1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   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).
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
  27 
  28 #include "gc_implementation/g1/heapRegion.hpp"
  29 
  30 class G1CollectedHeap;
  31 
  32 // 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
  33 #define G1_ALLOC_REGION_TRACING 0
  34 
  35 class ar_ext_msg;
  36 
  37 // A class that holds a region that is active in satisfying allocation
  38 // requests, potentially issued in parallel. When the active region is
  39 // full it will be retired and replaced with a new one. The
  40 // implementation assumes that fast-path allocations will be lock-free
  41 // and a lock will need to be taken when the active region needs to be
  42 // replaced.
  43 
  44 class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
  45   friend class ar_ext_msg;
  46 
  47 private:
  48   // The active allocating region we are currently allocating out
  49   // of. The invariant is that if this object is initialized (i.e.,
  50   // init() has been called and release() has not) then _alloc_region
  51   // is either an active allocating region or the dummy region (i.e.,
  52   // it can never be NULL) and this object can be used to satisfy
  53   // allocation requests. If this object is not initialized
  54   // (i.e. init() has not been called or release() has been called)
  55   // then _alloc_region is NULL and this object should not be used to
  56   // satisfy allocation requests (it was done this way to force the
  57   // correct use of init() and release()).
  58   HeapRegion* volatile _alloc_region;
  59 
  60   // Allocation context associated with this alloc region.
  61   AllocationContext_t _allocation_context;
  62 
  63   // It keeps track of the distinct number of regions that are used
  64   // for allocation in the active interval of this object, i.e.,
  65   // between a call to init() and a call to release(). The count
  66   // mostly includes regions that are freshly allocated, as well as
  67   // the region that is re-used using the set() method. This count can
  68   // be used in any heuristics that might want to bound how many
  69   // distinct regions this object can used during an active interval.
  70   uint _count;
  71 
  72   // When we set up a new active region we save its used bytes in this
  73   // field so that, when we retire it, we can calculate how much space
  74   // we allocated in it.
  75   size_t _used_bytes_before;
  76 
  77   // When true, indicates that allocate calls should do BOT updates.
  78   const bool _bot_updates;
  79 
  80   // Useful for debugging and tracing.
  81   const char* _name;
  82 
  83   // A dummy region (i.e., it's been allocated specially for this
  84   // purpose and it is not part of the heap) that is full (i.e., top()
  85   // == end()). When we don't have a valid active region we make
  86   // _alloc_region point to this. This allows us to skip checking
  87   // whether the _alloc_region is NULL or not.
  88   static HeapRegion* _dummy_region;
  89 
  90   // Some of the methods below take a bot_updates parameter. Its value
  91   // should be the same as the _bot_updates field. The idea is that
  92   // the parameter will be a constant for a particular alloc region
  93   // and, given that these methods will be hopefully inlined, the
  94   // compiler should compile out the test.
  95 
  96   // Perform a non-MT-safe allocation out of the given region.
  97   static inline HeapWord* allocate(HeapRegion* alloc_region,
  98                                    size_t word_size,
  99                                    bool bot_updates);
 100 
 101   // Perform a MT-safe allocation out of the given region.
 102   static inline HeapWord* par_allocate(HeapRegion* alloc_region,
 103                                        size_t word_size,
 104                                        bool bot_updates);
 105 
 106   // Ensure that the region passed as a parameter has been filled up
 107   // so that noone else can allocate out of it any more.
 108   static void fill_up_remaining_space(HeapRegion* alloc_region,
 109                                       bool bot_updates);
 110 
 111   // Retire the active allocating region. If fill_up is true then make
 112   // sure that the region is full before we retire it so that noone
 113   // else can allocate out of it.
 114   void retire(bool fill_up);
 115 
 116   // After a region is allocated by alloc_new_region, this
 117   // method is used to set it as the active alloc_region
 118   void update_alloc_region(HeapRegion* alloc_region);
 119 
 120   // Allocate a new active region and use it to perform a word_size
 121   // allocation. The force parameter will be passed on to
 122   // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
 123   // to allocate a new region even if the max has been reached.
 124   HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
 125 
 126   void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
 127 
 128 protected:
 129   // For convenience as subclasses use it.
 130   static G1CollectedHeap* _g1h;
 131 
 132   virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
 133   virtual void retire_region(HeapRegion* alloc_region,
 134                              size_t allocated_bytes) = 0;
 135 
 136   G1AllocRegion(const char* name, bool bot_updates);
 137 
 138 public:
 139   static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
 140 
 141   HeapRegion* get() const {
 142     HeapRegion * hr = _alloc_region;
 143     // Make sure that the dummy region does not escape this class.
 144     return (hr == _dummy_region) ? NULL : hr;
 145   }
 146 
 147   void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
 148   AllocationContext_t  allocation_context() { return _allocation_context; }
 149 
 150   uint count() { return _count; }
 151 
 152   // The following two are the building blocks for the allocation method.
 153 
 154   // First-level allocation: Should be called without holding a
 155   // lock. It will try to allocate lock-free out of the active region,
 156   // or return NULL if it was unable to.
 157   inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);
 158 
 159   // Second-level allocation: Should be called while holding a
 160   // lock. It will try to first allocate lock-free out of the active
 161   // region or, if it's unable to, it will try to replace the active
 162   // alloc region with a new one. We require that the caller takes the
 163   // appropriate lock before calling this so that it is easier to make
 164   // it conform to its locking protocol.
 165   inline HeapWord* attempt_allocation_locked(size_t word_size,
 166                                              bool bot_updates);
 167 
 168   // Should be called to allocate a new region even if the max of this
 169   // type of regions has been reached. Should only be called if other
 170   // allocation attempts have failed and we are not holding a valid
 171   // active region.
 172   inline HeapWord* attempt_allocation_force(size_t word_size,
 173                                             bool bot_updates);
 174 
 175   // Should be called before we start using this object.
 176   void init();
 177 
 178   // This can be used to set the active region to a specific
 179   // region. (Use Example: we try to retain the last old GC alloc
 180   // region that we've used during a GC and we can use set() to
 181   // re-instate it at the beginning of the next GC.)
 182   void set(HeapRegion* alloc_region);
 183 
 184   // Should be called when we want to release the active region which
 185   // is returned after it's been retired.
 186   virtual HeapRegion* release();
 187 
 188 #if G1_ALLOC_REGION_TRACING
 189   void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
 190 #else // G1_ALLOC_REGION_TRACING
 191   void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
 192 #endif // G1_ALLOC_REGION_TRACING
 193 };
 194 
 195 class MutatorAllocRegion : public G1AllocRegion {
 196 protected:
 197   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 198   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 199 public:
 200   MutatorAllocRegion()
 201     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 202 };
 203 
 204 class SurvivorGCAllocRegion : public G1AllocRegion {
 205 protected:
 206   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 207   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 208 public:
 209   SurvivorGCAllocRegion()
 210   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 211 };
 212 
 213 class OldGCAllocRegion : public G1AllocRegion {
 214 protected:
 215   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 216   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 217 public:
 218   OldGCAllocRegion()
 219   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 220 
 221   // This specialization of release() makes sure that the last card that has
 222   // been allocated into has been completely filled by a dummy object.  This
 223   // avoids races when remembered set scanning wants to update the BOT of the
 224   // last card in the retained old gc alloc region, and allocation threads
 225   // allocating into that card at the same time.
 226   virtual HeapRegion* release();
 227 };
 228 
 229 class ar_ext_msg : public err_msg {
 230 public:
 231   ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("%s", "") {
 232     alloc_region->fill_in_ext_msg(this, message);
 233   }
 234 };
 235 
 236 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP