src/share/vm/memory/genCollectedHeap.hpp - platform/external/jetbrains/jdk8u_hotspot - Git at Google

 /*
  * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP

 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
 #include "memory/collectorPolicy.hpp"
 #include "memory/generation.hpp"
 #include "memory/sharedHeap.hpp"

 class SubTasksDone;

 // A "GenCollectedHeap" is a SharedHeap that uses generational
 // collection.  It is represented with a sequence of Generation's.
 class GenCollectedHeap : public SharedHeap {
   friend class GenCollectorPolicy;
   friend class Generation;
   friend class DefNewGeneration;
   friend class TenuredGeneration;
   friend class ConcurrentMarkSweepGeneration;
   friend class CMSCollector;
   friend class GenMarkSweep;
   friend class VM_GenCollectForAllocation;
   friend class VM_GenCollectFull;
   friend class VM_GenCollectFullConcurrent;
   friend class VM_GC_HeapInspection;
   friend class VM_HeapDumper;
   friend class HeapInspection;
   friend class GCCauseSetter;
   friend class VMStructs;
 public:
   enum SomeConstants {
     max_gens = 10
   };

   friend class VM_PopulateDumpSharedSpace;

  protected:
   // Fields:
   static GenCollectedHeap* _gch;

  private:
   int _n_gens;
   Generation* _gens[max_gens];
   GenerationSpec** _gen_specs;

   // The generational collector policy.
   GenCollectorPolicy* _gen_policy;

   // Indicates that the most recent previous incremental collection failed.
   // The flag is cleared when an action is taken that might clear the
   // condition that caused that incremental collection to fail.
   bool _incremental_collection_failed;

   // In support of ExplicitGCInvokesConcurrent functionality
   unsigned int _full_collections_completed;

   // Data structure for claiming the (potentially) parallel tasks in
   // (gen-specific) roots processing.
   SubTasksDone* _process_strong_tasks;

   // In block contents verification, the number of header words to skip
   NOT_PRODUCT(static size_t _skip_header_HeapWords;)

 protected:
   // Helper functions for allocation
   HeapWord* attempt_allocation(size_t size,
                                bool   is_tlab,
                                bool   first_only);

   // Helper function for two callbacks below.
   // Considers collection of the first max_level+1 generations.
   void do_collection(bool   full,
                      bool   clear_all_soft_refs,
                      size_t size,
                      bool   is_tlab,
                      int    max_level);

   // Callback from VM_GenCollectForAllocation operation.
   // This function does everything necessary/possible to satisfy an
   // allocation request that failed in the youngest generation that should
   // have handled it (including collection, expansion, etc.)
   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);

   // Callback from VM_GenCollectFull operation.
   // Perform a full collection of the first max_level+1 generations.
   virtual void do_full_collection(bool clear_all_soft_refs);
   void do_full_collection(bool clear_all_soft_refs, int max_level);

   // Does the "cause" of GC indicate that
   // we absolutely __must__ clear soft refs?
   bool must_clear_all_soft_refs();

 public:
   GenCollectedHeap(GenCollectorPolicy *policy);

   GCStats* gc_stats(int level) const;

   // Returns JNI_OK on success
   virtual jint initialize();
   char* allocate(size_t alignment,
                  size_t* _total_reserved, int* _n_covered_regions,
                  ReservedSpace* heap_rs);

   // Does operations required after initialization has been done.
   void post_initialize();

   // Initialize ("weak") refs processing support
   virtual void ref_processing_init();

   virtual CollectedHeap::Name kind() const {
     return CollectedHeap::GenCollectedHeap;
   }

   // The generational collector policy.
   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }

   // Adaptive size policy
   virtual AdaptiveSizePolicy* size_policy() {
     return gen_policy()->size_policy();
   }

   // Return the (conservative) maximum heap alignment
   static size_t conservative_max_heap_alignment() {
     return Generation::GenGrain;
   }

   size_t capacity() const;
   size_t used() const;

   // Save the "used_region" for generations level and lower.
   void save_used_regions(int level);

   size_t max_capacity() const;

   HeapWord* mem_allocate(size_t size,
                          bool*  gc_overhead_limit_was_exceeded);

   // We may support a shared contiguous allocation area, if the youngest
   // generation does.
   bool supports_inline_contig_alloc() const;
   HeapWord** top_addr() const;
   HeapWord** end_addr() const;

   // Does this heap support heap inspection? (+PrintClassHistogram)
   virtual bool supports_heap_inspection() const { return true; }

   // Perform a full collection of the heap; intended for use in implementing
   // "System.gc". This implies as full a collection as the CollectedHeap
   // supports. Caller does not hold the Heap_lock on entry.
   void collect(GCCause::Cause cause);

   // The same as above but assume that the caller holds the Heap_lock.
   void collect_locked(GCCause::Cause cause);

   // Perform a full collection of the first max_level+1 generations.
   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
   void collect(GCCause::Cause cause, int max_level);

   // Returns "TRUE" iff "p" points into the committed areas of the heap.
   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
   // be expensive to compute in general, so, to prevent
   // their inadvertent use in product jvm's, we restrict their use to
   // assertion checking or verification only.
   bool is_in(const void* p) const;

   // override
   bool is_in_closed_subset(const void* p) const {
     if (UseConcMarkSweepGC) {
       return is_in_reserved(p);
     } else {
       return is_in(p);
     }
   }

   // Returns true if the reference is to an object in the reserved space
   // for the young generation.
   // Assumes the the young gen address range is less than that of the old gen.
   bool is_in_young(oop p);

 #ifdef ASSERT
   virtual bool is_in_partial_collection(const void* p);
 #endif

   virtual bool is_scavengable(const void* addr) {
     return is_in_young((oop)addr);
   }

   // Iteration functions.
   void oop_iterate(ExtendedOopClosure* cl);
   void object_iterate(ObjectClosure* cl);
   void safe_object_iterate(ObjectClosure* cl);
   Space* space_containing(const void* addr) const;

   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
   // each address in the (reserved) heap is a member of exactly
   // one block.  The defining characteristic of a block is that it is
   // possible to find its size, and thus to progress forward to the next
   // block.  (Blocks may be of different sizes.)  Thus, blocks may
   // represent Java objects, or they might be free blocks in a
   // free-list-based heap (or subheap), as long as the two kinds are
   // distinguishable and the size of each is determinable.

   // Returns the address of the start of the "block" that contains the
   // address "addr".  We say "blocks" instead of "object" since some heaps
   // may not pack objects densely; a chunk may either be an object or a
   // non-object.
   virtual HeapWord* block_start(const void* addr) const;

   // Requires "addr" to be the start of a chunk, and returns its size.
   // "addr + size" is required to be the start of a new chunk, or the end
   // of the active area of the heap. Assumes (and verifies in non-product
   // builds) that addr is in the allocated part of the heap and is
   // the start of a chunk.
   virtual size_t block_size(const HeapWord* addr) const;

   // Requires "addr" to be the start of a block, and returns "TRUE" iff
   // the block is an object. Assumes (and verifies in non-product
   // builds) that addr is in the allocated part of the heap and is
   // the start of a chunk.
   virtual bool block_is_obj(const HeapWord* addr) const;

   // Section on TLAB's.
   virtual bool supports_tlab_allocation() const;
   virtual size_t tlab_capacity(Thread* thr) const;
   virtual size_t tlab_used(Thread* thr) const;
   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
   virtual HeapWord* allocate_new_tlab(size_t size);

   // Can a compiler initialize a new object without store barriers?
   // This permission only extends from the creation of a new object
   // via a TLAB up to the first subsequent safepoint.
   virtual bool can_elide_tlab_store_barriers() const {
     return true;
   }

   virtual bool card_mark_must_follow_store() const {
     return UseConcMarkSweepGC;
   }

   // We don't need barriers for stores to objects in the
   // young gen and, a fortiori, for initializing stores to
   // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
   // only and may need to be re-examined in case other
   // kinds of collectors are implemented in the future.
   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
     // We wanted to assert that:-
     // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
     //       "Check can_elide_initializing_store_barrier() for this collector");
     // but unfortunately the flag UseSerialGC need not necessarily always
     // be set when DefNew+Tenured are being used.
     return is_in_young(new_obj);
   }

   // The "requestor" generation is performing some garbage collection
   // action for which it would be useful to have scratch space.  The
   // requestor promises to allocate no more than "max_alloc_words" in any
   // older generation (via promotion say.)   Any blocks of space that can
   // be provided are returned as a list of ScratchBlocks, sorted by
   // decreasing size.
   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
   // Allow each generation to reset any scratch space that it has
   // contributed as it needs.
   void release_scratch();

   // Ensure parsability: override
   virtual void ensure_parsability(bool retire_tlabs);

   // Time in ms since the longest time a collector ran in
   // in any generation.
   virtual jlong millis_since_last_gc();

   // Total number of full collections completed.
   unsigned int total_full_collections_completed() {
     assert(_full_collections_completed <= _total_full_collections,
            "Can't complete more collections than were started");
     return _full_collections_completed;
   }

   // Update above counter, as appropriate, at the end of a stop-world GC cycle
   unsigned int update_full_collections_completed();
   // Update above counter, as appropriate, at the end of a concurrent GC cycle
   unsigned int update_full_collections_completed(unsigned int count);

   // Update "time of last gc" for all constituent generations
   // to "now".
   void update_time_of_last_gc(jlong now) {
     for (int i = 0; i < _n_gens; i++) {
       _gens[i]->update_time_of_last_gc(now);
     }
   }

   // Update the gc statistics for each generation.
   // "level" is the level of the lastest collection
   void update_gc_stats(int current_level, bool full) {
     for (int i = 0; i < _n_gens; i++) {
       _gens[i]->update_gc_stats(current_level, full);
     }
   }

   // Override.
   bool no_gc_in_progress() { return !is_gc_active(); }

   // Override.
   void prepare_for_verify();

   // Override.
   void verify(bool silent, VerifyOption option);

   // Override.
   virtual void print_on(outputStream* st) const;
   virtual void print_gc_threads_on(outputStream* st) const;
   virtual void gc_threads_do(ThreadClosure* tc) const;
   virtual void print_tracing_info() const;
   virtual void print_on_error(outputStream* st) const;

   // PrintGC, PrintGCDetails support
   void print_heap_change(size_t prev_used) const;

   // The functions below are helper functions that a subclass of
   // "CollectedHeap" can use in the implementation of its virtual
   // functions.

   class GenClosure : public StackObj {
    public:
     virtual void do_generation(Generation* gen) = 0;
   };

   // Apply "cl.do_generation" to all generations in the heap
   // If "old_to_young" determines the order.
   void generation_iterate(GenClosure* cl, bool old_to_young);

   void space_iterate(SpaceClosure* cl);

   // Return "true" if all generations have reached the
   // maximal committed limit that they can reach, without a garbage
   // collection.
   virtual bool is_maximal_no_gc() const;

   // Return the generation before "gen".
   Generation* prev_gen(Generation* gen) const {
     int l = gen->level();
     guarantee(l > 0, "Out of bounds");
     return _gens[l-1];
   }

   // Return the generation after "gen".
   Generation* next_gen(Generation* gen) const {
     int l = gen->level() + 1;
     guarantee(l < _n_gens, "Out of bounds");
     return _gens[l];
   }

   Generation* get_gen(int i) const {
     guarantee(i >= 0 && i < _n_gens, "Out of bounds");
     return _gens[i];
   }

   int n_gens() const {
     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
     return _n_gens;
   }

   // Convenience function to be used in situations where the heap type can be
   // asserted to be this type.
   static GenCollectedHeap* heap();

   void set_par_threads(uint t);
   void set_n_termination(uint t);

   // Invoke the "do_oop" method of one of the closures "not_older_gens"
   // or "older_gens" on root locations for the generation at
   // "level".  (The "older_gens" closure is used for scanning references
   // from older generations; "not_older_gens" is used everywhere else.)
   // If "younger_gens_as_roots" is false, younger generations are
   // not scanned as roots; in this case, the caller must be arranging to
   // scan the younger generations itself.  (For example, a generation might
   // explicitly mark reachable objects in younger generations, to avoid
   // excess storage retention.)
   // The "so" argument determines which of the roots
   // the closure is applied to:
   // "SO_None" does none;
   enum ScanningOption {
     SO_None                =  0x0,
     SO_AllCodeCache        =  0x8,
     SO_ScavengeCodeCache   = 0x10
   };

  private:
   void process_roots(bool activate_scope,
                      ScanningOption so,
                      OopClosure* strong_roots,
                      OopClosure* weak_roots,
                      CLDClosure* strong_cld_closure,
                      CLDClosure* weak_cld_closure,
                      CodeBlobClosure* code_roots);

   void gen_process_roots(int level,
                          bool younger_gens_as_roots,
                          bool activate_scope,
                          ScanningOption so,
                          OopsInGenClosure* not_older_gens,
                          OopsInGenClosure* weak_roots,
                          OopsInGenClosure* older_gens,
                          CLDClosure* cld_closure,
                          CLDClosure* weak_cld_closure,
                          CodeBlobClosure* code_closure);

  public:
   static const bool StrongAndWeakRoots = false;
   static const bool StrongRootsOnly    = true;

   void gen_process_roots(int level,
                          bool younger_gens_as_roots,
                          bool activate_scope,
                          ScanningOption so,
                          bool only_strong_roots,
                          OopsInGenClosure* not_older_gens,
                          OopsInGenClosure* older_gens,
                          CLDClosure* cld_closure);

   // Apply "root_closure" to all the weak roots of the system.
   // These include JNI weak roots, string table,
   // and referents of reachable weak refs.
   void gen_process_weak_roots(OopClosure* root_closure);

   // Set the saved marks of generations, if that makes sense.
   // In particular, if any generation might iterate over the oops
   // in other generations, it should call this method.
   void save_marks();

   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
   // allocated since the last call to save_marks in generations at or above
   // "level".  The "cur" closure is
   // applied to references in the generation at "level", and the "older"
   // closure to older generations.
 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
   void oop_since_save_marks_iterate(int level,                          \
                                     OopClosureType* cur,                \
                                     OopClosureType* older);

   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)

 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL

   // Returns "true" iff no allocations have occurred in any generation at
   // "level" or above since the last
   // call to "save_marks".
   bool no_allocs_since_save_marks(int level);

   // Returns true if an incremental collection is likely to fail.
   // We optionally consult the young gen, if asked to do so;
   // otherwise we base our answer on whether the previous incremental
   // collection attempt failed with no corrective action as of yet.
   bool incremental_collection_will_fail(bool consult_young) {
     // Assumes a 2-generation system; the first disjunct remembers if an
     // incremental collection failed, even when we thought (second disjunct)
     // that it would not.
     assert(heap()->collector_policy()->is_two_generation_policy(),
            "the following definition may not be suitable for an n(>2)-generation system");
     return incremental_collection_failed() ||
            (consult_young && !get_gen(0)->collection_attempt_is_safe());
   }

   // If a generation bails out of an incremental collection,
   // it sets this flag.
   bool incremental_collection_failed() const {
     return _incremental_collection_failed;
   }
   void set_incremental_collection_failed() {
     _incremental_collection_failed = true;
   }
   void clear_incremental_collection_failed() {
     _incremental_collection_failed = false;
   }

   // Promotion of obj into gen failed.  Try to promote obj to higher
   // gens in ascending order; return the new location of obj if successful.
   // Otherwise, try expand-and-allocate for obj in both the young and old
   // generation; return the new location of obj if successful.  Otherwise, return NULL.
   oop handle_failed_promotion(Generation* old_gen,
                               oop obj,
                               size_t obj_size);

 private:
   // Accessor for memory state verification support
   NOT_PRODUCT(
     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
   )

   // Override
   void check_for_non_bad_heap_word_value(HeapWord* addr,
     size_t size) PRODUCT_RETURN;

   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
   // in an essential way: compaction is performed across generations, by
   // iterating over spaces.
   void prepare_for_compaction();

   // Perform a full collection of the first max_level+1 generations.
   // This is the low level interface used by the public versions of
   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
   void collect_locked(GCCause::Cause cause, int max_level);

   // Returns success or failure.
   bool create_cms_collector();

   // In support of ExplicitGCInvokesConcurrent functionality
   bool should_do_concurrent_full_gc(GCCause::Cause cause);
   void collect_mostly_concurrent(GCCause::Cause cause);

   // Save the tops of the spaces in all generations
   void record_gen_tops_before_GC() PRODUCT_RETURN;

 protected:
   virtual void gc_prologue(bool full);
   virtual void gc_epilogue(bool full);
 };

 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
	/*
	* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
	#define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP

	#include "gc_implementation/shared/adaptiveSizePolicy.hpp"
	#include "memory/collectorPolicy.hpp"
	#include "memory/generation.hpp"
	#include "memory/sharedHeap.hpp"

	class SubTasksDone;

	// A "GenCollectedHeap" is a SharedHeap that uses generational
	// collection. It is represented with a sequence of Generation's.
	class GenCollectedHeap : public SharedHeap {
	friend class GenCollectorPolicy;
	friend class Generation;
	friend class DefNewGeneration;
	friend class TenuredGeneration;
	friend class ConcurrentMarkSweepGeneration;
	friend class CMSCollector;
	friend class GenMarkSweep;
	friend class VM_GenCollectForAllocation;
	friend class VM_GenCollectFull;
	friend class VM_GenCollectFullConcurrent;
	friend class VM_GC_HeapInspection;
	friend class VM_HeapDumper;
	friend class HeapInspection;
	friend class GCCauseSetter;
	friend class VMStructs;
	public:
	enum SomeConstants {
	max_gens = 10
	};

	friend class VM_PopulateDumpSharedSpace;

	protected:
	// Fields:
	static GenCollectedHeap* _gch;

	private:
	int _n_gens;
	Generation* _gens[max_gens];
	GenerationSpec** _gen_specs;

	// The generational collector policy.
	GenCollectorPolicy* _gen_policy;

	// Indicates that the most recent previous incremental collection failed.
	// The flag is cleared when an action is taken that might clear the
	// condition that caused that incremental collection to fail.
	bool _incremental_collection_failed;

	// In support of ExplicitGCInvokesConcurrent functionality
	unsigned int _full_collections_completed;

	// Data structure for claiming the (potentially) parallel tasks in
	// (gen-specific) roots processing.
	SubTasksDone* _process_strong_tasks;

	// In block contents verification, the number of header words to skip
	NOT_PRODUCT(static size_t _skip_header_HeapWords;)

	protected:
	// Helper functions for allocation
	HeapWord* attempt_allocation(size_t size,
	bool is_tlab,
	bool first_only);

	// Helper function for two callbacks below.
	// Considers collection of the first max_level+1 generations.
	void do_collection(bool full,
	bool clear_all_soft_refs,
	size_t size,
	bool is_tlab,
	int max_level);

	// Callback from VM_GenCollectForAllocation operation.
	// This function does everything necessary/possible to satisfy an
	// allocation request that failed in the youngest generation that should
	// have handled it (including collection, expansion, etc.)
	HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);

	// Callback from VM_GenCollectFull operation.
	// Perform a full collection of the first max_level+1 generations.
	virtual void do_full_collection(bool clear_all_soft_refs);
	void do_full_collection(bool clear_all_soft_refs, int max_level);

	// Does the "cause" of GC indicate that
	// we absolutely __must__ clear soft refs?
	bool must_clear_all_soft_refs();

	public:
	GenCollectedHeap(GenCollectorPolicy *policy);

	GCStats* gc_stats(int level) const;

	// Returns JNI_OK on success
	virtual jint initialize();
	char* allocate(size_t alignment,
	size_t* _total_reserved, int* _n_covered_regions,
	ReservedSpace* heap_rs);

	// Does operations required after initialization has been done.
	void post_initialize();

	// Initialize ("weak") refs processing support
	virtual void ref_processing_init();

	virtual CollectedHeap::Name kind() const {
	return CollectedHeap::GenCollectedHeap;
	}

	// The generational collector policy.
	GenCollectorPolicy* gen_policy() const { return _gen_policy; }
	virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }

	// Adaptive size policy
	virtual AdaptiveSizePolicy* size_policy() {
	return gen_policy()->size_policy();
	}

	// Return the (conservative) maximum heap alignment
	static size_t conservative_max_heap_alignment() {
	return Generation::GenGrain;
	}

	size_t capacity() const;
	size_t used() const;

	// Save the "used_region" for generations level and lower.
	void save_used_regions(int level);

	size_t max_capacity() const;

	HeapWord* mem_allocate(size_t size,
	bool* gc_overhead_limit_was_exceeded);

	// We may support a shared contiguous allocation area, if the youngest
	// generation does.
	bool supports_inline_contig_alloc() const;
	HeapWord** top_addr() const;
	HeapWord** end_addr() const;

	// Does this heap support heap inspection? (+PrintClassHistogram)
	virtual bool supports_heap_inspection() const { return true; }

	// Perform a full collection of the heap; intended for use in implementing
	// "System.gc". This implies as full a collection as the CollectedHeap
	// supports. Caller does not hold the Heap_lock on entry.
	void collect(GCCause::Cause cause);

	// The same as above but assume that the caller holds the Heap_lock.
	void collect_locked(GCCause::Cause cause);

	// Perform a full collection of the first max_level+1 generations.
	// Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
	void collect(GCCause::Cause cause, int max_level);

	// Returns "TRUE" iff "p" points into the committed areas of the heap.
	// The methods is_in(), is_in_closed_subset() and is_in_youngest() may
	// be expensive to compute in general, so, to prevent
	// their inadvertent use in product jvm's, we restrict their use to
	// assertion checking or verification only.
	bool is_in(const void* p) const;

	// override
	bool is_in_closed_subset(const void* p) const {
	if (UseConcMarkSweepGC) {
	return is_in_reserved(p);
	} else {
	return is_in(p);
	}
	}

	// Returns true if the reference is to an object in the reserved space
	// for the young generation.
	// Assumes the the young gen address range is less than that of the old gen.
	bool is_in_young(oop p);

	#ifdef ASSERT
	virtual bool is_in_partial_collection(const void* p);
	#endif

	virtual bool is_scavengable(const void* addr) {
	return is_in_young((oop)addr);
	}

	// Iteration functions.
	void oop_iterate(ExtendedOopClosure* cl);
	void object_iterate(ObjectClosure* cl);
	void safe_object_iterate(ObjectClosure* cl);
	Space* space_containing(const void* addr) const;

	// A CollectedHeap is divided into a dense sequence of "blocks"; that is,
	// each address in the (reserved) heap is a member of exactly
	// one block. The defining characteristic of a block is that it is
	// possible to find its size, and thus to progress forward to the next
	// block. (Blocks may be of different sizes.) Thus, blocks may
	// represent Java objects, or they might be free blocks in a
	// free-list-based heap (or subheap), as long as the two kinds are
	// distinguishable and the size of each is determinable.

	// Returns the address of the start of the "block" that contains the
	// address "addr". We say "blocks" instead of "object" since some heaps
	// may not pack objects densely; a chunk may either be an object or a
	// non-object.
	virtual HeapWord* block_start(const void* addr) const;

	// Requires "addr" to be the start of a chunk, and returns its size.
	// "addr + size" is required to be the start of a new chunk, or the end
	// of the active area of the heap. Assumes (and verifies in non-product
	// builds) that addr is in the allocated part of the heap and is
	// the start of a chunk.
	virtual size_t block_size(const HeapWord* addr) const;

	// Requires "addr" to be the start of a block, and returns "TRUE" iff
	// the block is an object. Assumes (and verifies in non-product
	// builds) that addr is in the allocated part of the heap and is
	// the start of a chunk.
	virtual bool block_is_obj(const HeapWord* addr) const;

	// Section on TLAB's.
	virtual bool supports_tlab_allocation() const;
	virtual size_t tlab_capacity(Thread* thr) const;
	virtual size_t tlab_used(Thread* thr) const;
	virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
	virtual HeapWord* allocate_new_tlab(size_t size);

	// Can a compiler initialize a new object without store barriers?
	// This permission only extends from the creation of a new object
	// via a TLAB up to the first subsequent safepoint.
	virtual bool can_elide_tlab_store_barriers() const {
	return true;
	}

	virtual bool card_mark_must_follow_store() const {
	return UseConcMarkSweepGC;
	}

	// We don't need barriers for stores to objects in the
	// young gen and, a fortiori, for initializing stores to
	// objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
	// only and may need to be re-examined in case other
	// kinds of collectors are implemented in the future.
	virtual bool can_elide_initializing_store_barrier(oop new_obj) {
	// We wanted to assert that:-
	// assert(UseParNewGC \|\| UseSerialGC \|\| UseConcMarkSweepGC,
	// "Check can_elide_initializing_store_barrier() for this collector");
	// but unfortunately the flag UseSerialGC need not necessarily always
	// be set when DefNew+Tenured are being used.
	return is_in_young(new_obj);
	}

	// The "requestor" generation is performing some garbage collection
	// action for which it would be useful to have scratch space. The
	// requestor promises to allocate no more than "max_alloc_words" in any
	// older generation (via promotion say.) Any blocks of space that can
	// be provided are returned as a list of ScratchBlocks, sorted by
	// decreasing size.
	ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
	// Allow each generation to reset any scratch space that it has
	// contributed as it needs.
	void release_scratch();

	// Ensure parsability: override
	virtual void ensure_parsability(bool retire_tlabs);

	// Time in ms since the longest time a collector ran in
	// in any generation.
	virtual jlong millis_since_last_gc();

	// Total number of full collections completed.
	unsigned int total_full_collections_completed() {
	assert(_full_collections_completed <= _total_full_collections,
	"Can't complete more collections than were started");
	return _full_collections_completed;
	}

	// Update above counter, as appropriate, at the end of a stop-world GC cycle
	unsigned int update_full_collections_completed();
	// Update above counter, as appropriate, at the end of a concurrent GC cycle
	unsigned int update_full_collections_completed(unsigned int count);

	// Update "time of last gc" for all constituent generations
	// to "now".
	void update_time_of_last_gc(jlong now) {
	for (int i = 0; i < _n_gens; i++) {
	_gens[i]->update_time_of_last_gc(now);
	}
	}

	// Update the gc statistics for each generation.
	// "level" is the level of the lastest collection
	void update_gc_stats(int current_level, bool full) {
	for (int i = 0; i < _n_gens; i++) {
	_gens[i]->update_gc_stats(current_level, full);
	}
	}

	// Override.
	bool no_gc_in_progress() { return !is_gc_active(); }

	// Override.
	void prepare_for_verify();

	// Override.
	void verify(bool silent, VerifyOption option);

	// Override.
	virtual void print_on(outputStream* st) const;
	virtual void print_gc_threads_on(outputStream* st) const;
	virtual void gc_threads_do(ThreadClosure* tc) const;
	virtual void print_tracing_info() const;
	virtual void print_on_error(outputStream* st) const;

	// PrintGC, PrintGCDetails support
	void print_heap_change(size_t prev_used) const;

	// The functions below are helper functions that a subclass of
	// "CollectedHeap" can use in the implementation of its virtual
	// functions.

	class GenClosure : public StackObj {
	public:
	virtual void do_generation(Generation* gen) = 0;
	};

	// Apply "cl.do_generation" to all generations in the heap
	// If "old_to_young" determines the order.
	void generation_iterate(GenClosure* cl, bool old_to_young);

	void space_iterate(SpaceClosure* cl);

	// Return "true" if all generations have reached the
	// maximal committed limit that they can reach, without a garbage
	// collection.
	virtual bool is_maximal_no_gc() const;

	// Return the generation before "gen".
	Generation* prev_gen(Generation* gen) const {
	int l = gen->level();
	guarantee(l > 0, "Out of bounds");
	return _gens[l-1];
	}

	// Return the generation after "gen".
	Generation* next_gen(Generation* gen) const {
	int l = gen->level() + 1;
	guarantee(l < _n_gens, "Out of bounds");
	return _gens[l];
	}

	Generation* get_gen(int i) const {
	guarantee(i >= 0 && i < _n_gens, "Out of bounds");
	return _gens[i];
	}

	int n_gens() const {
	assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
	return _n_gens;
	}

	// Convenience function to be used in situations where the heap type can be
	// asserted to be this type.
	static GenCollectedHeap* heap();

	void set_par_threads(uint t);
	void set_n_termination(uint t);

	// Invoke the "do_oop" method of one of the closures "not_older_gens"
	// or "older_gens" on root locations for the generation at
	// "level". (The "older_gens" closure is used for scanning references
	// from older generations; "not_older_gens" is used everywhere else.)
	// If "younger_gens_as_roots" is false, younger generations are
	// not scanned as roots; in this case, the caller must be arranging to
	// scan the younger generations itself. (For example, a generation might
	// explicitly mark reachable objects in younger generations, to avoid
	// excess storage retention.)
	// The "so" argument determines which of the roots
	// the closure is applied to:
	// "SO_None" does none;
	enum ScanningOption {
	SO_None = 0x0,
	SO_AllCodeCache = 0x8,
	SO_ScavengeCodeCache = 0x10
	};

	private:
	void process_roots(bool activate_scope,
	ScanningOption so,
	OopClosure* strong_roots,
	OopClosure* weak_roots,
	CLDClosure* strong_cld_closure,
	CLDClosure* weak_cld_closure,
	CodeBlobClosure* code_roots);

	void gen_process_roots(int level,
	bool younger_gens_as_roots,
	bool activate_scope,
	ScanningOption so,
	OopsInGenClosure* not_older_gens,
	OopsInGenClosure* weak_roots,
	OopsInGenClosure* older_gens,
	CLDClosure* cld_closure,
	CLDClosure* weak_cld_closure,
	CodeBlobClosure* code_closure);

	public:
	static const bool StrongAndWeakRoots = false;
	static const bool StrongRootsOnly = true;

	void gen_process_roots(int level,
	bool younger_gens_as_roots,
	bool activate_scope,
	ScanningOption so,
	bool only_strong_roots,
	OopsInGenClosure* not_older_gens,
	OopsInGenClosure* older_gens,
	CLDClosure* cld_closure);

	// Apply "root_closure" to all the weak roots of the system.
	// These include JNI weak roots, string table,
	// and referents of reachable weak refs.
	void gen_process_weak_roots(OopClosure* root_closure);

	// Set the saved marks of generations, if that makes sense.
	// In particular, if any generation might iterate over the oops
	// in other generations, it should call this method.
	void save_marks();

	// Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
	// allocated since the last call to save_marks in generations at or above
	// "level". The "cur" closure is
	// applied to references in the generation at "level", and the "older"
	// closure to older generations.
	#define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
	void oop_since_save_marks_iterate(int level, \
	OopClosureType* cur, \
	OopClosureType* older);

	ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)

	#undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL

	// Returns "true" iff no allocations have occurred in any generation at
	// "level" or above since the last
	// call to "save_marks".
	bool no_allocs_since_save_marks(int level);

	// Returns true if an incremental collection is likely to fail.
	// We optionally consult the young gen, if asked to do so;
	// otherwise we base our answer on whether the previous incremental
	// collection attempt failed with no corrective action as of yet.
	bool incremental_collection_will_fail(bool consult_young) {
	// Assumes a 2-generation system; the first disjunct remembers if an
	// incremental collection failed, even when we thought (second disjunct)
	// that it would not.
	assert(heap()->collector_policy()->is_two_generation_policy(),
	"the following definition may not be suitable for an n(>2)-generation system");
	return incremental_collection_failed() \|\|
	(consult_young && !get_gen(0)->collection_attempt_is_safe());
	}

	// If a generation bails out of an incremental collection,
	// it sets this flag.
	bool incremental_collection_failed() const {
	return _incremental_collection_failed;
	}
	void set_incremental_collection_failed() {
	_incremental_collection_failed = true;
	}
	void clear_incremental_collection_failed() {
	_incremental_collection_failed = false;
	}

	// Promotion of obj into gen failed. Try to promote obj to higher
	// gens in ascending order; return the new location of obj if successful.
	// Otherwise, try expand-and-allocate for obj in both the young and old
	// generation; return the new location of obj if successful. Otherwise, return NULL.
	oop handle_failed_promotion(Generation* old_gen,
	oop obj,
	size_t obj_size);

	private:
	// Accessor for memory state verification support
	NOT_PRODUCT(
	static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
	)

	// Override
	void check_for_non_bad_heap_word_value(HeapWord* addr,
	size_t size) PRODUCT_RETURN;

	// For use by mark-sweep. As implemented, mark-sweep-compact is global
	// in an essential way: compaction is performed across generations, by
	// iterating over spaces.
	void prepare_for_compaction();

	// Perform a full collection of the first max_level+1 generations.
	// This is the low level interface used by the public versions of
	// collect() and collect_locked(). Caller holds the Heap_lock on entry.
	void collect_locked(GCCause::Cause cause, int max_level);

	// Returns success or failure.
	bool create_cms_collector();

	// In support of ExplicitGCInvokesConcurrent functionality
	bool should_do_concurrent_full_gc(GCCause::Cause cause);
	void collect_mostly_concurrent(GCCause::Cause cause);

	// Save the tops of the spaces in all generations
	void record_gen_tops_before_GC() PRODUCT_RETURN;

	protected:
	virtual void gc_prologue(bool full);
	virtual void gc_epilogue(bool full);
	};

	#endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP