1 /* 2 * Copyright (c) 2000, 2015, 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_MEMORY_GENCOLLECTEDHEAP_HPP 26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP 27 28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp" 29 #include "memory/collectorPolicy.hpp" 30 #include "memory/generation.hpp" 31 #include "memory/sharedHeap.hpp" 32 33 class SubTasksDone; 34 35 // A "GenCollectedHeap" is a SharedHeap that uses generational 36 // collection. It has two generations, young and old. 37 class GenCollectedHeap : public SharedHeap { 38 friend class GenCollectorPolicy; 39 friend class Generation; 40 friend class DefNewGeneration; 41 friend class TenuredGeneration; 42 friend class ConcurrentMarkSweepGeneration; 43 friend class CMSCollector; 44 friend class GenMarkSweep; 45 friend class VM_GenCollectForAllocation; 46 friend class VM_GenCollectFull; 47 friend class VM_GenCollectFullConcurrent; 48 friend class VM_GC_HeapInspection; 49 friend class VM_HeapDumper; 50 friend class HeapInspection; 51 friend class GCCauseSetter; 52 friend class VMStructs; 53 public: 54 enum SomeConstants { 55 max_gens = 10 56 }; 57 58 friend class VM_PopulateDumpSharedSpace; 59 60 protected: 61 // Fields: 62 static GenCollectedHeap* _gch; 63 64 private: 65 int _n_gens; 66 67 Generation* _young_gen; 68 Generation* _old_gen; 69 70 GenerationSpec** _gen_specs; 71 72 // The singleton Gen Remembered Set. 73 GenRemSet* _rem_set; 74 75 // The generational collector policy. 76 GenCollectorPolicy* _gen_policy; 77 78 // Indicates that the most recent previous incremental collection failed. 79 // The flag is cleared when an action is taken that might clear the 80 // condition that caused that incremental collection to fail. 81 bool _incremental_collection_failed; 82 83 // In support of ExplicitGCInvokesConcurrent functionality 84 unsigned int _full_collections_completed; 85 86 // Data structure for claiming the (potentially) parallel tasks in 87 // (gen-specific) roots processing. 88 SubTasksDone* _gen_process_roots_tasks; 89 SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; } 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 // In block contents verification, the number of header words to skip 97 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 98 99 protected: 100 // Helper functions for allocation 101 HeapWord* attempt_allocation(size_t size, 102 bool is_tlab, 103 bool first_only); 104 105 // Helper function for two callbacks below. 106 // Considers collection of the first max_level+1 generations. 107 void do_collection(bool full, 108 bool clear_all_soft_refs, 109 size_t size, 110 bool is_tlab, 111 int max_level); 112 113 // Callback from VM_GenCollectForAllocation operation. 114 // This function does everything necessary/possible to satisfy an 115 // allocation request that failed in the youngest generation that should 116 // have handled it (including collection, expansion, etc.) 117 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 118 119 // Callback from VM_GenCollectFull operation. 120 // Perform a full collection of the first max_level+1 generations. 121 virtual void do_full_collection(bool clear_all_soft_refs); 122 void do_full_collection(bool clear_all_soft_refs, int max_level); 123 124 // Does the "cause" of GC indicate that 125 // we absolutely __must__ clear soft refs? 126 bool must_clear_all_soft_refs(); 127 128 public: 129 GenCollectedHeap(GenCollectorPolicy *policy); 130 131 GCStats* gc_stats(int level) const; 132 133 // Returns JNI_OK on success 134 virtual jint initialize(); 135 136 // Reserve aligned space for the heap as needed by the contained generations. 137 char* allocate(size_t alignment, ReservedSpace* heap_rs); 138 139 // Does operations required after initialization has been done. 140 void post_initialize(); 141 142 // Initialize ("weak") refs processing support 143 virtual void ref_processing_init(); 144 145 virtual CollectedHeap::Name kind() const { 146 return CollectedHeap::GenCollectedHeap; 147 } 148 149 Generation* young_gen() { return _young_gen; } 150 Generation* old_gen() { return _old_gen; } 151 152 // The generational collector policy. 153 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 154 155 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 156 157 // Adaptive size policy 158 virtual AdaptiveSizePolicy* size_policy() { 159 return gen_policy()->size_policy(); 160 } 161 162 // Return the (conservative) maximum heap alignment 163 static size_t conservative_max_heap_alignment() { 164 return Generation::GenGrain; 165 } 166 167 size_t capacity() const; 168 size_t used() const; 169 170 // Save the "used_region" for generations level and lower. 