1 /* 2 * Copyright (c) 2000, 2013, 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 is represented with a sequence of Generation's. 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 Generation* _gens[max_gens]; 67 GenerationSpec** _gen_specs; 68 69 // The singleton Gen Remembered Set. 70 GenRemSet* _rem_set; 71 72 // The generational collector policy. 73 GenCollectorPolicy* _gen_policy; 74 75 // Indicates that the most recent previous incremental collection failed. 76 // The flag is cleared when an action is taken that might clear the 77 // condition that caused that incremental collection to fail. 78 bool _incremental_collection_failed; 79 80 // In support of ExplicitGCInvokesConcurrent functionality 81 unsigned int _full_collections_completed; 82 83 // Data structure for claiming the (potentially) parallel tasks in 84 // (gen-specific) roots processing. 85 SubTasksDone* _gen_process_roots_tasks; 86 SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; } 87 88 // In block contents verification, the number of header words to skip 89 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 90 91 protected: 92 // Helper functions for allocation 93 HeapWord* attempt_allocation(size_t size, 94 bool is_tlab, 95 bool first_only); 96 97 // Helper function for two callbacks below. 98 // Considers collection of the first max_level+1 generations. 99 void do_collection(bool full, 100 bool clear_all_soft_refs, 101 size_t size, 102 bool is_tlab, 103 int max_level); 104 105 // Callback from VM_GenCollectForAllocation operation. 106 // This function does everything necessary/possible to satisfy an 107 // allocation request that failed in the youngest generation that should 108 // have handled it (including collection, expansion, etc.) 109 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 110 111 // Callback from VM_GenCollectFull operation. 112 // Perform a full collection of the first max_level+1 generations. 113 virtual void do_full_collection(bool clear_all_soft_refs); 114 void do_full_collection(bool clear_all_soft_refs, int max_level); 115 116 // Does the "cause" of GC indicate that 117 // we absolutely __must__ clear soft refs? 118 bool must_clear_all_soft_refs(); 119 120 public: 121 GenCollectedHeap(GenCollectorPolicy *policy); 122 123 GCStats* gc_stats(int level) const; 124 125 // Returns JNI_OK on success 126 virtual jint initialize(); 127 char* allocate(size_t alignment, size_t* _total_reserved, ReservedSpace* heap_rs); 128 129 // Does operations required after initialization has been done. 130 void post_initialize(); 131 132 // Initialize ("weak") refs processing support 133 virtual void ref_processing_init(); 134 135 virtual CollectedHeap::Name kind() const { 136 return CollectedHeap::GenCollectedHeap; 137 } 138 139 // The generational collector policy. 140 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 141 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 142 143 // Adaptive size policy 144 virtual AdaptiveSizePolicy* size_policy() { 145 return gen_policy()->size_policy(); 146 } 147 148 // Return the (conservative) maximum heap alignment 149 static size_t conservative_max_heap_alignment() { 150 return Generation::GenGrain; 151 } 152 153 size_t capacity() const; 154 size_t used() const; 155 156 // Save the "used_region" for generations level and lower. 157 void save_used_regions(int level); 158 159 size_t max_capacity() const; 160 161 HeapWord* mem_allocate(size_t size, 162 bool* gc_overhead_limit_was_exceeded); 163 164 // We may support a shared contiguous allocation area, if the youngest 165 // generation does. 166 bool supports_inline_contig_alloc() const; 167 HeapWord** top_addr() const; 168 HeapWord** end_addr() const; 169 170 // Does this heap support heap inspection? (+PrintClassHistogram) 171 virtual bool supports_heap_inspection() const { return true; } 172 173 // Perform a full collection of the heap; intended for use in implementing 174 // "System.gc". This implies as full a collection as the CollectedHeap 175 // supports. Caller does not hold the Heap_lock on entry. 176 void collect(GCCause::Cause cause); 177 178 // The same as above but assume that the caller holds the Heap_lock. 179 void collect_locked(GCCause::Cause cause); 180 181 // Perform a full collection of the first max_level+1 generations. 182 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 183 void collect(GCCause::Cause cause, int max_level); 184 185 // Returns "TRUE" iff "p" points into the committed areas of the heap. 186 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 187 // be expensive to compute in general, so, to prevent 188 // their inadvertent use in product jvm's, we restrict their use to 189 // assertion checking or verification only. 190 bool is_in(const void* p) const; 191 192 // override 193 bool is_in_closed_subset(const void* p) const { 194 if (UseConcMarkSweepGC) { 195 return is_in_reserved(p); 196 } else { 197 return is_in(p); 198 } 199 } 200 201 // Returns true if the reference is to an object in the reserved space 202 // for the young generation. 203 // Assumes the the young gen address range is less than that of the old gen. 204 bool is_in_young(oop p); 205 206 #ifdef ASSERT 207 virtual bool is_in_partial_collection(const void* p); 208 #endif 209 210 virtual bool is_scavengable(const void* addr) { 211 return is_in_young((oop)addr); 212 } 213 214 // Iteration functions. 215 void oop_iterate(ExtendedOopClosure* cl); 216 void object_iterate(ObjectClosure* cl); 217 void safe_object_iterate(ObjectClosure* cl); 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 virtual HeapWord* block_start(const void* addr) const; 234 235 // Requires "addr" to be the start of a chunk, and returns its size. 236 // "addr + size" is required to be the start of a new chunk, or the end 237 // of the active area of the heap. Assumes (and verifies in non-product 238 // builds) that addr is in the allocated part of the heap and is 239 // the start of a chunk. 240 virtual size_t block_size(const HeapWord* addr) const; 241 242 // Requires "addr" to be the start of a block, and returns "TRUE" iff 243 // the block is an object. Assumes (and verifies in non-product 244 // builds) that addr is in the allocated part of the heap and is 245 // the start of a chunk. 246 virtual bool block_is_obj(const HeapWord* addr) const; 247 248 // Section on TLAB's. 249 virtual bool supports_tlab_allocation() const; 250 virtual size_t tlab_capacity(Thread* thr) const; 251 virtual size_t tlab_used(Thread* thr) const; 252 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 253 virtual HeapWord* allocate_new_tlab(size_t size); 254 255 // Can a compiler initialize a new object without store barriers? 256 // This permission only extends from the creation of a new object 257 // via a TLAB up to the first subsequent safepoint. 258 virtual bool can_elide_tlab_store_barriers() const { 259 return true; 260 } 261 262 virtual bool card_mark_must_follow_store() const { 263 return UseConcMarkSweepGC; 264 } 265 266 // We don't need barriers for stores to objects in the 267 // young gen and, a fortiori, for initializing stores to 268 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 269 // only and may need to be re-examined in case other 270 // kinds of collectors are implemented in the future. 271 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 272 // We wanted to assert that:- 273 // assert(UseSerialGC || UseConcMarkSweepGC, 274 // "Check can_elide_initializing_store_barrier() for this collector"); 275 // but unfortunately the flag UseSerialGC need not necessarily always 276 // be set when DefNew+Tenured are being used. 277 return is_in_young(new_obj); 278 } 279 280 // The "requestor" generation is performing some garbage collection 281 // action for which it would be useful to have scratch space. The 282 // requestor promises to allocate no more than "max_alloc_words" in any 283 // older generation (via promotion say.) Any blocks of space that can 284 // be provided are returned as a list of ScratchBlocks, sorted by 285 // decreasing size. 286 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 287 // Allow each generation to reset any scratch space that it has 288 // contributed as it needs. 289 void release_scratch(); 290 291 // Ensure parsability: override 292 virtual void ensure_parsability(bool retire_tlabs); 293 294 // Time in ms since the longest time a collector ran in 295 // in any generation. 296 virtual jlong millis_since_last_gc(); 297 298 // Total number of full collections completed. 299 unsigned int total_full_collections_completed() { 300 assert(_full_collections_completed <= _total_full_collections, 301 "Can't complete more collections than were started"); 302 return _full_collections_completed; 303 } 304 305 // Update above counter, as appropriate, at the end of a stop-world GC cycle 306 unsigned int update_full_collections_completed(); 307 // Update above counter, as appropriate, at the end of a concurrent GC cycle 308 unsigned int update_full_collections_completed(unsigned int count); 309 310 // Update "time of last gc" for all constituent generations 311 // to "now". 312 void update_time_of_last_gc(jlong now) { 313 for (int i = 0; i < _n_gens; i++) { 314 _gens[i]->update_time_of_last_gc(now); 315 } 316 } 317 318 // Update the gc statistics for each generation. 319 // "level" is the level of the latest collection. 320 void update_gc_stats(int current_level, bool full) { 321 for (int i = 0; i < _n_gens; i++) { 322 _gens[i]->update_gc_stats(current_level, full); 323 } 324 } 325 326 // Override. 327 bool no_gc_in_progress() { return !is_gc_active(); } 328 329 // Override. 330 void prepare_for_verify(); 331 332 // Override. 333 void verify(bool silent, VerifyOption option); 334 335 // Override. 336 virtual void print_on(outputStream* st) const; 337 virtual void print_gc_threads_on(outputStream* st) const; 338 virtual void gc_threads_do(ThreadClosure* tc) const; 339 virtual void print_tracing_info() const; 340 virtual void print_on_error(outputStream* st) const; 341 342 // PrintGC, PrintGCDetails support 343 void print_heap_change(size_t prev_used) const; 344 345 // The functions below are helper functions that a subclass of 346 // "CollectedHeap" can use in the implementation of its virtual 347 // functions. 348 349 class GenClosure : public StackObj { 350 public: 351 virtual void do_generation(Generation* gen) = 0; 352 }; 353 354 // Apply "cl.do_generation" to all generations in the heap 355 // If "old_to_young" determines the order. 356 void generation_iterate(GenClosure* cl, bool old_to_young); 357 358 void space_iterate(SpaceClosure* cl); 359 360 // Return "true" if all generations have reached the 361 // maximal committed limit that they can reach, without a garbage 362 // collection. 363 virtual bool is_maximal_no_gc() const; 364 365 // Return the generation before "gen". 366 Generation* prev_gen(Generation* gen) const { 367 int l = gen->level(); 368 guarantee(l > 0, "Out of bounds"); 369 return _gens[l-1]; 370 } 371 372 // Return the generation after "gen". 373 Generation* next_gen(Generation* gen) const { 374 int l = gen->level() + 1; 375 guarantee(l < _n_gens, "Out of bounds"); 376 return _gens[l]; 377 } 378 379 Generation* get_gen(int i) const { 380 guarantee(i >= 0 && i < _n_gens, "Out of bounds"); 381 return _gens[i]; 382 } 383 384 int n_gens() const { 385 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity"); 386 return _n_gens; 387 } 388 389 // This function returns the "GenRemSet" object that allows us to scan 390 // generations in a fully generational heap. 391 GenRemSet* rem_set() { return _rem_set; } 392 393 // Convenience function to be used in situations where the heap type can be 394 // asserted to be this type. 395 static GenCollectedHeap* heap(); 396 397 void set_par_threads(uint t); 398 399 // Invoke the "do_oop" method of one of the closures "not_older_gens" 400 // or "older_gens" on root locations for the generation at 401 // "level". (The "older_gens" closure is used for scanning references 402 // from older generations; "not_older_gens" is used everywhere else.) 403 // If "younger_gens_as_roots" is false, younger generations are 404 // not scanned as roots; in this case, the caller must be arranging to 405 // scan the younger generations itself. (For example, a generation might 406 // explicitly mark reachable objects in younger generations, to avoid 407 // excess storage retention.) 408 // The "so" argument determines which of the roots 409 // the closure is applied to: 410 // "SO_None" does none; 411 private: 412 void gen_process_roots(int level, 413 bool younger_gens_as_roots, 414 bool activate_scope, 415 SharedHeap::ScanningOption so, 416 OopsInGenClosure* not_older_gens, 417 OopsInGenClosure* weak_roots, 418 OopsInGenClosure* older_gens, 419 CLDClosure* cld_closure, 420 CLDClosure* weak_cld_closure, 421 CodeBlobClosure* code_closure); 422 423 public: 424 static const bool StrongAndWeakRoots = false; 425 static const bool StrongRootsOnly = true; 426 427 void gen_process_roots(int level, 428 bool younger_gens_as_roots, 429 bool activate_scope, 430 SharedHeap::ScanningOption so, 431 bool only_strong_roots, 432 OopsInGenClosure* not_older_gens, 433 OopsInGenClosure* older_gens, 434 CLDClosure* cld_closure); 435 436 // Apply "root_closure" to all the weak roots of the system. 437 // These include JNI weak roots, string table, 438 // and referents of reachable weak refs. 439 void gen_process_weak_roots(OopClosure* root_closure); 440 441 // Set the saved marks of generations, if that makes sense. 442 // In particular, if any generation might iterate over the oops 443 // in other generations, it should call this method. 444 void save_marks(); 445 446 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 447 // allocated since the last call to save_marks in generations at or above 448 // "level". The "cur" closure is 449 // applied to references in the generation at "level", and the "older" 450 // closure to older generations. 451 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 452 void oop_since_save_marks_iterate(int level, \ 453 OopClosureType* cur, \ 454 OopClosureType* older); 455 456 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 457 458 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 459 460 // Returns "true" iff no allocations have occurred in any generation at 461 // "level" or above since the last 462 // call to "save_marks". 463 bool no_allocs_since_save_marks(int level); 464 465 // Returns true if an incremental collection is likely to fail. 466 // We optionally consult the young gen, if asked to do so; 467 // otherwise we base our answer on whether the previous incremental 468 // collection attempt failed with no corrective action as of yet. 469 bool incremental_collection_will_fail(bool consult_young) { 470 // Assumes a 2-generation system; the first disjunct remembers if an 471 // incremental collection failed, even when we thought (second disjunct) 472 // that it would not. 473 assert(heap()->collector_policy()->is_generation_policy(), 474 "the following definition may not be suitable for an n(>2)-generation system"); 475 return incremental_collection_failed() || 476 (consult_young && !get_gen(0)->collection_attempt_is_safe()); 477 } 478 479 // If a generation bails out of an incremental collection, 480 // it sets this flag. 481 bool incremental_collection_failed() const { 482 return _incremental_collection_failed; 483 } 484 void set_incremental_collection_failed() { 485 _incremental_collection_failed = true; 486 } 487 void clear_incremental_collection_failed() { 488 _incremental_collection_failed = false; 489 } 490 491 // Promotion of obj into gen failed. Try to promote obj to higher 492 // gens in ascending order; return the new location of obj if successful. 493 // Otherwise, try expand-and-allocate for obj in both the young and old 494 // generation; return the new location of obj if successful. Otherwise, return NULL. 495 oop handle_failed_promotion(Generation* old_gen, 496 oop obj, 497 size_t obj_size); 498 499 private: 500 // Accessor for memory state verification support 501 NOT_PRODUCT( 502 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 503 ) 504 505 // Override 506 void check_for_non_bad_heap_word_value(HeapWord* addr, 507 size_t size) PRODUCT_RETURN; 508 509 // For use by mark-sweep. As implemented, mark-sweep-compact is global 510 // in an essential way: compaction is performed across generations, by 511 // iterating over spaces. 512 void prepare_for_compaction(); 513 514 // Perform a full collection of the first max_level+1 generations. 515 // This is the low level interface used by the public versions of 516 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 517 void collect_locked(GCCause::Cause cause, int max_level); 518 519 // Returns success or failure. 520 bool create_cms_collector(); 521 522 // In support of ExplicitGCInvokesConcurrent functionality 523 bool should_do_concurrent_full_gc(GCCause::Cause cause); 524 void collect_mostly_concurrent(GCCause::Cause cause); 525 526 // Save the tops of the spaces in all generations 527 void record_gen_tops_before_GC() PRODUCT_RETURN; 528 529 protected: 530 virtual void gc_prologue(bool full); 531 virtual void gc_epilogue(bool full); 532 }; 533 534 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP