--- /dev/null	2019-01-28 17:47:59.000000000 +0800
+++ new/src/share/vm/jfr/recorder/storage/jfrVirtualMemory.hpp	2019-01-28 17:47:58.000000000 +0800
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2017, 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_VM_JFR_RECORDER_STORAGE_JFRVIRTUALMEMORY_HPP
+#define SHARE_VM_JFR_RECORDER_STORAGE_JFRVIRTUALMEMORY_HPP
+
+#include "jfr/utilities/jfrAllocation.hpp"
+
+class JfrVirtualMemoryManager;
+
+class JfrVirtualMemory : public JfrCHeapObj {
+ private:
+  JfrVirtualMemoryManager* _vmm;
+  const u1* _reserved_low; // lowest address of reservation
+  const u1* _reserved_high; // highest address of reservation
+  u1* _top; // current allocation address
+  const u1* _commit_point; // synch points for committing new memory
+  size_t _physical_commit_size_request_words; // aligned to os::vm_allocation_granularity()
+  size_t _aligned_datum_size_bytes; // datum alignment
+
+  bool commit_memory_block();
+  void* commit(size_t block_size_request_words);
+  void* index_ptr(size_t index); // index to address map
+
+ public:
+  JfrVirtualMemory();
+  ~JfrVirtualMemory();
+
+  // initialization will do the reservation and return it
+  void* initialize(size_t reservation_size_request_bytes, size_t block_size_request_bytes, size_t datum_size_bytes = 1);
+
+  void* new_datum(); // datum oriented allocation
+  void* get(size_t index); // direct access retrieval
+  size_t aligned_datum_size_bytes() const;
+
+  bool is_full() const; // limit of reservation committed and in use
+  bool is_empty() const;
+
+  size_t count() const; // how many
+  size_t live_set() const; // how much resident memory (actually in use)
+  size_t reserved_size() const; // size of reservation
+  bool compact(size_t index);
+};
+
+#endif // SHARE_VM_JFR_RECORDER_STORAGE_JFRVIRTUALMEMORY_HPP