permGen.hpp

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// All heaps contains a "permanent generation," containing permanent
// (reflective) objects.  This is like a regular generation in some ways,
// but unlike one in others, and so is split apart.

class Generation;
class GenRemSet;
class CSpaceCounters;

// PermGen models the part of the heap used to allocate class meta-data.

class PermGen : public CHeapObj {
  friend class VMStructs;
 protected:
  size_t _capacity_expansion_limit;  // maximum expansion allowed without a
                                     // full gc occurring
  void set_capacity_expansion_limit(size_t limit) {
    assert_locked_or_safepoint(Heap_lock);
    _capacity_expansion_limit = limit;
  }

  HeapWord* mem_allocate_in_gen(size_t size, Generation* gen);
  // Along with mem_allocate_in_gen() above, implements policy for
  // "scheduling" allocation/expansion/collection of the perm gen.
  // The virtual method request_...() below can be overridden by
  // subtypes that want to implement a different expansion/collection
  // policy from the default provided.
  virtual HeapWord* request_expand_and_allocate(Generation* gen, size_t size,
                                                GCCause::Cause prev_cause);

 public:
  enum Name {
    MarkSweepCompact, MarkSweep, ConcurrentMarkSweep
  };

  // Permanent allocation (initialized)
  virtual HeapWord* mem_allocate(size_t size) = 0;

  // Mark sweep support
  virtual void compute_new_size() = 0;

  // Ideally, we would use MI (IMHO) but we'll do delegation instead.
  virtual Generation* as_gen() const = 0;

  virtual void oop_iterate(OopClosure* cl) {
    Generation* g = as_gen();
    assert(g != NULL, "as_gen() NULL");
    g->oop_iterate(cl);
  }

  virtual void object_iterate(ObjectClosure* cl) {
    Generation* g = as_gen();
    assert(g != NULL, "as_gen() NULL");
    g->object_iterate(cl);
  }

  // Performance Counter support
  virtual void update_counters() {
    Generation* g = as_gen();
    assert(g != NULL, "as_gen() NULL");
    g->update_counters();
  }
};