1 /* 2 * Copyright (c) 2011, 2014, 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_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