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 // The singleton Gen Remembered Set. 71 GenRemSet* _rem_set; 72 73 // The generational collector policy. 74 GenCollectorPolicy* _gen_policy; 75 76 // Indicates that the most recent previous incremental collection failed. 77 // The flag is cleared when an action is taken that might clear the 78 // condition that caused that incremental collection to fail. 79 bool _incremental_collection_failed; 80 81 // In support of ExplicitGCInvokesConcurrent functionality 82 unsigned int _full_collections_completed; 83 84 // Data structure for claiming the (potentially) parallel tasks in 85 // (gen-specific) roots processing. 86 SubTasksDone* _process_strong_tasks; 87 88 // Collects the given generation. 89 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 90 bool run_verification, bool clear_soft_refs, 91 bool restore_marks_for_biased_locking); 92 93 // In block contents verification, the number of header words to skip 94 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 95 96 protected: 97 // Helper functions for allocation 98 HeapWord* attempt_allocation(size_t size, 99 bool is_tlab, 100 bool first_only); 101 102 // Helper function for two callbacks below. 103 // Considers collection of the first max_level+1 generations. 104 void do_collection(bool full, 105 bool clear_all_soft_refs, 106 size_t size, 107 bool is_tlab, 108 int max_level); 109 110 // Callback from VM_GenCollectForAllocation operation. 111 // This function does everything necessary/possible to satisfy an 112 // allocation request that failed in the youngest generation that should 113 // have handled it (including collection, expansion, etc.) 114 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 115 116 // Callback from VM_GenCollectFull operation. 117 // Perform a full collection of the first max_level+1 generations. 118 virtual void do_full_collection(bool clear_all_soft_refs); 119 void do_full_collection(bool clear_all_soft_refs, int max_level); 120 121 // Does the "cause" of GC indicate that 122 // we absolutely __must__ clear soft refs? 123 bool must_clear_all_soft_refs(); 124 125 public: 126 GenCollectedHeap(GenCollectorPolicy *policy); 127 128 GCStats* gc_stats(int level) const; 129 130 // Returns JNI_OK on success 131 virtual jint initialize(); 132 133 // Reserve aligned space for the heap as needed by the contained generations. 134 char* allocate(size_t alignment, ReservedSpace* heap_rs); 135 136 // Does operations required after initialization has been done. 137 void post_initialize(); 138 139 // Initialize ("weak") refs processing support 140 virtual void ref_processing_init(); 141 142 virtual Name kind() const { 143 return CollectedHeap::GenCollectedHeap; 144 } 145 146 Generation* young_gen() const { return _young_gen; } 147 Generation* old_gen() const { return _old_gen; } 148 149 // The generational collector policy. 150 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 151 152 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 153 154 // Adaptive size policy 155 virtual AdaptiveSizePolicy* size_policy() { 156 return gen_policy()->size_policy(); 157 } 158 159 // Return the (conservative) maximum heap alignment 160 static size_t conservative_max_heap_alignment() { 161 return Generation::GenGrain; 162 } 163 164 size_t capacity() const; 165 size_t used() const; 166 167 // Save the "used_region" for generations level and lower. 168 void save_used_regions(int level); 169 170 size_t max_capacity() const; 171 172 HeapWord* mem_allocate(size_t size, 173 bool* gc_overhead_limit_was_exceeded); 174 175 // We may support a shared contiguous allocation area, if the youngest 176 // generation does. 177 bool supports_inline_contig_alloc() const; 178 HeapWord** top_addr() const; 179 HeapWord** end_addr() const; 180 181 // Does this heap support heap inspection? (+PrintClassHistogram) 182 virtual bool supports_heap_inspection() const { return true; } 183 184 // Perform a full collection of the heap; intended for use in implementing 185 // "System.gc". This implies as full a collection as the CollectedHeap 186 // supports. Caller does not hold the Heap_lock on entry. 187 void collect(GCCause::Cause cause); 188 189 // The same as above but assume that the caller holds the Heap_lock. 190 void collect_locked(GCCause::Cause cause); 191 192 // Perform a full collection of the first max_level+1 generations. 193 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 194 void collect(GCCause::Cause cause, int max_level); 195 196 // Returns "TRUE" iff "p" points into the committed areas of the heap. 197 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 198 // be expensive to compute in general, so, to prevent 199 // their inadvertent use in product jvm's, we restrict their use to 200 // assertion checking or verification only. 201 bool is_in(const void* p) const; 202 203 // override 204 bool is_in_closed_subset(const void* p) const { 205 if (UseConcMarkSweepGC) { 206 return is_in_reserved(p); 207 } else { 208 return is_in(p); 209 } 210 } 211 212 // Returns true if the reference is to an object in the reserved space 213 // for the young generation. 214 // Assumes the the young gen address range is less than that of the old gen. 215 bool is_in_young(oop p); 216 217 #ifdef ASSERT 218 bool is_in_partial_collection(const void* p); 219 #endif 220 221 virtual bool is_scavengable(const void* addr) { 222 return is_in_young((oop)addr); 223 } 224 225 // Iteration functions. 226 void oop_iterate_no_header(OopClosure* cl); 227 void oop_iterate(ExtendedOopClosure* cl); 228 void object_iterate(ObjectClosure* cl); 229 void safe_object_iterate(ObjectClosure* cl); 230 Space* space_containing(const void* addr) const; 231 232 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 233 // each address in the (reserved) heap is a member of exactly 234 // one block. The defining characteristic of a block is that it is 235 // possible to find its size, and thus to progress forward to the next 236 // block. (Blocks may be of different sizes.) Thus, blocks may 237 // represent Java objects, or they might be free blocks in a 238 // free-list-based heap (or subheap), as long as the two kinds are 239 // distinguishable and the size of each is determinable. 240 241 // Returns the address of the start of the "block" that contains the 242 // address "addr". We say "blocks" instead of "object" since some heaps 243 // may not pack objects densely; a chunk may either be an object or a 244 // non-object. 245 virtual HeapWord* block_start(const void* addr) const; 246 247 // Requires "addr" to be the start of a chunk, and returns its size. 248 // "addr + size" is required to be the start of a new chunk, or the end 249 // of the active area of the heap. Assumes (and verifies in non-product 250 // builds) that addr is in the allocated part of the heap and is 251 // the start of a chunk. 252 virtual size_t block_size(const HeapWord* addr) const; 253 254 // Requires "addr" to be the start of a block, and returns "TRUE" iff 255 // the block is an object. 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 bool block_is_obj(const HeapWord* addr) const; 259 260 // Section on TLAB's. 261 virtual bool supports_tlab_allocation() const; 262 virtual size_t tlab_capacity(Thread* thr) const; 263 virtual size_t tlab_used(Thread* thr) const; 264 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 265 virtual HeapWord* allocate_new_tlab(size_t size); 266 267 // Can a compiler initialize a new object without store barriers? 268 // This permission only extends from the creation of a new object 269 // via a TLAB up to the first subsequent safepoint. 270 virtual bool can_elide_tlab_store_barriers() const { 271 return true; 272 } 273 274 virtual bool card_mark_must_follow_store() const { 275 return UseConcMarkSweepGC; 276 } 277 278 // We don't need barriers for stores to objects in the 279 // young gen and, a fortiori, for initializing stores to 280 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 281 // only and may need to be re-examined in case other 282 // kinds of collectors are implemented in the future. 283 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 284 // We wanted to assert that:- 285 // assert(UseSerialGC || UseConcMarkSweepGC, 286 // "Check can_elide_initializing_store_barrier() for this collector"); 287 // but unfortunately the flag UseSerialGC need not necessarily always 288 // be set when DefNew+Tenured are being used. 289 return is_in_young(new_obj); 290 } 291 292 // The "requestor" generation is performing some garbage collection 293 // action for which it would be useful to have scratch space. The 294 // requestor promises to allocate no more than "max_alloc_words" in any 295 // older generation (via promotion say.) Any blocks of space that can 296 // be provided are returned as a list of ScratchBlocks, sorted by 297 // decreasing size. 298 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 299 // Allow each generation to reset any scratch space that it has 300 // contributed as it needs. 301 void release_scratch(); 302 303 // Ensure parsability: override 304 virtual void ensure_parsability(bool retire_tlabs); 305 306 // Time in ms since the longest time a collector ran in 307 // in any generation. 308 virtual jlong millis_since_last_gc(); 309 310 // Total number of full collections completed. 311 unsigned int total_full_collections_completed() { 312 assert(_full_collections_completed <= _total_full_collections, 313 "Can't complete more collections than were started"); 314 return _full_collections_completed; 315 } 316 317 // Update above counter, as appropriate, at the end of a stop-world GC cycle 318 unsigned int update_full_collections_completed(); 319 // Update above counter, as appropriate, at the end of a concurrent GC cycle 320 unsigned int update_full_collections_completed(unsigned int count); 321 322 // Update "time of last gc" for all generations to "now". 323 void update_time_of_last_gc(jlong now) { 324 _young_gen->update_time_of_last_gc(now); 325 _old_gen->update_time_of_last_gc(now); 326 } 327 328 // Update the gc statistics for each generation. 329 // "level" is the level of the latest collection. 330 void update_gc_stats(int current_level, bool full) { 331 _young_gen->update_gc_stats(current_level, full); 332 _old_gen->update_gc_stats(current_level, full); 333 } 334 335 bool no_gc_in_progress() { return !is_gc_active(); } 336 337 // Override. 338 void prepare_for_verify(); 339 340 // Override. 341 void verify(bool silent, VerifyOption option); 342 343 // Override. 344 virtual void print_on(outputStream* st) const; 345 virtual void print_gc_threads_on(outputStream* st) const; 346 virtual void gc_threads_do(ThreadClosure* tc) const; 347 virtual void print_tracing_info() const; 348 virtual void print_on_error(outputStream* st) const; 349 350 // PrintGC, PrintGCDetails support 351 void print_heap_change(size_t prev_used) const; 352 353 // The functions below are helper functions that a subclass of 354 // "CollectedHeap" can use in the implementation of its virtual 355 // functions. 356 357 class GenClosure : public StackObj { 358 public: 359 virtual void do_generation(Generation* gen) = 0; 360 }; 361 362 // Apply "cl.do_generation" to all generations in the heap 363 // If "old_to_young" determines the order. 364 void generation_iterate(GenClosure* cl, bool old_to_young); 365 366 // Return "true" if all generations have reached the 367 // maximal committed limit that they can reach, without a garbage 368 // collection. 369 virtual bool is_maximal_no_gc() const; 370 371 int n_gens() const { 372 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity"); 373 return _n_gens; 374 } 375 376 // This function returns the "GenRemSet" object that allows us to scan 377 // generations in a fully generational heap. 378 GenRemSet* rem_set() { return _rem_set; } 379 380 // Convenience function to be used in situations where the heap type can be 381 // asserted to be this type. 382 static GenCollectedHeap* heap(); 383 384 void set_par_threads(uint t); 385 void set_n_termination(uint t); 386 387 // Invoke the "do_oop" method of one of the closures "not_older_gens" 388 // or "older_gens" on root locations for the generation at 389 // "level". (The "older_gens" closure is used for scanning references 390 // from older generations; "not_older_gens" is used everywhere else.) 391 // If "younger_gens_as_roots" is false, younger generations are 392 // not scanned as roots; in this case, the caller must be arranging to 393 // scan the younger generations itself. (For example, a generation might 394 // explicitly mark reachable objects in younger generations, to avoid 395 // excess storage retention.) 396 // The "so" argument determines which of the roots 397 // the closure is applied to: 398 // "SO_None" does none; 399 enum ScanningOption { 400 SO_None = 0x0, 401 SO_AllCodeCache = 0x8, 402 SO_ScavengeCodeCache = 0x10 403 }; 404 405 private: 406 void process_roots(bool activate_scope, 407 ScanningOption so, 408 OopClosure* strong_roots, 409 OopClosure* weak_roots, 410 CLDClosure* strong_cld_closure, 411 CLDClosure* weak_cld_closure, 412 CodeBlobClosure* code_roots); 413 414 void gen_process_roots(int level, 415 bool younger_gens_as_roots, 416 bool activate_scope, 417 ScanningOption so, 418 OopsInGenClosure* not_older_gens, 419 OopsInGenClosure* weak_roots, 420 OopsInGenClosure* older_gens, 421 CLDClosure* cld_closure, 422 CLDClosure* weak_cld_closure, 423 CodeBlobClosure* code_closure); 424 425 public: 426 static const bool StrongAndWeakRoots = false; 427 static const bool StrongRootsOnly = true; 428 429 void gen_process_roots(int level, 430 bool younger_gens_as_roots, 431 bool activate_scope, 432 ScanningOption so, 433 bool only_strong_roots, 434 OopsInGenClosure* not_older_gens, 435 OopsInGenClosure* older_gens, 436 CLDClosure* cld_closure); 437 438 // Apply "root_closure" to all the weak roots of the system. 439 // These include JNI weak roots, string table, 440 // and referents of reachable weak refs. 441 void gen_process_weak_roots(OopClosure* root_closure); 442 443 // Set the saved marks of generations, if that makes sense. 444 // In particular, if any generation might iterate over the oops 445 // in other generations, it should call this method. 446 void save_marks(); 447 448 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 449 // allocated since the last call to save_marks in generations at or above 450 // "level". The "cur" closure is 451 // applied to references in the generation at "level", and the "older" 452 // closure to older generations. 453 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 454 void oop_since_save_marks_iterate(int level, \ 455 OopClosureType* cur, \ 456 OopClosureType* older); 457 458 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 459 460 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 461 462 // Returns "true" iff no allocations have occurred in any generation at 463 // "level" or above since the last 464 // call to "save_marks". 465 bool no_allocs_since_save_marks(int level); 466 467 // Returns true if an incremental collection is likely to fail. 468 // We optionally consult the young gen, if asked to do so; 469 // otherwise we base our answer on whether the previous incremental 470 // collection attempt failed with no corrective action as of yet. 471 bool incremental_collection_will_fail(bool consult_young) { 472 // Assumes a 2-generation system; the first disjunct remembers if an 473 // incremental collection failed, even when we thought (second disjunct) 474 // that it would not. 475 assert(heap()->collector_policy()->is_generation_policy(), 476 "the following definition may not be suitable for an n(>2)-generation system"); 477 return incremental_collection_failed() || 478 (consult_young && !_young_gen->collection_attempt_is_safe()); 479 } 480 481 // If a generation bails out of an incremental collection, 482 // it sets this flag. 483 bool incremental_collection_failed() const { 484 return _incremental_collection_failed; 485 } 486 void set_incremental_collection_failed() { 487 _incremental_collection_failed = true; 488 } 489 void clear_incremental_collection_failed() { 490 _incremental_collection_failed = false; 491 } 492 493 // Promotion of obj into gen failed. Try to promote obj to higher 494 // gens in ascending order; return the new location of obj if successful. 495 // Otherwise, try expand-and-allocate for obj in both the young and old 496 // generation; return the new location of obj if successful. Otherwise, return NULL. 497 oop handle_failed_promotion(Generation* old_gen, 498 oop obj, 499 size_t obj_size); 500 501 private: 502 // Accessor for memory state verification support 503 NOT_PRODUCT( 504 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 505 ) 506 507 // Override 508 void check_for_non_bad_heap_word_value(HeapWord* addr, 509 size_t size) PRODUCT_RETURN; 510 511 // For use by mark-sweep. As implemented, mark-sweep-compact is global 512 // in an essential way: compaction is performed across generations, by 513 // iterating over spaces. 514 void prepare_for_compaction(); 515 516 // Perform a full collection of the first max_level+1 generations. 517 // This is the low level interface used by the public versions of 518 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 519 void collect_locked(GCCause::Cause cause, int max_level); 520 521 // Returns success or failure. 522 bool create_cms_collector(); 523 524 // In support of ExplicitGCInvokesConcurrent functionality 525 bool should_do_concurrent_full_gc(GCCause::Cause cause); 526 void collect_mostly_concurrent(GCCause::Cause cause); 527 528 // Save the tops of the spaces in all generations 529 void record_gen_tops_before_GC() PRODUCT_RETURN; 530 531 protected: 532 void gc_prologue(bool full); 533 void gc_epilogue(bool full); 534 }; 535 536 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP