1 /* 2 * Copyright (c) 2011, 2018, 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_G1MONITORINGSUPPORT_HPP 26 #define SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP 27 28 #include "gc/shared/generationCounters.hpp" 29 30 class CollectorCounters; 31 class G1CollectedHeap; 32 class HSpaceCounters; 33 34 // Class for monitoring logical spaces in G1. It provides data for 35 // both G1's jstat counters as well as G1's memory pools. 36 // 37 // G1 splits the heap into heap regions and each heap region belongs 38 // to one of the following categories: 39 // 40 // * eden : regions that have been allocated since the last GC 41 // * survivors : regions with objects that survived the last few GCs 42 // * old : long-lived non-humongous regions 43 // * humongous : humongous regions 44 // * free : free regions 45 // 46 // The combination of eden and survivor regions form the equivalent of 47 // the young generation in the other GCs. The combination of old and 48 // humongous regions form the equivalent of the old generation in the 49 // other GCs. Free regions do not have a good equivalent in the other 50 // GCs given that they can be allocated as any of the other region types. 51 // 52 // The monitoring tools expect the heap to contain a number of 53 // generations (young, old, perm) and each generation to contain a 54 // number of spaces (young: eden, survivors, old). Given that G1 does 55 // not maintain those spaces physically (e.g., the set of 56 // non-contiguous eden regions can be considered as a "logical" 57 // space), we'll provide the illusion that those generations and 58 // spaces exist. In reality, each generation and space refers to a set 59 // of heap regions that are potentially non-contiguous. 60 // 61 // This class provides interfaces to access the min, current, and max 62 // capacity and current occupancy for each of G1's logical spaces and 63 // generations we expose to the monitoring tools. Also provided are 64 // counters for G1 concurrent collections and stop-the-world full heap 65 // collections. 66 // 67 // Below is a description of how the various sizes are calculated. 68 // 69 // * Current Capacity 70 // 71 // - heap_capacity = current heap capacity (e.g., current committed size) 72 // - young_gen_capacity = current max young gen target capacity 73 // (i.e., young gen target capacity + max allowed expansion capacity) 74 // - survivor_capacity = current survivor region capacity 75 // - eden_capacity = young_gen_capacity - survivor_capacity 76 // - old_capacity = heap_capacity - young_gen_capacity 77 // 78 // What we do in the above is to distribute the free regions among 79 // eden_capacity and old_capacity. 80 // 81 // * Occupancy 82 // 83 // - young_gen_used = current young region capacity 84 // - survivor_used = survivor_capacity 85 // - eden_used = young_gen_used - survivor_used 86 // - old_used = overall_used - young_gen_used 87 // 88 // Unfortunately, we currently only keep track of the number of 89 // currently allocated young and survivor regions + the overall used 90 // bytes in the heap, so the above can be a little inaccurate. 91 // 92 // * Min Capacity 93 // 94 // We set this to 0 for all spaces. 95 // 96 // * Max Capacity 97 // 98 // For jstat, we set the max capacity of all spaces to heap_capacity, 99 // given that we don't always have a reasonable upper bound on how big 100 // each space can grow. For the memory pools, we make the max 101 // capacity undefined with the exception of the old memory pool for 102 // which we make the max capacity same as the max heap capacity. 103 // 104 // If we had more accurate occupancy / capacity information per 105 // region set the above calculations would be greatly simplified and 106 // be made more accurate. 107 // 108 // We update all the above synchronously and we store the results in 109 // fields so that we just read said fields when needed. A subtle point 110 // is that all the above sizes need to be recalculated when the old 111 // gen changes capacity (after a GC or after a humongous allocation) 112 // but only the eden occupancy changes when a new eden region is 113 // allocated. So, in the latter case we have minimal recalculation to 114 // do which is important as we want to keep the eden region allocation 115 // path as low-overhead as possible. 116 117 class G1MonitoringSupport : public CHeapObj<mtGC> { 118 friend class VMStructs; 119 120 G1CollectedHeap* _g1h; 121 122 // jstat performance counters 123 // incremental collections both young and mixed 124 CollectorCounters* _incremental_collection_counters; 125 // full stop-the-world collections 126 CollectorCounters* _full_collection_counters; 127 // stop-the-world phases in G1 128 CollectorCounters* _conc_collection_counters; 129 // young collection set counters. The _eden_counters, 130 // _from_counters, and _to_counters are associated with 131 // this "generational" counter. 132 GenerationCounters* _young_collection_counters; 133 // old collection set counters. The _old_space_counters 134 // below are associated with this "generational" counter. 