1 /*

     2  * Copyright (c) 2011, 2015, 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 #ifndef SHARE_VM_GC_G1_G1ALLOCREGION_HPP

    26 #define SHARE_VM_GC_G1_G1ALLOCREGION_HPP

    27 

    28 #include "gc/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_G1_G1ALLOCREGION_HPP