1 /*
   2  * Copyright (c) 2001, 2009, 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.
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  23  */
  24 
  25 // A MutableSpace is a subtype of ImmutableSpace that supports the
  26 // concept of allocation. This includes the concepts that a space may
  27 // be only partially full, and the querry methods that go with such
  28 // an assumption. MutableSpace is also responsible for minimizing the
  29 // page allocation time by having the memory pretouched (with
  30 // AlwaysPretouch) and for optimizing page placement on NUMA systems
  31 // by make the underlying region interleaved (with UseNUMA).
  32 //
  33 // Invariant: (ImmutableSpace +) bottom() <= top() <= end()
  34 // top() is inclusive and end() is exclusive.
  35 
  36 class MutableSpaceMangler;
  37 
  38 class MutableSpace: public ImmutableSpace {
  39   friend class VMStructs;
  40 
  41   // Helper for mangling unused space in debug builds
  42   MutableSpaceMangler* _mangler;
  43   // The last region which page had been setup to be interleaved.
  44   MemRegion _last_setup_region;
  45   size_t _alignment;
  46  protected:
  47   HeapWord* _top;
  48 
  49   MutableSpaceMangler* mangler() { return _mangler; }
  50 
  51   void numa_setup_pages(MemRegion mr, bool clear_space);
  52   void pretouch_pages(MemRegion mr);
  53 
  54   void set_last_setup_region(MemRegion mr) { _last_setup_region = mr;   }
  55   MemRegion last_setup_region() const      { return _last_setup_region; }
  56 
  57  public:
  58   virtual ~MutableSpace();
  59   MutableSpace(size_t page_size);
  60 
  61   // Accessors
  62   HeapWord* top() const                    { return _top;    }
  63   virtual void set_top(HeapWord* value)    { _top = value;   }
  64 
  65   HeapWord** top_addr()                    { return &_top; }
  66   HeapWord** end_addr()                    { return &_end; }
  67 
  68   virtual void set_bottom(HeapWord* value) { _bottom = value; }
  69   virtual void set_end(HeapWord* value)    { _end = value; }
  70 
  71   size_t alignment()                       { return _alignment; }
  72 
  73   // Returns a subregion containing all objects in this space.
  74   MemRegion used_region() { return MemRegion(bottom(), top()); }
  75 
  76   static const bool SetupPages = true;
  77   static const bool DontSetupPages = false;
  78 
  79   // Initialization
  80   virtual void initialize(MemRegion mr,
  81                           bool clear_space,
  82                           bool mangle_space,
  83                           bool setup_pages = SetupPages);
  84 
  85   virtual void clear(bool mangle_space);
  86   // Does the usual initialization but optionally resets top to bottom.
  87 #if 0  // MANGLE_SPACE
  88   void initialize(MemRegion mr, bool clear_space, bool reset_top);
  89 #endif
  90   virtual void update() { }
  91   virtual void accumulate_statistics() { }
  92 
  93   // Methods used in mangling.  See descriptions under SpaceMangler.
  94   virtual void mangle_unused_area() PRODUCT_RETURN;
  95   virtual void mangle_unused_area_complete() PRODUCT_RETURN;
  96   virtual void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
  97   virtual void check_mangled_unused_area_complete() PRODUCT_RETURN;
  98   virtual void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
  99 
 100   // Used to save the space's current top for later use during mangling.
 101   virtual void set_top_for_allocations() PRODUCT_RETURN;
 102 
 103   virtual void ensure_parsability() { }
 104 
 105   virtual void mangle_region(MemRegion mr) PRODUCT_RETURN;
 106 
 107   // Boolean querries.
 108   bool is_empty() const              { return used_in_words() == 0; }
 109   bool not_empty() const             { return used_in_words() > 0; }
 110   bool contains(const void* p) const { return _bottom <= p && p < _end; }
 111 
 112   // Size computations.  Sizes are in bytes.
 113   size_t used_in_bytes() const                { return used_in_words() * HeapWordSize; }
 114   size_t free_in_bytes() const                { return free_in_words() * HeapWordSize; }
 115 
 116   // Size computations.  Sizes are in heapwords.
 117   virtual size_t used_in_words() const                    { return pointer_delta(top(), bottom()); }
 118   virtual size_t free_in_words() const                    { return pointer_delta(end(),    top()); }
 119   virtual size_t tlab_capacity(Thread* thr) const         { return capacity_in_bytes();            }
 120   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const { return free_in_bytes();                }
 121 
 122   // Allocation (return NULL if full)
 123   virtual HeapWord* allocate(size_t word_size);
 124   virtual HeapWord* cas_allocate(size_t word_size);
 125   // Optional deallocation. Used in NUMA-allocator.
 126   bool cas_deallocate(HeapWord *obj, size_t size);
 127 
 128   // Iteration.
 129   void oop_iterate(OopClosure* cl);
 130   void object_iterate(ObjectClosure* cl);
 131 
 132   // Debugging
 133   virtual void print() const;
 134   virtual void print_on(outputStream* st) const;
 135   virtual void print_short() const;
 136   virtual void print_short_on(outputStream* st) const;
 137   virtual void verify(bool allow_dirty);
 138 };