1 /* 2 * Copyright (c) 2011, 2017, 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 #include "gc/g1/g1EvacStats.hpp" 30 #include "gc/g1/g1InCSetState.hpp" 31 32 class G1CollectedHeap; 33 34 // A class that holds a region that is active in satisfying allocation 35 // requests, potentially issued in parallel. When the active region is 36 // full it will be retired and replaced with a new one. The 37 // implementation assumes that fast-path allocations will be lock-free 38 // and a lock will need to be taken when the active region needs to be 39 // replaced. 40 41 class G1AllocRegion { 42 43 private: 44 // The active allocating region we are currently allocating out 45 // of. The invariant is that if this object is initialized (i.e., 46 // init() has been called and release() has not) then _alloc_region 47 // is either an active allocating region or the dummy region (i.e., 48 // it can never be NULL) and this object can be used to satisfy 49 // allocation requests. If this object is not initialized 50 // (i.e. init() has not been called or release() has been called) 51 // then _alloc_region is NULL and this object should not be used to 52 // satisfy allocation requests (it was done this way to force the 53 // correct use of init() and release()). 54 HeapRegion* volatile _alloc_region; 55 56 // It keeps track of the distinct number of regions that are used 57 // for allocation in the active interval of this object, i.e., 58 // between a call to init() and a call to release(). The count 59 // mostly includes regions that are freshly allocated, as well as 60 // the region that is re-used using the set() method. This count can 61 // be used in any heuristics that might want to bound how many 62 // distinct regions this object can used during an active interval. 63 uint _count; 64 65 // When we set up a new active region we save its used bytes in this 66 // field so that, when we retire it, we can calculate how much space 67 // we allocated in it. 68 size_t _used_bytes_before; 69 70 // When true, indicates that allocate calls should do BOT updates. 71 const bool _bot_updates; 72 73 // Useful for debugging and tracing. 74 const char* _name; 75 76 // A dummy region (i.e., it's been allocated specially for this 77 // purpose and it is not part of the heap) that is full (i.e., top() 78 // == end()). When we don't have a valid active region we make 79 // _alloc_region point to this. This allows us to skip checking 80 // whether the _alloc_region is NULL or not. 81 static HeapRegion* _dummy_region; 82 83 // Perform a non-MT-safe allocation out of the given region. 84 inline HeapWord* allocate(HeapRegion* alloc_region, 85 size_t word_size); 86 87 // Perform a MT-safe allocation out of the given region. 88 inline HeapWord* par_allocate(HeapRegion* alloc_region, 89 size_t word_size); 90 // Perform a MT-safe allocation out of the given region, with the given 91 // minimum and desired size. Returns the actual size allocated (between 92 // minimum and desired size) in actual_word_size if the allocation has been 93 // successful. 94 inline HeapWord* par_allocate(HeapRegion* alloc_region, 95 size_t min_word_size, 96 size_t desired_word_size, 97 size_t* actual_word_size); 98 99 // Ensure that the region passed as a parameter has been filled up 100 // so that noone else can allocate out of it any more. 101 // Returns the number of bytes that have been wasted by filled up 102 // the space. 103 size_t fill_up_remaining_space(HeapRegion* alloc_region); 104 105 // After a region is allocated by alloc_new_region, this 106 // method is used to set it as the active alloc_region 107 void update_alloc_region(HeapRegion* alloc_region); 108 109 // Allocate a new active region and use it to perform a word_size 110 // allocation. The force parameter will be passed on to 111 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try 112 // to allocate a new region even if the max has been reached. 113 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force); 114 115 protected: 116 // Retire the active allocating region. If fill_up is true then make 117 // sure that the region is full before we retire it so that no one 118 // else can allocate out of it. 119 // Returns the number of bytes that have been filled up during retire. 120 virtual size_t retire(bool fill_up); 121 122 // For convenience as subclasses use it. 123 static G1CollectedHeap* _g1h; 124 125 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0; 126 virtual void retire_region(HeapRegion* alloc_region, 127 size_t allocated_bytes) = 0; 128 129 G1AllocRegion(const char* name, bool bot_updates); 130 131 public: 132 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region); 133 134 HeapRegion* get() const { 135 HeapRegion * hr = _alloc_region; 136 // Make sure that the dummy region does not escape this class. 137 return (hr == _dummy_region) ? NULL : hr; 138 } 139 140 uint count() { return _count; } 141 142 // The following two are the building blocks for the allocation method. 143 144 // First-level allocation: Should be called without holding a 145 // lock. It will try to allocate lock-free out of the active region, 146 // or return NULL if it was unable to. 147 inline HeapWord* attempt_allocation(size_t word_size); 148 // Perform an allocation out of the current allocation region, with the given 149 // minimum and desired size. Returns the actual size allocated (between 150 // minimum and desired size) in actual_word_size if the allocation has been 151 // successful. 152 // Should be called without holding a lock. It will try to allocate lock-free 153 // out of the active region, or return NULL if it was unable to. 154 inline HeapWord* attempt_allocation(size_t min_word_size, 155 size_t desired_word_size, 156 size_t* actual_word_size); 157 158 // Second-level allocation: Should be called while holding a 159 // lock. It will try to first allocate lock-free out of the active 160 // region or, if it's unable to, it will try to replace the active 161 // alloc region with a new one. We require that the caller takes the 162 // appropriate lock before calling this so that it is easier to make 163 // it conform to its locking protocol. 164 inline HeapWord* attempt_allocation_locked(size_t word_size); 165 // Same as attempt_allocation_locked(size_t, bool), but allowing specification 166 // of minimum word size of the block in min_word_size, and the maximum word 167 // size of the allocation in desired_word_size. The actual size of the block is 168 // returned in actual_word_size. 169 inline HeapWord* attempt_allocation_locked(size_t min_word_size, 170 size_t desired_word_size, 171 size_t* actual_word_size); 172 173 // Should be called to allocate a new region even if the max of this 174 // type of regions has been reached. Should only be called if other 175 // allocation attempts have failed and we are not holding a valid 176 // active region. 177 inline HeapWord* attempt_allocation_force(size_t word_size); 178 179 // Should be called before we start using this object. 180 void init(); 181 182 // This can be used to set the active region to a specific 183 // region. (Use Example: we try to retain the last old GC alloc 184 // region that we've used during a GC and we can use set() to 185 // re-instate it at the beginning of the next GC.) 186 void set(HeapRegion* alloc_region); 187 188 // Should be called when we want to release the active region which 189 // is returned after it's been retired. 190 virtual HeapRegion* release(); 191 192 void trace(const char* str, 193 size_t min_word_size = 0, 194 size_t desired_word_size = 0, 195 size_t actual_word_size = 0, 196 HeapWord* result = NULL) PRODUCT_RETURN; 197 }; 198 199 class MutatorAllocRegion : public G1AllocRegion { 200 protected: 201 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 202 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 203 public: 204 MutatorAllocRegion() 205 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { } 206 }; 207 208 // Common base class for allocation regions used during GC. 209 class G1GCAllocRegion : public G1AllocRegion { 210 protected: 211 G1EvacStats* _stats; 212 InCSetState::in_cset_state_t _purpose; 213 214 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 215 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 216 217 virtual size_t retire(bool fill_up); 218 219 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose) 220 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) { 221 assert(stats != NULL, "Must pass non-NULL PLAB statistics"); 222 } 223 }; 224 225 class SurvivorGCAllocRegion : public G1GCAllocRegion { 226 public: 227 SurvivorGCAllocRegion(G1EvacStats* stats) 228 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { } 229 }; 230 231 class OldGCAllocRegion : public G1GCAllocRegion { 232 public: 233 OldGCAllocRegion(G1EvacStats* stats) 234 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { } 235 236 // This specialization of release() makes sure that the last card that has 237 // been allocated into has been completely filled by a dummy object. This 238 // avoids races when remembered set scanning wants to update the BOT of the 239 // last card in the retained old gc alloc region, and allocation threads 240 // allocating into that card at the same time. 241 virtual HeapRegion* release(); 242 }; 243 244 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP