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 /*

  * Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * 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

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 // A "SharedHeap" is an implementation of a java heap for HotSpot.  This

 // is an abstract class: there may be many different kinds of heaps.  This

 // class defines the functions that a heap must implement, and contains

 // infrastructure common to all heaps.

 class PermGen;

 class Generation;

 class BarrierSet;

 class GenRemSet;

 class Space;

 class SpaceClosure;

 class OopClosure;

 class OopsInGenClosure;

 class ObjectClosure;

 class SubTasksDone;

 class WorkGang;

 class CollectorPolicy;

 class KlassHandle;

 class SharedHeap : public CollectedHeap {

   friend class VMStructs;

   friend class VM_GC_Operation;

   friend class VM_CGC_Operation;

 private:

   // For claiming strong_roots tasks.

   SubTasksDone* _process_strong_tasks;

 protected:

   // There should be only a single instance of "SharedHeap" in a program.

   // This is enforced with the protected constructor below, which will also

   // set the static pointer "_sh" to that instance.

   static SharedHeap* _sh;

   // All heaps contain a "permanent generation."  This is some ways

   // similar to a generation in a generational system, in other ways not.

   // See the "PermGen" class.

   PermGen* _perm_gen;

   // and the Gen Remembered Set, at least one good enough to scan the perm

   // gen.

   GenRemSet* _rem_set;

   // A gc policy, controls global gc resource issues

   CollectorPolicy *_collector_policy;

   // See the discussion below, in the specification of the reader function

   // for this variable.

   int _strong_roots_parity;

   // If we're doing parallel GC, use this gang of threads.

   WorkGang* _workers;

   // Number of parallel threads currently working on GC tasks.

   // O indicates use sequential code; 1 means use parallel code even with

   // only one thread, for performance testing purposes.

   int _n_par_threads;

   // Full initialization is done in a concrete subtype's "initialize"

   // function.

   SharedHeap(CollectorPolicy* policy_);

   // Returns true if the calling thread holds the heap lock,

   // or the calling thread is a par gc thread and the heap_lock is held

   // by the vm thread doing a gc operation.

   bool heap_lock_held_for_gc();

   // True if the heap_lock is held by the a non-gc thread invoking a gc

   // operation.

   bool _thread_holds_heap_lock_for_gc;

 public:

   static SharedHeap* heap() { return _sh; }

   CollectorPolicy *collector_policy() const { return _collector_policy; }

   void set_barrier_set(BarrierSet* bs);

   // Does operations required after initialization has been done.

   virtual void post_initialize();

   // Initialization of ("weak") reference processing support

   virtual void ref_processing_init();

   void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; }

   // This function returns the "GenRemSet" object that allows us to scan

   // generations; at least the perm gen, possibly more in a fully

   // generational heap.

   GenRemSet* rem_set() { return _rem_set; }

   // These function return the "permanent" generation, in which

   // reflective objects are allocated and stored.  Two versions, the second

   // of which returns the view of the perm gen as a generation.

   PermGen* perm() const { return _perm_gen; }

   Generation* perm_gen() const { return _perm_gen->as_gen(); }

   // Iteration functions.

   void oop_iterate(OopClosure* cl) = 0;

   // Same as above, restricted to a memory region.

   virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;

   // Iterate over all objects allocated since the last collection, calling

   // "cl->do_object" on each.  The heap must have been initialized properly

   // to support this function, or else this call will fail.

   virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;

   // Iterate over all spaces in use in the heap, in an undefined order.

   virtual void space_iterate(SpaceClosure* cl) = 0;

   // A SharedHeap will contain some number of spaces.  This finds the

   // space whose reserved area contains the given address, or else returns

   // NULL.

   virtual Space* space_containing(const void* addr) const = 0;

   bool no_gc_in_progress() { return !is_gc_active(); }

   // Some collectors will perform "process_strong_roots" in parallel.

   // Such a call will involve claiming some fine-grained tasks, such as

   // scanning of threads.  To make this process simpler, we provide the

   // "strong_roots_parity()" method.  Collectors that start parallel tasks

   // whose threads invoke "process_strong_roots" must

   // call "change_strong_roots_parity" in sequential code starting such a

   // task.  (This also means that a parallel thread may only call

   // process_strong_roots once.)

   //

   // For calls to process_strong_roots by sequential code, the parity is

   // updated automatically.

   //

   // The idea is that objects representing fine-grained tasks, such as

   // threads, will contain a "parity" field.  A task will is claimed in the

   // current "process_strong_roots" call only if its parity field is the

   // same as the "strong_roots_parity"; task claiming is accomplished by

   // updating the parity field to the strong_roots_parity with a CAS.

   //

   // If the client meats this spec, then strong_roots_parity() will have

   // the following properties:

   //   a) to return a different value than was returned before the last

   //      call to change_strong_roots_parity, and

   //   c) to never return a distinguished value (zero) with which such

   //      task-claiming variables may be initialized, to indicate "never

   //      claimed".

  private:

   void change_strong_roots_parity();

  public:

   int strong_roots_parity() { return _strong_roots_parity; }

   // Call these in sequential code around process_strong_roots.

   // strong_roots_prologue calls change_strong_roots_parity, if

   // parallel tasks are enabled.

   class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope {

   public:

     StrongRootsScope(SharedHeap* outer, bool activate = true);

     ~StrongRootsScope();

   };

   friend class StrongRootsScope;

   enum ScanningOption {

     SO_None                = 0x0,

     SO_AllClasses          = 0x1,

     SO_SystemClasses       = 0x2,

     SO_Symbols             = 0x4,

     SO_Strings             = 0x8,

     SO_CodeCache           = 0x10

   };

   WorkGang* workers() const { return _workers; }

   // Sets the number of parallel threads that will be doing tasks

   // (such as process strong roots) subsequently.

   virtual void set_par_threads(int t);

   // Number of threads currently working on GC tasks.

   int n_par_threads() { return _n_par_threads; }

   // Invoke the "do_oop" method the closure "roots" on all root locations.

   // If "collecting_perm_gen" is false, then roots that may only contain

   // references to permGen objects are not scanned.  If true, the

   // "perm_gen" closure is applied to all older-to-younger refs in the

   // permanent generation.  The "so" argument determines which of roots

   // the closure is applied to:

   // "SO_None" does none;

   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;

   // "SO_SystemClasses" to all the "system" classes and loaders;

   // "SO_Symbols" applies the closure to all entries in SymbolsTable;

   // "SO_Strings" applies the closure to all entries in StringTable;

   // "SO_CodeCache" applies the closure to all elements of the CodeCache.

   void process_strong_roots(bool activate_scope,

                             bool collecting_perm_gen,

                             ScanningOption so,

                             OopClosure* roots,

                             CodeBlobClosure* code_roots,

                             OopsInGenClosure* perm_blk);

   // Apply "blk" to all the weak roots of the system.  These include

   // JNI weak roots, the code cache, system dictionary, symbol table,

   // string table.

   void process_weak_roots(OopClosure* root_closure,

                           CodeBlobClosure* code_roots,

                           OopClosure* non_root_closure);

   // The functions below are helper functions that a subclass of

   // "SharedHeap" can use in the implementation of its virtual

   // functions.

 public:

   // Do anything common to GC's.

   virtual void gc_prologue(bool full) = 0;

   virtual void gc_epilogue(bool full) = 0;

   //

   // New methods from CollectedHeap

   //

   size_t permanent_capacity() const {

     assert(perm_gen(), "NULL perm gen");

     return perm_gen()->capacity();

   }

   size_t permanent_used() const {

     assert(perm_gen(), "NULL perm gen");

     return perm_gen()->used();

   }

   bool is_in_permanent(const void *p) const {

     assert(perm_gen(), "NULL perm gen");

     return perm_gen()->is_in_reserved(p);

   }

   // Different from is_in_permanent in that is_in_permanent

   // only checks if p is in the reserved area of the heap

   // and this checks to see if it in the commited area.

   // This is typically used by things like the forte stackwalker

   // during verification of suspicious frame values.

   bool is_permanent(const void *p) const {

     assert(perm_gen(), "NULL perm gen");

     return perm_gen()->is_in(p);

   }

   HeapWord* permanent_mem_allocate(size_t size) {

     assert(perm_gen(), "NULL perm gen");

     return _perm_gen->mem_allocate(size);

   }

   void permanent_oop_iterate(OopClosure* cl) {

     assert(perm_gen(), "NULL perm gen");

     _perm_gen->oop_iterate(cl);

   }

   void permanent_object_iterate(ObjectClosure* cl) {

     assert(perm_gen(), "NULL perm gen");

     _perm_gen->object_iterate(cl);

   }

   // Some utilities.

   void print_size_transition(outputStream* out,

                              size_t bytes_before,

                              size_t bytes_after,

                              size_t capacity);

 };