heapRegionSet.hpp

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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSET_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSET_HPP

#include "gc_implementation/g1/heapRegion.hpp"

// Large buffer for some cases where the output might be larger than normal.
#define HRS_ERR_MSG_BUFSZ 512
typedef FormatBuffer<HRS_ERR_MSG_BUFSZ> hrs_err_msg;

// Set verification will be forced either if someone defines
// HEAP_REGION_SET_FORCE_VERIFY to be 1, or in builds in which
// asserts are compiled in.
#ifndef HEAP_REGION_SET_FORCE_VERIFY
#define HEAP_REGION_SET_FORCE_VERIFY defined(ASSERT)
#endif // HEAP_REGION_SET_FORCE_VERIFY

class hrs_ext_msg;

class HRSMtSafeChecker : public CHeapObj<mtGC> {
public:
  virtual void check() = 0;
};

class MasterFreeRegionListMtSafeChecker    : public HRSMtSafeChecker { public: void check(); };
class SecondaryFreeRegionListMtSafeChecker : public HRSMtSafeChecker { public: void check(); };
class HumongousRegionSetMtSafeChecker      : public HRSMtSafeChecker { public: void check(); };
class OldRegionSetMtSafeChecker            : public HRSMtSafeChecker { public: void check(); };

class HeapRegionSetCount VALUE_OBJ_CLASS_SPEC {
  friend class VMStructs;
  uint   _length;
  size_t _capacity;

public:
  HeapRegionSetCount() : _length(0), _capacity(0) { }

  const uint   length()   const { return _length;   }
  const size_t capacity() const { return _capacity; }

  void increment(uint length_to_add, size_t capacity_to_add) {
    _length += length_to_add;
    _capacity += capacity_to_add;
  }

  void decrement(const uint length_to_remove, const size_t capacity_to_remove) {
    _length -= length_to_remove;
    _capacity -= capacity_to_remove;
  }
};

// Base class for all the classes that represent heap region sets. It
// contains the basic attributes that each set needs to maintain
// (e.g., length, region num, used bytes sum) plus any shared
// functionality (e.g., verification).

class HeapRegionSetBase VALUE_OBJ_CLASS_SPEC {
  friend class VMStructs;
private:
  bool _is_humongous;
  bool _is_empty;
  HRSMtSafeChecker* _mt_safety_checker;

protected:
  // The number of regions added to the set. If the set contains
  // only humongous regions, this reflects only 'starts humongous'
  // regions and does not include 'continues humongous' ones.
  HeapRegionSetCount _count;

  const char* _name;

  bool _verify_in_progress;

  // verify_region() is used to ensure that the contents of a region
  // added to / removed from a set are consistent.
  void verify_region(HeapRegion* hr) PRODUCT_RETURN;

  // Indicates whether all regions in the set should be humongous or
  // not. Only used during verification.
  bool regions_humongous() { return _is_humongous; }

  // Indicates whether all regions in the set should be empty or
  // not. Only used during verification.
  bool regions_empty() { return _is_empty; }

  void check_mt_safety() {
    if (_mt_safety_checker != NULL) {
      _mt_safety_checker->check();
    }
  }

  virtual void fill_in_ext_msg_extra(hrs_ext_msg* msg) { }

  HeapRegionSetBase(const char* name, bool humongous, bool empty, HRSMtSafeChecker* mt_safety_checker);

public:
  const char* name() { return _name; }

  uint length() { return _count.length(); }

  bool is_empty() { return _count.length() == 0; }

  size_t total_capacity_bytes() {
    return _count.capacity();
  }

  // It updates the fields of the set to reflect hr being added to
  // the set and tags the region appropriately.
  inline void add(HeapRegion* hr);

  // It updates the fields of the set to reflect hr being removed
  // from the set and tags the region appropriately.
  inline void remove(HeapRegion* hr);

  // fill_in_ext_msg() writes the the values of the set's attributes
  // in the custom err_msg (hrs_ext_msg). fill_in_ext_msg_extra()
  // allows subclasses to append further information.
  void fill_in_ext_msg(hrs_ext_msg* msg, const char* message);

  virtual void verify();
  void verify_start();
  void verify_next_region(HeapRegion* hr);
  void verify_end();

#if HEAP_REGION_SET_FORCE_VERIFY
  void verify_optional() {
    verify();
  }
#else // HEAP_REGION_SET_FORCE_VERIFY
  void verify_optional() { }
#endif // HEAP_REGION_SET_FORCE_VERIFY

  virtual void print_on(outputStream* out, bool print_contents = false);
};

// Customized err_msg for heap region sets. Apart from a
// assert/guarantee-specific message it also prints out the values of
// the fields of the associated set. This can be very helpful in
// diagnosing failures.
class hrs_ext_msg : public hrs_err_msg {
public:
  hrs_ext_msg(HeapRegionSetBase* set, const char* message) : hrs_err_msg("") {
    set->fill_in_ext_msg(this, message);
  }
};

#define hrs_assert_sets_match(_set1_, _set2_)                                 \
  do {                                                                        \
    assert(((_set1_)->regions_humongous() ==                                  \
                                            (_set2_)->regions_humongous()) && \
           ((_set1_)->regions_empty() == (_set2_)->regions_empty()),          \
           hrs_err_msg("the contents of set %s and set %s should match",      \
                       (_set1_)->name(), (_set2_)->name()));                  \
  } while (0)

// This class represents heap region sets whose members are not
// explicitly tracked. It's helpful to group regions using such sets
// so that we can reason about all the region groups in the heap using
// the same interface (namely, the HeapRegionSetBase API).

class HeapRegionSet : public HeapRegionSetBase {
public:
  HeapRegionSet(const char* name, bool humongous, HRSMtSafeChecker* mt_safety_checker):
    HeapRegionSetBase(name, humongous, false /* empty */, mt_safety_checker) { }

  void bulk_remove(const HeapRegionSetCount& removed) {
    _count.decrement(removed.length(), removed.capacity());
  }
};

// A set that links all the regions added to it in a doubly-linked
// list. We should try to avoid doing operations that iterate over
// such lists in performance critical paths. Typically we should
// add / remove one region at a time or concatenate two lists. There are
// two ways to treat your lists, ordered and un-ordered. All un-ordered
// operations are done in constant time. To keep a list ordered only use
// add_ordered() to add elements to the list. If a list is not ordered
// from start, there is no way to sort it later.

class FreeRegionListIterator;

class FreeRegionList : public HeapRegionSetBase {
  friend class FreeRegionListIterator;

private:
  HeapRegion* _head;
  HeapRegion* _tail;

  // _last is used to keep track of where we added an element the last
  // time in ordered lists. It helps to improve performance when adding
  // several ordered items in a row.
  HeapRegion* _last;

  static uint _unrealistically_long_length;

  void add_as_head_or_tail(FreeRegionList* from_list, bool as_head);

protected:
  virtual void fill_in_ext_msg_extra(hrs_ext_msg* msg);

  // See the comment for HeapRegionSetBase::clear()
  virtual void clear();

public:
  FreeRegionList(const char* name, HRSMtSafeChecker* mt_safety_checker = NULL):
    HeapRegionSetBase(name, false /* humongous */, true /* empty */, mt_safety_checker) {
    clear();
  }

  void verify_list();

  HeapRegion* head() { return _head; }
  HeapRegion* tail() { return _tail; }

  static void set_unrealistically_long_length(uint len);

  // Add hr to the list. The region should not be a member of another set.
  // Assumes that the list is ordered and will preserve that order. The order
  // is determined by hrs_index.
  inline void add_ordered(HeapRegion* hr);

  // It adds hr to the list as the new head. The region should not be
  // a member of another set.
  inline void add_as_head(HeapRegion* hr);

  // It adds hr to the list as the new tail. The region should not be
  // a member of another set.
  inline void add_as_tail(HeapRegion* hr);

  // It removes and returns the head of the list. It assumes that the
  // list is not empty so it will return a non-NULL value.
  inline HeapRegion* remove_head();

  // Convenience method.
  inline HeapRegion* remove_head_or_null();

  // Removes and returns the last element (_tail) of the list. It assumes
  // that the list isn't empty so that it can return a non-NULL value.
  inline HeapRegion* remove_tail();

  // Convenience method
  inline HeapRegion* remove_tail_or_null();

  // Removes from head or tail based on the given argument.
  inline HeapRegion* remove_region(bool from_head);

  // Merge two ordered lists. The result is also ordered. The order is
  // determined by hrs_index.
  void add_ordered(FreeRegionList* from_list);

  // It moves the regions from from_list to this list and empties
  // from_list. The new regions will appear in the same order as they
  // were in from_list and be linked in the beginning of this list.
  void add_as_head(FreeRegionList* from_list);

  // It moves the regions from from_list to this list and empties
  // from_list. The new regions will appear in the same order as they
  // were in from_list and be linked in the end of this list.
  void add_as_tail(FreeRegionList* from_list);

  // It empties the list by removing all regions from it.
  void remove_all();

  // It removes all regions in the list that are pending for removal
  // (i.e., they have been tagged with "pending_removal"). The list
  // must not be empty, target_count should reflect the exact number
  // of regions that are pending for removal in the list, and
  // target_count should be > 1 (currently, we never need to remove a
  // single region using this).
  void remove_all_pending(uint target_count);

  virtual void verify();

  virtual void print_on(outputStream* out, bool print_contents = false);
};

// Iterator class that provides a convenient way to iterate over the
// regions of a HeapRegionLinkedList instance.

class FreeRegionListIterator : public StackObj {
private:
  FreeRegionList* _list;
  HeapRegion*     _curr;

public:
  bool more_available() {
    return _curr != NULL;
  }

  HeapRegion* get_next() {
    assert(more_available(),
           "get_next() should be called when more regions are available");

    // If we are going to introduce a count in the iterator we should
    // do the "cycle" check.

    HeapRegion* hr = _curr;
    _list->verify_region(hr);
    _curr = hr->next();
    return hr;
  }

  FreeRegionListIterator(FreeRegionList* list) : _curr(NULL), _list(list) {
    _curr = list->head();
  }
};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSET_HPP