1 /* 2 * Copyright (c) 2000, 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_SHARED_GENCOLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP 27 28 #include "gc/shared/adaptiveSizePolicy.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "gc/shared/collectorPolicy.hpp" 31 #include "gc/shared/generation.hpp" 32 33 class StrongRootsScope; 34 class SubTasksDone; 35 class WorkGang; 36 37 // A "GenCollectedHeap" is a CollectedHeap that uses generational 38 // collection. It has two generations, young and old. 39 class GenCollectedHeap : public CollectedHeap { 40 friend class GenCollectorPolicy; 41 friend class Generation; 42 friend class DefNewGeneration; 43 friend class TenuredGeneration; 44 friend class ConcurrentMarkSweepGeneration; 45 friend class CMSCollector; 46 friend class GenMarkSweep; 47 friend class VM_GenCollectForAllocation; 48 friend class VM_GenCollectFull; 49 friend class VM_GenCollectFullConcurrent; 50 friend class VM_GC_HeapInspection; 51 friend class VM_HeapDumper; 52 friend class HeapInspection; 53 friend class GCCauseSetter; 54 friend class VMStructs; 55 public: 56 friend class VM_PopulateDumpSharedSpace; 57 58 enum GenerationType { 59 YoungGen, 60 OldGen 61 }; 62 63 private: 64 Generation* _young_gen; 65 Generation* _old_gen; 66 67 // The singleton CardTable Remembered Set. 68 CardTableRS* _rem_set; 69 70 // The generational collector policy. 71 GenCollectorPolicy* _gen_policy; 72 73 // Indicates that the most recent previous incremental collection failed. 74 // The flag is cleared when an action is taken that might clear the 75 // condition that caused that incremental collection to fail. 76 bool _incremental_collection_failed; 77 78 // In support of ExplicitGCInvokesConcurrent functionality 79 unsigned int _full_collections_completed; 80 81 // Collects the given generation. 82 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 83 bool run_verification, bool clear_soft_refs, 84 bool restore_marks_for_biased_locking); 85 86 // Reserve aligned space for the heap as needed by the contained generations. 87 char* allocate(size_t alignment, ReservedSpace* heap_rs); 88 89 // Initialize ("weak") refs processing support 90 void ref_processing_init(); 91 92 protected: 93 94 // The set of potentially parallel tasks in root scanning. 95 enum GCH_strong_roots_tasks { 96 GCH_PS_Universe_oops_do, 97 GCH_PS_JNIHandles_oops_do, 98 GCH_PS_ObjectSynchronizer_oops_do, 99 GCH_PS_FlatProfiler_oops_do, 100 GCH_PS_Management_oops_do, 101 GCH_PS_SystemDictionary_oops_do, 102 GCH_PS_ClassLoaderDataGraph_oops_do, 103 GCH_PS_jvmti_oops_do, 104 GCH_PS_CodeCache_oops_do, 105 GCH_PS_aot_oops_do, 106 GCH_PS_younger_gens, 107 // Leave this one last. 108 GCH_PS_NumElements 109 }; 110 111 // Data structure for claiming the (potentially) parallel tasks in 112 // (gen-specific) roots processing. 113 SubTasksDone* _process_strong_tasks; 114 115 GCMemoryManager* _young_manager; 116 GCMemoryManager* _old_manager; 117 118 // Helper functions for allocation 119 HeapWord* attempt_allocation(size_t size, 120 bool is_tlab, 121 bool first_only); 122 123 // Helper function for two callbacks below. 124 // Considers collection of the first max_level+1 generations. 125 void do_collection(bool full, 126 bool clear_all_soft_refs, 127 size_t size, 128 bool is_tlab, 129 GenerationType max_generation); 130 131 // Callback from VM_GenCollectForAllocation operation. 132 // This function does everything necessary/possible to satisfy an 133 // allocation request that failed in the youngest generation that should 134 // have handled it (including collection, expansion, etc.) 135 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 136 137 // Callback from VM_GenCollectFull operation. 138 // Perform a full collection of the first max_level+1 generations. 139 virtual void do_full_collection(bool clear_all_soft_refs); 140 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 141 142 // Does the "cause" of GC indicate that 143 // we absolutely __must__ clear soft refs? 144 bool must_clear_all_soft_refs(); 145 146 GenCollectedHeap(GenCollectorPolicy *policy); 147 148 virtual void check_gen_kinds() = 0; 149 150 public: 151 152 // Returns JNI_OK on success 153 virtual jint initialize(); 154 155 // Does operations required after initialization has been done. 156 void post_initialize(); 157 158 Generation* young_gen() const { return _young_gen; } 159 Generation* old_gen() const { return _old_gen; } 160 161 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 162 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 163 164 // The generational collector policy. 165 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 166 167 virtual CollectorPolicy* collector_policy() const { return gen_policy(); } 168 169 // Adaptive size policy 170 virtual AdaptiveSizePolicy* size_policy() { 171 return gen_policy()->size_policy(); 172 } 173 174 // Return the (conservative) maximum heap alignment 175 static size_t conservative_max_heap_alignment() { 176 return Generation::GenGrain; 177 } 178 179 size_t capacity() const; 180 size_t used() const; 181 182 // Save the "used_region" for both generations. 183 void save_used_regions(); 184 185 size_t max_capacity() const; 186 187 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 188 189 // We may support a shared contiguous allocation area, if the youngest 190 // generation does. 191 bool supports_inline_contig_alloc() const; 192 HeapWord* volatile* top_addr() const; 193 HeapWord** end_addr() const; 194 195 // Perform a full collection of the heap; intended for use in implementing 196 // "System.gc". This implies as full a collection as the CollectedHeap 197 // supports. Caller does not hold the Heap_lock on entry. 198 virtual void collect(GCCause::Cause cause); 199 200 // The same as above but assume that the caller holds the Heap_lock. 201 void collect_locked(GCCause::Cause cause); 202 203 // Perform a full collection of generations up to and including max_generation. 204 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 205 void collect(GCCause::Cause cause, GenerationType max_generation); 206 207 // Returns "TRUE" iff "p" points into the committed areas of the heap. 208 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 209 // be expensive to compute in general, so, to prevent 210 // their inadvertent use in product jvm's, we restrict their use to 211 // assertion checking or verification only. 212 bool is_in(const void* p) const; 213 214 // Returns true if the reference is to an object in the reserved space 215 // for the young generation. 216 // Assumes the the young gen address range is less than that of the old gen. 217 bool is_in_young(oop p); 218 219 #ifdef ASSERT 220 bool is_in_partial_collection(const void* p); 221 #endif 222 223 virtual bool is_scavengable(oop obj) { 224 return is_in_young(obj); 225 } 226 227 // Optimized nmethod scanning support routines 228 virtual void register_nmethod(nmethod* nm); 229 virtual void verify_nmethod(nmethod* nmethod); 230 231 // Iteration functions. 232 void oop_iterate_no_header(OopClosure* cl); 233 void oop_iterate(ExtendedOopClosure* cl); 234 void object_iterate(ObjectClosure* cl); 235 void safe_object_iterate(ObjectClosure* cl); 236 Space* space_containing(const void* addr) const; 237 238 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 239 // each address in the (reserved) heap is a member of exactly 240 // one block. The defining characteristic of a block is that it is 241 // possible to find its size, and thus to progress forward to the next 242 // block. (Blocks may be of different sizes.) Thus, blocks may 243 // represent Java objects, or they might be free blocks in a 244 // free-list-based heap (or subheap), as long as the two kinds are 245 // distinguishable and the size of each is determinable. 246 247 // Returns the address of the start of the "block" that contains the 248 // address "addr". We say "blocks" instead of "object" since some heaps 249 // may not pack objects densely; a chunk may either be an object or a 250 // non-object. 251 virtual HeapWord* block_start(const void* addr) const; 252 253 // Requires "addr" to be the start of a chunk, and returns its size. 254 // "addr + size" is required to be the start of a new chunk, or the end 255 // of the active area of the heap. Assumes (and verifies in non-product 256 // builds) that addr is in the allocated part of the heap and is 257 // the start of a chunk. 258 virtual size_t block_size(const HeapWord* addr) const; 259 260 // Requires "addr" to be the start of a block, and returns "TRUE" iff 261 // the block is an object. Assumes (and verifies in non-product 262 // builds) that addr is in the allocated part of the heap and is 263 // the start of a chunk. 264 virtual bool block_is_obj(const HeapWord* addr) const; 265 266 // Section on TLAB's. 267 virtual bool supports_tlab_allocation() const; 268 virtual size_t tlab_capacity(Thread* thr) const; 269 virtual size_t tlab_used(Thread* thr) const; 270 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 271 virtual HeapWord* allocate_new_tlab(size_t size); 272 273 // Can a compiler initialize a new object without store barriers? 274 // This permission only extends from the creation of a new object 275 // via a TLAB up to the first subsequent safepoint. 276 virtual bool can_elide_tlab_store_barriers() const { 277 return true; 278 } 279 280 // We don't need barriers for stores to objects in the 281 // young gen and, a fortiori, for initializing stores to 282 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 283 // only and may need to be re-examined in case other 284 // kinds of collectors are implemented in the future. 285 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 286 return is_in_young(new_obj); 287 } 288 289 // The "requestor" generation is performing some garbage collection 290 // action for which it would be useful to have scratch space. The 291 // requestor promises to allocate no more than "max_alloc_words" in any 292 // older generation (via promotion say.) Any blocks of space that can 293 // be provided are returned as a list of ScratchBlocks, sorted by 294 // decreasing size. 295 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 296 // Allow each generation to reset any scratch space that it has 297 // contributed as it needs. 298 void release_scratch(); 299 300 // Ensure parsability: override 301 virtual void ensure_parsability(bool retire_tlabs); 302 303 // Time in ms since the longest time a collector ran in 304 // in any generation. 305 virtual jlong millis_since_last_gc(); 306 307 // Total number of full collections completed. 308 unsigned int total_full_collections_completed() { 309 assert(_full_collections_completed <= _total_full_collections, 310 "Can't complete more collections than were started"); 311 return _full_collections_completed; 312 } 313 314 // Update above counter, as appropriate, at the end of a stop-world GC cycle 315 unsigned int update_full_collections_completed(); 316 // Update above counter, as appropriate, at the end of a concurrent GC cycle 317 unsigned int update_full_collections_completed(unsigned int count); 318 319 // Update "time of last gc" for all generations to "now". 320 void update_time_of_last_gc(jlong now) { 321 _young_gen->update_time_of_last_gc(now); 322 _old_gen->update_time_of_last_gc(now); 323 } 324 325 // Update the gc statistics for each generation. 326 void update_gc_stats(Generation* current_generation, bool full) { 327 _old_gen->update_gc_stats(current_generation, full); 328 } 329 330 bool no_gc_in_progress() { return !is_gc_active(); } 331 332 // Override. 333 void prepare_for_verify(); 334 335 // Override. 336 void verify(VerifyOption option); 337 338 // Override. 339 virtual void print_on(outputStream* st) const; 340 virtual void print_gc_threads_on(outputStream* st) const; 341 virtual void gc_threads_do(ThreadClosure* tc) const; 342 virtual void print_tracing_info() const; 343 344 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const; 345 346 // The functions below are helper functions that a subclass of 347 // "CollectedHeap" can use in the implementation of its virtual 348 // functions. 349 350 class GenClosure : public StackObj { 351 public: 352 virtual void do_generation(Generation* gen) = 0; 353 }; 354 355 // Apply "cl.do_generation" to all generations in the heap 356 // If "old_to_young" determines the order. 357 void generation_iterate(GenClosure* cl, bool old_to_young); 358 359 // Return "true" if all generations have reached the 360 // maximal committed limit that they can reach, without a garbage 361 // collection. 362 virtual bool is_maximal_no_gc() const; 363 364 // This function returns the CardTableRS object that allows us to scan 365 // generations in a fully generational heap. 366 CardTableRS* rem_set() { return _rem_set; } 367 368 // Convenience function to be used in situations where the heap type can be 369 // asserted to be this type. 370 static GenCollectedHeap* heap(); 371 372 // The ScanningOption determines which of the roots 373 // the closure is applied to: 374 // "SO_None" does none; 375 enum ScanningOption { 376 SO_None = 0x0, 377 SO_AllCodeCache = 0x8, 378 SO_ScavengeCodeCache = 0x10 379 }; 380 381 protected: 382 void process_roots(StrongRootsScope* scope, 383 ScanningOption so, 384 OopClosure* strong_roots, 385 OopClosure* weak_roots, 386 CLDClosure* strong_cld_closure, 387 CLDClosure* weak_cld_closure, 388 CodeBlobToOopClosure* code_roots); 389 390 void process_string_table_roots(StrongRootsScope* scope, 391 OopClosure* root_closure); 392 393 // Accessor for memory state verification support 394 NOT_PRODUCT( 395 virtual size_t skip_header_HeapWords() { return 0; } 396 ) 397 398 virtual void gc_prologue(bool full); 399 virtual void gc_epilogue(bool full); 400 401 public: 402 void young_process_roots(StrongRootsScope* scope, 403 OopsInGenClosure* root_closure, 404 OopsInGenClosure* old_gen_closure, 405 CLDClosure* cld_closure); 406 407 void full_process_roots(StrongRootsScope* scope, 408 bool is_adjust_phase, 409 ScanningOption so, 410 bool only_strong_roots, 411 OopsInGenClosure* root_closure, 412 CLDClosure* cld_closure); 413 414 // Apply "root_closure" to all the weak roots of the system. 415 // These include JNI weak roots, string table, 416 // and referents of reachable weak refs. 417 void gen_process_weak_roots(OopClosure* root_closure); 418 419 // Set the saved marks of generations, if that makes sense. 420 // In particular, if any generation might iterate over the oops 421 // in other generations, it should call this method. 422 void save_marks(); 423 424 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 425 // allocated since the last call to save_marks in generations at or above 426 // "level". The "cur" closure is 427 // applied to references in the generation at "level", and the "older" 428 // closure to older generations. 429 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 430 void oop_since_save_marks_iterate(GenerationType start_gen, \ 431 OopClosureType* cur, \ 432 OopClosureType* older); 433 434 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 435 436 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 437 438 // Returns "true" iff no allocations have occurred since the last 439 // call to "save_marks". 440 bool no_allocs_since_save_marks(); 441 442 // Returns true if an incremental collection is likely to fail. 443 // We optionally consult the young gen, if asked to do so; 444 // otherwise we base our answer on whether the previous incremental 445 // collection attempt failed with no corrective action as of yet. 446 bool incremental_collection_will_fail(bool consult_young) { 447 // The first disjunct remembers if an incremental collection failed, even 448 // when we thought (second disjunct) that it would not. 449 return incremental_collection_failed() || 450 (consult_young && !_young_gen->collection_attempt_is_safe()); 451 } 452 453 // If a generation bails out of an incremental collection, 454 // it sets this flag. 455 bool incremental_collection_failed() const { 456 return _incremental_collection_failed; 457 } 458 void set_incremental_collection_failed() { 459 _incremental_collection_failed = true; 460 } 461 void clear_incremental_collection_failed() { 462 _incremental_collection_failed = false; 463 } 464 465 // Promotion of obj into gen failed. Try to promote obj to higher 466 // gens in ascending order; return the new location of obj if successful. 467 // Otherwise, try expand-and-allocate for obj in both the young and old 468 // generation; return the new location of obj if successful. Otherwise, return NULL. 469 oop handle_failed_promotion(Generation* old_gen, 470 oop obj, 471 size_t obj_size); 472 473 474 private: 475 // Override 476 void check_for_non_bad_heap_word_value(HeapWord* addr, 477 size_t size) PRODUCT_RETURN; 478 479 // For use by mark-sweep. As implemented, mark-sweep-compact is global 480 // in an essential way: compaction is performed across generations, by 481 // iterating over spaces. 482 void prepare_for_compaction(); 483 484 // Perform a full collection of the generations up to and including max_generation. 485 // This is the low level interface used by the public versions of 486 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 487 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 488 489 // Save the tops of the spaces in all generations 490 void record_gen_tops_before_GC() PRODUCT_RETURN; 491 }; 492 493 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP