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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP

#define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP

#include "gc_implementation/g1/heapRegion.hpp"

class G1CollectedHeap;

// 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing

#define G1_ALLOC_REGION_TRACING 0

class ar_ext_msg;

// A class that holds a region that is active in satisfying allocation

// requests, potentially issued in parallel. When the active region is

// full it will be retired and replaced with a new one. The

// implementation assumes that fast-path allocations will be lock-free

// and a lock will need to be taken when the active region needs to be

// replaced.

class G1AllocRegion VALUE_OBJ_CLASS_SPEC {

  friend class ar_ext_msg;

private:

  // The active allocating region we are currently allocating out

  // of. The invariant is that if this object is initialized (i.e.,

  // init() has been called and release() has not) then _alloc_region

  // is either an active allocating region or the dummy region (i.e.,

  // it can never be NULL) and this object can be used to satisfy

  // allocation requests. If this object is not initialized

  // (i.e. init() has not been called or release() has been called)

  // then _alloc_region is NULL and this object should not be used to

  // satisfy allocation requests (it was done this way to force the

  // correct use of init() and release()).

  HeapRegion* volatile _alloc_region;

  // It keeps track of the distinct number of regions that are used

  // for allocation in the active interval of this object, i.e.,

  // between a call to init() and a call to release(). The count

  // mostly includes regions that are freshly allocated, as well as

  // the region that is re-used using the set() method. This count can

  // be used in any heuristics that might want to bound how many

  // distinct regions this object can used during an active interval.

  uint _count;

  // When we set up a new active region we save its used bytes in this

  // field so that, when we retire it, we can calculate how much space

  // we allocated in it.

  size_t _used_bytes_before;

  // When true, indicates that allocate calls should do BOT updates.

  const bool _bot_updates;

  // Useful for debugging and tracing.

  const char* _name;

  // A dummy region (i.e., it's been allocated specially for this

  // purpose and it is not part of the heap) that is full (i.e., top()

  // == end()). When we don't have a valid active region we make

  // _alloc_region point to this. This allows us to skip checking

  // whether the _alloc_region is NULL or not.

  static HeapRegion* _dummy_region;

  // Some of the methods below take a bot_updates parameter. Its value

  // should be the same as the _bot_updates field. The idea is that

  // the parameter will be a constant for a particular alloc region

  // and, given that these methods will be hopefully inlined, the

  // compiler should compile out the test.

  // Perform a non-MT-safe allocation out of the given region.

  static inline HeapWord* allocate(HeapRegion* alloc_region,

                                   size_t word_size,

                                   bool bot_updates);

  // Perform a MT-safe allocation out of the given region.

  static inline HeapWord* par_allocate(HeapRegion* alloc_region,

                                       size_t word_size,

                                       bool bot_updates);

  // Ensure that the region passed as a parameter has been filled up

  // so that noone else can allocate out of it any more.

  static void fill_up_remaining_space(HeapRegion* alloc_region,

                                      bool bot_updates);

  // Retire the active allocating region. If fill_up is true then make

  // sure that the region is full before we retire it so that noone

  // else can allocate out of it.

  void retire(bool fill_up);

  // Allocate a new active region and use it to perform a word_size

  // allocation. The force parameter will be passed on to

  // G1CollectedHeap::allocate_new_alloc_region() and tells it to try

  // to allocate a new region even if the max has been reached.

  HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);

  void fill_in_ext_msg(ar_ext_msg* msg, const char* message);

protected:

  // For convenience as subclasses use it.

  static G1CollectedHeap* _g1h;

  virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;

  virtual void retire_region(HeapRegion* alloc_region,

                             size_t allocated_bytes) = 0;

  G1AllocRegion(const char* name, bool bot_updates);

public:

  static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);

  HeapRegion* get() const {

    HeapRegion * hr = _alloc_region;

    // Make sure that the dummy region does not escape this class.

    return (hr == _dummy_region) ? NULL : hr;

  }

  uint count() { return _count; }

  // The following two are the building blocks for the allocation method.

  // First-level allocation: Should be called without holding a

  // lock. It will try to allocate lock-free out of the active region,

  // or return NULL if it was unable to.

  inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);

  // Second-level allocation: Should be called while holding a

  // lock. It will try to first allocate lock-free out of the active

  // region or, if it's unable to, it will try to replace the active

  // alloc region with a new one. We require that the caller takes the

  // appropriate lock before calling this so that it is easier to make

  // it conform to its locking protocol.

  inline HeapWord* attempt_allocation_locked(size_t word_size,

                                             bool bot_updates);

  // Should be called to allocate a new region even if the max of this

  // type of regions has been reached. Should only be called if other

  // allocation attempts have failed and we are not holding a valid

  // active region.

  inline HeapWord* attempt_allocation_force(size_t word_size,

                                            bool bot_updates);

  // Should be called before we start using this object.

  void init();

  // This can be used to set the active region to a specific

  // region. (Use Example: we try to retain the last old GC alloc

  // region that we've used during a GC and we can use set() to

  // re-instate it at the beginning of the next GC.)

  void set(HeapRegion* alloc_region);

  // Should be called when we want to release the active region which

  // is returned after it's been retired.

  HeapRegion* release();

#if G1_ALLOC_REGION_TRACING

  void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);

#else // G1_ALLOC_REGION_TRACING

  void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }

#endif // G1_ALLOC_REGION_TRACING

};

class ar_ext_msg : public err_msg {

public:

    alloc_region->fill_in_ext_msg(this, message);

  }

};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP