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 class FlexibleWorkGang; 35 36 // A "GenCollectedHeap" is a SharedHeap that uses generational 37 // collection. It has two generations, young and old. 38 class GenCollectedHeap : public SharedHeap { 39 friend class GenCollectorPolicy; 40 friend class Generation; 41 friend class DefNewGeneration; 42 friend class TenuredGeneration; 43 friend class ConcurrentMarkSweepGeneration; 44 friend class CMSCollector; 45 friend class GenMarkSweep; 46 friend class VM_GenCollectForAllocation; 47 friend class VM_GenCollectFull; 48 friend class VM_GenCollectFullConcurrent; 49 friend class VM_GC_HeapInspection; 50 friend class VM_HeapDumper; 51 friend class HeapInspection; 52 friend class GCCauseSetter; 53 friend class VMStructs; 54 public: 55 enum SomeConstants { 56 max_gens = 10 57 }; 58 59 friend class VM_PopulateDumpSharedSpace; 60 61 protected: 62 // Fields: 63 static GenCollectedHeap* _gch; 64 65 private: 66 int _n_gens; 67 68 Generation* _young_gen; 69 Generation* _old_gen; 70 71 // The singleton Gen Remembered Set. 72 GenRemSet* _rem_set; 73 74 // The generational collector policy. 75 GenCollectorPolicy* _gen_policy; 76 77 // Indicates that the most recent previous incremental collection failed. 78 // The flag is cleared when an action is taken that might clear the 79 // condition that caused that incremental collection to fail. 80 bool _incremental_collection_failed; 81 82 // In support of ExplicitGCInvokesConcurrent functionality 83 unsigned int _full_collections_completed; 84 85 // Data structure for claiming the (potentially) parallel tasks in 86 // (gen-specific) roots processing. 87 SubTasksDone* _process_strong_tasks; 88 89 // Collects the given generation. 90 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 91 bool run_verification, bool clear_soft_refs, 92 bool restore_marks_for_biased_locking); 93 94 // In block contents verification, the number of header words to skip 95 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 96 97 FlexibleWorkGang* _workers; 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 FlexibleWorkGang* workers() const { return _workers; } 132 133 GCStats* gc_stats(int level) const; 134 135 // Returns JNI_OK on success 136 virtual jint initialize(); 137 138 // Reserve aligned space for the heap as needed by the contained generations. 139 char* allocate(size_t alignment, ReservedSpace* heap_rs); 140 141 // Does operations required after initialization has been done. 142 void post_initialize(); 143 144 // Initialize ("weak") refs processing support 145 virtual void ref_processing_init(); 146 147 virtual Name kind() const { 148 return CollectedHeap::GenCollectedHeap; 149 } 150 151 Generation* young_gen() const { return _young_gen; } 152 Generation* old_gen() const { return _old_gen; } 153 154 // The generational collector policy. 155 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 156 157 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 158 159 // Adaptive size policy 160 virtual AdaptiveSizePolicy* size_policy() { 161 return gen_policy()->size_policy(); 162 } 163 164 // Return the (conservative) maximum heap alignment 165 static size_t conservative_max_heap_alignment() { 166 return Generation::GenGrain; 167 } 168 169 size_t capacity() const; 170 size_t used() const; 171 172 // Save the "used_region" for generations level and lower. 173 void save_used_regions(int level); 174 175 size_t max_capacity() const; 176 177 HeapWord* mem_allocate(size_t size, 178 bool* gc_overhead_limit_was_exceeded); 179 180 // We may support a shared contiguous allocation area, if the youngest 181 // generation does. 182 bool supports_inline_contig_alloc() const; 183 HeapWord** top_addr() const; 184 HeapWord** end_addr() const; 185 186 // Does this heap support heap inspection? (+PrintClassHistogram) 187 virtual bool supports_heap_inspection() const { return true; } 188 189 // Perform a full collection of the heap; intended for use in implementing 190 // "System.gc". This implies as full a collection as the CollectedHeap 191 // supports. Caller does not hold the Heap_lock on entry. 192 void collect(GCCause::Cause cause); 193 194 // The same as above but assume that the caller holds the Heap_lock. 195 void collect_locked(GCCause::Cause cause); 196 197 // Perform a full collection of the first max_level+1 generations. 198 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 199 void collect(GCCause::Cause cause, int max_level); 200 201 // Returns "TRUE" iff "p" points into the committed areas of the heap. 202 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 203 // be expensive to compute in general, so, to prevent 204 // their inadvertent use in product jvm's, we restrict their use to 205 // assertion checking or verification only. 206 bool is_in(const void* p) const; 207 208 // override 209 bool is_in_closed_subset(const void* p) const { 210 if (UseConcMarkSweepGC) { 211 return is_in_reserved(p); 212 } else { 213 return is_in(p); 214 } 215 } 216 217 // Returns true if the reference is to an object in the reserved space 218 // for the young generation. 219 // Assumes the the young gen address range is less than that of the old gen. 220 bool is_in_young(oop p); 221 222 #ifdef ASSERT 223 bool is_in_partial_collection(const void* p); 224 #endif 225 226 virtual bool is_scavengable(const void* addr) { 227 return is_in_young((oop)addr); 228 } 229 230 // Iteration functions. 231 void oop_iterate_no_header(OopClosure* cl); 232 void oop_iterate(ExtendedOopClosure* cl); 233 void object_iterate(ObjectClosure* cl); 234 void safe_object_iterate(ObjectClosure* cl); 235 Space* space_containing(const void* addr) const; 236 237 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 238 // each address in the (reserved) heap is a member of exactly 239 // one block. The defining characteristic of a block is that it is 240 // possible to find its size, and thus to progress forward to the next 241 // block. (Blocks may be of different sizes.) Thus, blocks may 242 // represent Java objects, or they might be free blocks in a 243 // free-list-based heap (or subheap), as long as the two kinds are 244 // distinguishable and the size of each is determinable. 245 246 // Returns the address of the start of the "block" that contains the 247 // address "addr". We say "blocks" instead of "object" since some heaps 248 // may not pack objects densely; a chunk may either be an object or a 249 // non-object. 250 virtual HeapWord* block_start(const void* addr) const; 251 252 // Requires "addr" to be the start of a chunk, and returns its size. 253 // "addr + size" is required to be the start of a new chunk, or the end 254 // of the active area of the heap. Assumes (and verifies in non-product 255 // builds) that addr is in the allocated part of the heap and is 256 // the start of a chunk. 257 virtual size_t block_size(const HeapWord* addr) const; 258 259 // Requires "addr" to be the start of a block, and returns "TRUE" iff 260 // the block is an object. Assumes (and verifies in non-product 261 // builds) that addr is in the allocated part of the heap and is 262 // the start of a chunk. 263 virtual bool block_is_obj(const HeapWord* addr) const; 264 265 // Section on TLAB's. 266 virtual bool supports_tlab_allocation() const; 267 virtual size_t tlab_capacity(Thread* thr) const; 268 virtual size_t tlab_used(Thread* thr) const; 269 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 270 virtual HeapWord* allocate_new_tlab(size_t size); 271 272 // Can a compiler initialize a new object without store barriers? 273 // This permission only extends from the creation of a new object 274 // via a TLAB up to the first subsequent safepoint. 275 virtual bool can_elide_tlab_store_barriers() const { 276 return true; 277 } 278 279 virtual bool card_mark_must_follow_store() const { 280 return UseConcMarkSweepGC; 281 } 282 283 // We don't need barriers for stores to objects in the 284 // young gen and, a fortiori, for initializing stores to 285 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 286 // only and may need to be re-examined in case other 287 // kinds of collectors are implemented in the future. 288 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 289 // We wanted to assert that:- 290 // assert(UseSerialGC || UseConcMarkSweepGC, 291 // "Check can_elide_initializing_store_barrier() for this collector"); 292 // but unfortunately the flag UseSerialGC need not necessarily always 293 // be set when DefNew+Tenured are being used. 294 return is_in_young(new_obj); 295 } 296 297 // The "requestor" generation is performing some garbage collection 298 // action for which it would be useful to have scratch space. The 299 // requestor promises to allocate no more than "max_alloc_words" in any 300 // older generation (via promotion say.) Any blocks of space that can 301 // be provided are returned as a list of ScratchBlocks, sorted by 302 // decreasing size. 303 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 304 // Allow each generation to reset any scratch space that it has 305 // contributed as it needs. 306 void release_scratch(); 307 308 // Ensure parsability: override 309 virtual void ensure_parsability(bool retire_tlabs); 310 311 // Time in ms since the longest time a collector ran in 312 // in any generation. 313 virtual jlong millis_since_last_gc(); 314 315 // Total number of full collections completed. 316 unsigned int total_full_collections_completed() { 317 assert(_full_collections_completed <= _total_full_collections, 318 "Can't complete more collections than were started"); 319 return _full_collections_completed; 320 } 321 322 // Update above counter, as appropriate, at the end of a stop-world GC cycle 323 unsigned int update_full_collections_completed(); 324 // Update above counter, as appropriate, at the end of a concurrent GC cycle 325 unsigned int update_full_collections_completed(unsigned int count); 326 327 // Update "time of last gc" for all generations to "now". 328 void update_time_of_last_gc(jlong now) { 329 _young_gen->update_time_of_last_gc(now); 330 _old_gen->update_time_of_last_gc(now); 331 } 332 333 // Update the gc statistics for each generation. 334 // "level" is the level of the latest collection. 335 void update_gc_stats(int current_level, bool full) { 336 _young_gen->update_gc_stats(current_level, full); 337 _old_gen->update_gc_stats(current_level, full); 338 } 339 340 bool no_gc_in_progress() { return !is_gc_active(); } 341 342 // Override. 343 void prepare_for_verify(); 344 345 // Override. 346 void verify(bool silent, VerifyOption option); 347 348 // Override. 349 virtual void print_on(outputStream* st) const; 350 virtual void print_gc_threads_on(outputStream* st) const; 351 virtual void gc_threads_do(ThreadClosure* tc) const; 352 virtual void print_tracing_info() const; 353 virtual void print_on_error(outputStream* st) const; 354 355 // PrintGC, PrintGCDetails support 356 void print_heap_change(size_t prev_used) const; 357 358 // The functions below are helper functions that a subclass of 359 // "CollectedHeap" can use in the implementation of its virtual 360 // functions. 361 362 class GenClosure : public StackObj { 363 public: 364 virtual void do_generation(Generation* gen) = 0; 365 }; 366 367 // Apply "cl.do_generation" to all generations in the heap 368 // If "old_to_young" determines the order. 369 void generation_iterate(GenClosure* cl, bool old_to_young); 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 void set_n_termination(uint t); 391 392 // Invoke the "do_oop" method of one of the closures "not_older_gens" 393 // or "older_gens" on root locations for the generation at 394 // "level". (The "older_gens" closure is used for scanning references 395 // from older generations; "not_older_gens" is used everywhere else.) 396 // If "younger_gens_as_roots" is false, younger generations are 397 // not scanned as roots; in this case, the caller must be arranging to 398 // scan the younger generations itself. (For example, a generation might 399 // explicitly mark reachable objects in younger generations, to avoid 400 // excess storage retention.) 401 // The "so" argument determines which of the roots 402 // the closure is applied to: 403 // "SO_None" does none; 404 enum ScanningOption { 405 SO_None = 0x0, 406 SO_AllCodeCache = 0x8, 407 SO_ScavengeCodeCache = 0x10 408 }; 409 410 private: 411 void process_roots(bool activate_scope, 412 ScanningOption so, 413 OopClosure* strong_roots, 414 OopClosure* weak_roots, 415 CLDClosure* strong_cld_closure, 416 CLDClosure* weak_cld_closure, 417 CodeBlobClosure* code_roots); 418 419 void gen_process_roots(int level, 420 bool younger_gens_as_roots, 421 bool activate_scope, 422 ScanningOption so, 423 OopsInGenClosure* not_older_gens, 424 OopsInGenClosure* weak_roots, 425 OopsInGenClosure* older_gens, 426 CLDClosure* cld_closure, 427 CLDClosure* weak_cld_closure, 428 CodeBlobClosure* code_closure); 429 430 public: 431 static const bool StrongAndWeakRoots = false; 432 static const bool StrongRootsOnly = true; 433 434 void gen_process_roots(int level, 435 bool younger_gens_as_roots, 436 bool activate_scope, 437 ScanningOption so, 438 bool only_strong_roots, 439 OopsInGenClosure* not_older_gens, 440 OopsInGenClosure* older_gens, 441 CLDClosure* cld_closure); 442 443 // Apply "root_closure" to all the weak roots of the system. 444 // These include JNI weak roots, string table, 445 // and referents of reachable weak refs. 446 void gen_process_weak_roots(OopClosure* root_closure); 447 448 // Set the saved marks of generations, if that makes sense. 449 // In particular, if any generation might iterate over the oops 450 // in other generations, it should call this method. 451 void save_marks(); 452 453 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 454 // allocated since the last call to save_marks in generations at or above 455 // "level". The "cur" closure is 456 // applied to references in the generation at "level", and the "older" 457 // closure to older generations. 458 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 459 void oop_since_save_marks_iterate(int level, \ 460 OopClosureType* cur, \ 461 OopClosureType* older); 462 463 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 464 465 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 466 467 // Returns "true" iff no allocations have occurred in any generation at 468 // "level" or above since the last 469 // call to "save_marks". 470 bool no_allocs_since_save_marks(int level); 471 472 // Returns true if an incremental collection is likely to fail. 473 // We optionally consult the young gen, if asked to do so; 474 // otherwise we base our answer on whether the previous incremental 475 // collection attempt failed with no corrective action as of yet. 476 bool incremental_collection_will_fail(bool consult_young) { 477 // Assumes a 2-generation system; the first disjunct remembers if an 478 // incremental collection failed, even when we thought (second disjunct) 479 // that it would not. 480 assert(heap()->collector_policy()->is_generation_policy(), 481 "the following definition may not be suitable for an n(>2)-generation system"); 482 return incremental_collection_failed() || 483 (consult_young && !_young_gen->collection_attempt_is_safe()); 484 } 485 486 // If a generation bails out of an incremental collection, 487 // it sets this flag. 488 bool incremental_collection_failed() const { 489 return _incremental_collection_failed; 490 } 491 void set_incremental_collection_failed() { 492 _incremental_collection_failed = true; 493 } 494 void clear_incremental_collection_failed() { 495 _incremental_collection_failed = false; 496 } 497 498 // Promotion of obj into gen failed. Try to promote obj to higher 499 // gens in ascending order; return the new location of obj if successful. 500 // Otherwise, try expand-and-allocate for obj in both the young and old 501 // generation; return the new location of obj if successful. Otherwise, return NULL. 502 oop handle_failed_promotion(Generation* old_gen, 503 oop obj, 504 size_t obj_size); 505 506 private: 507 // Accessor for memory state verification support 508 NOT_PRODUCT( 509 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 510 ) 511 512 // Override 513 void check_for_non_bad_heap_word_value(HeapWord* addr, 514 size_t size) PRODUCT_RETURN; 515 516 // For use by mark-sweep. As implemented, mark-sweep-compact is global 517 // in an essential way: compaction is performed across generations, by 518 // iterating over spaces. 519 void prepare_for_compaction(); 520 521 // Perform a full collection of the first max_level+1 generations. 522 // This is the low level interface used by the public versions of 523 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 524 void collect_locked(GCCause::Cause cause, int max_level); 525 526 // Returns success or failure. 527 bool create_cms_collector(); 528 529 // In support of ExplicitGCInvokesConcurrent functionality 530 bool should_do_concurrent_full_gc(GCCause::Cause cause); 531 void collect_mostly_concurrent(GCCause::Cause cause); 532 533 // Save the tops of the spaces in all generations 534 void record_gen_tops_before_GC() PRODUCT_RETURN; 535 536 protected: 537 void gc_prologue(bool full); 538 void gc_epilogue(bool full); 539 }; 540 541 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP