/*

 * Copyright (c) 2001, 2015, 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_GC_G1_HEAPREGION_HPP

#define SHARE_VM_GC_G1_HEAPREGION_HPP

#include "gc/g1/g1AllocationContext.hpp"

#include "gc/g1/g1BlockOffsetTable.hpp"

#include "gc/g1/heapRegionType.hpp"

#include "gc/g1/survRateGroup.hpp"

#include "gc/shared/ageTable.hpp"

#include "gc/shared/spaceDecorator.hpp"

#include "utilities/macros.hpp"

// A HeapRegion is the smallest piece of a G1CollectedHeap that

// can be collected independently.

// NOTE: Although a HeapRegion is a Space, its

// Space::initDirtyCardClosure method must not be called.

// The problem is that the existence of this method breaks

// the independence of barrier sets from remembered sets.

// The solution is to remove this method from the definition

// of a Space.

// Each heap region is self contained. top() and end() can never

// be set beyond the end of the region. For humongous objects,

// the first region is a StartsHumongous region. If the humongous

// object is larger than a heap region, the following regions will

// be of type ContinuesHumongous. In this case the top() of the

// StartHumongous region and all ContinuesHumongous regions except

// the last will point to their own end. For the last ContinuesHumongous

// region, top() will equal the object's top.

class G1CollectedHeap;

class HeapRegionRemSet;

class HeapRegionRemSetIterator;

class HeapRegion;

class HeapRegionSetBase;

class nmethod;

#define HR_FORMAT "%u:(%s)[" PTR_FORMAT "," PTR_FORMAT "," PTR_FORMAT "]"

#define HR_FORMAT_PARAMS(_hr_) \

                (_hr_)->hrm_index(), \

                (_hr_)->get_short_type_str(), \

                p2i((_hr_)->bottom()), p2i((_hr_)->top()), p2i((_hr_)->end())

// sentinel value for hrm_index

#define G1_NO_HRM_INDEX ((uint) -1)

// A dirty card to oop closure for heap regions. It

// knows how to get the G1 heap and how to use the bitmap

// in the concurrent marker used by G1 to filter remembered

// sets.

class HeapRegionDCTOC : public DirtyCardToOopClosure {

private:

  HeapRegion* _hr;

  G1ParPushHeapRSClosure* _rs_scan;

  G1CollectedHeap* _g1;

  // Walk the given memory region from bottom to (actual) top

  // looking for objects and applying the oop closure (_cl) to

  // them. The base implementation of this treats the area as

  // blocks, where a block may or may not be an object. Sub-

  // classes should override this to provide more accurate

  // or possibly more efficient walking.

  void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);

public:

  HeapRegionDCTOC(G1CollectedHeap* g1,

                  HeapRegion* hr,

                  G1ParPushHeapRSClosure* cl,

                  CardTableModRefBS::PrecisionStyle precision);

};

// The complicating factor is that BlockOffsetTable diverged

// significantly, and we need functionality that is only in the G1 version.

// So I copied that code, which led to an alternate G1 version of

// OffsetTableContigSpace.  If the two versions of BlockOffsetTable could

// be reconciled, then G1OffsetTableContigSpace could go away.

// The idea behind time stamps is the following. We want to keep track of

// the highest address where it's safe to scan objects for each region.

// This is only relevant for current GC alloc regions so we keep a time stamp

// per region to determine if the region has been allocated during the current

// GC or not. If the time stamp is current we report a scan_top value which

// was saved at the end of the previous GC for retained alloc regions and which is

// equal to the bottom for all other regions.

// There is a race between card scanners and allocating gc workers where we must ensure

// that card scanners do not read the memory allocated by the gc workers.

// In order to enforce that, we must not return a value of _top which is more recent than the

// time stamp. This is due to the fact that a region may become a gc alloc region at

// some point after we've read the timestamp value as being < the current time stamp.

// The time stamps are re-initialized to zero at cleanup and at Full GCs.

// The current scheme that uses sequential unsigned ints will fail only if we have 4b

// evacuation pauses between two cleanups, which is _highly_ unlikely.

class G1OffsetTableContigSpace: public CompactibleSpace {

  friend class VMStructs;

  HeapWord* volatile _top;

  HeapWord* volatile _scan_top;

 protected:

  G1BlockOffsetArrayContigSpace _offsets;

  Mutex _par_alloc_lock;

  volatile unsigned _gc_time_stamp;

  // When we need to retire an allocation region, while other threads

  // are also concurrently trying to allocate into it, we typically

  // allocate a dummy object at the end of the region to ensure that

  // no more allocations can take place in it. However, sometimes we

  // want to know where the end of the last "real" object we allocated

  // into the region was and this is what this keeps track.

  HeapWord* _pre_dummy_top;

 public:

  G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,

                           MemRegion mr);

  void set_top(HeapWord* value) { _top = value; }

  HeapWord* top() const { return _top; }

 protected:

  // Reset the G1OffsetTableContigSpace.

  virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);

  HeapWord* volatile* top_addr() { return &_top; }

  // Try to allocate at least min_word_size and up to desired_size from this Space.

  // Returns NULL if not possible, otherwise sets actual_word_size to the amount of

  // space allocated.

  // This version assumes that all allocation requests to this Space are properly

  // synchronized.

  inline HeapWord* allocate_impl(size_t min_word_size, size_t desired_word_size, size_t* actual_word_size);

  // Try to allocate at least min_word_size and up to desired_size from this Space.

  // Returns NULL if not possible, otherwise sets actual_word_size to the amount of

  // space allocated.

  // This version synchronizes with other calls to par_allocate_impl().

  inline HeapWord* par_allocate_impl(size_t min_word_size, size_t desired_word_size, size_t* actual_word_size);

 public:

  void reset_after_compaction() { set_top(compaction_top()); }

  size_t used() const { return byte_size(bottom(), top()); }

  size_t free() const { return byte_size(top(), end()); }

  bool is_free_block(const HeapWord* p) const { return p >= top(); }

  MemRegion used_region() const { return MemRegion(bottom(), top()); }

  void object_iterate(ObjectClosure* blk);

  void safe_object_iterate(ObjectClosure* blk);

  void set_bottom(HeapWord* value);

  void set_end(HeapWord* value);

  void mangle_unused_area() PRODUCT_RETURN;

  void mangle_unused_area_complete() PRODUCT_RETURN;

  HeapWord* scan_top() const;

  void record_timestamp();

  void reset_gc_time_stamp() { _gc_time_stamp = 0; }

  unsigned get_gc_time_stamp() { return _gc_time_stamp; }

  void record_retained_region();

  // See the comment above in the declaration of _pre_dummy_top for an

  // explanation of what it is.

  void set_pre_dummy_top(HeapWord* pre_dummy_top) {

    assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");

    _pre_dummy_top = pre_dummy_top;

  }

  HeapWord* pre_dummy_top() {

    return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;

  }

  void reset_pre_dummy_top() { _pre_dummy_top = NULL; }

  virtual void clear(bool mangle_space);

  HeapWord* block_start(const void* p);

  HeapWord* block_start_const(const void* p) const;

  // Allocation (return NULL if full).  Assumes the caller has established

  // mutually exclusive access to the space.

  HeapWord* allocate(size_t min_word_size, size_t desired_word_size, size_t* actual_word_size);

  // Allocation (return NULL if full).  Enforces mutual exclusion internally.

  HeapWord* par_allocate(size_t min_word_size, size_t desired_word_size, size_t* actual_word_size);

  virtual HeapWord* allocate(size_t word_size);

  virtual HeapWord* par_allocate(size_t word_size);

  HeapWord* saved_mark_word() const { ShouldNotReachHere(); return NULL; }

  // MarkSweep support phase3

  virtual HeapWord* initialize_threshold();

  virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);

  virtual void print() const;

  void reset_bot() {

    _offsets.reset_bot();

  }

  void print_bot_on(outputStream* out) {

    _offsets.print_on(out);

  }

};

class HeapRegion: public G1OffsetTableContigSpace {

  friend class VMStructs;

  // Allow scan_and_forward to call (private) overrides for auxiliary functions on this class

  template <typename SpaceType>

  friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);

 private:

  // The remembered set for this region.

  // (Might want to make this "inline" later, to avoid some alloc failure

  // issues.)

  HeapRegionRemSet* _rem_set;

  G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }

  // Auxiliary functions for scan_and_forward support.

  // See comments for CompactibleSpace for more information.

  inline HeapWord* scan_limit() const {

    return top();

  }

  inline bool scanned_block_is_obj(const HeapWord* addr) const {

    return true; // Always true, since scan_limit is top

  }

  inline size_t scanned_block_size(const HeapWord* addr) const {

    return HeapRegion::block_size(addr); // Avoid virtual call

  }

 protected:

  // The index of this region in the heap region sequence.

  uint  _hrm_index;

  AllocationContext_t _allocation_context;

  HeapRegionType _type;

  // For a humongous region, region in which it starts.

  HeapRegion* _humongous_start_region;

  // True iff an attempt to evacuate an object in the region failed.

  bool _evacuation_failed;

  // A heap region may be a member one of a number of special subsets, each

  // represented as linked lists through the field below.  Currently, there

  // is only one set:

  //   The collection set.

  HeapRegion* _next_in_special_set;

  // next region in the young "generation" region set

  HeapRegion* _next_young_region;

  // Next region whose cards need cleaning

  HeapRegion* _next_dirty_cards_region;

  // Fields used by the HeapRegionSetBase class and subclasses.

  HeapRegion* _next;

  HeapRegion* _prev;

#ifdef ASSERT

  HeapRegionSetBase* _containing_set;

#endif // ASSERT

  // We use concurrent marking to determine the amount of live data

  // in each heap region.

  size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.

  size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.

  // The calculated GC efficiency of the region.

  double _gc_efficiency;

  int  _young_index_in_cset;

  SurvRateGroup* _surv_rate_group;

  int  _age_index;

  // The start of the unmarked area. The unmarked area extends from this

  // word until the top and/or end of the region, and is the part

  // of the region for which no marking was done, i.e. objects may

  // have been allocated in this part since the last mark phase.

  // "prev" is the top at the start of the last completed marking.

  // "next" is the top at the start of the in-progress marking (if any.)

  HeapWord* _prev_top_at_mark_start;

  HeapWord* _next_top_at_mark_start;

  // If a collection pause is in progress, this is the top at the start

  // of that pause.

  void init_top_at_mark_start() {

    assert(_prev_marked_bytes == 0 &&

           _next_marked_bytes == 0,

           "Must be called after zero_marked_bytes.");

    HeapWord* bot = bottom();

    _prev_top_at_mark_start = bot;

    _next_top_at_mark_start = bot;

  }

  // Cached attributes used in the collection set policy information

  // The RSet length that was added to the total value

  // for the collection set.

  size_t _recorded_rs_length;

  // The predicted elapsed time that was added to total value

  // for the collection set.

  double _predicted_elapsed_time_ms;

  // The predicted number of bytes to copy that was added to

  // the total value for the collection set.

  size_t _predicted_bytes_to_copy;

 public:

  HeapRegion(uint hrm_index,

             G1BlockOffsetSharedArray* sharedOffsetArray,

             MemRegion mr);

  // Initializing the HeapRegion not only resets the data structure, but also

  // resets the BOT for that heap region.

  // The default values for clear_space means that we will do the clearing if

  // there's clearing to be done ourselves. We also always mangle the space.

  virtual void initialize(MemRegion mr, bool clear_space = false, bool mangle_space = SpaceDecorator::Mangle);

  static int    LogOfHRGrainBytes;

  static int    LogOfHRGrainWords;

  static size_t GrainBytes;

  static size_t GrainWords;

  static size_t CardsPerRegion;

  static size_t align_up_to_region_byte_size(size_t sz) {

    return (sz + (size_t) GrainBytes - 1) &

                                      ~((1 << (size_t) LogOfHRGrainBytes) - 1);

  }

  static size_t max_region_size();

  static size_t min_region_size_in_words();

  // It sets up the heap region size (GrainBytes / GrainWords), as

  // well as other related fields that are based on the heap region

  // size (LogOfHRGrainBytes / LogOfHRGrainWords /

  // CardsPerRegion). All those fields are considered constant

  // throughout the JVM's execution, therefore they should only be set

  // up once during initialization time.

  static void setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size);

  // All allocated blocks are occupied by objects in a HeapRegion

  bool block_is_obj(const HeapWord* p) const;

  // Returns the object size for all valid block starts

  // and the amount of unallocated words if called on top()

  size_t block_size(const HeapWord* p) const;

  // Override for scan_and_forward support.

  void prepare_for_compaction(CompactPoint* cp);

  inline HeapWord* par_allocate_no_bot_updates(size_t min_word_size, size_t desired_word_size, size_t* word_size);

  inline HeapWord* allocate_no_bot_updates(size_t word_size);

  inline HeapWord* allocate_no_bot_updates(size_t min_word_size, size_t desired_word_size, size_t* actual_size);

  // If this region is a member of a HeapRegionManager, the index in that

  // sequence, otherwise -1.

  uint hrm_index() const { return _hrm_index; }

  // The number of bytes marked live in the region in the last marking phase.

  size_t marked_bytes()    { return _prev_marked_bytes; }

  size_t live_bytes() {

    return (top() - prev_top_at_mark_start()) * HeapWordSize + marked_bytes();

  }

  // The number of bytes counted in the next marking.

  size_t next_marked_bytes() { return _next_marked_bytes; }

  // The number of bytes live wrt the next marking.

  size_t next_live_bytes() {

    return

      (top() - next_top_at_mark_start()) * HeapWordSize + next_marked_bytes();

  }

  // A lower bound on the amount of garbage bytes in the region.

  size_t garbage_bytes() {

    size_t used_at_mark_start_bytes =

      (prev_top_at_mark_start() - bottom()) * HeapWordSize;

    return used_at_mark_start_bytes - marked_bytes();

  }

  // Return the amount of bytes we'll reclaim if we collect this

  // region. This includes not only the known garbage bytes in the

  // region but also any unallocated space in it, i.e., [top, end),

  // since it will also be reclaimed if we collect the region.

  size_t reclaimable_bytes() {

    size_t known_live_bytes = live_bytes();

    assert(known_live_bytes <= capacity(), "sanity");

    return capacity() - known_live_bytes;

  }

  // An upper bound on the number of live bytes in the region.

  size_t max_live_bytes() { return used() - garbage_bytes(); }

  void add_to_marked_bytes(size_t incr_bytes) {

    _next_marked_bytes = _next_marked_bytes + incr_bytes;

  }

  void zero_marked_bytes()      {

    _prev_marked_bytes = _next_marked_bytes = 0;

  }

  const char* get_type_str() const { return _type.get_str(); }

  const char* get_short_type_str() const { return _type.get_short_str(); }

  bool is_free() const { return _type.is_free(); }

  bool is_young()    const { return _type.is_young();    }

  bool is_eden()     const { return _type.is_eden();     }

  bool is_survivor() const { return _type.is_survivor(); }

  bool is_humongous() const { return _type.is_humongous(); }

  bool is_starts_humongous() const { return _type.is_starts_humongous(); }

  bool is_continues_humongous() const { return _type.is_continues_humongous();   }

  bool is_old() const { return _type.is_old(); }

  // A pinned region contains objects which are not moved by garbage collections.

  // Humongous regions and archive regions are pinned.

  bool is_pinned() const { return _type.is_pinned(); }

  // An archive region is a pinned region, also tagged as old, which

  // should not be marked during mark/sweep. This allows the address

  // space to be shared by JVM instances.

  bool is_archive() const { return _type.is_archive(); }

  // For a humongous region, region in which it starts.

  HeapRegion* humongous_start_region() const {

    return _humongous_start_region;

  }

  // Makes the current region be a "starts humongous" region, i.e.,

  // the first region in a series of one or more contiguous regions

  // that will contain a single "humongous" object.

  //

  // obj_top : points to the top of the humongous object.

  // fill_size : size of the filler object at the end of the region series.

  void set_starts_humongous(HeapWord* obj_top, size_t fill_size);

  // Makes the current region be a "continues humongous'

  // region. first_hr is the "start humongous" region of the series

  // which this region will be part of.

  void set_continues_humongous(HeapRegion* first_hr);

  // Unsets the humongous-related fields on the region.

  void clear_humongous();

  // If the region has a remembered set, return a pointer to it.

  HeapRegionRemSet* rem_set() const {

    return _rem_set;

  }

  inline bool in_collection_set() const;

  inline HeapRegion* next_in_collection_set() const;

  inline void set_next_in_collection_set(HeapRegion* r);

  void set_allocation_context(AllocationContext_t context) {

    _allocation_context = context;

  }

  AllocationContext_t  allocation_context() const {

    return _allocation_context;

  }

  // Methods used by the HeapRegionSetBase class and subclasses.

  // Getter and setter for the next and prev fields used to link regions into

  // linked lists.

  HeapRegion* next()              { return _next; }

  HeapRegion* prev()              { return _prev; }

  void set_next(HeapRegion* next) { _next = next; }

  void set_prev(HeapRegion* prev) { _prev = prev; }

  // Every region added to a set is tagged with a reference to that