171 void save_used_regions(int level); 172 173 size_t max_capacity() const; 174 175 HeapWord* mem_allocate(size_t size, 176 bool* gc_overhead_limit_was_exceeded); 177 178 // We may support a shared contiguous allocation area, if the youngest 179 // generation does. 180 bool supports_inline_contig_alloc() const; 181 HeapWord** top_addr() const; 182 HeapWord** end_addr() const; 183 184 // Does this heap support heap inspection? (+PrintClassHistogram) 185 virtual bool supports_heap_inspection() const { return true; } 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); 191 192 // The same as above but assume that the caller holds the Heap_lock. 193 void collect_locked(GCCause::Cause cause); 194 195 // Perform a full collection of the first max_level+1 generations. 196 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 197 void collect(GCCause::Cause cause, int max_level); 198 199 // Returns "TRUE" iff "p" points into the committed areas of the heap. 200 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 201 // be expensive to compute in general, so, to prevent 202 // their inadvertent use in product jvm's, we restrict their use to 203 // assertion checking or verification only. 204 bool is_in(const void* p) const; 205 206 // override 207 bool is_in_closed_subset(const void* p) const { 208 if (UseConcMarkSweepGC) { 209 return is_in_reserved(p); 210 } else { 211 return is_in(p); 212 } 213 } 214 215 // Returns true if the reference is to an object in the reserved space 216 // for the young generation. 217 // Assumes the the young gen address range is less than that of the old gen. 218 bool is_in_young(oop p); 219 220 #ifdef ASSERT 221 virtual bool is_in_partial_collection(const void* p); 222 #endif 223 224 virtual bool is_scavengable(const void* addr) { 225 return is_in_young((oop)addr); 226 } 227 228 // Iteration functions. 229 void oop_iterate(ExtendedOopClosure* cl); 230 void object_iterate(ObjectClosure* cl); 231 void safe_object_iterate(ObjectClosure* cl); 232 Space* space_containing(const void* addr) const; 233 234 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 235 // each address in the (reserved) heap is a member of exactly 236 // one block. The defining characteristic of a block is that it is 237 // possible to find its size, and thus to progress forward to the next 238 // block. (Blocks may be of different sizes.) Thus, blocks may 239 // represent Java objects, or they might be free blocks in a 240 // free-list-based heap (or subheap), as long as the two kinds are 241 // distinguishable and the size of each is determinable. 242 243 // Returns the address of the start of the "block" that contains the 244 // address "addr". We say "blocks" instead of "object" since some heaps 245 // may not pack objects densely; a chunk may either be an object or a 246 // non-object. 247 virtual HeapWord* block_start(const void* addr) const; 248 249 // Requires "addr" to be the start of a chunk, and returns its size. 250 // "addr + size" is required to be the start of a new chunk, or the end 251 // of the active area of the heap. Assumes (and verifies in non-product 252 // builds) that addr is in the allocated part of the heap and is 253 // the start of a chunk. 254 virtual size_t block_size(const HeapWord* addr) const; 255 256 // Requires "addr" to be the start of a block, and returns "TRUE" iff 257 // the block is an object. Assumes (and verifies in non-product 258 // builds) that addr is in the allocated part of the heap and is 259 // the start of a chunk. 260 virtual bool block_is_obj(const HeapWord* addr) const; 261 262 // Section on TLAB's. 263 virtual bool supports_tlab_allocation() const; 264 virtual size_t tlab_capacity(Thread* thr) const; 265 virtual size_t tlab_used(Thread* thr) const; 266 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 267 virtual HeapWord* allocate_new_tlab(size_t size); 268 269 // Can a compiler initialize a new object without store barriers? 270 // This permission only extends from the creation of a new object 271 // via a TLAB up to the first subsequent safepoint. 272 virtual bool can_elide_tlab_store_barriers() const { 273 return true; 274 } 275 276 virtual bool card_mark_must_follow_store() const { 277 return UseConcMarkSweepGC; 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 // We wanted to assert that:- 287 // assert(UseSerialGC || UseConcMarkSweepGC, 288 // "Check can_elide_initializing_store_barrier() for this collector"); 289 // but unfortunately the flag UseSerialGC need not necessarily always 290 // be set when DefNew+Tenured are being used. 291 return is_in_young(new_obj); 292 } 293 294 // The "requestor" generation is performing some garbage collection 295 // action for which it would be useful to have scratch space. The 296 // requestor promises to allocate no more than "max_alloc_words" in any 297 // older generation (via promotion say.) Any blocks of space that can 298 // be provided are returned as a list of ScratchBlocks, sorted by 299 // decreasing size. 300 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 301 // Allow each generation to reset any scratch space that it has 302 // contributed as it needs. 303 void release_scratch(); 304 305 // Ensure parsability: override 306 virtual void ensure_parsability(bool retire_tlabs); 307 308 // Time in ms since the longest time a collector ran in 309 // in any generation. 310 virtual jlong millis_since_last_gc(); 311 312 // Total number of full collections completed. 313 unsigned int total_full_collections_completed() { 314 assert(_full_collections_completed <= _total_full_collections, 315 "Can't complete more collections than were started"); 316 return _full_collections_completed; 317 } 318 319 // Update above counter, as appropriate, at the end of a stop-world GC cycle 320 unsigned int update_full_collections_completed(); 321 // Update above counter, as appropriate, at the end of a concurrent GC cycle 322 unsigned int update_full_collections_completed(unsigned int count); 323 324 // Update "time of last gc" for all generations to "now". 325 void update_time_of_last_gc(jlong now) { 326 _young_gen->update_time_of_last_gc(now); 327 _old_gen->update_time_of_last_gc(now); 328 } 329 330 // Update the gc statistics for each generation. 331 // "level" is the level of the latest collection. 332 void update_gc_stats(int current_level, bool full) { 333 _young_gen->update_gc_stats(current_level, full); 334 _old_gen->update_gc_stats(current_level, full); 335 } 336 337 // Override. 338 bool no_gc_in_progress() { return !is_gc_active(); } 339 340 // Override. 341 void prepare_for_verify(); 342 343 // Override. 344 void verify(bool silent, VerifyOption option); 345 346 // Override. 347 virtual void print_on(outputStream* st) const; 348 virtual void print_gc_threads_on(outputStream* st) const; 349 virtual void gc_threads_do(ThreadClosure* tc) const; 350 virtual void print_tracing_info() const; 351 virtual void print_on_error(outputStream* st) const; 352 353 // PrintGC, PrintGCDetails support 354 void print_heap_change(size_t prev_used) const; 355 356 // The functions below are helper functions that a subclass of 357 // "CollectedHeap" can use in the implementation of its virtual 358 // functions. 359 360 class GenClosure : public StackObj { 361 public: 362 virtual void do_generation(Generation* gen) = 0; 363 }; 364 365 // Apply "cl.do_generation" to all generations in the heap 366 // If "old_to_young" determines the order. 367 void generation_iterate(GenClosure* cl, bool old_to_young); 368 369 void space_iterate(SpaceClosure* cl); 370 371 // Return "true" if all generations have reached the 372 // maximal committed limit that they can reach, without a garbage 373 // collection. 374 virtual bool is_maximal_no_gc() const; 375 376 int n_gens() const { 377 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity"); 378 return _n_gens; 379 } 380 381 // This function returns the "GenRemSet" object that allows us to scan 382 // generations in a fully generational heap. 383 GenRemSet* rem_set() { return _rem_set; } 384 385 // Convenience function to be used in situations where the heap type can be 386 // asserted to be this type. 387 static GenCollectedHeap* heap(); 388 389 void set_par_threads(uint t); 390 391 // Invoke the "do_oop" method of one of the closures "not_older_gens" 392 // or "older_gens" on root locations for the generation at 393 // "level". (The "older_gens" closure is used for scanning references 394 // from older generations; "not_older_gens" is used everywhere else.) 395 // If "younger_gens_as_roots" is false, younger generations are 396 // not scanned as roots; in this case, the caller must be arranging to 397 // scan the younger generations itself. (For example, a generation might 398 // explicitly mark reachable objects in younger generations, to avoid 399 // excess storage retention.) 