Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2003-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_dump.cpp.incl"

 // Closure to set up the fingerprint field for all methods.

 class FingerprintMethodsClosure: public ObjectClosure {

 public:

   void do_object(oop obj) {

     if (obj->is_method()) {

       methodOop mobj = (methodOop)obj;

       ResourceMark rm;

       (new Fingerprinter(mobj))->fingerprint();

     }

   }

 };

 // Closure to set the hash value (String.hash field) in all of the

 // String objects in the heap.  Setting the hash value is not required.

 // However, setting the value in advance prevents the value from being

 // written later, increasing the likelihood that the shared page contain

 // the hash can be shared.

 //

 // NOTE THAT the algorithm in StringTable::hash_string() MUST MATCH the

 // algorithm in java.lang.String.hashCode().

 class StringHashCodeClosure: public OopClosure {

 private:

   Thread* THREAD;

   int hash_offset;

 public:

   StringHashCodeClosure(Thread* t) {

     THREAD = t;

     hash_offset = java_lang_String::hash_offset_in_bytes();

   }

   void do_oop(oop* pobj) {

     if (pobj != NULL) {

       oop obj = *pobj;

       if (obj->klass() == SystemDictionary::string_klass()) {

         int hash;

         typeArrayOop value = java_lang_String::value(obj);

         int length = java_lang_String::length(obj);

         if (length == 0) {

           hash = 0;

         } else {

           int offset = java_lang_String::offset(obj);

           jchar* s = value->char_at_addr(offset);

           hash = StringTable::hash_string(s, length);

         }

         obj->int_field_put(hash_offset, hash);

       }

     }

   }

 };

 // Remove data from objects which should not appear in the shared file

 // (as it pertains only to the current JVM).

 class RemoveUnshareableInfoClosure : public ObjectClosure {

 public:

   void do_object(oop obj) {

     // Zap data from the objects which is pertains only to this JVM.  We

     // want that data recreated in new JVMs when the shared file is used.

     if (obj->is_method()) {

       ((methodOop)obj)->remove_unshareable_info();

     }

     else if (obj->is_klass()) {

       Klass::cast((klassOop)obj)->remove_unshareable_info();

     }

     // Don't save compiler related special oops (shouldn't be any yet).

     if (obj->is_methodData() || obj->is_compiledICHolder()) {

       ShouldNotReachHere();

     }

   }

 };

 static bool mark_object(oop obj) {

   if (obj != NULL &&

       !obj->is_shared() &&

       !obj->is_forwarded() &&

       !obj->is_gc_marked()) {

     obj->set_mark(markOopDesc::prototype()->set_marked());

     return true;

   }

   return false;

 }

 // Closure:  mark objects closure.

 class MarkObjectsOopClosure : public OopClosure {

 public:

   void do_oop(oop* pobj) {

     mark_object(*pobj);

   }

 };

 class MarkObjectsSkippingKlassesOopClosure : public OopClosure {

 public:

   void do_oop(oop* pobj) {

     oop obj = *pobj;

     if (obj != NULL &&

         !obj->is_klass()) {

       mark_object(obj);

     }

   }

 };

 static void mark_object_recursive_skipping_klasses(oop obj) {

   mark_object(obj);

   if (obj != NULL) {

     MarkObjectsSkippingKlassesOopClosure mark_all;

     obj->oop_iterate(&mark_all);

   }

 }

 // Closure:  mark common read-only objects, excluding symbols

 class MarkCommonReadOnly : public ObjectClosure {

 private:

   MarkObjectsOopClosure mark_all;

 public:

   void do_object(oop obj) {

     // Mark all constMethod objects.

     if (obj->is_constMethod()) {

       mark_object(obj);

       mark_object(constMethodOop(obj)->stackmap_data());

       // Exception tables are needed by ci code during compilation.

       mark_object(constMethodOop(obj)->exception_table());

     }

     // Mark objects referenced by klass objects which are read-only.

     else if (obj->is_klass()) {

       Klass* k = Klass::cast((klassOop)obj);

       mark_object(k->secondary_supers());

       // The METHODS() OBJARRAYS CANNOT BE MADE READ-ONLY, even though

       // it is never modified. Otherwise, they will be pre-marked; the

       // GC marking phase will skip them; and by skipping them will fail

       // to mark the methods objects referenced by the array.

       if (obj->blueprint()->oop_is_instanceKlass()) {

         instanceKlass* ik = instanceKlass::cast((klassOop)obj);

         mark_object(ik->method_ordering());

         mark_object(ik->local_interfaces());

         mark_object(ik->transitive_interfaces());

         mark_object(ik->fields());

         mark_object(ik->class_annotations());

         mark_object_recursive_skipping_klasses(ik->fields_annotations());

         mark_object_recursive_skipping_klasses(ik->methods_annotations());

         mark_object_recursive_skipping_klasses(ik->methods_parameter_annotations());

         mark_object_recursive_skipping_klasses(ik->methods_default_annotations());

         typeArrayOop inner_classes = ik->inner_classes();

         if (inner_classes != NULL) {

           mark_object(inner_classes);

         }

       }

     }

   }

 };

 // Closure:  mark common symbols

 class MarkCommonSymbols : public ObjectClosure {

 private:

   MarkObjectsOopClosure mark_all;

 public:

   void do_object(oop obj) {

     // Mark symbols refered to by method objects.

     if (obj->is_method()) {

       methodOop m = methodOop(obj);

       mark_object(m->name());

       mark_object(m->signature());

     }

     // Mark symbols referenced by klass objects which are read-only.

     else if (obj->is_klass()) {

       if (obj->blueprint()->oop_is_instanceKlass()) {

         instanceKlass* ik = instanceKlass::cast((klassOop)obj);

         mark_object(ik->name());

         mark_object(ik->generic_signature());

         mark_object(ik->source_file_name());

         mark_object(ik->source_debug_extension());

         typeArrayOop inner_classes = ik->inner_classes();

         if (inner_classes != NULL) {

           int length = inner_classes->length();

           for (int i = 0;

                    i < length;

                    i += instanceKlass::inner_class_next_offset) {

             int ioff = i + instanceKlass::inner_class_inner_name_offset;

             int index = inner_classes->ushort_at(ioff);

             if (index != 0) {

               mark_object(ik->constants()->symbol_at(index));

             }

           }

         }

         ik->field_names_and_sigs_iterate(&mark_all);

       }

     }

     // Mark symbols referenced by other constantpool entries.

     if (obj->is_constantPool()) {

       constantPoolOop(obj)->shared_symbols_iterate(&mark_all);

     }

   }

 };

 // Closure:  mark char arrays used by strings

 class MarkStringValues : public ObjectClosure {

 private:

   MarkObjectsOopClosure mark_all;

 public:

   void do_object(oop obj) {

     // Character arrays referenced by String objects are read-only.

     if (java_lang_String::is_instance(obj)) {

       mark_object(java_lang_String::value(obj));

     }

   }

 };

 #ifdef DEBUG

 // Closure:  Check for objects left in the heap which have not been moved.

 class CheckRemainingObjects : public ObjectClosure {

 private:

   int count;

 public:

   CheckRemainingObjects() {

     count = 0;

   }

   void do_object(oop obj) {

     if (!obj->is_shared() &&

         !obj->is_forwarded()) {

       ++count;

       if (Verbose) {

         tty->print("Unreferenced object: ");

         obj->print_on(tty);

       }

     }

   }

   void status() {

     tty->print_cr("%d objects no longer referenced, not shared.", count);

   }

 };

 #endif

 // Closure:  Mark remaining objects read-write, except Strings.

 class MarkReadWriteObjects : public ObjectClosure {

 private:

   MarkObjectsOopClosure mark_objects;

 public:

   void do_object(oop obj) {

       // The METHODS() OBJARRAYS CANNOT BE MADE READ-ONLY, even though

       // it is never modified. Otherwise, they will be pre-marked; the

       // GC marking phase will skip them; and by skipping them will fail

       // to mark the methods objects referenced by the array.

     if (obj->is_klass()) {

       mark_object(obj);

       Klass* k = klassOop(obj)->klass_part();

       mark_object(k->java_mirror());

       if (obj->blueprint()->oop_is_instanceKlass()) {

         instanceKlass* ik = (instanceKlass*)k;

         mark_object(ik->methods());

         mark_object(ik->constants());

       }

       if (obj->blueprint()->oop_is_javaArray()) {

         arrayKlass* ak = (arrayKlass*)k;

         mark_object(ak->component_mirror());

       }

       return;

     }

     // Mark constantPool tags and the constantPoolCache.

     else if (obj->is_constantPool()) {

       constantPoolOop pool = constantPoolOop(obj);

       mark_object(pool->cache());

       pool->shared_tags_iterate(&mark_objects);

       return;

     }

     // Mark all method objects.

     if (obj->is_method()) {

       mark_object(obj);

     }

   }

 };

 // Closure:  Mark String objects read-write.

 class MarkStringObjects : public ObjectClosure {

 private:

   MarkObjectsOopClosure mark_objects;

 public:

   void do_object(oop obj) {

     // Mark String objects referenced by constant pool entries.

     if (obj->is_constantPool()) {

       constantPoolOop pool = constantPoolOop(obj);

       pool->shared_strings_iterate(&mark_objects);

       return;

     }

   }

 };

 // Move objects matching specified type (ie. lock_bits) to the specified

 // space.

 class MoveMarkedObjects : public ObjectClosure {

 private:

   OffsetTableContigSpace* _space;

   bool _read_only;

 public:

   MoveMarkedObjects(OffsetTableContigSpace* space, bool read_only) {

     _space = space;

     _read_only = read_only;

   }

   void do_object(oop obj) {

     if (obj->is_shared()) {

       return;

     }

     if (obj->is_gc_marked() && obj->forwardee() == NULL) {

       int s = obj->size();

       oop sh_obj = (oop)_space->allocate(s);

       if (sh_obj == NULL) {

         if (_read_only) {

           warning("\nThe permanent generation read only space is not large "

                   "enough to \npreload requested classes.  Use "

                   "-XX:SharedReadOnlySize= to increase \nthe initial "

                   "size of the read only space.\n");

         } else {

           warning("\nThe permanent generation read write space is not large "

                   "enough to \npreload requested classes.  Use "

                   "-XX:SharedReadWriteSize= to increase \nthe initial "

                   "size of the read write space.\n");

         }

         exit(2);

       }

       if (PrintSharedSpaces && Verbose && WizardMode) {

         tty->print_cr("\nMoveMarkedObjects: " PTR_FORMAT " -> " PTR_FORMAT " %s", obj, sh_obj,

                       (_read_only ? "ro" : "rw"));

       }

       Copy::aligned_disjoint_words((HeapWord*)obj, (HeapWord*)sh_obj, s);

       obj->forward_to(sh_obj);

       if (_read_only) {

         // Readonly objects: set hash value to self pointer and make gc_marked.

         sh_obj->forward_to(sh_obj);

       } else {

         sh_obj->init_mark();

       }

     }

   }

 };

 static void mark_and_move(oop obj, MoveMarkedObjects* move) {

   if (mark_object(obj)) move->do_object(obj);

 }

 enum order_policy {

   OP_favor_startup = 0,

   OP_balanced = 1,

   OP_favor_runtime = 2

 };

 static void mark_and_move_for_policy(order_policy policy, oop obj, MoveMarkedObjects* move) {

   if (SharedOptimizeColdStartPolicy >= policy) mark_and_move(obj, move);

 }

 class MarkAndMoveOrderedReadOnly : public ObjectClosure {

 private:

   MoveMarkedObjects *_move_ro;

 public:

   MarkAndMoveOrderedReadOnly(MoveMarkedObjects *move_ro) : _move_ro(move_ro) {}

   void do_object(oop obj) {

     if (obj->is_klass() && obj->blueprint()->oop_is_instanceKlass()) {

       instanceKlass* ik = instanceKlass::cast((klassOop)obj);

       int i;

       mark_and_move_for_policy(OP_favor_startup, ik->name(), _move_ro);

       if (ik->super() != NULL) {

         do_object(ik->super());

       }

       objArrayOop interfaces = ik->local_interfaces();

       mark_and_move_for_policy(OP_favor_startup, interfaces, _move_ro);

       for(i = 0; i < interfaces->length(); i++) {

         klassOop k = klassOop(interfaces->obj_at(i));

         mark_and_move_for_policy(OP_favor_startup, k->klass_part()->name(), _move_ro);

         do_object(k);

       }

       objArrayOop methods = ik->methods();

       for(i = 0; i < methods->length(); i++) {

         methodOop m = methodOop(methods->obj_at(i));

         mark_and_move_for_policy(OP_favor_startup, m->constMethod(), _move_ro);

         mark_and_move_for_policy(OP_favor_runtime, m->constMethod()->exception_table(), _move_ro);

         mark_and_move_for_policy(OP_favor_runtime, m->constMethod()->stackmap_data(), _move_ro);

         // We don't move the name symbolOop here because it may invalidate

         // method ordering, which is dependent on the address of the name

         // symbolOop.  It will get promoted later with the other symbols.

         // Method name is rarely accessed during classloading anyway.

         // mark_and_move_for_policy(OP_balanced, m->name(), _move_ro);

         mark_and_move_for_policy(OP_favor_startup, m->signature(), _move_ro);

       }

       mark_and_move_for_policy(OP_favor_startup, ik->transitive_interfaces(), _move_ro);

       mark_and_move_for_policy(OP_favor_startup, ik->fields(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->secondary_supers(),  _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->method_ordering(),   _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->class_annotations(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->fields_annotations(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->methods_annotations(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->methods_parameter_annotations(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->methods_default_annotations(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->inner_classes(), _move_ro);

       mark_and_move_for_policy(OP_favor_runtime, ik->secondary_supers(), _move_ro);

     }

   }

 };

 class MarkAndMoveOrderedReadWrite: public ObjectClosure {

 private:

   MoveMarkedObjects *_move_rw;

 public:

   MarkAndMoveOrderedReadWrite(MoveMarkedObjects *move_rw) : _move_rw(move_rw) {}

   void do_object(oop obj) {

     if (obj->is_klass() && obj->blueprint()->oop_is_instanceKlass()) {

       instanceKlass* ik = instanceKlass::cast((klassOop)obj);

       int i;

       mark_and_move_for_policy(OP_favor_startup, ik->as_klassOop(), _move_rw);

       if (ik->super() != NULL) {

         do_object(ik->super());

       }

       objArrayOop interfaces = ik->local_interfaces();

       for(i = 0; i < interfaces->length(); i++) {

         klassOop k = klassOop(interfaces->obj_at(i));

         mark_and_move_for_policy(OP_favor_startup, k, _move_rw);

         do_object(k);

       }

       objArrayOop methods = ik->methods();

       mark_and_move_for_policy(OP_favor_startup, methods, _move_rw);

       for(i = 0; i < methods->length(); i++) {

         methodOop m = methodOop(methods->obj_at(i));

         mark_and_move_for_policy(OP_favor_startup, m, _move_rw);

         mark_and_move_for_policy(OP_favor_startup, ik->constants(), _move_rw);          // idempotent

         mark_and_move_for_policy(OP_balanced, ik->constants()->cache(), _move_rw); // idempotent

         mark_and_move_for_policy(OP_balanced, ik->constants()->tags(), _move_rw);  // idempotent

       }

       mark_and_move_for_policy(OP_favor_startup, ik->as_klassOop()->klass(), _move_rw);

       mark_and_move_for_policy(OP_favor_startup, ik->constants()->klass(), _move_rw);

       // Although Java mirrors are marked in MarkReadWriteObjects,

       // apparently they were never moved into shared spaces since

       // MoveMarkedObjects skips marked instance oops.  This may

       // be a bug in the original implementation or simply the vestige

       // of an abandoned experiment.  Nevertheless we leave a hint

       // here in case this capability is ever correctly implemented.

       //

       // mark_and_move_for_policy(OP_favor_runtime, ik->java_mirror(), _move_rw);

     }

   }

 };

 // Adjust references in oops to refer to shared spaces.

 class ResolveForwardingClosure: public OopClosure {

 public:

   void do_oop(oop* p) {

     oop obj = *p;

     if (!obj->is_shared()) {

       if (obj != NULL) {

         oop f = obj->forwardee();

         guarantee(f->is_shared(), "Oop doesn't refer to shared space.");

         *p = f;

       }

     }

   }

 };

 void sort_methods(instanceKlass* ik, TRAPS) {

   klassOop super = ik->super();

   if (super != NULL) {

     sort_methods(instanceKlass::cast(super), THREAD);

   }

   // The methods array must be ordered by symbolOop address. (See

   // classFileParser.cpp where methods in a class are originally

   // sorted.)  Since objects have just be reordered, this must be

   // corrected.

   methodOopDesc::sort_methods(ik->methods(),

                               ik->methods_annotations(),

                               ik->methods_parameter_annotations(),

                               ik->methods_default_annotations(),

                               true /* idempotent, slow */);

   // Itable indices are calculated based on methods array order

   // (see klassItable::compute_itable_index()).  Must reinitialize.

   // We assume that since checkconstraints is false, this method

   // cannot throw an exception.  An exception here would be

   // problematic since this is the VMThread, not a JavaThread.

   ik->itable()->initialize_itable(false, THREAD);

 }

 // Sort methods if the oop is an instanceKlass.

 class SortMethodsClosure: public ObjectClosure {

 private:

   Thread* _thread;

 public:

   SortMethodsClosure(Thread* thread) : _thread(thread) {}

   void do_object(oop obj) {

     // instanceKlass objects need some adjustment.

     if (obj->blueprint()->oop_is_instanceKlass()) {

       instanceKlass* ik = instanceKlass::cast((klassOop)obj);

       sort_methods(ik, _thread);

     }

   }

 };

 // Adjust references in oops to refer to shared spaces.

 class PatchOopsClosure: public ObjectClosure {

 private:

   Thread* _thread;

   ResolveForwardingClosure resolve;

 public:

   PatchOopsClosure(Thread* thread) : _thread(thread) {}

   void do_object(oop obj) {

     obj->oop_iterate_header(&resolve);

     obj->oop_iterate(&resolve);

     assert(obj->klass()->is_shared(), "Klass not pointing into shared space.");

     // If the object is a Java object or class which might (in the

     // future) contain a reference to a young gen object, add it to the

     // list.

     if (obj->is_klass() || obj->is_instance()) {

       if (obj->is_klass() ||

           obj->is_a(SystemDictionary::class_klass()) ||

           obj->is_a(SystemDictionary::throwable_klass())) {

         // Do nothing

       }

       else if (obj->is_a(SystemDictionary::string_klass())) {

         // immutable objects.

       } else {

         // someone added an object we hadn't accounted for.

         ShouldNotReachHere();

       }

     }

   }

 };

 // Empty the young and old generations.

 class ClearSpaceClosure : public SpaceClosure {

 public:

   void do_space(Space* s) {

     s->clear();

   }

 };

 // Closure for serializing initialization data out to a data area to be

 // written to the shared file.

 class WriteClosure : public SerializeOopClosure {

 private:

   oop* top;

   char* end;

   void out_of_space() {

     warning("\nThe shared miscellaneous data space is not large "

             "enough to \npreload requested classes.  Use "

             "-XX:SharedMiscDataSize= to increase \nthe initial "

             "size of the miscellaneous data space.\n");

     exit(2);

   }

   inline void check_space() {

     if ((char*)top + sizeof(oop) > end) {

       out_of_space();

     }

   }

 public:

   WriteClosure(char* md_top, char* md_end) {

     top = (oop*)md_top;

     end = md_end;

   }

   char* get_top() { return (char*)top; }

   void do_oop(oop* p) {

     check_space();

     oop obj = *p;

     assert(obj->is_oop_or_null(), "invalid oop");

     assert(obj == NULL || obj->is_shared(),

            "Oop in shared space not pointing into shared space.");

     *top = obj;

     ++top;

   }

   void do_int(int* p) {

     check_space();

     *top = (oop)(intptr_t)*p;

     ++top;

   }

   void do_size_t(size_t* p) {

     check_space();

     *top = (oop)(intptr_t)*p;

     ++top;

   }

   void do_ptr(void** p) {

     check_space();

     *top = (oop)*p;

     ++top;

   }

   void do_ptr(HeapWord** p) { do_ptr((void **) p); }

   void do_tag(int tag) {

     check_space();

     *top = (oop)(intptr_t)tag;

     ++top;

   }

   void do_region(u_char* start, size_t size) {

     if ((char*)top + size > end) {

       out_of_space();

     }

     assert((intptr_t)start % sizeof(oop) == 0, "bad alignment");

     assert(size % sizeof(oop) == 0, "bad size");

     do_tag((int)size);

     while (size > 0) {

       *top = *(oop*)start;

       ++top;

       start += sizeof(oop);

       size -= sizeof(oop);

     }

   }

   bool reading() const { return false; }

 };

 class ResolveConstantPoolsClosure : public ObjectClosure {

 private:

   TRAPS;

 public:

   ResolveConstantPoolsClosure(Thread *t) {

     __the_thread__ = t;

   }

   void do_object(oop obj) {

     if (obj->is_constantPool()) {

       constantPoolOop cpool = (constantPoolOop)obj;

       int unresolved = cpool->pre_resolve_shared_klasses(THREAD);

     }

   }

 };

 // Print a summary of the contents of the read/write spaces to help

 // identify objects which might be able to be made read-only.  At this

 // point, the objects have been written, and we can trash them as

 // needed.

 static void print_contents() {

   if (PrintSharedSpaces) {

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     CompactingPermGenGen* gen = (CompactingPermGenGen*)gch->perm_gen();

     // High level summary of the read-only space:

     ClassifyObjectClosure coc;

     tty->cr(); tty->print_cr("ReadOnly space:");

     gen->ro_space()->object_iterate(&coc);

     coc.print();

     // High level summary of the read-write space:

     coc.reset();

     tty->cr(); tty->print_cr("ReadWrite space:");

     gen->rw_space()->object_iterate(&coc);

     coc.print();

     // Reset counters

     ClearAllocCountClosure cacc;

     gen->ro_space()->object_iterate(&cacc);

     gen->rw_space()->object_iterate(&cacc);

     coc.reset();

     // Lower level summary of the read-only space:

     gen->ro_space()->object_iterate(&coc);

     tty->cr(); tty->print_cr("ReadOnly space:");

     ClassifyInstanceKlassClosure cikc;

     gen->rw_space()->object_iterate(&cikc);

     cikc.print();

     // Reset counters

     gen->ro_space()->object_iterate(&cacc);

     gen->rw_space()->object_iterate(&cacc);

     coc.reset();

     // Lower level summary of the read-write space:

     gen->rw_space()->object_iterate(&coc);

     cikc.reset();

     tty->cr();  tty->print_cr("ReadWrite space:");

     gen->rw_space()->object_iterate(&cikc);

     cikc.print();

   }

 }

 // Patch C++ vtable pointer in klass oops.

 // Klass objects contain references to c++ vtables in the JVM library.

 // Fix them to point to our constructed vtables.  However, don't iterate

 // across the space while doing this, as that causes the vtables to be

 // patched, undoing our useful work.  Instead, iterate to make a list,

 // then use the list to do the fixing.

 class PatchKlassVtables: public ObjectClosure {

 private:

   void*         _vtbl_ptr;

   VirtualSpace* _md_vs;

   GrowableArray<klassOop>* _klass_objects;

 public:

   PatchKlassVtables(void* vtbl_ptr, VirtualSpace* md_vs) {

     _vtbl_ptr = vtbl_ptr;

     _md_vs = md_vs;

     _klass_objects = new GrowableArray<klassOop>();

   }

   void do_object(oop obj) {

     if (obj->is_klass()) {

       _klass_objects->append(klassOop(obj));

     }

   }

   void patch(void** vtbl_list, int vtbl_list_size) {

     for (int i = 0; i < _klass_objects->length(); ++i) {

       klassOop obj = (klassOop)_klass_objects->at(i);

       Klass* k = obj->klass_part();

       void* v =  *(void**)k;

       int n;

       for (n = 0; n < vtbl_list_size; ++n) {

         *(void**)k = NULL;

         if (vtbl_list[n] == v) {

           *(void**)k = (void**)_vtbl_ptr +

                                  (n * CompactingPermGenGen::num_virtuals);

           break;

         }

       }

       guarantee(n < vtbl_list_size, "unable to find matching vtbl pointer");

     }

   }

 };

 // Populate the shared space.

 class VM_PopulateDumpSharedSpace: public VM_Operation {

 private:

   GrowableArray<oop> *_class_promote_order;

   OffsetTableContigSpace* _ro_space;

   OffsetTableContigSpace* _rw_space;

   VirtualSpace* _md_vs;

   VirtualSpace* _mc_vs;

 public:

   VM_PopulateDumpSharedSpace(GrowableArray<oop> *class_promote_order,

                              OffsetTableContigSpace* ro_space,

                              OffsetTableContigSpace* rw_space,

                              VirtualSpace* md_vs, VirtualSpace* mc_vs) {

     _class_promote_order = class_promote_order;

     _ro_space = ro_space;

     _rw_space = rw_space;

     _md_vs = md_vs;

     _mc_vs = mc_vs;

   }

   VMOp_Type type() const { return VMOp_PopulateDumpSharedSpace; }

   void 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");

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     // At this point, many classes have been loaded.

     // Update all the fingerprints in the shared methods.

     tty->print("Calculating fingerprints ... ");

     FingerprintMethodsClosure fpmc;

     gch->object_iterate(&fpmc);

     tty->print_cr("done. ");

     // Remove all references outside the heap.

     tty->print("Removing unshareable information ... ");

     RemoveUnshareableInfoClosure ruic;

     gch->object_iterate(&ruic);

     tty->print_cr("done. ");

     // Move the objects in three passes.

     MarkObjectsOopClosure mark_all;

     MarkCommonReadOnly mark_common_ro;

     MarkCommonSymbols mark_common_symbols;

     MarkStringValues mark_string_values;

     MarkReadWriteObjects mark_rw;

     MarkStringObjects mark_strings;

     MoveMarkedObjects move_ro(_ro_space, true);

     MoveMarkedObjects move_rw(_rw_space, false);

     // The SharedOptimizeColdStart VM option governs the new layout

     // algorithm for promoting classes into the shared archive.

     // The general idea is to minimize cold start time by laying

     // out the objects in the order they are accessed at startup time.

     // By doing this we are trying to eliminate out-of-order accesses

     // in the shared archive.  This benefits cold startup time by making

     // disk reads as sequential as possible during class loading and

     // bootstrapping activities.  There may also be a small secondary

     // effect of better "packing" of more commonly used data on a smaller

     // number of pages, although no direct benefit has been measured from

     // this effect.

     //

     // At the class level of granularity, the promotion order is dictated

     // by the classlist file whose generation is discussed elsewhere.

     //

     // At smaller granularity, optimal ordering was determined by an

     // offline analysis of object access order in the shared archive.

     // The dbx watchpoint facility, combined with SA post-processing,

     // was used to observe common access patterns primarily during

     // classloading.  This information was used to craft the promotion

     // order seen in the following closures.

     //

     // The observed access order is mostly governed by what happens

     // in SystemDictionary::load_shared_class().  NOTE WELL - care

     // should be taken when making changes to this method, because it

     // may invalidate assumptions made about access order!

     //

     // (Ideally, there would be a better way to manage changes to

     //  the access order.  Unfortunately a generic in-VM solution for

     //  dynamically observing access order and optimizing shared

     //  archive layout is pretty difficult.  We go with the static

     //  analysis because the code is fairly mature at this point

     //  and we're betting that the access order won't change much.)

     MarkAndMoveOrderedReadOnly  mark_and_move_ordered_ro(&move_ro);

     MarkAndMoveOrderedReadWrite mark_and_move_ordered_rw(&move_rw);

     // Phase 1a: move commonly used read-only objects to the read-only space.

     if (SharedOptimizeColdStart) {

       tty->print("Moving pre-ordered read-only objects to shared space at " PTR_FORMAT " ... ",

                  _ro_space->top());

       for (int i = 0; i < _class_promote_order->length(); i++) {

         oop obj = _class_promote_order->at(i);

         mark_and_move_ordered_ro.do_object(obj);

       }

       tty->print_cr("done. ");

     }

     tty->print("Moving read-only objects to shared space at " PTR_FORMAT " ... ",

                _ro_space->top());

     gch->object_iterate(&mark_common_ro);

     gch->object_iterate(&move_ro);

     tty->print_cr("done. ");

     // Phase 1b: move commonly used symbols to the read-only space.

     tty->print("Moving common symbols to shared space at " PTR_FORMAT " ... ",

                _ro_space->top());

     gch->object_iterate(&mark_common_symbols);

     gch->object_iterate(&move_ro);

     tty->print_cr("done. ");

     // Phase 1c: move remaining symbols to the read-only space

     // (e.g. String initializers).

     tty->print("Moving remaining symbols to shared space at " PTR_FORMAT " ... ",

                _ro_space->top());

     vmSymbols::oops_do(&mark_all, true);

     gch->object_iterate(&move_ro);

     tty->print_cr("done. ");

     // Phase 1d: move String character arrays to the read-only space.

     tty->print("Moving string char arrays to shared space at " PTR_FORMAT " ... ",

                _ro_space->top());

     gch->object_iterate(&mark_string_values);

     gch->object_iterate(&move_ro);

     tty->print_cr("done. ");

     // Phase 2: move all remaining symbols to the read-only space.  The

     // remaining symbols are assumed to be string initializers no longer

     // referenced.

     void* extra_symbols = _ro_space->top();

     tty->print("Moving additional symbols to shared space at " PTR_FORMAT " ... ",

                _ro_space->top());

     SymbolTable::oops_do(&mark_all);

     gch->object_iterate(&move_ro);

     tty->print_cr("done. ");

     tty->print_cr("Read-only space ends at " PTR_FORMAT ", %d bytes.",

                   _ro_space->top(), _ro_space->used());

     // Phase 3: move read-write objects to the read-write space, except

     // Strings.

     if (SharedOptimizeColdStart) {

       tty->print("Moving pre-ordered read-write objects to shared space at " PTR_FORMAT " ... ",

                  _rw_space->top());

       for (int i = 0; i < _class_promote_order->length(); i++) {

         oop obj = _class_promote_order->at(i);

         mark_and_move_ordered_rw.do_object(obj);

       }

       tty->print_cr("done. ");

     }

     tty->print("Moving read-write objects to shared space at " PTR_FORMAT " ... ",

                _rw_space->top());

     Universe::oops_do(&mark_all, true);

     SystemDictionary::oops_do(&mark_all);

     oop tmp = Universe::arithmetic_exception_instance();

     mark_object(java_lang_Throwable::message(tmp));

     gch->object_iterate(&mark_rw);

     gch->object_iterate(&move_rw);

     tty->print_cr("done. ");

     // Phase 4: move String objects to the read-write space.

     tty->print("Moving String objects to shared space at " PTR_FORMAT " ... ",

                _rw_space->top());

     StringTable::oops_do(&mark_all);

     gch->object_iterate(&mark_strings);

     gch->object_iterate(&move_rw);

     tty->print_cr("done. ");

     tty->print_cr("Read-write space ends at " PTR_FORMAT ", %d bytes.",

                   _rw_space->top(), _rw_space->used());

 #ifdef DEBUG

     // Check: scan for objects which were not moved.

     CheckRemainingObjects check_objects;

     gch->object_iterate(&check_objects);

     check_objects.status();

 #endif

     // Resolve forwarding in objects and saved C++ structures

     tty->print("Updating references to shared objects ... ");

     ResolveForwardingClosure resolve;

     Universe::oops_do(&resolve);

     SystemDictionary::oops_do(&resolve);

     StringTable::oops_do(&resolve);

     SymbolTable::oops_do(&resolve);

     vmSymbols::oops_do(&resolve);

     // Set up the share data and shared code segments.

     char* md_top = _md_vs->low();

     char* md_end = _md_vs->high();

     char* mc_top = _mc_vs->low();

     char* mc_end = _mc_vs->high();

     // Reserve space for the list of klassOops whose vtables are used

     // for patching others as needed.

     void** vtbl_list = (void**)md_top;

     int vtbl_list_size = CompactingPermGenGen::vtbl_list_size;

     Universe::init_self_patching_vtbl_list(vtbl_list, vtbl_list_size);

     md_top += vtbl_list_size * sizeof(void*);

     void* vtable = md_top;

     // Reserve space for a new dummy vtable for klass objects in the

     // heap.  Generate self-patching vtable entries.

     CompactingPermGenGen::generate_vtable_methods(vtbl_list,

                                                   &vtable,

                                                   &md_top, md_end,

                                                   &mc_top, mc_end);

     // Fix (forward) all of the references in these shared objects (which

     // are required to point ONLY to objects in the shared spaces).

     // Also, create a list of all objects which might later contain a

     // reference to a younger generation object.

     CompactingPermGenGen* gen = (CompactingPermGenGen*)gch->perm_gen();

     PatchOopsClosure patch(THREAD);

     gen->ro_space()->object_iterate(&patch);

     gen->rw_space()->object_iterate(&patch);

     // Previously method sorting was done concurrently with forwarding

     // pointer resolution in the shared spaces.  This imposed an ordering

     // restriction in that methods were required to be promoted/patched

     // before their holder classes.  (Because constant pool pointers in

     // methodKlasses are required to be resolved before their holder class

     // is visited for sorting, otherwise methods are sorted by incorrect,

     // pre-forwarding addresses.)

     //

     // Now, we reorder methods as a separate step after ALL forwarding

     // pointer resolution, so that methods can be promoted in any order

     // with respect to their holder classes.

     SortMethodsClosure sort(THREAD);

     gen->ro_space()->object_iterate(&sort);

     gen->rw_space()->object_iterate(&sort);

     tty->print_cr("done. ");

     tty->cr();

     // Reorder the system dictionary.  (Moving the symbols opps affects

     // how the hash table indices are calculated.)

     SystemDictionary::reorder_dictionary();

     // Empty the non-shared heap (because most of the objects were

     // copied out, and the remainder cannot be considered valid oops).

     ClearSpaceClosure csc;

     for (int i = 0; i < gch->n_gens(); ++i) {

       gch->get_gen(i)->space_iterate(&csc);

     }

     csc.do_space(gen->the_space());

     NOT_PRODUCT(SystemDictionary::verify();)

     // Copy the String table, the symbol table, and the system

     // dictionary to the shared space in usable form.  Copy the hastable

     // buckets first [read-write], then copy the linked lists of entries

     // [read-only].

     SymbolTable::reverse(extra_symbols);

     NOT_PRODUCT(SymbolTable::verify());

     SymbolTable::copy_buckets(&md_top, md_end);

     StringTable::reverse();

     NOT_PRODUCT(StringTable::verify());

     StringTable::copy_buckets(&md_top, md_end);

     SystemDictionary::reverse();

     SystemDictionary::copy_buckets(&md_top, md_end);

     ClassLoader::verify();

     ClassLoader::copy_package_info_buckets(&md_top, md_end);

     ClassLoader::verify();

     SymbolTable::copy_table(&md_top, md_end);

     StringTable::copy_table(&md_top, md_end);

     SystemDictionary::copy_table(&md_top, md_end);

     ClassLoader::verify();

     ClassLoader::copy_package_info_table(&md_top, md_end);

     ClassLoader::verify();

     // Print debug data.

     if (PrintSharedSpaces) {

       const char* fmt = "%s space: " PTR_FORMAT " out of " PTR_FORMAT " bytes allocated at " PTR_FORMAT ".";

       tty->print_cr(fmt, "ro", _ro_space->used(), _ro_space->capacity(),

                     _ro_space->bottom());

       tty->print_cr(fmt, "rw", _rw_space->used(), _rw_space->capacity(),

                     _rw_space->bottom());

     }

     // Write the oop data to the output array.

     WriteClosure wc(md_top, md_end);

     CompactingPermGenGen::serialize_oops(&wc);

     md_top = wc.get_top();

     // Update the vtable pointers in all of the Klass objects in the

     // heap. They should point to newly generated vtable.

     PatchKlassVtables pkvt(vtable, _md_vs);

     _rw_space->object_iterate(&pkvt);

     pkvt.patch(vtbl_list, vtbl_list_size);

     char* saved_vtbl = (char*)malloc(vtbl_list_size * sizeof(void*));

     memmove(saved_vtbl, vtbl_list, vtbl_list_size * sizeof(void*));

     memset(vtbl_list, 0, vtbl_list_size * sizeof(void*));

     // Create and write the archive file that maps the shared spaces.

     FileMapInfo* mapinfo = new FileMapInfo();

     mapinfo->populate_header(gch->gen_policy()->max_alignment());

     // Pass 1 - update file offsets in header.

     mapinfo->write_header();

     mapinfo->write_space(CompactingPermGenGen::ro, _ro_space, true);

     _ro_space->set_saved_mark();

     mapinfo->write_space(CompactingPermGenGen::rw, _rw_space, false);

     _rw_space->set_saved_mark();

     mapinfo->write_region(CompactingPermGenGen::md, _md_vs->low(),

                           md_top - _md_vs->low(), SharedMiscDataSize,

                           false, false);

     mapinfo->write_region(CompactingPermGenGen::mc, _mc_vs->low(),

                           mc_top - _mc_vs->low(), SharedMiscCodeSize,

                           true, true);

     // Pass 2 - write data.

     mapinfo->open_for_write();

     mapinfo->write_header();

     mapinfo->write_space(CompactingPermGenGen::ro, _ro_space, true);

     mapinfo->write_space(CompactingPermGenGen::rw, _rw_space, false);

     mapinfo->write_region(CompactingPermGenGen::md, _md_vs->low(),

                           md_top - _md_vs->low(), SharedMiscDataSize,

                           false, false);

     mapinfo->write_region(CompactingPermGenGen::mc, _mc_vs->low(),

                           mc_top - _mc_vs->low(), SharedMiscCodeSize,

                           true, true);

     mapinfo->close();

     // Summarize heap.

     memmove(vtbl_list, saved_vtbl, vtbl_list_size * sizeof(void*));

     print_contents();

   }

 }; // class VM_PopulateDumpSharedSpace

 // Populate the shared spaces and dump to a file.

 jint CompactingPermGenGen::dump_shared(GrowableArray<oop>* class_promote_order, TRAPS) {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   // Calculate hash values for all of the (interned) strings to avoid

   // writes to shared pages in the future.

   tty->print("Calculating hash values for String objects .. ");

   StringHashCodeClosure shcc(THREAD);

   StringTable::oops_do(&shcc);

   tty->print_cr("done. ");

   CompactingPermGenGen* gen = (CompactingPermGenGen*)gch->perm_gen();

   VM_PopulateDumpSharedSpace op(class_promote_order,

                                 gen->ro_space(), gen->rw_space(),

                                 gen->md_space(), gen->mc_space());

   VMThread::execute(&op);

   return JNI_OK;

 }

 class LinkClassesClosure : public ObjectClosure {

  private:

   Thread* THREAD;

  public:

   LinkClassesClosure(Thread* thread) : THREAD(thread) {}

   void do_object(oop obj) {

     if (obj->is_klass()) {

       Klass* k = Klass::cast((klassOop) obj);

       if (k->oop_is_instance()) {

         instanceKlass* ik = (instanceKlass*) k;

         // Link the class to cause the bytecodes to be rewritten and the

         // cpcache to be created.

         if (ik->get_init_state() < instanceKlass::linked) {

           ik->link_class(THREAD);

           guarantee(!HAS_PENDING_EXCEPTION, "exception in class rewriting");

         }

         // Create String objects from string initializer symbols.

         ik->constants()->resolve_string_constants(THREAD);

         guarantee(!HAS_PENDING_EXCEPTION, "exception resolving string constants");

       }

     }

   }

 };

 // Support for a simple checksum of the contents of the class list

 // file to prevent trivial tampering. The algorithm matches that in

 // the MakeClassList program used by the J2SE build process.

 #define JSUM_SEED ((jlong)CONST64(0xcafebabebabecafe))

 static jlong

 jsum(jlong start, const char *buf, const int len)

 {

     jlong h = start;

     char *p = (char *)buf, *e = p + len;

     while (p < e) {

         char c = *p++;

         if (c <= ' ') {

             /* Skip spaces and control characters */

             continue;

         }

         h = 31 * h + c;

     }

     return h;

 }

 // Preload classes from a list, populate the shared spaces and dump to a

 // file.

 void GenCollectedHeap::preload_and_dump(TRAPS) {

   TraceTime timer("Dump Shared Spaces", TraceStartupTime);

   ResourceMark rm;

   // Preload classes to be shared.

   // Should use some hpi:: method rather than fopen() here. aB.

   // 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)

   char class_list_path[JVM_MAXPATHLEN];

   os::jvm_path(class_list_path, sizeof(class_list_path));

   for (int i = 0; i < 3; i++) {

     char *end = strrchr(class_list_path, *os::file_separator());

     if (end != NULL) *end = '\0';

   }

   int class_list_path_len = (int)strlen(class_list_path);

   if (class_list_path_len >= 3) {

     if (strcmp(class_list_path + class_list_path_len - 3, "lib") != 0) {

       strcat(class_list_path, os::file_separator());

       strcat(class_list_path, "lib");

     }

   }

   strcat(class_list_path, os::file_separator());

   strcat(class_list_path, "classlist");

   FILE* file = fopen(class_list_path, "r");

   if (file != NULL) {

     jlong computed_jsum  = JSUM_SEED;

     jlong file_jsum      = 0;

     char class_name[256];

     int class_count = 0;

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     gch->_preloading_shared_classes = true;

     GrowableArray<oop>* class_promote_order = new GrowableArray<oop>();

     // Preload (and intern) strings which will be used later.

     StringTable::intern("main", THREAD);

     StringTable::intern("([Ljava/lang/String;)V", THREAD);

     StringTable::intern("Ljava/lang/Class;", THREAD);

     StringTable::intern("I", THREAD);   // Needed for StringBuffer persistence?

     StringTable::intern("Z", THREAD);   // Needed for StringBuffer persistence?

     // sun.io.Converters

     static const char obj_array_sig[] = "[[Ljava/lang/Object;";

     SymbolTable::lookup(obj_array_sig, (int)strlen(obj_array_sig), THREAD);

     // java.util.HashMap

     static const char map_entry_array_sig[] = "[Ljava/util/Map$Entry;";

     SymbolTable::lookup(map_entry_array_sig, (int)strlen(map_entry_array_sig),

                         THREAD);

     tty->print("Loading classes to share ... ");

     while ((fgets(class_name, sizeof class_name, file)) != NULL) {

       if (*class_name == '#') {

         jint fsh, fsl;

         if (sscanf(class_name, "# %8x%8x\n", &fsh, &fsl) == 2) {

           file_jsum = ((jlong)(fsh) << 32) | (fsl & 0xffffffff);

         }

         continue;

       }

       // Remove trailing newline

       size_t name_len = strlen(class_name);

       class_name[name_len-1] = '\0';

       computed_jsum = jsum(computed_jsum, class_name, (const int)name_len - 1);

       // Got a class name - load it.

       symbolHandle class_name_symbol = oopFactory::new_symbol(class_name,

                                                               THREAD);

       guarantee(!HAS_PENDING_EXCEPTION, "Exception creating a symbol.");

       klassOop klass = SystemDictionary::resolve_or_null(class_name_symbol,

                                                          THREAD);

       guarantee(!HAS_PENDING_EXCEPTION, "Exception resolving a class.");

       if (klass != NULL) {

         if (PrintSharedSpaces) {

           tty->print_cr("Shared spaces preloaded: %s", class_name);

         }

         instanceKlass* ik = instanceKlass::cast(klass);

         // Should be class load order as per -XX:+TraceClassLoadingPreorder

         class_promote_order->append(ik->as_klassOop());

         // 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,

         // cpCache, Sting constants) are located together.

         if (ik->get_init_state() < instanceKlass::linked) {

           ik->link_class(THREAD);

           guarantee(!(HAS_PENDING_EXCEPTION), "exception in class rewriting");

         }

         // Create String objects from string initializer symbols.

         ik->constants()->resolve_string_constants(THREAD);

         class_count++;

       } else {

         if (PrintSharedSpaces) {

           tty->cr();

           tty->print_cr(" Preload failed: %s", class_name);

         }

       }

       file_jsum = 0; // Checksum must be on last line of file

     }

     if (computed_jsum != file_jsum) {

       tty->cr();

       tty->print_cr("Preload failed: checksum of class list was incorrect.");

       exit(1);

     }

     tty->print_cr("done. ");

     if (PrintSharedSpaces) {

       tty->print_cr("Shared spaces: preloaded %d classes", class_count);

     }

     // Rewrite and unlink classes.

     tty->print("Rewriting and unlinking classes ... ");

     // Make heap parsable

     ensure_parsability(false); // arg is actually don't care

     // Link any classes which got missed.  (It's not quite clear why

     // they got missed.)  This iteration would be unsafe if we weren't

     // single-threaded at this point; however we can't do it on the VM

     // thread because it requires object allocation.

     LinkClassesClosure lcc(Thread::current());

     object_iterate(&lcc);

     tty->print_cr("done. ");

     // Create and dump the shared spaces.

     jint err = CompactingPermGenGen::dump_shared(class_promote_order, THREAD);

     if (err != JNI_OK) {

       fatal("Dumping shared spaces failed.");

     }

   } else {

     char errmsg[JVM_MAXPATHLEN];

     hpi::lasterror(errmsg, JVM_MAXPATHLEN);

     tty->print_cr("Loading classlist failed: %s", errmsg);

     exit(1);

   }

   // Since various initialization steps have been undone by this process,

   // it is not reasonable to continue running a java process.

   exit(0);

 }