
+}