135 GenerationCounters* _old_collection_counters; 136 // Counters for the capacity and used for 137 // the whole heap 138 HSpaceCounters* _old_space_counters; 139 // the young collection 140 HSpaceCounters* _eden_counters; 141 // the survivor collection (only one, _to_counters, is actively used) 142 HSpaceCounters* _from_counters; 143 HSpaceCounters* _to_counters; 144 145 // When it's appropriate to recalculate the various sizes (at the 146 // end of a GC, when a new eden region is allocated, etc.) we store 147 // them here so that we can easily report them when needed and not 148 // have to recalculate them every time. 149 150 size_t _overall_reserved; 151 size_t _overall_committed; 152 size_t _overall_used; 153 154 uint _young_region_num; 155 size_t _young_gen_committed; 156 size_t _eden_committed; 157 size_t _eden_used; 158 size_t _survivor_committed; 159 size_t _survivor_used; 160 161 size_t _old_committed; 162 size_t _old_used; 163 164 G1CollectedHeap* g1h() { return _g1h; } 165 166 // It returns x - y if x > y, 0 otherwise. 167 // As described in the comment above, some of the inputs to the 168 // calculations we have to do are obtained concurrently and hence 169 // may be inconsistent with each other. So, this provides a 170 // defensive way of performing the subtraction and avoids the value 171 // going negative (which would mean a very large result, given that 172 // the parameter are size_t). 173 static size_t subtract_up_to_zero(size_t x, size_t y) { 174 if (x > y) { 175 return x - y; 176 } else { 177 return 0; 178 } 179 } 180 181 // Recalculate all the sizes. 182 void recalculate_sizes(); 183 // Recalculate only what's necessary when a new eden region is allocated. 184 void recalculate_eden_size(); 185 186 public: 187 G1MonitoringSupport(G1CollectedHeap* g1h); 188 189 // Unfortunately, the jstat tool assumes that no space has 0 190 // capacity. In our case, given that each space is logical, it's 191 // possible that no regions will be allocated to it, hence to have 0 192 // capacity (e.g., if there are no survivor regions, the survivor 193 // space has 0 capacity). The way we deal with this is to always pad 194 // each capacity value we report to jstat by a very small amount to 195 // make sure that it's never zero. Given that we sometimes have to 196 // report a capacity of a generation that contains several spaces 197 // (e.g., young gen includes one eden, two survivor spaces), the 198 // mult parameter is provided in order to adding the appropriate 199 // padding multiple times so that the capacities add up correctly. 200 static size_t pad_capacity(size_t size_bytes, size_t mult = 1) { 201 return size_bytes + MinObjAlignmentInBytes * mult; 202 } 203 204 // Recalculate all the sizes from scratch and update all the jstat 205 // counters accordingly. 206 void update_sizes(); 207 // Recalculate only what's necessary when a new eden region is 208 // allocated and update any jstat counters that need to be updated. 209 void update_eden_size(); 210 211 CollectorCounters* incremental_collection_counters() { 212 return _incremental_collection_counters; 213 } 214 CollectorCounters* full_collection_counters() { 215 return _full_collection_counters; 216 } 217 CollectorCounters* conc_collection_counters() { 218 return _conc_collection_counters; 219 } 220 GenerationCounters* young_collection_counters() { 221 return _young_collection_counters; 222 } 223 GenerationCounters* old_collection_counters() { 224 return _old_collection_counters; 225 } 226 HSpaceCounters* old_space_counters() { return _old_space_counters; } 227 HSpaceCounters* eden_counters() { return _eden_counters; } 228 HSpaceCounters* from_counters() { return _from_counters; } 229 HSpaceCounters* to_counters() { return _to_counters; } 230 231 // Monitoring support used by 232 // MemoryService 233 // jstat counters 234 // Tracing 235 236 size_t overall_reserved() { return _overall_reserved; } 237 size_t overall_committed() { return _overall_committed; } 238 size_t overall_used() { return _overall_used; } 239 240 size_t young_gen_committed() { return _young_gen_committed; } 241 size_t young_gen_max() { return overall_reserved(); } 242 size_t eden_space_committed() { return _eden_committed; } 243 size_t eden_space_used() { return _eden_used; } 244 size_t survivor_space_committed() { return _survivor_committed; } 245 size_t survivor_space_used() { return _survivor_used; } 246 247 size_t old_gen_committed() { return old_space_committed(); } 248 size_t old_gen_max() { return overall_reserved(); } 249 size_t old_space_committed() { return _old_committed; } 250 size_t old_space_used() { return _old_used; } 251 }; 252 253 class G1GenerationCounters: public GenerationCounters { 254 protected: 255 G1MonitoringSupport* _g1mm; 256 257 public: 258 G1GenerationCounters(G1MonitoringSupport* g1mm, 259 const char* name, int ordinal, int spaces, 260 size_t min_capacity, size_t max_capacity, 261 size_t curr_capacity); 262 }; 263 264 class G1YoungGenerationCounters: public G1GenerationCounters { 265 public: 266 G1YoungGenerationCounters(G1MonitoringSupport* g1mm, const char* name); 267 virtual void update_all(); 268 }; 269 270 class G1OldGenerationCounters: public G1GenerationCounters { 271 public: 272 G1OldGenerationCounters(G1MonitoringSupport* g1mm, const char* name); 273 virtual void update_all(); 274 }; 275 276 #endif // SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP --- EOF ---