1 /*
   2  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // All heaps contains a "permanent generation," containing permanent
  26 // (reflective) objects.  This is like a regular generation in some ways,
  27 // but unlike one in others, and so is split apart.
  28 
  29 class Generation;
  30 class GenRemSet;
  31 class CSpaceCounters;
  32 
  33 // PermGen models the part of the heap used to allocate class meta-data.
  34 
  35 class PermGen : public CHeapObj {
  36   friend class VMStructs;
  37  protected:
  38   size_t _capacity_expansion_limit;  // maximum expansion allowed without a
  39                                      // full gc occurring
  40   void set_capacity_expansion_limit(size_t limit) {
  41     assert_locked_or_safepoint(Heap_lock);
  42     _capacity_expansion_limit = limit;
  43   }
  44 
  45   HeapWord* mem_allocate_in_gen(size_t size, Generation* gen);
  46   // Along with mem_allocate_in_gen() above, implements policy for
  47   // "scheduling" allocation/expansion/collection of the perm gen.
  48   // The virtual method request_...() below can be overridden by
  49   // subtypes that want to implement a different expansion/collection
  50   // policy from the default provided.
  51   virtual HeapWord* request_expand_and_allocate(Generation* gen, size_t size,
  52                                                 GCCause::Cause prev_cause);
  53 
  54  public:
  55   enum Name {
  56     MarkSweepCompact, MarkSweep, ConcurrentMarkSweep
  57   };
  58 
  59   // Permanent allocation (initialized)
  60   virtual HeapWord* mem_allocate(size_t size) = 0;
  61 
  62   // Mark sweep support
  63   virtual void compute_new_size() = 0;
  64 
  65   // Ideally, we would use MI (IMHO) but we'll do delegation instead.
  66   virtual Generation* as_gen() const = 0;
  67 
  68   virtual void oop_iterate(OopClosure* cl) {
  69     Generation* g = as_gen();
  70     assert(g != NULL, "as_gen() NULL");
  71     g->oop_iterate(cl);
  72   }
  73 
  74   virtual void object_iterate(ObjectClosure* cl) {
  75     Generation* g = as_gen();
  76     assert(g != NULL, "as_gen() NULL");
  77     g->object_iterate(cl);
  78   }
  79 
  80   // Performance Counter support
  81   virtual void update_counters() {
  82     Generation* g = as_gen();
  83     assert(g != NULL, "as_gen() NULL");
  84     g->update_counters();
  85   }
  86 };