400 // The "so" argument determines which of the roots 401 // the closure is applied to: 402 // "SO_None" does none; 403 private: 404 void gen_process_roots(int level, 405 bool younger_gens_as_roots, 406 bool activate_scope, 407 SharedHeap::ScanningOption so, 408 OopsInGenClosure* not_older_gens, 409 OopsInGenClosure* weak_roots, 410 OopsInGenClosure* older_gens, 411 CLDClosure* cld_closure, 412 CLDClosure* weak_cld_closure, 413 CodeBlobClosure* code_closure); 414 415 public: 416 static const bool StrongAndWeakRoots = false; 417 static const bool StrongRootsOnly = true; 418 419 void gen_process_roots(int level, 420 bool younger_gens_as_roots, 421 bool activate_scope, 422 SharedHeap::ScanningOption so, 423 bool only_strong_roots, 424 OopsInGenClosure* not_older_gens, 425 OopsInGenClosure* older_gens, 426 CLDClosure* cld_closure); 427 428 // Apply "root_closure" to all the weak roots of the system. 429 // These include JNI weak roots, string table, 430 // and referents of reachable weak refs. 431 void gen_process_weak_roots(OopClosure* root_closure); 432 433 // Set the saved marks of generations, if that makes sense. 434 // In particular, if any generation might iterate over the oops 435 // in other generations, it should call this method. 436 void save_marks(); 437 438 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 439 // allocated since the last call to save_marks in generations at or above 440 // "level". The "cur" closure is 441 // applied to references in the generation at "level", and the "older" 442 // closure to older generations. 443 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 444 void oop_since_save_marks_iterate(int level, \ 445 OopClosureType* cur, \ 446 OopClosureType* older); 447 448 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 449 450 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 451 452 // Returns "true" iff no allocations have occurred in any generation at 453 // "level" or above since the last 454 // call to "save_marks". 455 bool no_allocs_since_save_marks(int level); 456 457 // Returns true if an incremental collection is likely to fail. 458 // We optionally consult the young gen, if asked to do so; 459 // otherwise we base our answer on whether the previous incremental 460 // collection attempt failed with no corrective action as of yet. 461 bool incremental_collection_will_fail(bool consult_young) { 462 // Assumes a 2-generation system; the first disjunct remembers if an 463 // incremental collection failed, even when we thought (second disjunct) 464 // that it would not. 465 assert(heap()->collector_policy()->is_generation_policy(), 466 "the following definition may not be suitable for an n(>2)-generation system"); 467 return incremental_collection_failed() || 468 (consult_young && !_young_gen->collection_attempt_is_safe()); 469 } 470 471 // If a generation bails out of an incremental collection, 472 // it sets this flag. 473 bool incremental_collection_failed() const { 474 return _incremental_collection_failed; 475 } 476 void set_incremental_collection_failed() { 477 _incremental_collection_failed = true; 478 } 479 void clear_incremental_collection_failed() { 480 _incremental_collection_failed = false; 481 } 482 483 // Promotion of obj into gen failed. Try to promote obj to higher 484 // gens in ascending order; return the new location of obj if successful. 485 // Otherwise, try expand-and-allocate for obj in both the young and old 486 // generation; return the new location of obj if successful. Otherwise, return NULL. 487 oop handle_failed_promotion(Generation* old_gen, 488 oop obj, 489 size_t obj_size); 490 491 private: 492 // Accessor for memory state verification support 493 NOT_PRODUCT( 494 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 495 ) 496 497 // Override 498 void check_for_non_bad_heap_word_value(HeapWord* addr, 499 size_t size) PRODUCT_RETURN; 500 501 // For use by mark-sweep. As implemented, mark-sweep-compact is global 502 // in an essential way: compaction is performed across generations, by 503 // iterating over spaces. 504 void prepare_for_compaction(); 505 506 // Perform a full collection of the first max_level+1 generations. 507 // This is the low level interface used by the public versions of 508 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 509 void collect_locked(GCCause::Cause cause, int max_level); 510 511 // Returns success or failure. 512 bool create_cms_collector(); 513 514 // In support of ExplicitGCInvokesConcurrent functionality 515 bool should_do_concurrent_full_gc(GCCause::Cause cause); 516 void collect_mostly_concurrent(GCCause::Cause cause); 517 518 // Save the tops of the spaces in all generations 519 void record_gen_tops_before_GC() PRODUCT_RETURN; 520 521 protected: 522 virtual void gc_prologue(bool full); 523 virtual void gc_epilogue(bool full); 524 }; 525 526 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP