/*

 * Copyright 2001-2008 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.

 *

 */

// A "CollectedHeap" 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 BarrierSet;

class ThreadClosure;

class AdaptiveSizePolicy;

class Thread;

//

// CollectedHeap

//   SharedHeap

//     GenCollectedHeap

//     G1CollectedHeap

//   ParallelScavengeHeap

//

class CollectedHeap : public CHeapObj {

  friend class VMStructs;

  friend class IsGCActiveMark; // Block structured external access to _is_gc_active

#ifdef ASSERT

  static int       _fire_out_of_memory_count;

#endif

  // Used for filler objects (static, but initialized in ctor).

  static size_t _filler_array_max_size;

 protected:

  MemRegion _reserved;

  BarrierSet* _barrier_set;

  bool _is_gc_active;

  unsigned int _total_collections;          // ... started

  unsigned int _total_full_collections;     // ... started

  NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)

  NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)

  // Reason for current garbage collection.  Should be set to

  // a value reflecting no collection between collections.

  GCCause::Cause _gc_cause;

  GCCause::Cause _gc_lastcause;

  PerfStringVariable* _perf_gc_cause;

  PerfStringVariable* _perf_gc_lastcause;

  // Constructor

  CollectedHeap();

  // Create a new tlab

  virtual HeapWord* allocate_new_tlab(size_t size);

  // Fix up tlabs to make the heap well-formed again,

  // optionally retiring the tlabs.

  virtual void fill_all_tlabs(bool retire);

  // Accumulate statistics on all tlabs.

  virtual void accumulate_statistics_all_tlabs();

  // Reinitialize tlabs before resuming mutators.

  virtual void resize_all_tlabs();

  debug_only(static void check_for_valid_allocation_state();)

 protected:

  // Allocate from the current thread's TLAB, with broken-out slow path.

  inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);

  static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);

  // Allocate an uninitialized block of the given size, or returns NULL if

  // this is impossible.

  inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS);

  // Like allocate_init, but the block returned by a successful allocation

  // is guaranteed initialized to zeros.

  inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS);

  // Same as common_mem version, except memory is allocated in the permanent area

  // If there is no permanent area, revert to common_mem_allocate_noinit

  inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);

  // Same as common_mem version, except memory is allocated in the permanent area

  // If there is no permanent area, revert to common_mem_allocate_init

  inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);

  // Helper functions for (VM) allocation.

  inline static void post_allocation_setup_common(KlassHandle klass,

                                                  HeapWord* obj, size_t size);

  inline static void post_allocation_setup_no_klass_install(KlassHandle klass,

                                                            HeapWord* objPtr,

                                                            size_t size);

  inline static void post_allocation_setup_obj(KlassHandle klass,

                                               HeapWord* obj, size_t size);

  inline static void post_allocation_setup_array(KlassHandle klass,

                                                 HeapWord* obj, size_t size,

                                                 int length);

  // Clears an allocated object.

  inline static void init_obj(HeapWord* obj, size_t size);

  // Filler object utilities.

  static inline size_t filler_array_hdr_size();

  static inline size_t filler_array_min_size();

  static inline size_t filler_array_max_size();

  DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)

  DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words);)

  // Fill with a single array; caller must ensure filler_array_min_size() <=

  // words <= filler_array_max_size().

  static inline void fill_with_array(HeapWord* start, size_t words);

  // Fill with a single object (either an int array or a java.lang.Object).

  static inline void fill_with_object_impl(HeapWord* start, size_t words);

  // Verification functions

  virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)

    PRODUCT_RETURN;

  virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)

    PRODUCT_RETURN;

 public:

  enum Name {

    Abstract,

    SharedHeap,

    GenCollectedHeap,

    ParallelScavengeHeap,

    G1CollectedHeap

  };

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

  /**

   * Returns JNI error code JNI_ENOMEM if memory could not be allocated,

   * and JNI_OK on success.

   */

  virtual jint initialize() = 0;

  // In many heaps, there will be a need to perform some initialization activities

  // after the Universe is fully formed, but before general heap allocation is allowed.

  // This is the correct place to place such initialization methods.

  virtual void post_initialize() = 0;

  MemRegion reserved_region() const { return _reserved; }

  address base() const { return (address)reserved_region().start(); }

  // Future cleanup here. The following functions should specify bytes or

  // heapwords as part of their signature.

  virtual size_t capacity() const = 0;

  virtual size_t used() const = 0;

  // Return "true" if the part of the heap that allocates Java

  // objects has reached the maximal committed limit that it can

  // reach, without a garbage collection.

  virtual bool is_maximal_no_gc() const = 0;

  virtual size_t permanent_capacity() const = 0;

  virtual size_t permanent_used() const = 0;

  // Support for java.lang.Runtime.maxMemory():  return the maximum amount of

  // memory that the vm could make available for storing 'normal' java objects.

  // This is based on the reserved address space, but should not include space

  // that the vm uses internally for bookkeeping or temporary storage (e.g.,

  // perm gen space or, in the case of the young gen, one of the survivor

  // spaces).

  virtual size_t max_capacity() const = 0;

  // Returns "TRUE" if "p" points into the reserved area of the heap.

  bool is_in_reserved(const void* p) const {

    return _reserved.contains(p);

  }

  bool is_in_reserved_or_null(const void* p) const {

    return p == NULL || is_in_reserved(p);

  }

  // Returns "TRUE" if "p" points to the head of an allocated object in the

  // heap. Since this method can be expensive in general, we restrict its

  // use to assertion checking only.

  virtual bool is_in(const void* p) const = 0;

  bool is_in_or_null(const void* p) const {

    return p == NULL || is_in(p);

  }

  // Let's define some terms: a "closed" subset of a heap is one that

  //

  // 1) contains all currently-allocated objects, and

  //

  // 2) is closed under reference: no object in the closed subset

  //    references one outside the closed subset.

  //

  // Membership in a heap's closed subset is useful for assertions.

  // Clearly, the entire heap is a closed subset, so the default

  // implementation is to use "is_in_reserved".  But this may not be too

  // liberal to perform useful checking.  Also, the "is_in" predicate

  // defines a closed subset, but may be too expensive, since "is_in"

  // verifies that its argument points to an object head.  The

  // "closed_subset" method allows a heap to define an intermediate

  // predicate, allowing more precise checking than "is_in_reserved" at

  // lower cost than "is_in."

  // One important case is a heap composed of disjoint contiguous spaces,

  // such as the Garbage-First collector.  Such heaps have a convenient

  // closed subset consisting of the allocated portions of those

  // contiguous spaces.

  // Return "TRUE" iff the given pointer points into the heap's defined

  // closed subset (which defaults to the entire heap).

  virtual bool is_in_closed_subset(const void* p) const {

    return is_in_reserved(p);

  }

  bool is_in_closed_subset_or_null(const void* p) const {

    return p == NULL || is_in_closed_subset(p);

  }

  // Returns "TRUE" if "p" is allocated as "permanent" data.

  // If the heap does not use "permanent" data, returns the same

  // value is_in_reserved() would return.

  // NOTE: this actually returns true if "p" is in reserved space

  // for the space not that it is actually allocated (i.e. in committed

  // space). If you need the more conservative answer use is_permanent().

  virtual bool is_in_permanent(const void *p) const = 0;

  // Returns "TRUE" if "p" is in the committed area of  "permanent" data.

  // If the heap does not use "permanent" data, returns the same

  // value is_in() would return.

  virtual bool is_permanent(const void *p) const = 0;

  bool is_in_permanent_or_null(const void *p) const {

    return p == NULL || is_in_permanent(p);

  }

  // Returns "TRUE" if "p" is a method oop in the

  // current heap, with high probability. This predicate

  // is not stable, in general.

  bool is_valid_method(oop p) const;

  void set_gc_cause(GCCause::Cause v) {

     if (UsePerfData) {

       _gc_lastcause = _gc_cause;

       _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));

       _perf_gc_cause->set_value(GCCause::to_string(v));

     }

    _gc_cause = v;

  }

  GCCause::Cause gc_cause() { return _gc_cause; }

  // Preload classes into the shared portion of the heap, and then dump

  // that data to a file so that it can be loaded directly by another

  // VM (then terminate).

  virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }

  // General obj/array allocation facilities.

  inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);

  inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);

  inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS);

  // Special obj/array allocation facilities.

  // Some heaps may want to manage "permanent" data uniquely. These default

  // to the general routines if the heap does not support such handling.

  inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);

  // permanent_obj_allocate_no_klass_install() does not do the installation of

  // the klass pointer in the newly created object (as permanent_obj_allocate()

  // above does).  This allows for a delay in the installation of the klass

  // pointer that is needed during the create of klassKlass's.  The

  // method post_allocation_install_obj_klass() is used to install the

  // klass pointer.

  inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,

                                                            int size,

                                                            TRAPS);

  inline static void post_allocation_install_obj_klass(KlassHandle klass,

                                                       oop obj,

                                                       int size);

  inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);

  // Raw memory allocation facilities

  // The obj and array allocate methods are covers for these methods.

  // The permanent allocation method should default to mem_allocate if

  // permanent memory isn't supported.

  virtual HeapWord* mem_allocate(size_t size,

                                 bool is_noref,

                                 bool is_tlab,

                                 bool* gc_overhead_limit_was_exceeded) = 0;

  virtual HeapWord* permanent_mem_allocate(size_t size) = 0;

  // The boundary between a "large" and "small" array of primitives, in words.

  virtual size_t large_typearray_limit() = 0;

  // Utilities for turning raw memory into filler objects.

  //

  // min_fill_size() is the smallest region that can be filled.

  // fill_with_objects() can fill arbitrary-sized regions of the heap using

  // multiple objects.  fill_with_object() is for regions known to be smaller

  // than the largest array of integers; it uses a single object to fill the

  // region and has slightly less overhead.

  static size_t min_fill_size() {

    return size_t(align_object_size(oopDesc::header_size()));

  }

  static void fill_with_objects(HeapWord* start, size_t words);

  static void fill_with_object(HeapWord* start, size_t words);

  static void fill_with_object(MemRegion region) {

    fill_with_object(region.start(), region.word_size());

  }

  static void fill_with_object(HeapWord* start, HeapWord* end) {

    fill_with_object(start, pointer_delta(end, start));

  }

  // Some heaps may offer a contiguous region for shared non-blocking

  // allocation, via inlined code (by exporting the address of the top and

  // end fields defining the extent of the contiguous allocation region.)

  // This function returns "true" iff the heap supports this kind of

  // allocation.  (Default is "no".)

  virtual bool supports_inline_contig_alloc() const {

    return false;

  }

  // These functions return the addresses of the fields that define the

  // boundaries of the contiguous allocation area.  (These fields should be

  // physically near to one another.)

  virtual HeapWord** top_addr() const {

    guarantee(false, "inline contiguous allocation not supported");

    return NULL;

  }

  virtual HeapWord** end_addr() const {

    guarantee(false, "inline contiguous allocation not supported");

    return NULL;

  }

  // Some heaps may be in an unparseable state at certain times between

  // collections. This may be necessary for efficient implementation of

  // certain allocation-related activities. Calling this function before

  // attempting to parse a heap ensures that the heap is in a parsable

  // state (provided other concurrent activity does not introduce

  // unparsability). It is normally expected, therefore, that this

  // method is invoked with the world stopped.

  // NOTE: if you override this method, make sure you call

  // super::ensure_parsability so that the non-generational

  // part of the work gets done. See implementation of

  // CollectedHeap::ensure_parsability and, for instance,

  // that of GenCollectedHeap::ensure_parsability().

  // The argument "retire_tlabs" controls whether existing TLABs

  // are merely filled or also retired, thus preventing further

  // allocation from them and necessitating allocation of new TLABs.

  virtual void ensure_parsability(bool retire_tlabs);

  // Return an estimate of the maximum allocation that could be performed

  // without triggering any collection or expansion activity.  In a

  // generational collector, for example, this is probably the largest

  // allocation that could be supported (without expansion) in the youngest

  // generation.  It is "unsafe" because no locks are taken; the result

  // should be treated as an approximation, not a guarantee, for use in

  // heuristic resizing decisions.

  virtual size_t unsafe_max_alloc() = 0;

  // Section on thread-local allocation buffers (TLABs)

  // If the heap supports thread-local allocation buffers, it should override

  // the following methods:

  // Returns "true" iff the heap supports thread-local allocation buffers.

  // The default is "no".

  virtual bool supports_tlab_allocation() const {

    return false;

  }

  // The amount of space available for thread-local allocation buffers.

  virtual size_t tlab_capacity(Thread *thr) const {

    guarantee(false, "thread-local allocation buffers not supported");

    return 0;

  }

  // An estimate of the maximum allocation that could be performed

  // for thread-local allocation buffers without triggering any

  // collection or expansion activity.

  virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {

    guarantee(false, "thread-local allocation buffers not supported");

    return 0;

  }

  // 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 = 0;

  // If a compiler is eliding store barriers for TLAB-allocated objects,

  // there is probably a corresponding slow path which can produce

  // an object allocated anywhere.  The compiler's runtime support

  // promises to call this function on such a slow-path-allocated

  // object before performing initializations that have elided

  // store barriers.  Returns new_obj, or maybe a safer copy thereof.

  virtual oop new_store_barrier(oop new_obj);

  // Can a compiler elide a store barrier when it writes

  // a permanent oop into the heap?  Applies when the compiler

  // is storing x to the heap, where x->is_perm() is true.

  virtual bool can_elide_permanent_oop_store_barriers() const = 0;

  // Does this heap support heap inspection (+PrintClassHistogram?)

  virtual bool supports_heap_inspection() const = 0;

  // Perform a collection of the heap; intended for use in implementing

  // "System.gc".  This probably implies as full a collection as the

  // "CollectedHeap" supports.

  virtual void collect(GCCause::Cause cause) = 0;

  // This interface assumes that it's being called by the

  // vm thread. It collects the heap assuming that the

  // heap lock is already held and that we are executing in

  // the context of the vm thread.

  virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;

  // Returns the barrier set for this heap

  BarrierSet* barrier_set() { return _barrier_set; }

  // Returns "true" iff there is a stop-world GC in progress.  (I assume

  // that it should answer "false" for the concurrent part of a concurrent

  // collector -- dld).

  bool is_gc_active() const { return _is_gc_active; }

  // Total number of GC collections (started)

  unsigned int total_collections() const { return _total_collections; }

  unsigned int total_full_collections() const { return _total_full_collections;}

  // Increment total number of GC collections (started)

  // Should be protected but used by PSMarkSweep - cleanup for 1.4.2

  void increment_total_collections(bool full = false) {

    _total_collections++;

    if (full) {

      increment_total_full_collections();

    }

  }

  void increment_total_full_collections() { _total_full_collections++; }

  // Return the AdaptiveSizePolicy for the heap.

  virtual AdaptiveSizePolicy* size_policy() = 0;

  // Iterate over all the ref-containing fields of all objects, calling

  // "cl.do_oop" on each. This includes objects in permanent memory.

  virtual void oop_iterate(OopClosure* cl) = 0;

  // Iterate over all objects, calling "cl.do_object" on each.

  // This includes objects in permanent memory.

  virtual void object_iterate(ObjectClosure* cl) = 0;

  // Behaves the same as oop_iterate, except only traverses

  // interior pointers contained in permanent memory. If there

  // is no permanent memory, does nothing.

  virtual void permanent_oop_iterate(OopClosure* cl) = 0;

  // Behaves the same as object_iterate, except only traverses

  // object contained in permanent memory. If there is no

  // permanent memory, does nothing.

  virtual void permanent_object_iterate(ObjectClosure* cl) = 0;

  // NOTE! There is no requirement that a collector implement these

  // functions.

  //

  // 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 = 0;

  // 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.

  virtual size_t block_size(const HeapWord* addr) const = 0;

  // Requires "addr" to be the start of a block, and returns "TRUE" iff

  // the block is an object.

  virtual bool block_is_obj(const HeapWord* addr) const = 0;

  // Returns the longest time (in ms) that has elapsed since the last

  // time that any part of the heap was examined by a garbage collection.

  virtual jlong millis_since_last_gc() = 0;

  // Perform any cleanup actions necessary before allowing a verification.

  virtual void prepare_for_verify() = 0;

  virtual void print() const = 0;

  virtual void print_on(outputStream* st) const = 0;

  // Print all GC threads (other than the VM thread)

  // used by this heap.

  virtual void print_gc_threads_on(outputStream* st) const = 0;

  void print_gc_threads() { print_gc_threads_on(tty); }

  // Iterator for all GC threads (other than VM thread)