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 SlidingForwarding; 39 class StrongRootsScope; 40 class SubTasksDone; 41 class WorkerThreads; 42 43 // A "GenCollectedHeap" is a CollectedHeap that uses generational 44 // collection. It has two generations, young and old. 45 class GenCollectedHeap : public CollectedHeap { 46 friend class Generation; 47 friend class DefNewGeneration; 48 friend class TenuredGeneration; 49 friend class GenMarkSweep; 50 friend class VM_GenCollectForAllocation; 51 friend class VM_GenCollectFull; 52 friend class VM_GC_HeapInspection; 53 friend class VM_HeapDumper; 54 friend class HeapInspection; 55 friend class GCCauseSetter; 56 friend class VMStructs; 57 public: 58 friend class VM_PopulateDumpSharedSpace; 59 60 enum GenerationType { 61 YoungGen, 62 OldGen 63 }; 64 65 protected: 66 Generation* _young_gen; 67 Generation* _old_gen; 68 69 private: 70 GenerationSpec* _young_gen_spec; 71 GenerationSpec* _old_gen_spec; 72 73 // The singleton CardTable Remembered Set. 74 CardTableRS* _rem_set; 75 76 SoftRefGenPolicy _soft_ref_gen_policy; 77 78 // The sizing of the heap is controlled by a sizing policy. 79 AdaptiveSizePolicy* _size_policy; 80 81 GCPolicyCounters* _gc_policy_counters; 82 83 // Indicates that the most recent previous incremental collection failed. 84 // The flag is cleared when an action is taken that might clear the 85 // condition that caused that incremental collection to fail. 86 bool _incremental_collection_failed; 87 88 // In support of ExplicitGCInvokesConcurrent functionality 89 unsigned int _full_collections_completed; 90 91 SlidingForwarding* _forwarding; 92 93 // Collects the given generation. 94 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 95 bool run_verification, bool clear_soft_refs); 96 97 // Reserve aligned space for the heap as needed by the contained generations. 98 ReservedHeapSpace allocate(size_t alignment); 99 100 // Initialize ("weak") refs processing support 101 void ref_processing_init(); 102 103 PreGenGCValues get_pre_gc_values() const; 104 105 protected: 106 107 GCMemoryManager* _young_manager; 108 GCMemoryManager* _old_manager; 109 110 // Helper functions for allocation 111 HeapWord* attempt_allocation(size_t size, 112 bool is_tlab, 113 bool first_only); 114 115 // Helper function for two callbacks below. 116 // Considers collection of the first max_level+1 generations. 117 void do_collection(bool full, 118 bool clear_all_soft_refs, 119 size_t size, 120 bool is_tlab, 121 GenerationType max_generation); 122 123 // Callback from VM_GenCollectForAllocation operation. 124 // This function does everything necessary/possible to satisfy an 125 // allocation request that failed in the youngest generation that should 126 // have handled it (including collection, expansion, etc.) 127 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 128 129 // Callback from VM_GenCollectFull operation. 130 // Perform a full collection of the first max_level+1 generations. 131 void do_full_collection(bool clear_all_soft_refs) override; 132 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 133 134 // Does the "cause" of GC indicate that 135 // we absolutely __must__ clear soft refs? 136 bool must_clear_all_soft_refs(); 137 138 GenCollectedHeap(Generation::Name young, 139 Generation::Name old, 140 const char* policy_counters_name); 141 142 public: 143 144 // Returns JNI_OK on success 145 jint initialize() override; 146 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region); 147 148 void initialize_size_policy(size_t init_eden_size, 149 size_t init_promo_size, 150 size_t init_survivor_size); 151 152 // Does operations required after initialization has been done. 153 void post_initialize() override; 154 155 Generation* young_gen() const { return _young_gen; } 156 Generation* old_gen() const { return _old_gen; } 157 158 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 159 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 160 161 MemRegion reserved_region() const { return _reserved; } 162 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); } 163 164 GenerationSpec* young_gen_spec() const; 165 GenerationSpec* old_gen_spec() const; 166 167 SoftRefPolicy* soft_ref_policy() override { return &_soft_ref_gen_policy; } 168 169 // Adaptive size policy 170 virtual AdaptiveSizePolicy* size_policy() { 171 return _size_policy; 172 } 173 174 // Performance Counter support 175 GCPolicyCounters* counters() { return _gc_policy_counters; } 176 177 size_t capacity() const override; 178 size_t used() const override; 179 180 // Save the "used_region" for both generations. 181 void save_used_regions(); 182 183 size_t max_capacity() const override; 184 185 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded) override; 186 187 // Perform a full collection of the heap; intended for use in implementing 188 // "System.gc". This implies as full a collection as the CollectedHeap 189 // supports. Caller does not hold the Heap_lock on entry. 190 void collect(GCCause::Cause cause) override; 191 192 // Returns "TRUE" iff "p" points into the committed areas of the heap. 193 // The methods is_in() and is_in_youngest() may be expensive to compute 194 // in general, so, to prevent their inadvertent use in product jvm's, we 195 // restrict their use to assertion checking or verification only. 196 bool is_in(const void* p) const override; 197 198 // Returns true if p points into the reserved space for the young generation. 199 // Assumes the young gen address range is less than that of the old gen. 200 bool is_in_young(const void* p) const; 201 202 bool requires_barriers(stackChunkOop obj) const override; 203 204 #ifdef ASSERT 205 bool is_in_partial_collection(const void* p); 206 #endif 207 208 // Optimized nmethod scanning support routines 209 void register_nmethod(nmethod* nm) override; 210 void unregister_nmethod(nmethod* nm) override; 211 void verify_nmethod(nmethod* nm) override; 212 213 void prune_scavengable_nmethods(); 214 215 // Iteration functions. 216 void oop_iterate(OopIterateClosure* cl); 217 void object_iterate(ObjectClosure* cl) override; 218 Space* space_containing(const void* addr) const; 219 220 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 221 // each address in the (reserved) heap is a member of exactly 222 // one block. The defining characteristic of a block is that it is 223 // possible to find its size, and thus to progress forward to the next 224 // block. (Blocks may be of different sizes.) Thus, blocks may 225 // represent Java objects, or they might be free blocks in a 226 // free-list-based heap (or subheap), as long as the two kinds are 227 // distinguishable and the size of each is determinable. 228 229 // Returns the address of the start of the "block" that contains the 230 // address "addr". We say "blocks" instead of "object" since some heaps 231 // may not pack objects densely; a chunk may either be an object or a 232 // non-object. 233 HeapWord* block_start(const void* addr) const; 234 235 // Requires "addr" to be the start of a block, and returns "TRUE" iff 236 // the block is an object. Assumes (and verifies in non-product 237 // builds) that addr is in the allocated part of the heap and is 238 // the start of a chunk. 239 bool block_is_obj(const HeapWord* addr) const; 240 241 // Section on TLAB's. 242 size_t tlab_capacity(Thread* thr) const override; 243 size_t tlab_used(Thread* thr) const override; 244 size_t unsafe_max_tlab_alloc(Thread* thr) const override; 245 HeapWord* allocate_new_tlab(size_t min_size, 246 size_t requested_size, 247 size_t* actual_size) override; 248 249 // The "requestor" generation is performing some garbage collection 250 // action for which it would be useful to have scratch space. The 251 // requestor promises to allocate no more than "max_alloc_words" in any 252 // older generation (via promotion say.) Any blocks of space that can 253 // be provided are returned as a list of ScratchBlocks, sorted by 254 // decreasing size. 255 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 256 // Allow each generation to reset any scratch space that it has 257 // contributed as it needs. 258 void release_scratch(); 259 260 // Ensure parsability 261 void ensure_parsability(bool retire_tlabs) override; 262 263 // Total number of full collections completed. 264 unsigned int total_full_collections_completed() { 265 assert(_full_collections_completed <= _total_full_collections, 266 "Can't complete more collections than were started"); 267 return _full_collections_completed; 268 } 269 270 // Update above counter, as appropriate, at the end of a stop-world GC cycle 271 unsigned int update_full_collections_completed(); 272 273 // Update the gc statistics for each generation. 274 void update_gc_stats(Generation* current_generation, bool full) { 275 _old_gen->update_gc_stats(current_generation, full); 276 } 277 278 bool no_gc_in_progress() { return !is_gc_active(); } 279 280 void prepare_for_verify() override; 281 void verify(VerifyOption option) override; 282 283 void print_on(outputStream* st) const override; 284 void gc_threads_do(ThreadClosure* tc) const override; 285 void print_tracing_info() const override; 286 287 // Used to print information about locations in the hs_err file. 288 bool print_location(outputStream* st, void* addr) const override; 289 290 void print_heap_change(const PreGenGCValues& pre_gc_values) const; 291 292 // The functions below are helper functions that a subclass of 293 // "CollectedHeap" can use in the implementation of its virtual 294 // functions. 295 296 class GenClosure : public StackObj { 297 public: 298 virtual void do_generation(Generation* gen) = 0; 299 }; 300 301 // Apply "cl.do_generation" to all generations in the heap 302 // If "old_to_young" determines the order. 303 void generation_iterate(GenClosure* cl, bool old_to_young); 304 305 // Return "true" if all generations have reached the 306 // maximal committed limit that they can reach, without a garbage 307 // collection. 308 virtual bool is_maximal_no_gc() const override; 309 310 // This function returns the CardTableRS object that allows us to scan 311 // generations in a fully generational heap. 312 CardTableRS* rem_set() { return _rem_set; } 313 314 // Convenience function to be used in situations where the heap type can be 315 // asserted to be this type. 316 static GenCollectedHeap* heap(); 317 318 SlidingForwarding* forwarding() const { 319 return _forwarding; 320 } 321 322 // The ScanningOption determines which of the roots 323 // the closure is applied to: 324 // "SO_None" does none; 325 enum ScanningOption { 326 SO_None = 0x0, 327 SO_AllCodeCache = 0x8, 328 SO_ScavengeCodeCache = 0x10 329 }; 330 331 protected: 332 virtual void gc_prologue(bool full); 333 virtual void gc_epilogue(bool full); 334 335 public: 336 // Apply closures on various roots in Young GC or marking/adjust phases of Full GC. 337 void process_roots(ScanningOption so, 338 OopClosure* strong_roots, 339 CLDClosure* strong_cld_closure, 340 CLDClosure* weak_cld_closure, 341 CodeBlobToOopClosure* code_roots); 342 343 // Apply "root_closure" to all the weak roots of the system. 344 // These include JNI weak roots, string table, 345 // and referents of reachable weak refs. 346 void gen_process_weak_roots(OopClosure* root_closure); 347 348 // Set the saved marks of generations, if that makes sense. 349 // In particular, if any generation might iterate over the oops 350 // in other generations, it should call this method. 351 void save_marks(); 352 353 // Returns "true" iff no allocations have occurred since the last 354 // call to "save_marks". 355 bool no_allocs_since_save_marks(); 356 357 // Returns true if an incremental collection is likely to fail. 358 // We optionally consult the young gen, if asked to do so; 359 // otherwise we base our answer on whether the previous incremental 360 // collection attempt failed with no corrective action as of yet. 361 bool incremental_collection_will_fail(bool consult_young) { 362 // The first disjunct remembers if an incremental collection failed, even 363 // when we thought (second disjunct) that it would not. 364 return incremental_collection_failed() || 365 (consult_young && !_young_gen->collection_attempt_is_safe()); 366 } 367 368 // If a generation bails out of an incremental collection, 369 // it sets this flag. 370 bool incremental_collection_failed() const { 371 return _incremental_collection_failed; 372 } 373 void set_incremental_collection_failed() { 374 _incremental_collection_failed = true; 375 } 376 void clear_incremental_collection_failed() { 377 _incremental_collection_failed = false; 378 } 379 380 private: 381 // Return true if an allocation should be attempted in the older generation 382 // if it fails in the younger generation. Return false, otherwise. 383 bool should_try_older_generation_allocation(size_t word_size) const; 384 385 // Try to allocate space by expanding the heap. 386 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab); 387 388 HeapWord* mem_allocate_work(size_t size, 389 bool is_tlab, 390 bool* gc_overhead_limit_was_exceeded); 391 392 #if INCLUDE_SERIALGC 393 // For use by mark-sweep. As implemented, mark-sweep-compact is global 394 // in an essential way: compaction is performed across generations, by 395 // iterating over spaces. 396 void prepare_for_compaction(); 397 #endif 398 399 // Save the tops of the spaces in all generations 400 void record_gen_tops_before_GC() PRODUCT_RETURN; 401 402 // Return true if we need to perform full collection. 403 bool should_do_full_collection(size_t size, bool full, 404 bool is_tlab, GenerationType max_gen) const; 405 }; 406 407 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP