1 /* 2 * Copyright (c) 2000, 2020, 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 WorkGang; 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_GenCollectFullConcurrent; 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 // Collects the given generation. 92 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 93 bool run_verification, bool clear_soft_refs, 94 bool restore_marks_for_biased_locking); 95 96 // Reserve aligned space for the heap as needed by the contained generations. 97 ReservedHeapSpace allocate(size_t alignment); 98 99 // Initialize ("weak") refs processing support 100 void ref_processing_init(); 101 102 PreGenGCValues get_pre_gc_values() const; 103 104 protected: 105 106 // The set of potentially parallel tasks in root scanning. 107 enum GCH_strong_roots_tasks { 108 GCH_PS_Universe_oops_do, 109 GCH_PS_ObjectSynchronizer_oops_do, 110 GCH_PS_OopStorageSet_oops_do, 111 GCH_PS_ClassLoaderDataGraph_oops_do, 112 GCH_PS_CodeCache_oops_do, 113 AOT_ONLY(GCH_PS_aot_oops_do COMMA) 114 GCH_PS_younger_gens, 115 // Leave this one last. 116 GCH_PS_NumElements 117 }; 118 119 // Data structure for claiming the (potentially) parallel tasks in 120 // (gen-specific) roots processing. 121 SubTasksDone* _process_strong_tasks; 122 123 GCMemoryManager* _young_manager; 124 GCMemoryManager* _old_manager; 125 126 // Helper functions for allocation 127 HeapWord* attempt_allocation(size_t size, 128 bool is_tlab, 129 bool first_only); 130 131 // Helper function for two callbacks below. 132 // Considers collection of the first max_level+1 generations. 133 void do_collection(bool full, 134 bool clear_all_soft_refs, 135 size_t size, 136 bool is_tlab, 137 GenerationType max_generation); 138 139 // Callback from VM_GenCollectForAllocation operation. 140 // This function does everything necessary/possible to satisfy an 141 // allocation request that failed in the youngest generation that should 142 // have handled it (including collection, expansion, etc.) 143 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 144 145 // Callback from VM_GenCollectFull operation. 146 // Perform a full collection of the first max_level+1 generations. 147 virtual void do_full_collection(bool clear_all_soft_refs); 148 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 149 150 // Does the "cause" of GC indicate that 151 // we absolutely __must__ clear soft refs? 152 bool must_clear_all_soft_refs(); 153 154 GenCollectedHeap(Generation::Name young, 155 Generation::Name old, 156 const char* policy_counters_name); 157 158 public: 159 160 // Returns JNI_OK on success 161 virtual jint initialize(); 162 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region); 163 164 void initialize_size_policy(size_t init_eden_size, 165 size_t init_promo_size, 166 size_t init_survivor_size); 167 168 // Does operations required after initialization has been done. 169 void post_initialize(); 170 171 Generation* young_gen() const { return _young_gen; } 172 Generation* old_gen() const { return _old_gen; } 173 174 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 175 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 176 177 MemRegion reserved_region() const { return _reserved; } 178 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); } 179 180 GenerationSpec* young_gen_spec() const; 181 GenerationSpec* old_gen_spec() const; 182 183 virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; } 184 185 // Adaptive size policy 186 virtual AdaptiveSizePolicy* size_policy() { 187 return _size_policy; 188 } 189 190 // Performance Counter support 191 GCPolicyCounters* counters() { return _gc_policy_counters; } 192 193 size_t capacity() const; 194 size_t used() const; 195 196 // Save the "used_region" for both generations. 197 void save_used_regions(); 198 199 size_t max_capacity() const; 200 201 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 202 203 // We may support a shared contiguous allocation area, if the youngest 204 // generation does. 205 bool supports_inline_contig_alloc() const; 206 HeapWord* volatile* top_addr() const; 207 HeapWord** end_addr() const; 208 209 // Perform a full collection of the heap; intended for use in implementing 210 // "System.gc". This implies as full a collection as the CollectedHeap 211 // supports. Caller does not hold the Heap_lock on entry. 212 virtual void collect(GCCause::Cause cause); 213 214 // The same as above but assume that the caller holds the Heap_lock. 215 void collect_locked(GCCause::Cause cause); 216 217 // Perform a full collection of generations up to and including max_generation. 218 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 219 void collect(GCCause::Cause cause, GenerationType max_generation); 220 221 // Returns "TRUE" iff "p" points into the committed areas of the heap. 222 // The methods is_in() and is_in_youngest() may be expensive to compute 223 // in general, so, to prevent their inadvertent use in product jvm's, we 224 // restrict their use to assertion checking or verification only. 225 bool is_in(const void* p) const; 226 227 // Returns true if the reference is to an object in the reserved space 228 // for the young generation. 229 // Assumes the the young gen address range is less than that of the old gen. 230 bool is_in_young(oop p); 231 232 #ifdef ASSERT 233 bool is_in_partial_collection(const void* p); 234 #endif 235 236 // Optimized nmethod scanning support routines 237 virtual void register_nmethod(nmethod* nm); 238 virtual void unregister_nmethod(nmethod* nm); 239 virtual void verify_nmethod(nmethod* nm); 240 virtual void flush_nmethod(nmethod* nm); 241 242 void prune_scavengable_nmethods(); 243 244 // Iteration functions. 245 void oop_iterate(OopIterateClosure* cl); 246 void object_iterate(ObjectClosure* cl); 247 Space* space_containing(const void* addr) const; 248 249 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 250 // each address in the (reserved) heap is a member of exactly 251 // one block. The defining characteristic of a block is that it is 252 // possible to find its size, and thus to progress forward to the next 253 // block. (Blocks may be of different sizes.) Thus, blocks may 254 // represent Java objects, or they might be free blocks in a 255 // free-list-based heap (or subheap), as long as the two kinds are 256 // distinguishable and the size of each is determinable. 257 258 // Returns the address of the start of the "block" that contains the 259 // address "addr". We say "blocks" instead of "object" since some heaps 260 // may not pack objects densely; a chunk may either be an object or a 261 // non-object. 262 HeapWord* block_start(const void* addr) const; 263 264 // Requires "addr" to be the start of a block, and returns "TRUE" iff 265 // the block is an object. Assumes (and verifies in non-product 266 // builds) that addr is in the allocated part of the heap and is 267 // the start of a chunk. 268 bool block_is_obj(const HeapWord* addr) const; 269 270 // Section on TLAB's. 271 virtual bool supports_tlab_allocation() const; 272 virtual size_t tlab_capacity(Thread* thr) const; 273 virtual size_t tlab_used(Thread* thr) const; 274 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 275 virtual HeapWord* allocate_new_tlab(size_t min_size, 276 size_t requested_size, 277 size_t* actual_size); 278 279 // The "requestor" generation is performing some garbage collection 280 // action for which it would be useful to have scratch space. The 281 // requestor promises to allocate no more than "max_alloc_words" in any 282 // older generation (via promotion say.) Any blocks of space that can 283 // be provided are returned as a list of ScratchBlocks, sorted by 284 // decreasing size. 285 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 286 // Allow each generation to reset any scratch space that it has 287 // contributed as it needs. 288 void release_scratch(); 289 290 // Ensure parsability: override 291 virtual void ensure_parsability(bool retire_tlabs); 292 293 // Total number of full collections completed. 294 unsigned int total_full_collections_completed() { 295 assert(_full_collections_completed <= _total_full_collections, 296 "Can't complete more collections than were started"); 297 return _full_collections_completed; 298 } 299 300 // Update above counter, as appropriate, at the end of a stop-world GC cycle 301 unsigned int update_full_collections_completed(); 302 // Update above counter, as appropriate, at the end of a concurrent GC cycle 303 unsigned int update_full_collections_completed(unsigned int count); 304 305 // Update the gc statistics for each generation. 306 void update_gc_stats(Generation* current_generation, bool full) { 307 _old_gen->update_gc_stats(current_generation, full); 308 } 309 310 bool no_gc_in_progress() { return !is_gc_active(); } 311 312 // Override. 313 void prepare_for_verify(); 314 315 // Override. 316 void verify(VerifyOption option); 317 318 // Override. 319 virtual void print_on(outputStream* st) const; 320 virtual void gc_threads_do(ThreadClosure* tc) const; 321 virtual void print_tracing_info() const; 322 323 // Used to print information about locations in the hs_err file. 324 virtual bool print_location(outputStream* st, void* addr) const; 325 326 void print_heap_change(const PreGenGCValues& pre_gc_values) const; 327 328 // The functions below are helper functions that a subclass of 329 // "CollectedHeap" can use in the implementation of its virtual 330 // functions. 331 332 class GenClosure : public StackObj { 333 public: 334 virtual void do_generation(Generation* gen) = 0; 335 }; 336 337 // Apply "cl.do_generation" to all generations in the heap 338 // If "old_to_young" determines the order. 339 void generation_iterate(GenClosure* cl, bool old_to_young); 340 341 // Return "true" if all generations have reached the 342 // maximal committed limit that they can reach, without a garbage 343 // collection. 344 virtual bool is_maximal_no_gc() const; 345 346 // This function returns the CardTableRS object that allows us to scan 347 // generations in a fully generational heap. 348 CardTableRS* rem_set() { return _rem_set; } 349 350 // Convenience function to be used in situations where the heap type can be 351 // asserted to be this type. 352 static GenCollectedHeap* heap(); 353 354 // The ScanningOption determines which of the roots 355 // the closure is applied to: 356 // "SO_None" does none; 357 enum ScanningOption { 358 SO_None = 0x0, 359 SO_AllCodeCache = 0x8, 360 SO_ScavengeCodeCache = 0x10 361 }; 362 363 protected: 364 void process_roots(StrongRootsScope* scope, 365 ScanningOption so, 366 OopClosure* strong_roots, 367 CLDClosure* strong_cld_closure, 368 CLDClosure* weak_cld_closure, 369 CodeBlobToOopClosure* code_roots); 370 371 virtual void gc_prologue(bool full); 372 virtual void gc_epilogue(bool full); 373 374 public: 375 void young_process_roots(StrongRootsScope* scope, 376 OopsInGenClosure* root_closure, 377 OopsInGenClosure* old_gen_closure, 378 CLDClosure* cld_closure); 379 380 void full_process_roots(StrongRootsScope* scope, 381 bool is_adjust_phase, 382 ScanningOption so, 383 bool only_strong_roots, 384 OopsInGenClosure* root_closure, 385 CLDClosure* cld_closure); 386 387 // Apply "root_closure" to all the weak roots of the system. 388 // These include JNI weak roots, string table, 389 // and referents of reachable weak refs. 390 void gen_process_weak_roots(OopClosure* root_closure); 391 392 // Set the saved marks of generations, if that makes sense. 393 // In particular, if any generation might iterate over the oops 394 // in other generations, it should call this method. 395 void save_marks(); 396 397 // Returns "true" iff no allocations have occurred since the last 398 // call to "save_marks". 399 bool no_allocs_since_save_marks(); 400 401 // Returns true if an incremental collection is likely to fail. 402 // We optionally consult the young gen, if asked to do so; 403 // otherwise we base our answer on whether the previous incremental 404 // collection attempt failed with no corrective action as of yet. 405 bool incremental_collection_will_fail(bool consult_young) { 406 // The first disjunct remembers if an incremental collection failed, even 407 // when we thought (second disjunct) that it would not. 408 return incremental_collection_failed() || 409 (consult_young && !_young_gen->collection_attempt_is_safe()); 410 } 411 412 // If a generation bails out of an incremental collection, 413 // it sets this flag. 414 bool incremental_collection_failed() const { 415 return _incremental_collection_failed; 416 } 417 void set_incremental_collection_failed() { 418 _incremental_collection_failed = true; 419 } 420 void clear_incremental_collection_failed() { 421 _incremental_collection_failed = false; 422 } 423 424 // Promotion of obj into gen failed. Try to promote obj to higher 425 // gens in ascending order; return the new location of obj if successful. 426 // Otherwise, try expand-and-allocate for obj in both the young and old 427 // generation; return the new location of obj if successful. Otherwise, return NULL. 428 oop handle_failed_promotion(Generation* old_gen, 429 oop obj, 430 size_t obj_size); 431 432 433 private: 434 // Return true if an allocation should be attempted in the older generation 435 // if it fails in the younger generation. Return false, otherwise. 436 bool should_try_older_generation_allocation(size_t word_size) const; 437 438 // Try to allocate space by expanding the heap. 439 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab); 440 441 HeapWord* mem_allocate_work(size_t size, 442 bool is_tlab, 443 bool* gc_overhead_limit_was_exceeded); 444 445 #if INCLUDE_SERIALGC 446 // For use by mark-sweep. As implemented, mark-sweep-compact is global 447 // in an essential way: compaction is performed across generations, by 448 // iterating over spaces. 449 void prepare_for_compaction(); 450 #endif 451 452 // Perform a full collection of the generations up to and including max_generation. 453 // This is the low level interface used by the public versions of 454 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 455 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 456 457 // Save the tops of the spaces in all generations 458 void record_gen_tops_before_GC() PRODUCT_RETURN; 459 460 // Return true if we need to perform full collection. 461 bool should_do_full_collection(size_t size, bool full, 462 bool is_tlab, GenerationType max_gen) const; 463 }; 464 465 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP