1 /* 2 * Copyright (c) 2000, 2023, 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_GC_SHARED_GENCOLLECTEDHEAP_HPP 26 #define SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP 27 28 #include "gc/shared/collectedHeap.hpp" 29 #include "gc/shared/generation.hpp" 30 #include "gc/shared/oopStorageParState.hpp" 31 #include "gc/shared/preGCValues.hpp" 32 #include "gc/shared/softRefGenPolicy.hpp" 33 34 class AdaptiveSizePolicy; 35 class CardTableRS; 36 class GCPolicyCounters; 37 class GenerationSpec; 38 class StrongRootsScope; 39 class SubTasksDone; 40 class WorkerThreads; 41 42 // A "GenCollectedHeap" is a CollectedHeap that uses generational 43 // collection. It has two generations, young and old. 44 class GenCollectedHeap : public CollectedHeap { 45 friend class Generation; 46 friend class DefNewGeneration; 47 friend class TenuredGeneration; 48 friend class GenMarkSweep; 49 friend class VM_GenCollectForAllocation; 50 friend class VM_GenCollectFull; 51 friend class VM_GC_HeapInspection; 52 friend class VM_HeapDumper; 53 friend class HeapInspection; 54 friend class GCCauseSetter; 55 friend class VMStructs; 56 public: 57 friend class VM_PopulateDumpSharedSpace; 58 59 enum GenerationType { 60 YoungGen, 61 OldGen 62 }; 63 64 protected: 65 Generation* _young_gen; 66 Generation* _old_gen; 67 68 private: 69 GenerationSpec* _young_gen_spec; 70 GenerationSpec* _old_gen_spec; 71 72 // The singleton CardTable Remembered Set. 73 CardTableRS* _rem_set; 74 75 SoftRefGenPolicy _soft_ref_gen_policy; 76 77 // The sizing of the heap is controlled by a sizing policy. 78 AdaptiveSizePolicy* _size_policy; 79 80 GCPolicyCounters* _gc_policy_counters; 81 82 // Indicates that the most recent previous incremental collection failed. 83 // The flag is cleared when an action is taken that might clear the 84 // condition that caused that incremental collection to fail. 85 bool _incremental_collection_failed; 86 87 // In support of ExplicitGCInvokesConcurrent functionality 88 unsigned int _full_collections_completed; 89 90 // Collects the given generation. 91 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 92 bool run_verification, bool clear_soft_refs); 93 94 // Reserve aligned space for the heap as needed by the contained generations. 95 ReservedHeapSpace allocate(size_t alignment); 96 97 // Initialize ("weak") refs processing support 98 void ref_processing_init(); 99 100 PreGenGCValues get_pre_gc_values() const; 101 102 protected: 103 104 GCMemoryManager* _young_manager; 105 GCMemoryManager* _old_manager; 106 107 // Helper functions for allocation 108 HeapWord* attempt_allocation(size_t size, 109 bool is_tlab, 110 bool first_only); 111 112 // Helper function for two callbacks below. 113 // Considers collection of the first max_level+1 generations. 114 void do_collection(bool full, 115 bool clear_all_soft_refs, 116 size_t size, 117 bool is_tlab, 118 GenerationType max_generation); 119 120 // Callback from VM_GenCollectForAllocation operation. 121 // This function does everything necessary/possible to satisfy an 122 // allocation request that failed in the youngest generation that should 123 // have handled it (including collection, expansion, etc.) 124 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 125 126 // Callback from VM_GenCollectFull operation. 127 // Perform a full collection of the first max_level+1 generations. 128 void do_full_collection(bool clear_all_soft_refs) override; 129 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 130 131 // Does the "cause" of GC indicate that 132 // we absolutely __must__ clear soft refs? 133 bool must_clear_all_soft_refs(); 134 135 GenCollectedHeap(Generation::Name young, 136 Generation::Name old, 137 const char* policy_counters_name); 138 139 public: 140 141 // Returns JNI_OK on success 142 jint initialize() override; 143 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region); 144 145 void initialize_size_policy(size_t init_eden_size, 146 size_t init_promo_size, 147 size_t init_survivor_size); 148 149 // Does operations required after initialization has been done. 150 void post_initialize() override; 151 152 Generation* young_gen() const { return _young_gen; } 153 Generation* old_gen() const { return _old_gen; } 154 155 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 156 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 157 158 MemRegion reserved_region() const { return _reserved; } 159 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); } 160 161 GenerationSpec* young_gen_spec() const; 162 GenerationSpec* old_gen_spec() const; 163 164 SoftRefPolicy* soft_ref_policy() override { return &_soft_ref_gen_policy; } 165 166 // Adaptive size policy 167 virtual AdaptiveSizePolicy* size_policy() { 168 return _size_policy; 169 } 170 171 // Performance Counter support 172 GCPolicyCounters* counters() { return _gc_policy_counters; } 173 174 size_t capacity() const override; 175 size_t used() const override; 176 177 // Save the "used_region" for both generations. 178 void save_used_regions(); 179 180 size_t max_capacity() const override; 181 182 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded) override; 183 184 // Perform a full collection of the heap; intended for use in implementing 185 // "System.gc". This implies as full a collection as the CollectedHeap 186 // supports. Caller does not hold the Heap_lock on entry. 187 void collect(GCCause::Cause cause) override; 188 189 // Returns "TRUE" iff "p" points into the committed areas of the heap. 190 // The methods is_in() and is_in_youngest() may be expensive to compute 191 // in general, so, to prevent their inadvertent use in product jvm's, we 192 // restrict their use to assertion checking or verification only. 193 bool is_in(const void* p) const override; 194 195 // Returns true if p points into the reserved space for the young generation. 196 // Assumes the young gen address range is less than that of the old gen. 197 bool is_in_young(const void* p) const; 198 199 bool requires_barriers(stackChunkOop obj) const override; 200 201 #ifdef ASSERT 202 bool is_in_partial_collection(const void* p); 203 #endif 204 205 // Optimized nmethod scanning support routines 206 void register_nmethod(nmethod* nm) override; 207 void unregister_nmethod(nmethod* nm) override; 208 void verify_nmethod(nmethod* nm) override; 209 210 void prune_scavengable_nmethods(); 211 212 // Iteration functions. 213 void oop_iterate(OopIterateClosure* cl); 214 void object_iterate(ObjectClosure* cl) override; 215 Space* space_containing(const void* addr) const; 216 217 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 218 // each address in the (reserved) heap is a member of exactly 219 // one block. The defining characteristic of a block is that it is 220 // possible to find its size, and thus to progress forward to the next 221 // block. (Blocks may be of different sizes.) Thus, blocks may 222 // represent Java objects, or they might be free blocks in a 223 // free-list-based heap (or subheap), as long as the two kinds are 224 // distinguishable and the size of each is determinable. 225 226 // Returns the address of the start of the "block" that contains the 227 // address "addr". We say "blocks" instead of "object" since some heaps 228 // may not pack objects densely; a chunk may either be an object or a 229 // non-object. 230 HeapWord* block_start(const void* addr) const; 231 232 // Requires "addr" to be the start of a block, and returns "TRUE" iff 233 // the block is an object. Assumes (and verifies in non-product 234 // builds) that addr is in the allocated part of the heap and is 235 // the start of a chunk. 236 bool block_is_obj(const HeapWord* addr) const; 237 238 // Section on TLAB's. 239 size_t tlab_capacity(Thread* thr) const override; 240 size_t tlab_used(Thread* thr) const override; 241 size_t unsafe_max_tlab_alloc(Thread* thr) const override; 242 HeapWord* allocate_new_tlab(size_t min_size, 243 size_t requested_size, 244 size_t* actual_size) override; 245 246 // The "requestor" generation is performing some garbage collection 247 // action for which it would be useful to have scratch space. The 248 // requestor promises to allocate no more than "max_alloc_words" in any 249 // older generation (via promotion say.) Any blocks of space that can 250 // be provided are returned as a list of ScratchBlocks, sorted by 251 // decreasing size. 252 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 253 // Allow each generation to reset any scratch space that it has 254 // contributed as it needs. 255 void release_scratch(); 256 257 // Ensure parsability 258 void ensure_parsability(bool retire_tlabs) override; 259 260 // Total number of full collections completed. 261 unsigned int total_full_collections_completed() { 262 assert(_full_collections_completed <= _total_full_collections, 263 "Can't complete more collections than were started"); 264 return _full_collections_completed; 265 } 266 267 // Update above counter, as appropriate, at the end of a stop-world GC cycle 268 unsigned int update_full_collections_completed(); 269 270 // Update the gc statistics for each generation. 271 void update_gc_stats(Generation* current_generation, bool full) { 272 _old_gen->update_gc_stats(current_generation, full); 273 } 274 275 bool no_gc_in_progress() { return !is_gc_active(); } 276 277 void prepare_for_verify() override; 278 void verify(VerifyOption option) override; 279 280 void print_on(outputStream* st) const override; 281 void gc_threads_do(ThreadClosure* tc) const override; 282 void print_tracing_info() const override; 283 284 // Used to print information about locations in the hs_err file. 285 bool print_location(outputStream* st, void* addr) const override; 286 287 void print_heap_change(const PreGenGCValues& pre_gc_values) const; 288 289 // The functions below are helper functions that a subclass of 290 // "CollectedHeap" can use in the implementation of its virtual 291 // functions. 292 293 class GenClosure : public StackObj { 294 public: 295 virtual void do_generation(Generation* gen) = 0; 296 }; 297 298 // Apply "cl.do_generation" to all generations in the heap 299 // If "old_to_young" determines the order. 300 void generation_iterate(GenClosure* cl, bool old_to_young); 301 302 // Return "true" if all generations have reached the 303 // maximal committed limit that they can reach, without a garbage 304 // collection. 305 virtual bool is_maximal_no_gc() const override; 306 307 // This function returns the CardTableRS object that allows us to scan 308 // generations in a fully generational heap. 309 CardTableRS* rem_set() { return _rem_set; } 310 311 // Convenience function to be used in situations where the heap type can be 312 // asserted to be this type. 313 static GenCollectedHeap* heap(); 314 315 // The ScanningOption determines which of the roots 316 // the closure is applied to: 317 // "SO_None" does none; 318 enum ScanningOption { 319 SO_None = 0x0, 320 SO_AllCodeCache = 0x8, 321 SO_ScavengeCodeCache = 0x10 322 }; 323 324 protected: 325 virtual void gc_prologue(bool full); 326 virtual void gc_epilogue(bool full); 327 328 public: 329 // Apply closures on various roots in Young GC or marking/adjust phases of Full GC. 330 void process_roots(ScanningOption so, 331 OopClosure* strong_roots, 332 CLDClosure* strong_cld_closure, 333 CLDClosure* weak_cld_closure, 334 CodeBlobToOopClosure* code_roots); 335 336 // Apply "root_closure" to all the weak roots of the system. 337 // These include JNI weak roots, string table, 338 // and referents of reachable weak refs. 339 void gen_process_weak_roots(OopClosure* root_closure); 340 341 // Set the saved marks of generations, if that makes sense. 342 // In particular, if any generation might iterate over the oops 343 // in other generations, it should call this method. 344 void save_marks(); 345 346 // Returns "true" iff no allocations have occurred since the last 347 // call to "save_marks". 348 bool no_allocs_since_save_marks(); 349 350 // Returns true if an incremental collection is likely to fail. 351 // We optionally consult the young gen, if asked to do so; 352 // otherwise we base our answer on whether the previous incremental 353 // collection attempt failed with no corrective action as of yet. 354 bool incremental_collection_will_fail(bool consult_young) { 355 // The first disjunct remembers if an incremental collection failed, even 356 // when we thought (second disjunct) that it would not. 357 return incremental_collection_failed() || 358 (consult_young && !_young_gen->collection_attempt_is_safe()); 359 } 360 361 // If a generation bails out of an incremental collection, 362 // it sets this flag. 363 bool incremental_collection_failed() const { 364 return _incremental_collection_failed; 365 } 366 void set_incremental_collection_failed() { 367 _incremental_collection_failed = true; 368 } 369 void clear_incremental_collection_failed() { 370 _incremental_collection_failed = false; 371 } 372 373 private: 374 // Return true if an allocation should be attempted in the older generation 375 // if it fails in the younger generation. Return false, otherwise. 376 bool should_try_older_generation_allocation(size_t word_size) const; 377 378 // Try to allocate space by expanding the heap. 379 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab); 380 381 HeapWord* mem_allocate_work(size_t size, 382 bool is_tlab, 383 bool* gc_overhead_limit_was_exceeded); 384 385 #if INCLUDE_SERIALGC 386 // For use by mark-sweep. As implemented, mark-sweep-compact is global 387 // in an essential way: compaction is performed across generations, by 388 // iterating over spaces. 389 void prepare_for_compaction(); 390 #endif 391 392 // Save the tops of the spaces in all generations 393 void record_gen_tops_before_GC() PRODUCT_RETURN; 394 395 // Return true if we need to perform full collection. 396 bool should_do_full_collection(size_t size, bool full, 397 bool is_tlab, GenerationType max_gen) const; 398 }; 399 400 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP