src/hotspot/share/memory/metaspaceShared.cpp
changeset 47216 71c04702a3d5
parent 47103 a993ec29ec75
child 47574 15294343ba19
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/memory/metaspaceShared.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1960 @@
+/*
+ * Copyright (c) 2012, 2017, 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 "classfile/classListParser.hpp"
+#include "classfile/classLoaderExt.hpp"
+#include "classfile/dictionary.hpp"
+#include "classfile/loaderConstraints.hpp"
+#include "classfile/placeholders.hpp"
+#include "classfile/sharedClassUtil.hpp"
+#include "classfile/symbolTable.hpp"
+#include "classfile/stringTable.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "classfile/systemDictionaryShared.hpp"
+#include "code/codeCache.hpp"
+#if INCLUDE_ALL_GCS
+#include "gc/g1/g1Allocator.inline.hpp"
+#include "gc/g1/g1CollectedHeap.hpp"
+#include "gc/g1/g1SATBCardTableModRefBS.hpp"
+#endif
+#include "gc/shared/gcLocker.hpp"
+#include "interpreter/bytecodeStream.hpp"
+#include "interpreter/bytecodes.hpp"
+#include "logging/log.hpp"
+#include "logging/logMessage.hpp"
+#include "memory/filemap.hpp"
+#include "memory/metaspace.hpp"
+#include "memory/metaspaceShared.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/instanceClassLoaderKlass.hpp"
+#include "oops/instanceMirrorKlass.hpp"
+#include "oops/instanceRefKlass.hpp"
+#include "oops/objArrayKlass.hpp"
+#include "oops/objArrayOop.hpp"
+#include "oops/oop.inline.hpp"
+#include "oops/typeArrayKlass.hpp"
+#include "prims/jvm.h"
+#include "prims/jvmtiRedefineClasses.hpp"
+#include "runtime/timerTrace.hpp"
+#include "runtime/os.hpp"
+#include "runtime/signature.hpp"
+#include "runtime/vmThread.hpp"
+#include "runtime/vm_operations.hpp"
+#include "utilities/align.hpp"
+#include "utilities/defaultStream.hpp"
+#include "utilities/hashtable.inline.hpp"
+#include "memory/metaspaceClosure.hpp"
+
+ReservedSpace MetaspaceShared::_shared_rs;
+VirtualSpace MetaspaceShared::_shared_vs;
+MetaspaceSharedStats MetaspaceShared::_stats;
+bool MetaspaceShared::_has_error_classes;
+bool MetaspaceShared::_archive_loading_failed = false;
+bool MetaspaceShared::_remapped_readwrite = false;
+bool MetaspaceShared::_open_archive_heap_region_mapped = false;
+address MetaspaceShared::_cds_i2i_entry_code_buffers = NULL;
+size_t MetaspaceShared::_cds_i2i_entry_code_buffers_size = 0;
+size_t MetaspaceShared::_core_spaces_size = 0;
+
+// The CDS archive is divided into the following regions:
+//     mc  - misc code (the method entry trampolines)
+//     rw  - read-write metadata
+//     ro  - read-only metadata and read-only tables
+//     md  - misc data (the c++ vtables)
+//     od  - optional data (original class files)
+//
+//     s0  - shared strings(closed archive heap space) #0
+//     s1  - shared strings(closed archive heap space) #1 (may be empty)
+//     oa0 - open archive heap space #0
+//     oa1 - open archive heap space #1 (may be empty)
+//
+// The mc, rw, ro, md and od regions are linearly allocated, starting from
+// SharedBaseAddress, in the order of mc->rw->ro->md->od. The size of these 5 regions
+// are page-aligned, and there's no gap between any consecutive regions.
+//
+// These 5 regions are populated in the following steps:
+// [1] All classes are loaded in MetaspaceShared::preload_classes(). All metadata are
+//     temporarily allocated outside of the shared regions. Only the method entry
+//     trampolines are written into the mc region.
+// [2] ArchiveCompactor copies RW metadata into the rw region.
+// [3] ArchiveCompactor copies RO metadata into the ro region.
+// [4] SymbolTable, StringTable, SystemDictionary, and a few other read-only data
+//     are copied into the ro region as read-only tables.
+// [5] C++ vtables are copied into the md region.
+// [6] Original class files are copied into the od region.
+//
+// The s0/s1 and oa0/oa1 regions are populated inside MetaspaceShared::dump_java_heap_objects.
+// Their layout is independent of the other 5 regions.
+
+class DumpRegion {
+private:
+  const char* _name;
+  char* _base;
+  char* _top;
+  char* _end;
+  bool _is_packed;
+
+  char* expand_top_to(char* newtop) {
+    assert(is_allocatable(), "must be initialized and not packed");
+    assert(newtop >= _top, "must not grow backwards");
+    if (newtop > _end) {
+      MetaspaceShared::report_out_of_space(_name, newtop - _top);
+      ShouldNotReachHere();
+    }
+    MetaspaceShared::commit_shared_space_to(newtop);
+    _top = newtop;
+    return _top;
+  }
+
+public:
+  DumpRegion(const char* name) : _name(name), _base(NULL), _top(NULL), _end(NULL), _is_packed(false) {}
+
+  char* allocate(size_t num_bytes, size_t alignment=BytesPerWord) {
+    char* p = (char*)align_up(_top, alignment);
+    char* newtop = p + align_up(num_bytes, alignment);
+    expand_top_to(newtop);
+    memset(p, 0, newtop - p);
+    return p;
+  }
+
+  void append_intptr_t(intptr_t n) {
+    assert(is_aligned(_top, sizeof(intptr_t)), "bad alignment");
+    intptr_t *p = (intptr_t*)_top;
+    char* newtop = _top + sizeof(intptr_t);
+    expand_top_to(newtop);
+    *p = n;
+  }
+
+  char* base()      const { return _base;        }
+  char* top()       const { return _top;         }
+  char* end()       const { return _end;         }
+  size_t reserved() const { return _end - _base; }
+  size_t used()     const { return _top - _base; }
+  bool is_packed()  const { return _is_packed;   }
+  bool is_allocatable() const {
+    return !is_packed() && _base != NULL;
+  }
+
+  double perc(size_t used, size_t total) const {
+    if (total == 0) {
+      total = 1;
+    }
+    return used / double(total) * 100.0;
+  }
+
+  void print(size_t total_bytes) const {
+    tty->print_cr("%s space: " SIZE_FORMAT_W(9) " [ %4.1f%% of total] out of " SIZE_FORMAT_W(9) " bytes [%5.1f%% used] at " INTPTR_FORMAT,
+                  _name, used(), perc(used(), total_bytes), reserved(), perc(used(), reserved()), p2i(_base));
+  }
+  void print_out_of_space_msg(const char* failing_region, size_t needed_bytes) {
+    tty->print("[%-8s] " PTR_FORMAT " - " PTR_FORMAT " capacity =%9d, allocated =%9d",
+               _name, p2i(_base), p2i(_top), int(_end - _base), int(_top - _base));
+    if (strcmp(_name, failing_region) == 0) {
+      tty->print_cr(" required = %d", int(needed_bytes));
+    } else {
+      tty->cr();
+    }
+  }
+
+  void init(const ReservedSpace* rs) {
+    _base = _top = rs->base();
+    _end = rs->end();
+  }
+  void init(char* b, char* t, char* e) {
+    _base = b;
+    _top = t;
+    _end = e;
+  }
+
+  void pack(DumpRegion* next = NULL) {
+    assert(!is_packed(), "sanity");
+    _end = (char*)align_up(_top, Metaspace::reserve_alignment());
+    _is_packed = true;
+    if (next != NULL) {
+      next->_base = next->_top = this->_end;
+      next->_end = MetaspaceShared::shared_rs()->end();
+    }
+  }
+  bool contains(char* p) {
+    return base() <= p && p < top();
+  }
+};
+
+
+DumpRegion _mc_region("mc"), _ro_region("ro"), _rw_region("rw"), _md_region("md"), _od_region("od");
+size_t _total_string_region_size = 0, _total_open_archive_region_size = 0;
+
+char* MetaspaceShared::misc_code_space_alloc(size_t num_bytes) {
+  return _mc_region.allocate(num_bytes);
+}
+
+char* MetaspaceShared::read_only_space_alloc(size_t num_bytes) {
+  return _ro_region.allocate(num_bytes);
+}
+
+void MetaspaceShared::initialize_shared_rs() {
+  const size_t reserve_alignment = Metaspace::reserve_alignment();
+  bool large_pages = false; // No large pages when dumping the CDS archive.
+  char* shared_base = (char*)align_up((char*)SharedBaseAddress, reserve_alignment);
+
+#ifdef _LP64
+  // On 64-bit VM, the heap and class space layout will be the same as if
+  // you're running in -Xshare:on mode:
+  //
+  //                         +-- SharedBaseAddress (default = 0x800000000)
+  //                         v
+  // +-..---------+----+ ... +----+----+----+----+----+---------------+
+  // |    Heap    | ST |     | MC | RW | RO | MD | OD | class space   |
+  // +-..---------+----+ ... +----+----+----+----+----+---------------+
+  // |<--MaxHeapSize->|     |<-- UnscaledClassSpaceMax = 4GB ------->|
+  //
+  const uint64_t UnscaledClassSpaceMax = (uint64_t(max_juint) + 1);
+  const size_t cds_total = align_down(UnscaledClassSpaceMax, reserve_alignment);
+#else
+  // We don't support archives larger than 256MB on 32-bit due to limited virtual address space.
+  size_t cds_total = align_down(256*M, reserve_alignment);
+#endif
+
+  // First try to reserve the space at the specified SharedBaseAddress.
+  _shared_rs = ReservedSpace(cds_total, reserve_alignment, large_pages, shared_base);
+  if (_shared_rs.is_reserved()) {
+    assert(shared_base == 0 || _shared_rs.base() == shared_base, "should match");
+  } else {
+    // Get a mmap region anywhere if the SharedBaseAddress fails.
+    _shared_rs = ReservedSpace(cds_total, reserve_alignment, large_pages);
+  }
+  if (!_shared_rs.is_reserved()) {
+    vm_exit_during_initialization("Unable to reserve memory for shared space",
+                                  err_msg(SIZE_FORMAT " bytes.", cds_total));
+  }
+
+#ifdef _LP64
+  // During dump time, we allocate 4GB (UnscaledClassSpaceMax) of space and split it up:
+  // + The upper 1 GB is used as the "temporary compressed class space" -- preload_classes()
+  //   will store Klasses into this space.
+  // + The lower 3 GB is used for the archive -- when preload_classes() is done,
+  //   ArchiveCompactor will copy the class metadata into this space, first the RW parts,
+  //   then the RO parts.
+
+  assert(UseCompressedOops && UseCompressedClassPointers,
+      "UseCompressedOops and UseCompressedClassPointers must be set");
+
+  size_t max_archive_size = align_down(cds_total * 3 / 4, reserve_alignment);
+  ReservedSpace tmp_class_space = _shared_rs.last_part(max_archive_size);
+  CompressedClassSpaceSize = align_down(tmp_class_space.size(), reserve_alignment);
+  _shared_rs = _shared_rs.first_part(max_archive_size);
+
+  // Set up compress class pointers.
+  Universe::set_narrow_klass_base((address)_shared_rs.base());
+  if (UseAOT || cds_total > UnscaledClassSpaceMax) {
+    // AOT forces narrow_klass_shift=LogKlassAlignmentInBytes
+    Universe::set_narrow_klass_shift(LogKlassAlignmentInBytes);
+  } else {
+    Universe::set_narrow_klass_shift(0);
+  }
+
+  Metaspace::initialize_class_space(tmp_class_space);
+  tty->print_cr("narrow_klass_base = " PTR_FORMAT ", narrow_klass_shift = %d",
+                p2i(Universe::narrow_klass_base()), Universe::narrow_klass_shift());
+
+  tty->print_cr("Allocated temporary class space: " SIZE_FORMAT " bytes at " PTR_FORMAT,
+                CompressedClassSpaceSize, p2i(tmp_class_space.base()));
+#endif
+
+  // Start with 0 committed bytes. The memory will be committed as needed by
+  // MetaspaceShared::commit_shared_space_to().
+  if (!_shared_vs.initialize(_shared_rs, 0)) {
+    vm_exit_during_initialization("Unable to allocate memory for shared space");
+  }
+
+  _mc_region.init(&_shared_rs);
+  tty->print_cr("Allocated shared space: " SIZE_FORMAT " bytes at " PTR_FORMAT,
+                _shared_rs.size(), p2i(_shared_rs.base()));
+}
+
+void MetaspaceShared::commit_shared_space_to(char* newtop) {
+  assert(DumpSharedSpaces, "dump-time only");
+  char* base = _shared_rs.base();
+  size_t need_committed_size = newtop - base;
+  size_t has_committed_size = _shared_vs.committed_size();
+  if (need_committed_size < has_committed_size) {
+    return;
+  }
+
+  size_t min_bytes = need_committed_size - has_committed_size;
+  size_t preferred_bytes = 1 * M;
+  size_t uncommitted = _shared_vs.reserved_size() - has_committed_size;
+
+  size_t commit = MAX2(min_bytes, preferred_bytes);
+  assert(commit <= uncommitted, "sanity");
+
+  bool result = _shared_vs.expand_by(commit, false);
+  if (!result) {
+    vm_exit_during_initialization(err_msg("Failed to expand shared space to " SIZE_FORMAT " bytes",
+                                          need_committed_size));
+  }
+
+  log_info(cds)("Expanding shared spaces by " SIZE_FORMAT_W(7) " bytes [total " SIZE_FORMAT_W(9)  " bytes ending at %p]",
+                commit, _shared_vs.actual_committed_size(), _shared_vs.high());
+}
+
+// Read/write a data stream for restoring/preserving metadata pointers and
+// miscellaneous data from/to the shared archive file.
+
+void MetaspaceShared::serialize(SerializeClosure* soc) {
+  int tag = 0;
+  soc->do_tag(--tag);
+
+  // Verify the sizes of various metadata in the system.
+  soc->do_tag(sizeof(Method));
+  soc->do_tag(sizeof(ConstMethod));
+  soc->do_tag(arrayOopDesc::base_offset_in_bytes(T_BYTE));
+  soc->do_tag(sizeof(ConstantPool));
+  soc->do_tag(sizeof(ConstantPoolCache));
+  soc->do_tag(objArrayOopDesc::base_offset_in_bytes());
+  soc->do_tag(typeArrayOopDesc::base_offset_in_bytes(T_BYTE));
+  soc->do_tag(sizeof(Symbol));
+
+  // Dump/restore miscellaneous metadata.
+  Universe::serialize(soc, true);
+  soc->do_tag(--tag);
+
+  // Dump/restore references to commonly used names and signatures.
+  vmSymbols::serialize(soc);
+  soc->do_tag(--tag);
+
+  // Dump/restore the symbol and string tables
+  SymbolTable::serialize(soc);
+  StringTable::serialize(soc);
+  soc->do_tag(--tag);
+
+  soc->do_tag(666);
+}
+
+address MetaspaceShared::cds_i2i_entry_code_buffers(size_t total_size) {
+  if (DumpSharedSpaces) {
+    if (_cds_i2i_entry_code_buffers == NULL) {
+      _cds_i2i_entry_code_buffers = (address)misc_code_space_alloc(total_size);
+      _cds_i2i_entry_code_buffers_size = total_size;
+    }
+  } else if (UseSharedSpaces) {
+    assert(_cds_i2i_entry_code_buffers != NULL, "must already been initialized");
+  } else {
+    return NULL;
+  }
+
+  assert(_cds_i2i_entry_code_buffers_size == total_size, "must not change");
+  return _cds_i2i_entry_code_buffers;
+}
+
+// CDS code for dumping shared archive.
+
+// Global object for holding classes that have been loaded.  Since this
+// is run at a safepoint just before exit, this is the entire set of classes.
+static GrowableArray<Klass*>* _global_klass_objects;
+
+static void collect_array_classes(Klass* k) {
+  _global_klass_objects->append_if_missing(k);
+  if (k->is_array_klass()) {
+    // Add in the array classes too
+    ArrayKlass* ak = ArrayKlass::cast(k);
+    Klass* h = ak->higher_dimension();
+    if (h != NULL) {
+      h->array_klasses_do(collect_array_classes);
+    }
+  }
+}
+
+class CollectClassesClosure : public KlassClosure {
+  void do_klass(Klass* k) {
+    if (!(k->is_instance_klass() && InstanceKlass::cast(k)->is_in_error_state())) {
+      _global_klass_objects->append_if_missing(k);
+    }
+    if (k->is_array_klass()) {
+      // Add in the array classes too
+      ArrayKlass* ak = ArrayKlass::cast(k);
+      Klass* h = ak->higher_dimension();
+      if (h != NULL) {
+        h->array_klasses_do(collect_array_classes);
+      }
+    }
+  }
+};
+
+static void remove_unshareable_in_classes() {
+  for (int i = 0; i < _global_klass_objects->length(); i++) {
+    Klass* k = _global_klass_objects->at(i);
+    if (!k->is_objArray_klass()) {
+      // InstanceKlass and TypeArrayKlass will in turn call remove_unshareable_info
+      // on their array classes.
+      assert(k->is_instance_klass() || k->is_typeArray_klass(), "must be");
+      k->remove_unshareable_info();
+    }
+  }
+}
+
+static void remove_java_mirror_in_classes() {
+  for (int i = 0; i < _global_klass_objects->length(); i++) {
+    Klass* k = _global_klass_objects->at(i);
+    if (!k->is_objArray_klass()) {
+      // InstanceKlass and TypeArrayKlass will in turn call remove_unshareable_info
+      // on their array classes.
+      assert(k->is_instance_klass() || k->is_typeArray_klass(), "must be");
+      k->remove_java_mirror();
+    }
+  }
+}
+
+static void rewrite_nofast_bytecode(Method* method) {
+  BytecodeStream bcs(method);
+  while (!bcs.is_last_bytecode()) {
+    Bytecodes::Code opcode = bcs.next();
+    switch (opcode) {
+    case Bytecodes::_getfield:      *bcs.bcp() = Bytecodes::_nofast_getfield;      break;
+    case Bytecodes::_putfield:      *bcs.bcp() = Bytecodes::_nofast_putfield;      break;
+    case Bytecodes::_aload_0:       *bcs.bcp() = Bytecodes::_nofast_aload_0;       break;
+    case Bytecodes::_iload: {
+      if (!bcs.is_wide()) {
+        *bcs.bcp() = Bytecodes::_nofast_iload;
+      }
+      break;
+    }
+    default: break;
+    }
+  }
+}
+
+// Walk all methods in the class list to ensure that they won't be modified at
+// run time. This includes:
+// [1] Rewrite all bytecodes as needed, so that the ConstMethod* will not be modified
+//     at run time by RewriteBytecodes/RewriteFrequentPairs
+// [2] Assign a fingerprint, so one doesn't need to be assigned at run-time.
+static void rewrite_nofast_bytecodes_and_calculate_fingerprints() {
+  for (int i = 0; i < _global_klass_objects->length(); i++) {
+    Klass* k = _global_klass_objects->at(i);
+    if (k->is_instance_klass()) {
+      InstanceKlass* ik = InstanceKlass::cast(k);
+      for (int i = 0; i < ik->methods()->length(); i++) {
+        Method* m = ik->methods()->at(i);
+        rewrite_nofast_bytecode(m);
+        Fingerprinter fp(m);
+        // The side effect of this call sets method's fingerprint field.
+        fp.fingerprint();
+      }
+    }
+  }
+}
+
+static void relocate_cached_class_file() {
+  for (int i = 0; i < _global_klass_objects->length(); i++) {
+    Klass* k = _global_klass_objects->at(i);
+    if (k->is_instance_klass()) {
+      InstanceKlass* ik = InstanceKlass::cast(k);
+      JvmtiCachedClassFileData* p = ik->get_archived_class_data();
+      if (p != NULL) {
+        int size = offset_of(JvmtiCachedClassFileData, data) + p->length;
+        JvmtiCachedClassFileData* q = (JvmtiCachedClassFileData*)_od_region.allocate(size);
+        q->length = p->length;
+        memcpy(q->data, p->data, p->length);
+        ik->set_archived_class_data(q);
+      }
+    }
+  }
+}
+
+NOT_PRODUCT(
+static void assert_not_anonymous_class(InstanceKlass* k) {
+  assert(!(k->is_anonymous()), "cannot archive anonymous classes");
+}
+
+// Anonymous classes are not stored inside any dictionaries. They are created by
+// SystemDictionary::parse_stream() with a non-null host_klass.
+static void assert_no_anonymoys_classes_in_dictionaries() {
+  ClassLoaderDataGraph::dictionary_classes_do(assert_not_anonymous_class);
+})
+
+// Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
+// (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
+//
+// Addresses of the vtables and the methods may be different across JVM runs,
+// if libjvm.so is dynamically loaded at a different base address.
+//
+// To ensure that the Metadata objects in the CDS archive always have the correct vtable:
+//
+// + at dump time:  we redirect the _vptr to point to our own vtables inside
+//                  the CDS image
+// + at run time:   we clone the actual contents of the vtables from libjvm.so
+//                  into our own tables.
+
+// Currently, the archive contain ONLY the following types of objects that have C++ vtables.
+#define CPP_VTABLE_PATCH_TYPES_DO(f) \
+  f(ConstantPool) \
+  f(InstanceKlass) \
+  f(InstanceClassLoaderKlass) \
+  f(InstanceMirrorKlass) \
+  f(InstanceRefKlass) \
+  f(Method) \
+  f(ObjArrayKlass) \
+  f(TypeArrayKlass)
+
+class CppVtableInfo {
+  intptr_t _vtable_size;
+  intptr_t _cloned_vtable[1];
+public:
+  static int num_slots(int vtable_size) {
+    return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
+  }
+  int vtable_size()           { return int(uintx(_vtable_size)); }
+  void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
+  intptr_t* cloned_vtable()   { return &_cloned_vtable[0]; }
+  void zero()                 { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); }
+  // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
+  static size_t byte_size(int vtable_size) {
+    CppVtableInfo i;
+    return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1));
+  }
+};
+
+template <class T> class CppVtableCloner : public T {
+  static intptr_t* vtable_of(Metadata& m) {
+    return *((intptr_t**)&m);
+  }
+  static CppVtableInfo* _info;
+
+  static int get_vtable_length(const char* name);
+
+public:
+  // Allocate and initialize the C++ vtable, starting from top, but do not go past end.
+  static intptr_t* allocate(const char* name);
+
+  // Clone the vtable to ...
+  static intptr_t* clone_vtable(const char* name, CppVtableInfo* info);
+
+  static void zero_vtable_clone() {
+    assert(DumpSharedSpaces, "dump-time only");
+    _info->zero();
+  }
+
+  // Switch the vtable pointer to point to the cloned vtable.
+  static void patch(Metadata* obj) {
+    assert(DumpSharedSpaces, "dump-time only");
+    *(void**)obj = (void*)(_info->cloned_vtable());
+  }
+
+  static bool is_valid_shared_object(const T* obj) {
+    intptr_t* vptr = *(intptr_t**)obj;
+    return vptr == _info->cloned_vtable();
+  }
+};
+
+template <class T> CppVtableInfo* CppVtableCloner<T>::_info = NULL;
+
+template <class T>
+intptr_t* CppVtableCloner<T>::allocate(const char* name) {
+  assert(is_aligned(_md_region.top(), sizeof(intptr_t)), "bad alignment");
+  int n = get_vtable_length(name);
+  _info = (CppVtableInfo*)_md_region.allocate(CppVtableInfo::byte_size(n), sizeof(intptr_t));
+  _info->set_vtable_size(n);
+
+  intptr_t* p = clone_vtable(name, _info);
+  assert((char*)p == _md_region.top(), "must be");
+
+  return p;
+}
+
+template <class T>
+intptr_t* CppVtableCloner<T>::clone_vtable(const char* name, CppVtableInfo* info) {
+  if (!DumpSharedSpaces) {
+    assert(_info == 0, "_info is initialized only at dump time");
+    _info = info; // Remember it -- it will be used by MetaspaceShared::is_valid_shared_method()
+  }
+  T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
+  int n = info->vtable_size();
+  intptr_t* srcvtable = vtable_of(tmp);
+  intptr_t* dstvtable = info->cloned_vtable();
+
+  // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
+  // safe to do memcpy.
+  log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
+  memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
+  return dstvtable + n;
+}
+
+// To determine the size of the vtable for each type, we use the following
+// trick by declaring 2 subclasses:
+//
+//   class CppVtableTesterA: public InstanceKlass {virtual int   last_virtual_method() {return 1;}    };
+//   class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return NULL}; };
+//
+// CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
+// - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
+// - The first N entries have are exactly the same as in InstanceKlass's vtable.
+// - Their last entry is different.
+//
+// So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
+// and find the first entry that's different.
+//
+// This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
+// esoteric compilers.
+
+template <class T> class CppVtableTesterB: public T {
+public:
+  virtual int last_virtual_method() {return 1;}
+};
+
+template <class T> class CppVtableTesterA : public T {
+public:
+  virtual void* last_virtual_method() {
+    // Make this different than CppVtableTesterB::last_virtual_method so the C++
+    // compiler/linker won't alias the two functions.
+    return NULL;
+  }
+};
+
+template <class T>
+int CppVtableCloner<T>::get_vtable_length(const char* name) {
+  CppVtableTesterA<T> a;
+  CppVtableTesterB<T> b;
+
+  intptr_t* avtable = vtable_of(a);
+  intptr_t* bvtable = vtable_of(b);
+
+  // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
+  int vtable_len = 1;
+  for (; ; vtable_len++) {
+    if (avtable[vtable_len] != bvtable[vtable_len]) {
+      break;
+    }
+  }
+  log_debug(cds, vtables)("Found   %3d vtable entries for %s", vtable_len, name);
+
+  return vtable_len;
+}
+
+#define ALLOC_CPP_VTABLE_CLONE(c) \
+  CppVtableCloner<c>::allocate(#c);
+
+#define CLONE_CPP_VTABLE(c) \
+  p = CppVtableCloner<c>::clone_vtable(#c, (CppVtableInfo*)p);
+
+#define ZERO_CPP_VTABLE(c) \
+ CppVtableCloner<c>::zero_vtable_clone();
+
+// This can be called at both dump time and run time.
+intptr_t* MetaspaceShared::clone_cpp_vtables(intptr_t* p) {
+  assert(DumpSharedSpaces || UseSharedSpaces, "sanity");
+  CPP_VTABLE_PATCH_TYPES_DO(CLONE_CPP_VTABLE);
+  return p;
+}
+
+void MetaspaceShared::zero_cpp_vtable_clones_for_writing() {
+  assert(DumpSharedSpaces, "dump-time only");
+  CPP_VTABLE_PATCH_TYPES_DO(ZERO_CPP_VTABLE);
+}
+
+// Allocate and initialize the C++ vtables, starting from top, but do not go past end.
+void MetaspaceShared::allocate_cpp_vtable_clones() {
+  assert(DumpSharedSpaces, "dump-time only");
+  // Layout (each slot is a intptr_t):
+  //   [number of slots in the first vtable = n1]
+  //   [ <n1> slots for the first vtable]
+  //   [number of slots in the first second = n2]
+  //   [ <n2> slots for the second vtable]
+  //   ...
+  // The order of the vtables is the same as the CPP_VTAB_PATCH_TYPES_DO macro.
+  CPP_VTABLE_PATCH_TYPES_DO(ALLOC_CPP_VTABLE_CLONE);
+}
+
+// Switch the vtable pointer to point to the cloned vtable. We assume the
+// vtable pointer is in first slot in object.
+void MetaspaceShared::patch_cpp_vtable_pointers() {
+  int n = _global_klass_objects->length();
+  for (int i = 0; i < n; i++) {
+    Klass* obj = _global_klass_objects->at(i);
+    if (obj->is_instance_klass()) {
+      InstanceKlass* ik = InstanceKlass::cast(obj);
+      if (ik->is_class_loader_instance_klass()) {
+        CppVtableCloner<InstanceClassLoaderKlass>::patch(ik);
+      } else if (ik->is_reference_instance_klass()) {
+        CppVtableCloner<InstanceRefKlass>::patch(ik);
+      } else if (ik->is_mirror_instance_klass()) {
+        CppVtableCloner<InstanceMirrorKlass>::patch(ik);
+      } else {
+        CppVtableCloner<InstanceKlass>::patch(ik);
+      }
+      ConstantPool* cp = ik->constants();
+      CppVtableCloner<ConstantPool>::patch(cp);
+      for (int j = 0; j < ik->methods()->length(); j++) {
+        Method* m = ik->methods()->at(j);
+        CppVtableCloner<Method>::patch(m);
+        assert(CppVtableCloner<Method>::is_valid_shared_object(m), "must be");
+      }
+    } else if (obj->is_objArray_klass()) {
+      CppVtableCloner<ObjArrayKlass>::patch(obj);
+    } else {
+      assert(obj->is_typeArray_klass(), "sanity");
+      CppVtableCloner<TypeArrayKlass>::patch(obj);
+    }
+  }
+}
+
+bool MetaspaceShared::is_valid_shared_method(const Method* m) {
+  assert(is_in_shared_space(m), "must be");
+  return CppVtableCloner<Method>::is_valid_shared_object(m);
+}
+
+// Closure for serializing initialization data out to a data area to be
+// written to the shared file.
+
+class WriteClosure : public SerializeClosure {
+private:
+  DumpRegion* _dump_region;
+
+public:
+  WriteClosure(DumpRegion* r) {
+    _dump_region = r;
+  }
+
+  void do_ptr(void** p) {
+    _dump_region->append_intptr_t((intptr_t)*p);
+  }
+
+  void do_u4(u4* p) {
+    void* ptr = (void*)(uintx(*p));
+    do_ptr(&ptr);
+  }
+
+  void do_tag(int tag) {
+    _dump_region->append_intptr_t((intptr_t)tag);
+  }
+
+  void do_region(u_char* start, size_t size) {
+    assert((intptr_t)start % sizeof(intptr_t) == 0, "bad alignment");
+    assert(size % sizeof(intptr_t) == 0, "bad size");
+    do_tag((int)size);
+    while (size > 0) {
+      _dump_region->append_intptr_t(*(intptr_t*)start);
+      start += sizeof(intptr_t);
+      size -= sizeof(intptr_t);
+    }
+  }
+
+  bool reading() const { return false; }
+};
+
+// This is for dumping detailed statistics for the allocations
+// in the shared spaces.
+class DumpAllocStats : public ResourceObj {
+public:
+
+  // Here's poor man's enum inheritance
+#define SHAREDSPACE_OBJ_TYPES_DO(f) \
+  METASPACE_OBJ_TYPES_DO(f) \
+  f(SymbolHashentry) \
+  f(SymbolBucket) \
+  f(StringHashentry) \
+  f(StringBucket) \
+  f(Other)
+
+  enum Type {
+    // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
+    SHAREDSPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
+    _number_of_types
+  };
+
+  static const char * type_name(Type type) {
+    switch(type) {
+    SHAREDSPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_NAME_CASE)
+    default:
+      ShouldNotReachHere();
+      return NULL;
+    }
+  }
+
+public:
+  enum { RO = 0, RW = 1 };
+
+  int _counts[2][_number_of_types];
+  int _bytes [2][_number_of_types];
+
+  DumpAllocStats() {
+    memset(_counts, 0, sizeof(_counts));
+    memset(_bytes,  0, sizeof(_bytes));
+  };
+
+  void record(MetaspaceObj::Type type, int byte_size, bool read_only) {
+    assert(int(type) >= 0 && type < MetaspaceObj::_number_of_types, "sanity");
+    int which = (read_only) ? RO : RW;
+    _counts[which][type] ++;
+    _bytes [which][type] += byte_size;
+  }
+
+  void record_other_type(int byte_size, bool read_only) {
+    int which = (read_only) ? RO : RW;
+    _bytes [which][OtherType] += byte_size;
+  }
+  void print_stats(int ro_all, int rw_all, int mc_all, int md_all);
+};
+
+void DumpAllocStats::print_stats(int ro_all, int rw_all, int mc_all, int md_all) {
+  // Calculate size of data that was not allocated by Metaspace::allocate()
+  MetaspaceSharedStats *stats = MetaspaceShared::stats();
+
+  // symbols
+  _counts[RO][SymbolHashentryType] = stats->symbol.hashentry_count;
+  _bytes [RO][SymbolHashentryType] = stats->symbol.hashentry_bytes;
+
+  _counts[RO][SymbolBucketType] = stats->symbol.bucket_count;
+  _bytes [RO][SymbolBucketType] = stats->symbol.bucket_bytes;
+
+  // strings
+  _counts[RO][StringHashentryType] = stats->string.hashentry_count;
+  _bytes [RO][StringHashentryType] = stats->string.hashentry_bytes;
+
+  _counts[RO][StringBucketType] = stats->string.bucket_count;
+  _bytes [RO][StringBucketType] = stats->string.bucket_bytes;
+
+  // TODO: count things like dictionary, vtable, etc
+  _bytes[RW][OtherType] += mc_all + md_all;
+  rw_all += mc_all + md_all; // mc/md are mapped Read/Write
+
+  // prevent divide-by-zero
+  if (ro_all < 1) {
+    ro_all = 1;
+  }
+  if (rw_all < 1) {
+    rw_all = 1;
+  }
+
+  int all_ro_count = 0;
+  int all_ro_bytes = 0;
+  int all_rw_count = 0;
+  int all_rw_bytes = 0;
+
+// To make fmt_stats be a syntactic constant (for format warnings), use #define.
+#define fmt_stats "%-20s: %8d %10d %5.1f | %8d %10d %5.1f | %8d %10d %5.1f"
+  const char *sep = "--------------------+---------------------------+---------------------------+--------------------------";
+  const char *hdr = "                        ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %";
+
+  ResourceMark rm;
+  LogMessage(cds) msg;
+  stringStream info_stream;
+
+  info_stream.print_cr("Detailed metadata info (excluding od/st regions; rw stats include md/mc regions):");
+  info_stream.print_cr("%s", hdr);
+  info_stream.print_cr("%s", sep);
+  for (int type = 0; type < int(_number_of_types); type ++) {
+    const char *name = type_name((Type)type);
+    int ro_count = _counts[RO][type];
+    int ro_bytes = _bytes [RO][type];
+    int rw_count = _counts[RW][type];
+    int rw_bytes = _bytes [RW][type];
+    int count = ro_count + rw_count;
+    int bytes = ro_bytes + rw_bytes;
+
+    double ro_perc = 100.0 * double(ro_bytes) / double(ro_all);
+    double rw_perc = 100.0 * double(rw_bytes) / double(rw_all);
+    double perc    = 100.0 * double(bytes)    / double(ro_all + rw_all);
+
+    info_stream.print_cr(fmt_stats, name,
+                         ro_count, ro_bytes, ro_perc,
+                         rw_count, rw_bytes, rw_perc,
+                         count, bytes, perc);
+
+    all_ro_count += ro_count;
+    all_ro_bytes += ro_bytes;
+    all_rw_count += rw_count;
+    all_rw_bytes += rw_bytes;
+  }
+
+  int all_count = all_ro_count + all_rw_count;
+  int all_bytes = all_ro_bytes + all_rw_bytes;
+
+  double all_ro_perc = 100.0 * double(all_ro_bytes) / double(ro_all);
+  double all_rw_perc = 100.0 * double(all_rw_bytes) / double(rw_all);
+  double all_perc    = 100.0 * double(all_bytes)    / double(ro_all + rw_all);
+
+  info_stream.print_cr("%s", sep);
+  info_stream.print_cr(fmt_stats, "Total",
+                       all_ro_count, all_ro_bytes, all_ro_perc,
+                       all_rw_count, all_rw_bytes, all_rw_perc,
+                       all_count, all_bytes, all_perc);
+
+  assert(all_ro_bytes == ro_all, "everything should have been counted");
+  assert(all_rw_bytes == rw_all, "everything should have been counted");
+
+  msg.info("%s", info_stream.as_string());
+#undef fmt_stats
+}
+
+// Populate the shared space.
+
+class VM_PopulateDumpSharedSpace: public VM_Operation {
+private:
+  GrowableArray<MemRegion> *_string_regions;
+  GrowableArray<MemRegion> *_open_archive_heap_regions;
+
+  void dump_java_heap_objects() NOT_CDS_JAVA_HEAP_RETURN;
+  void dump_symbols();
+  char* dump_read_only_tables();
+  void print_region_stats();
+  void print_heap_region_stats(GrowableArray<MemRegion> *heap_mem,
+                               const char *name, const size_t total_size);
+public:
+
+  VMOp_Type type() const { return VMOp_PopulateDumpSharedSpace; }
+  void doit();   // outline because gdb sucks
+  static void write_region(FileMapInfo* mapinfo, int region, DumpRegion* space, bool read_only,  bool allow_exec);
+}; // class VM_PopulateDumpSharedSpace
+
+class SortedSymbolClosure: public SymbolClosure {
+  GrowableArray<Symbol*> _symbols;
+  virtual void do_symbol(Symbol** sym) {
+    assert((*sym)->is_permanent(), "archived symbols must be permanent");
+    _symbols.append(*sym);
+  }
+  static int compare_symbols_by_address(Symbol** a, Symbol** b) {
+    if (a[0] < b[0]) {
+      return -1;
+    } else if (a[0] == b[0]) {
+      return 0;
+    } else {
+      return 1;
+    }
+  }
+
+public:
+  SortedSymbolClosure() {
+    SymbolTable::symbols_do(this);
+    _symbols.sort(compare_symbols_by_address);
+  }
+  GrowableArray<Symbol*>* get_sorted_symbols() {
+    return &_symbols;
+  }
+};
+
+// ArchiveCompactor --
+//
+// This class is the central piece of shared archive compaction -- all metaspace data are
+// initially allocated outside of the shared regions. ArchiveCompactor copies the
+// metaspace data into their final location in the shared regions.
+
+class ArchiveCompactor : AllStatic {
+  static DumpAllocStats* _alloc_stats;
+  static SortedSymbolClosure* _ssc;
+
+  static unsigned my_hash(const address& a) {
+    return primitive_hash<address>(a);
+  }
+  static bool my_equals(const address& a0, const address& a1) {
+    return primitive_equals<address>(a0, a1);
+  }
+  typedef ResourceHashtable<
+      address, address,
+      ArchiveCompactor::my_hash,   // solaris compiler doesn't like: primitive_hash<address>
+      ArchiveCompactor::my_equals, // solaris compiler doesn't like: primitive_equals<address>
+      16384, ResourceObj::C_HEAP> RelocationTable;
+  static RelocationTable* _new_loc_table;
+
+public:
+  static void initialize() {
+    _alloc_stats = new(ResourceObj::C_HEAP, mtInternal)DumpAllocStats;
+    _new_loc_table = new(ResourceObj::C_HEAP, mtInternal)RelocationTable;
+  }
+  static DumpAllocStats* alloc_stats() {
+    return _alloc_stats;
+  }
+
+  static void allocate(MetaspaceClosure::Ref* ref, bool read_only) {
+    address obj = ref->obj();
+    int bytes = ref->size() * BytesPerWord;
+    char* p;
+    size_t alignment = BytesPerWord;
+    char* oldtop;
+    char* newtop;
+
+    if (read_only) {
+      oldtop = _ro_region.top();
+      p = _ro_region.allocate(bytes, alignment);
+      newtop = _ro_region.top();
+    } else {
+      oldtop = _rw_region.top();
+      p = _rw_region.allocate(bytes, alignment);
+      newtop = _rw_region.top();
+    }
+    memcpy(p, obj, bytes);
+    bool isnew = _new_loc_table->put(obj, (address)p);
+    log_trace(cds)("Copy: " PTR_FORMAT " ==> " PTR_FORMAT " %d", p2i(obj), p2i(p), bytes);
+    assert(isnew, "must be");
+
+    _alloc_stats->record(ref->msotype(), int(newtop - oldtop), read_only);
+    if (ref->msotype() == MetaspaceObj::SymbolType) {
+      uintx delta = MetaspaceShared::object_delta(p);
+      if (delta > MAX_SHARED_DELTA) {
+        // This is just a sanity check and should not appear in any real world usage. This
+        // happens only if you allocate more than 2GB of Symbols and would require
+        // millions of shared classes.
+        vm_exit_during_initialization("Too many Symbols in the CDS archive",
+                                      "Please reduce the number of shared classes.");
+      }
+    }
+  }
+
+  static address get_new_loc(MetaspaceClosure::Ref* ref) {
+    address* pp = _new_loc_table->get(ref->obj());
+    assert(pp != NULL, "must be");
+    return *pp;
+  }
+
+private:
+  // Makes a shallow copy of visited MetaspaceObj's
+  class ShallowCopier: public UniqueMetaspaceClosure {
+    bool _read_only;
+  public:
+    ShallowCopier(bool read_only) : _read_only(read_only) {}
+
+    virtual void do_unique_ref(Ref* ref, bool read_only) {
+      if (read_only == _read_only) {
+        allocate(ref, read_only);
+      }
+    }
+  };
+
+  // Relocate embedded pointers within a MetaspaceObj's shallow copy
+  class ShallowCopyEmbeddedRefRelocator: public UniqueMetaspaceClosure {
+  public:
+    virtual void do_unique_ref(Ref* ref, bool read_only) {
+      address new_loc = get_new_loc(ref);
+      RefRelocator refer;
+      ref->metaspace_pointers_do_at(&refer, new_loc);
+    }
+  };
+
+  // Relocate a reference to point to its shallow copy
+  class RefRelocator: public MetaspaceClosure {
+  public:
+    virtual bool do_ref(Ref* ref, bool read_only) {
+      if (ref->not_null()) {
+        ref->update(get_new_loc(ref));
+      }
+      return false; // Do not recurse.
+    }
+  };
+
+#ifdef ASSERT
+  class IsRefInArchiveChecker: public MetaspaceClosure {
+  public:
+    virtual bool do_ref(Ref* ref, bool read_only) {
+      if (ref->not_null()) {
+        char* obj = (char*)ref->obj();
+        assert(_ro_region.contains(obj) || _rw_region.contains(obj),
+               "must be relocated to point to CDS archive");
+      }
+      return false; // Do not recurse.
+    }
+  };
+#endif
+
+public:
+  static void copy_and_compact() {
+    // We should no longer allocate anything from the metaspace, so that
+    // we can have a stable set of MetaspaceObjs to work with.
+    Metaspace::freeze();
+
+    ResourceMark rm;
+    SortedSymbolClosure the_ssc; // StackObj
+    _ssc = &the_ssc;
+
+    tty->print_cr("Scanning all metaspace objects ... ");
+    {
+      // allocate and shallow-copy RW objects, immediately following the MC region
+      tty->print_cr("Allocating RW objects ... ");
+      _mc_region.pack(&_rw_region);
+
+      ResourceMark rm;
+      ShallowCopier rw_copier(false);
+      iterate_roots(&rw_copier);
+    }
+    {
+      // allocate and shallow-copy of RO object, immediately following the RW region
+      tty->print_cr("Allocating RO objects ... ");
+      _rw_region.pack(&_ro_region);
+
+      ResourceMark rm;
+      ShallowCopier ro_copier(true);
+      iterate_roots(&ro_copier);
+    }
+    {
+      tty->print_cr("Relocating embedded pointers ... ");
+      ResourceMark rm;
+      ShallowCopyEmbeddedRefRelocator emb_reloc;
+      iterate_roots(&emb_reloc);
+    }
+    {
+      tty->print_cr("Relocating external roots ... ");
+      ResourceMark rm;
+      RefRelocator ext_reloc;
+      iterate_roots(&ext_reloc);
+    }
+
+#ifdef ASSERT
+    {
+      tty->print_cr("Verifying external roots ... ");
+      ResourceMark rm;
+      IsRefInArchiveChecker checker;
+      iterate_roots(&checker);
+    }
+#endif
+
+
+    // cleanup
+    _ssc = NULL;
+  }
+
+  // We must relocate the System::_well_known_klasses only after we have copied the
+  // java objects in during dump_java_heap_objects(): during the object copy, we operate on
+  // old objects which assert that their klass is the original klass.
+  static void relocate_well_known_klasses() {
+    {
+      tty->print_cr("Relocating SystemDictionary::_well_known_klasses[] ... ");
+      ResourceMark rm;
+      RefRelocator ext_reloc;
+      SystemDictionary::well_known_klasses_do(&ext_reloc);
+    }
+    // NOTE: after this point, we shouldn't have any globals that can reach the old
+    // objects.
+
+    // We cannot use any of the objects in the heap anymore (except for the objects
+    // in the CDS shared string regions) because their headers no longer point to
+    // valid Klasses.
+  }
+
+  static void iterate_roots(MetaspaceClosure* it) {
+    GrowableArray<Symbol*>* symbols = _ssc->get_sorted_symbols();
+    for (int i=0; i<symbols->length(); i++) {
+      it->push(symbols->adr_at(i));
+    }
+    if (_global_klass_objects != NULL) {
+      // Need to fix up the pointers
+      for (int i = 0; i < _global_klass_objects->length(); i++) {
+        // NOTE -- this requires that the vtable is NOT yet patched, or else we are hosed.
+        it->push(_global_klass_objects->adr_at(i));
+      }
+    }
+    FileMapInfo::metaspace_pointers_do(it);
+    SystemDictionary::classes_do(it);
+    Universe::metaspace_pointers_do(it);
+    SymbolTable::metaspace_pointers_do(it);
+    vmSymbols::metaspace_pointers_do(it);
+  }
+
+  static Klass* get_relocated_klass(Klass* orig_klass) {
+    address* pp = _new_loc_table->get((address)orig_klass);
+    assert(pp != NULL, "must be");
+    Klass* klass = (Klass*)(*pp);
+    assert(klass->is_klass(), "must be");
+    return klass;
+  }
+};
+
+DumpAllocStats* ArchiveCompactor::_alloc_stats;
+SortedSymbolClosure* ArchiveCompactor::_ssc;
+ArchiveCompactor::RelocationTable* ArchiveCompactor::_new_loc_table;
+
+void VM_PopulateDumpSharedSpace::write_region(FileMapInfo* mapinfo, int region_idx,
+                                              DumpRegion* dump_region, bool read_only,  bool allow_exec) {
+  mapinfo->write_region(region_idx, dump_region->base(), dump_region->used(), read_only, allow_exec);
+}
+
+void VM_PopulateDumpSharedSpace::dump_symbols() {
+  tty->print_cr("Dumping symbol table ...");
+
+  NOT_PRODUCT(SymbolTable::verify());
+  SymbolTable::write_to_archive();
+}
+
+char* VM_PopulateDumpSharedSpace::dump_read_only_tables() {
+  char* oldtop = _ro_region.top();
+  // Reorder the system dictionary. Moving the symbols affects
+  // how the hash table indices are calculated.
+  SystemDictionary::reorder_dictionary_for_sharing();
+  tty->print("Removing java_mirror ... ");
+  remove_java_mirror_in_classes();
+  tty->print_cr("done. ");
+  NOT_PRODUCT(SystemDictionary::verify();)
+
+  size_t buckets_bytes = SystemDictionary::count_bytes_for_buckets();
+  char* buckets_top = _ro_region.allocate(buckets_bytes, sizeof(intptr_t));
+  SystemDictionary::copy_buckets(buckets_top, _ro_region.top());
+
+  size_t table_bytes = SystemDictionary::count_bytes_for_table();
+  char* table_top = _ro_region.allocate(table_bytes, sizeof(intptr_t));
+  SystemDictionary::copy_table(table_top, _ro_region.top());
+
+  // Write the other data to the output array.
+  WriteClosure wc(&_ro_region);
+  MetaspaceShared::serialize(&wc);
+
+  char* newtop = _ro_region.top();
+  ArchiveCompactor::alloc_stats()->record_other_type(int(newtop - oldtop), true);
+  return buckets_top;
+}
+
+void VM_PopulateDumpSharedSpace::doit() {
+  Thread* THREAD = VMThread::vm_thread();
+
+  NOT_PRODUCT(SystemDictionary::verify();)
+  // The following guarantee is meant to ensure that no loader constraints
+  // exist yet, since the constraints table is not shared.  This becomes
+  // more important now that we don't re-initialize vtables/itables for
+  // shared classes at runtime, where constraints were previously created.
+  guarantee(SystemDictionary::constraints()->number_of_entries() == 0,
+            "loader constraints are not saved");
+  guarantee(SystemDictionary::placeholders()->number_of_entries() == 0,
+          "placeholders are not saved");
+  // Revisit and implement this if we prelink method handle call sites:
+  guarantee(SystemDictionary::invoke_method_table() == NULL ||
+            SystemDictionary::invoke_method_table()->number_of_entries() == 0,
+            "invoke method table is not saved");
+
+  // At this point, many classes have been loaded.
+  // Gather systemDictionary classes in a global array and do everything to
+  // that so we don't have to walk the SystemDictionary again.
+  _global_klass_objects = new GrowableArray<Klass*>(1000);
+  CollectClassesClosure collect_classes;
+  ClassLoaderDataGraph::loaded_classes_do(&collect_classes);
+
+  tty->print_cr("Number of classes %d", _global_klass_objects->length());
+  {
+    int num_type_array = 0, num_obj_array = 0, num_inst = 0;
+    for (int i = 0; i < _global_klass_objects->length(); i++) {
+      Klass* k = _global_klass_objects->at(i);
+      if (k->is_instance_klass()) {
+        num_inst ++;
+      } else if (k->is_objArray_klass()) {
+        num_obj_array ++;
+      } else {
+        assert(k->is_typeArray_klass(), "sanity");
+        num_type_array ++;
+      }
+    }
+    tty->print_cr("    instance classes   = %5d", num_inst);
+    tty->print_cr("    obj array classes  = %5d", num_obj_array);
+    tty->print_cr("    type array classes = %5d", num_type_array);
+  }
+
+  // Ensure the ConstMethods won't be modified at run-time
+  tty->print("Updating ConstMethods ... ");
+  rewrite_nofast_bytecodes_and_calculate_fingerprints();
+  tty->print_cr("done. ");
+
+  // Move classes from platform/system dictionaries into the boot dictionary
+  SystemDictionary::combine_shared_dictionaries();
+
+  // Remove all references outside the metadata
+  tty->print("Removing unshareable information ... ");
+  remove_unshareable_in_classes();
+  tty->print_cr("done. ");
+
+  // We don't support archiving anonymous classes. Verify that they are not stored in
+  // the any dictionaries.
+  NOT_PRODUCT(assert_no_anonymoys_classes_in_dictionaries());
+
+  SystemDictionaryShared::finalize_verification_constraints();
+
+  ArchiveCompactor::initialize();
+  ArchiveCompactor::copy_and_compact();
+
+  dump_symbols();
+
+  // Dump supported java heap objects
+  _string_regions = NULL;
+  _open_archive_heap_regions = NULL;
+  dump_java_heap_objects();
+
+  ArchiveCompactor::relocate_well_known_klasses();
+
+  char* read_only_tables_start = dump_read_only_tables();
+  _ro_region.pack(&_md_region);
+
+  char* vtbl_list = _md_region.top();
+  MetaspaceShared::allocate_cpp_vtable_clones();
+  _md_region.pack(&_od_region);
+
+  // Relocate the archived class file data into the od region
+  relocate_cached_class_file();
+  _od_region.pack();
+
+  // The 5 core spaces are allocated consecutively mc->rw->ro->md->od, so there total size
+  // is just the spaces between the two ends.
+  size_t core_spaces_size = _od_region.end() - _mc_region.base();
+  assert(core_spaces_size == (size_t)align_up(core_spaces_size, Metaspace::reserve_alignment()),
+         "should already be aligned");
+
+  // During patching, some virtual methods may be called, so at this point
+  // the vtables must contain valid methods (as filled in by CppVtableCloner::allocate).
+  MetaspaceShared::patch_cpp_vtable_pointers();
+
+  // The vtable clones contain addresses of the current process.
+  // We don't want to write these addresses into the archive.
+  MetaspaceShared::zero_cpp_vtable_clones_for_writing();
+
+  // Create and write the archive file that maps the shared spaces.
+
+  FileMapInfo* mapinfo = new FileMapInfo();
+  mapinfo->populate_header(os::vm_allocation_granularity());
+  mapinfo->set_read_only_tables_start(read_only_tables_start);
+  mapinfo->set_misc_data_patching_start(vtbl_list);
+  mapinfo->set_cds_i2i_entry_code_buffers(MetaspaceShared::cds_i2i_entry_code_buffers());
+  mapinfo->set_cds_i2i_entry_code_buffers_size(MetaspaceShared::cds_i2i_entry_code_buffers_size());
+  mapinfo->set_core_spaces_size(core_spaces_size);
+
+  for (int pass=1; pass<=2; pass++) {
+    if (pass == 1) {
+      // The first pass doesn't actually write the data to disk. All it
+      // does is to update the fields in the mapinfo->_header.
+    } else {
+      // After the first pass, the contents of mapinfo->_header are finalized,
+      // so we can compute the header's CRC, and write the contents of the header
+      // and the regions into disk.
+      mapinfo->open_for_write();
+      mapinfo->set_header_crc(mapinfo->compute_header_crc());
+    }
+    mapinfo->write_header();
+
+    // NOTE: md contains the trampoline code for method entries, which are patched at run time,
+    // so it needs to be read/write.
+    write_region(mapinfo, MetaspaceShared::mc, &_mc_region, /*read_only=*/false,/*allow_exec=*/true);
+    write_region(mapinfo, MetaspaceShared::rw, &_rw_region, /*read_only=*/false,/*allow_exec=*/false);
+    write_region(mapinfo, MetaspaceShared::ro, &_ro_region, /*read_only=*/true, /*allow_exec=*/false);
+    write_region(mapinfo, MetaspaceShared::md, &_md_region, /*read_only=*/false,/*allow_exec=*/false);
+    write_region(mapinfo, MetaspaceShared::od, &_od_region, /*read_only=*/true, /*allow_exec=*/false);
+
+    _total_string_region_size = mapinfo->write_archive_heap_regions(
+                                        _string_regions,
+                                        MetaspaceShared::first_string,
+                                        MetaspaceShared::max_strings);
+    _total_open_archive_region_size = mapinfo->write_archive_heap_regions(
+                                        _open_archive_heap_regions,
+                                        MetaspaceShared::first_open_archive_heap_region,
+                                        MetaspaceShared::max_open_archive_heap_region);
+  }
+
+  mapinfo->close();
+
+  // Restore the vtable in case we invoke any virtual methods.
+  MetaspaceShared::clone_cpp_vtables((intptr_t*)vtbl_list);
+
+  print_region_stats();
+
+  if (log_is_enabled(Info, cds)) {
+    ArchiveCompactor::alloc_stats()->print_stats(int(_ro_region.used()), int(_rw_region.used()),
+                                                 int(_mc_region.used()), int(_md_region.used()));
+  }
+
+  if (PrintSystemDictionaryAtExit) {
+    SystemDictionary::print();
+  }
+  // There may be other pending VM operations that operate on the InstanceKlasses,
+  // which will fail because InstanceKlasses::remove_unshareable_info()
+  // has been called. Forget these operations and exit the VM directly.
+  vm_direct_exit(0);
+}
+
+void VM_PopulateDumpSharedSpace::print_region_stats() {
+  // Print statistics of all the regions
+  const size_t total_reserved = _ro_region.reserved()  + _rw_region.reserved() +
+                                _mc_region.reserved()  + _md_region.reserved() +
+                                _od_region.reserved()  +
+                                _total_string_region_size +
+                                _total_open_archive_region_size;
+  const size_t total_bytes = _ro_region.used()  + _rw_region.used() +
+                             _mc_region.used()  + _md_region.used() +
+                             _od_region.used()  +
+                             _total_string_region_size +
+                             _total_open_archive_region_size;
+  const double total_u_perc = total_bytes / double(total_reserved) * 100.0;
+
+  _mc_region.print(total_reserved);
+  _rw_region.print(total_reserved);
+  _ro_region.print(total_reserved);
+  _md_region.print(total_reserved);
+  _od_region.print(total_reserved);
+  print_heap_region_stats(_string_regions, "st", total_reserved);
+  print_heap_region_stats(_open_archive_heap_regions, "oa", total_reserved);
+
+  tty->print_cr("total   : " SIZE_FORMAT_W(9) " [100.0%% of total] out of " SIZE_FORMAT_W(9) " bytes [%5.1f%% used]",
+                 total_bytes, total_reserved, total_u_perc);
+}
+
+void VM_PopulateDumpSharedSpace::print_heap_region_stats(GrowableArray<MemRegion> *heap_mem,
+                                                         const char *name, const size_t total_size) {
+  int arr_len = heap_mem == NULL ? 0 : heap_mem->length();
+  for (int i = 0; i < arr_len; i++) {
+      char* start = (char*)heap_mem->at(i).start();
+      size_t size = heap_mem->at(i).byte_size();
+      char* top = start + size;
+      tty->print_cr("%s%d space: " SIZE_FORMAT_W(9) " [ %4.1f%% of total] out of " SIZE_FORMAT_W(9) " bytes [100%% used] at " INTPTR_FORMAT,
+                    name, i, size, size/double(total_size)*100.0, size, p2i(start));
+
+  }
+}
+
+// Update a Java object to point its Klass* to the new location after
+// shared archive has been compacted.
+void MetaspaceShared::relocate_klass_ptr(oop o) {
+  assert(DumpSharedSpaces, "sanity");
+  Klass* k = ArchiveCompactor::get_relocated_klass(o->klass());
+  o->set_klass(k);
+}
+
+class LinkSharedClassesClosure : public KlassClosure {
+  Thread* THREAD;
+  bool    _made_progress;
+ public:
+  LinkSharedClassesClosure(Thread* thread) : THREAD(thread), _made_progress(false) {}
+
+  void reset()               { _made_progress = false; }
+  bool made_progress() const { return _made_progress; }
+
+  void do_klass(Klass* k) {
+    if (k->is_instance_klass()) {
+      InstanceKlass* ik = InstanceKlass::cast(k);
+      // Link the class to cause the bytecodes to be rewritten and the
+      // cpcache to be created. Class verification is done according
+      // to -Xverify setting.
+      _made_progress |= MetaspaceShared::try_link_class(ik, THREAD);
+      guarantee(!HAS_PENDING_EXCEPTION, "exception in link_class");
+
+      ik->constants()->resolve_class_constants(THREAD);
+    }
+  }
+};
+
+class CheckSharedClassesClosure : public KlassClosure {
+  bool    _made_progress;
+ public:
+  CheckSharedClassesClosure() : _made_progress(false) {}
+
+  void reset()               { _made_progress = false; }
+  bool made_progress() const { return _made_progress; }
+  void do_klass(Klass* k) {
+    if (k->is_instance_klass() && InstanceKlass::cast(k)->check_sharing_error_state()) {
+      _made_progress = true;
+    }
+  }
+};
+
+void MetaspaceShared::check_shared_class_loader_type(Klass* k) {
+  if (k->is_instance_klass()) {
+    InstanceKlass* ik = InstanceKlass::cast(k);
+    u2 loader_type = ik->loader_type();
+    ResourceMark rm;
+    guarantee(loader_type != 0,
+              "Class loader type is not set for this class %s", ik->name()->as_C_string());
+  }
+}
+
+void MetaspaceShared::link_and_cleanup_shared_classes(TRAPS) {
+  // We need to iterate because verification may cause additional classes
+  // to be loaded.
+  LinkSharedClassesClosure link_closure(THREAD);
+  do {
+    link_closure.reset();
+    ClassLoaderDataGraph::loaded_classes_do(&link_closure);
+    guarantee(!HAS_PENDING_EXCEPTION, "exception in link_class");
+  } while (link_closure.made_progress());
+
+  if (_has_error_classes) {
+    // Mark all classes whose super class or interfaces failed verification.
+    CheckSharedClassesClosure check_closure;
+    do {
+      // Not completely sure if we need to do this iteratively. Anyway,
+      // we should come here only if there are unverifiable classes, which
+      // shouldn't happen in normal cases. So better safe than sorry.
+      check_closure.reset();
+      ClassLoaderDataGraph::loaded_classes_do(&check_closure);
+    } while (check_closure.made_progress());
+
+    if (IgnoreUnverifiableClassesDuringDump) {
+      // This is useful when running JCK or SQE tests. You should not
+      // enable this when running real apps.
+      SystemDictionary::remove_classes_in_error_state();
+    } else {
+      tty->print_cr("Please remove the unverifiable classes from your class list and try again");
+      exit(1);
+    }
+  }
+}
+
+void MetaspaceShared::prepare_for_dumping() {
+  Arguments::check_unsupported_dumping_properties();
+  ClassLoader::initialize_shared_path();
+  FileMapInfo::allocate_classpath_entry_table();
+}
+
+// Preload classes from a list, populate the shared spaces and dump to a
+// file.
+void MetaspaceShared::preload_and_dump(TRAPS) {
+  { TraceTime timer("Dump Shared Spaces", TRACETIME_LOG(Info, startuptime));
+    ResourceMark rm;
+    char class_list_path_str[JVM_MAXPATHLEN];
+    // Preload classes to be shared.
+    // Should use some os:: method rather than fopen() here. aB.
+    const char* class_list_path;
+    if (SharedClassListFile == NULL) {
+      // Construct the path to the class list (in jre/lib)
+      // Walk up two directories from the location of the VM and
+      // optionally tack on "lib" (depending on platform)
+      os::jvm_path(class_list_path_str, sizeof(class_list_path_str));
+      for (int i = 0; i < 3; i++) {
+        char *end = strrchr(class_list_path_str, *os::file_separator());
+        if (end != NULL) *end = '\0';
+      }
+      int class_list_path_len = (int)strlen(class_list_path_str);
+      if (class_list_path_len >= 3) {
+        if (strcmp(class_list_path_str + class_list_path_len - 3, "lib") != 0) {
+          if (class_list_path_len < JVM_MAXPATHLEN - 4) {
+            jio_snprintf(class_list_path_str + class_list_path_len,
+                         sizeof(class_list_path_str) - class_list_path_len,
+                         "%slib", os::file_separator());
+            class_list_path_len += 4;
+          }
+        }
+      }
+      if (class_list_path_len < JVM_MAXPATHLEN - 10) {
+        jio_snprintf(class_list_path_str + class_list_path_len,
+                     sizeof(class_list_path_str) - class_list_path_len,
+                     "%sclasslist", os::file_separator());
+      }
+      class_list_path = class_list_path_str;
+    } else {
+      class_list_path = SharedClassListFile;
+    }
+
+    tty->print_cr("Loading classes to share ...");
+    _has_error_classes = false;
+    int class_count = preload_classes(class_list_path, THREAD);
+    if (ExtraSharedClassListFile) {
+      class_count += preload_classes(ExtraSharedClassListFile, THREAD);
+    }
+    tty->print_cr("Loading classes to share: done.");
+
+    log_info(cds)("Shared spaces: preloaded %d classes", class_count);
+
+    // Rewrite and link classes
+    tty->print_cr("Rewriting and linking classes ...");
+
+    // Link any classes which got missed. This would happen if we have loaded classes that
+    // were not explicitly specified in the classlist. E.g., if an interface implemented by class K
+    // fails verification, all other interfaces that were not specified in the classlist but
+    // are implemented by K are not verified.
+    link_and_cleanup_shared_classes(CATCH);
+    tty->print_cr("Rewriting and linking classes: done");
+
+    SystemDictionary::clear_invoke_method_table();
+
+    VM_PopulateDumpSharedSpace op;
+    VMThread::execute(&op);
+  }
+}
+
+
+int MetaspaceShared::preload_classes(const char* class_list_path, TRAPS) {
+  ClassListParser parser(class_list_path);
+  int class_count = 0;
+
+    while (parser.parse_one_line()) {
+      Klass* klass = ClassLoaderExt::load_one_class(&parser, THREAD);
+      if (HAS_PENDING_EXCEPTION) {
+        if (klass == NULL &&
+             (PENDING_EXCEPTION->klass()->name() == vmSymbols::java_lang_ClassNotFoundException())) {
+          // print a warning only when the pending exception is class not found
+          tty->print_cr("Preload Warning: Cannot find %s", parser.current_class_name());
+        }
+        CLEAR_PENDING_EXCEPTION;
+      }
+      if (klass != NULL) {
+        if (log_is_enabled(Trace, cds)) {
+          ResourceMark rm;
+          log_trace(cds)("Shared spaces preloaded: %s", klass->external_name());
+        }
+
+        InstanceKlass* ik = InstanceKlass::cast(klass);
+
+        // Link the class to cause the bytecodes to be rewritten and the
+        // cpcache to be created. The linking is done as soon as classes
+        // are loaded in order that the related data structures (klass and
+        // cpCache) are located together.
+        try_link_class(ik, THREAD);
+        guarantee(!HAS_PENDING_EXCEPTION, "exception in link_class");
+
+        class_count++;
+      }
+    }
+
+  return class_count;
+}
+
+// Returns true if the class's status has changed
+bool MetaspaceShared::try_link_class(InstanceKlass* ik, TRAPS) {
+  assert(DumpSharedSpaces, "should only be called during dumping");
+  if (ik->init_state() < InstanceKlass::linked) {
+    bool saved = BytecodeVerificationLocal;
+    if (!(ik->is_shared_boot_class())) {
+      // The verification decision is based on BytecodeVerificationRemote
+      // for non-system classes. Since we are using the NULL classloader
+      // to load non-system classes during dumping, we need to temporarily
+      // change BytecodeVerificationLocal to be the same as
+      // BytecodeVerificationRemote. Note this can cause the parent system
+      // classes also being verified. The extra overhead is acceptable during
+      // dumping.
+      BytecodeVerificationLocal = BytecodeVerificationRemote;
+    }
+    ik->link_class(THREAD);
+    if (HAS_PENDING_EXCEPTION) {
+      ResourceMark rm;
+      tty->print_cr("Preload Warning: Verification failed for %s",
+                    ik->external_name());
+      CLEAR_PENDING_EXCEPTION;
+      ik->set_in_error_state();
+      _has_error_classes = true;
+    }
+    BytecodeVerificationLocal = saved;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+#if INCLUDE_CDS_JAVA_HEAP
+void VM_PopulateDumpSharedSpace::dump_java_heap_objects() {
+  if (!MetaspaceShared::is_heap_object_archiving_allowed()) {
+    if (log_is_enabled(Info, cds)) {
+      log_info(cds)(
+        "Archived java heap is not supported as UseG1GC, "
+        "UseCompressedOops and UseCompressedClassPointers are required."
+        "Current settings: UseG1GC=%s, UseCompressedOops=%s, UseCompressedClassPointers=%s.",
+        BOOL_TO_STR(UseG1GC), BOOL_TO_STR(UseCompressedOops),
+        BOOL_TO_STR(UseCompressedClassPointers));
+    }
+    return;
+  }
+
+  {
+    NoSafepointVerifier nsv;
+
+    // Cache for recording where the archived objects are copied to
+    MetaspaceShared::create_archive_object_cache();
+
+    tty->print_cr("Dumping String objects to closed archive heap region ...");
+    NOT_PRODUCT(StringTable::verify());
+    // The string space has maximum two regions. See FileMapInfo::write_archive_heap_regions() for details.
+    _string_regions = new GrowableArray<MemRegion>(2);
+    StringTable::write_to_archive(_string_regions);
+
+    tty->print_cr("Dumping objects to open archive heap region ...");
+    _open_archive_heap_regions = new GrowableArray<MemRegion>(2);
+    MetaspaceShared::dump_open_archive_heap_objects(_open_archive_heap_regions);
+
+    MetaspaceShared::destroy_archive_object_cache();
+  }
+
+  G1HeapVerifier::verify_archive_regions();
+}
+
+void MetaspaceShared::dump_open_archive_heap_objects(
+                                    GrowableArray<MemRegion> * open_archive) {
+  assert(UseG1GC, "Only support G1 GC");
+  assert(UseCompressedOops && UseCompressedClassPointers,
+         "Only support UseCompressedOops and UseCompressedClassPointers enabled");
+
+  Thread* THREAD = Thread::current();
+  G1CollectedHeap::heap()->begin_archive_alloc_range(true /* open */);
+
+  MetaspaceShared::archive_resolved_constants(THREAD);
+
+  G1CollectedHeap::heap()->end_archive_alloc_range(open_archive,
+                                                   os::vm_allocation_granularity());
+}
+
+MetaspaceShared::ArchivedObjectCache* MetaspaceShared::_archive_object_cache = NULL;
+oop MetaspaceShared::archive_heap_object(oop obj, Thread* THREAD) {
+  assert(DumpSharedSpaces, "dump-time only");
+
+  ArchivedObjectCache* cache = MetaspaceShared::archive_object_cache();
+  oop* p = cache->get(obj);
+  if (p != NULL) {
+    // already archived
+    return *p;
+  }
+
+  int len = obj->size();
+  if (G1CollectedHeap::heap()->is_archive_alloc_too_large(len)) {
+    return NULL;
+  }
+
+  int hash = obj->identity_hash();
+  oop archived_oop = (oop)G1CollectedHeap::heap()->archive_mem_allocate(len);
+  if (archived_oop != NULL) {
+    Copy::aligned_disjoint_words((HeapWord*)obj, (HeapWord*)archived_oop, len);
+    relocate_klass_ptr(archived_oop);
+    cache->put(obj, archived_oop);
+  }
+  return archived_oop;
+}
+
+void MetaspaceShared::archive_resolved_constants(Thread* THREAD) {
+  int i;
+  for (i = 0; i < _global_klass_objects->length(); i++) {
+    Klass* k = _global_klass_objects->at(i);
+    if (k->is_instance_klass()) {
+      InstanceKlass* ik = InstanceKlass::cast(k);
+      ik->constants()->archive_resolved_references(THREAD);
+    }
+  }
+}
+
+void MetaspaceShared::fixup_mapped_heap_regions() {
+  FileMapInfo *mapinfo = FileMapInfo::current_info();
+  mapinfo->fixup_mapped_heap_regions();
+}
+#endif // INCLUDE_CDS_JAVA_HEAP
+
+// Closure for serializing initialization data in from a data area
+// (ptr_array) read from the shared file.
+
+class ReadClosure : public SerializeClosure {
+private:
+  intptr_t** _ptr_array;
+
+  inline intptr_t nextPtr() {
+    return *(*_ptr_array)++;
+  }
+
+public:
+  ReadClosure(intptr_t** ptr_array) { _ptr_array = ptr_array; }
+
+  void do_ptr(void** p) {
+    assert(*p == NULL, "initializing previous initialized pointer.");
+    intptr_t obj = nextPtr();
+    assert((intptr_t)obj >= 0 || (intptr_t)obj < -100,
+           "hit tag while initializing ptrs.");
+    *p = (void*)obj;
+  }
+
+  void do_u4(u4* p) {
+    intptr_t obj = nextPtr();
+    *p = (u4)(uintx(obj));
+  }
+
+  void do_tag(int tag) {
+    int old_tag;
+    old_tag = (int)(intptr_t)nextPtr();
+    // do_int(&old_tag);
+    assert(tag == old_tag, "old tag doesn't match");
+    FileMapInfo::assert_mark(tag == old_tag);
+  }
+
+  void do_region(u_char* start, size_t size) {
+    assert((intptr_t)start % sizeof(intptr_t) == 0, "bad alignment");
+    assert(size % sizeof(intptr_t) == 0, "bad size");
+    do_tag((int)size);
+    while (size > 0) {
+      *(intptr_t*)start = nextPtr();
+      start += sizeof(intptr_t);
+      size -= sizeof(intptr_t);
+    }
+  }
+
+  bool reading() const { return true; }
+};
+
+// Return true if given address is in the mapped shared space.
+bool MetaspaceShared::is_in_shared_space(const void* p) {
+  return UseSharedSpaces && FileMapInfo::current_info()->is_in_shared_space(p);
+}
+
+// Return true if given address is in the misc data region
+bool MetaspaceShared::is_in_shared_region(const void* p, int idx) {
+  return UseSharedSpaces && FileMapInfo::current_info()->is_in_shared_region(p, idx);
+}
+
+bool MetaspaceShared::is_in_trampoline_frame(address addr) {
+  if (UseSharedSpaces && is_in_shared_region(addr, MetaspaceShared::mc)) {
+    return true;
+  }
+  return false;
+}
+
+void MetaspaceShared::print_shared_spaces() {
+  if (UseSharedSpaces) {
+    FileMapInfo::current_info()->print_shared_spaces();
+  }
+}
+
+
+// Map shared spaces at requested addresses and return if succeeded.
+bool MetaspaceShared::map_shared_spaces(FileMapInfo* mapinfo) {
+  size_t image_alignment = mapinfo->alignment();
+
+#ifndef _WINDOWS
+  // Map in the shared memory and then map the regions on top of it.
+  // On Windows, don't map the memory here because it will cause the
+  // mappings of the regions to fail.
+  ReservedSpace shared_rs = mapinfo->reserve_shared_memory();
+  if (!shared_rs.is_reserved()) return false;
+#endif
+
+  assert(!DumpSharedSpaces, "Should not be called with DumpSharedSpaces");
+
+  char* _ro_base = NULL;
+  char* _rw_base = NULL;
+  char* _mc_base = NULL;
+  char* _md_base = NULL;
+  char* _od_base = NULL;
+
+  // Map each shared region
+  if ((_mc_base = mapinfo->map_region(mc)) != NULL &&
+      mapinfo->verify_region_checksum(mc) &&
+      (_rw_base = mapinfo->map_region(rw)) != NULL &&
+      mapinfo->verify_region_checksum(rw) &&
+      (_ro_base = mapinfo->map_region(ro)) != NULL &&
+      mapinfo->verify_region_checksum(ro) &&
+      (_md_base = mapinfo->map_region(md)) != NULL &&
+      mapinfo->verify_region_checksum(md) &&
+      (_od_base = mapinfo->map_region(od)) != NULL &&
+      mapinfo->verify_region_checksum(od) &&
+      (image_alignment == (size_t)os::vm_allocation_granularity()) &&
+      mapinfo->validate_classpath_entry_table()) {
+    // Success (no need to do anything)
+    return true;
+  } else {
+    // If there was a failure in mapping any of the spaces, unmap the ones
+    // that succeeded
+    if (_ro_base != NULL) mapinfo->unmap_region(ro);
+    if (_rw_base != NULL) mapinfo->unmap_region(rw);
+    if (_mc_base != NULL) mapinfo->unmap_region(mc);
+    if (_md_base != NULL) mapinfo->unmap_region(md);
+    if (_od_base != NULL) mapinfo->unmap_region(od);
+#ifndef _WINDOWS
+    // Release the entire mapped region
+    shared_rs.release();
+#endif
+    // If -Xshare:on is specified, print out the error message and exit VM,
+    // otherwise, set UseSharedSpaces to false and continue.
+    if (RequireSharedSpaces || PrintSharedArchiveAndExit) {
+      vm_exit_during_initialization("Unable to use shared archive.", "Failed map_region for using -Xshare:on.");
+    } else {
+      FLAG_SET_DEFAULT(UseSharedSpaces, false);
+    }
+    return false;
+  }
+}
+
+// Read the miscellaneous data from the shared file, and
+// serialize it out to its various destinations.
+
+void MetaspaceShared::initialize_shared_spaces() {
+  FileMapInfo *mapinfo = FileMapInfo::current_info();
+  _cds_i2i_entry_code_buffers = mapinfo->cds_i2i_entry_code_buffers();
+  _cds_i2i_entry_code_buffers_size = mapinfo->cds_i2i_entry_code_buffers_size();
+  _core_spaces_size = mapinfo->core_spaces_size();
+  char* buffer = mapinfo->misc_data_patching_start();
+  clone_cpp_vtables((intptr_t*)buffer);
+
+  // The rest of the data is now stored in the RW region
+  buffer = mapinfo->read_only_tables_start();
+  int sharedDictionaryLen = *(intptr_t*)buffer;
+  buffer += sizeof(intptr_t);
+  int number_of_entries = *(intptr_t*)buffer;
+  buffer += sizeof(intptr_t);
+  SystemDictionary::set_shared_dictionary((HashtableBucket<mtClass>*)buffer,
+                                          sharedDictionaryLen,
+                                          number_of_entries);
+  buffer += sharedDictionaryLen;
+
+  // The following data are the linked list elements
+  // (HashtableEntry objects) for the shared dictionary table.
+
+  int len = *(intptr_t*)buffer;     // skip over shared dictionary entries
+  buffer += sizeof(intptr_t);
+  buffer += len;
+
+  // Verify various attributes of the archive, plus initialize the
+  // shared string/symbol tables
+  intptr_t* array = (intptr_t*)buffer;
+  ReadClosure rc(&array);
+  serialize(&rc);
+
+  // Initialize the run-time symbol table.
+  SymbolTable::create_table();
+
+  // Close the mapinfo file
+  mapinfo->close();
+
+  if (PrintSharedArchiveAndExit) {
+    if (PrintSharedDictionary) {
+      tty->print_cr("\nShared classes:\n");
+      SystemDictionary::print_shared(tty);
+    }
+    if (_archive_loading_failed) {
+      tty->print_cr("archive is invalid");
+      vm_exit(1);
+    } else {
+      tty->print_cr("archive is valid");
+      vm_exit(0);
+    }
+  }
+}
+
+// JVM/TI RedefineClasses() support:
+bool MetaspaceShared::remap_shared_readonly_as_readwrite() {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+
+  if (UseSharedSpaces) {
+    // remap the shared readonly space to shared readwrite, private
+    FileMapInfo* mapinfo = FileMapInfo::current_info();
+    if (!mapinfo->remap_shared_readonly_as_readwrite()) {
+      return false;
+    }
+    _remapped_readwrite = true;
+  }
+  return true;
+}
+
+void MetaspaceShared::report_out_of_space(const char* name, size_t needed_bytes) {
+  // This is highly unlikely to happen on 64-bits because we have reserved a 4GB space.
+  // On 32-bit we reserve only 256MB so you could run out of space with 100,000 classes
+  // or so.
+  _mc_region.print_out_of_space_msg(name, needed_bytes);
+  _rw_region.print_out_of_space_msg(name, needed_bytes);
+  _ro_region.print_out_of_space_msg(name, needed_bytes);
+  _md_region.print_out_of_space_msg(name, needed_bytes);
+  _od_region.print_out_of_space_msg(name, needed_bytes);
+
+  vm_exit_during_initialization(err_msg("Unable to allocate from '%s' region", name),
+                                "Please reduce the number of shared classes.");
+}