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 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 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 // Data structure for claiming the (potentially) parallel tasks in 82 // (gen-specific) roots processing. 83 SubTasksDone* _gen_process_roots_tasks; 84 SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; } 85 86 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 87 bool run_verification, bool clear_soft_refs); 88 89 // In block contents verification, the number of header words to skip 90 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 91 92 protected: 93 // Helper functions for allocation 94 HeapWord* attempt_allocation(size_t size, 95 bool is_tlab, 96 bool first_only); 97 98 // Helper function for two callbacks below. 99 // Considers collection of the first max_level+1 generations. 100 void do_collection(bool full, 101 bool clear_all_soft_refs, 102 size_t size, 103 bool is_tlab, 104 int max_level); 105 106 // Callback from VM_GenCollectForAllocation operation. 107 // This function does everything necessary/possible to satisfy an 108 // allocation request that failed in the youngest generation that should 109 // have handled it (including collection, expansion, etc.) 110 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 111 112 // Callback from VM_GenCollectFull operation. 113 // Perform a full collection of the first max_level+1 generations. 114 virtual void do_full_collection(bool clear_all_soft_refs); 115 void do_full_collection(bool clear_all_soft_refs, int max_level); 116 117 // Does the "cause" of GC indicate that 118 // we absolutely __must__ clear soft refs? 119 bool must_clear_all_soft_refs(); 120 121 public: 122 GenCollectedHeap(GenCollectorPolicy *policy); 123 124 GCStats* gc_stats(int level) const; 125 126 // Returns JNI_OK on success 127 virtual jint initialize(); 128 129 char* allocate(size_t alignment, 130 size_t* _total_reserved, int* _n_covered_regions, 131 ReservedSpace* heap_rs); 132 133 // Does operations required after initialization has been done. 134 void post_initialize(); 135 136 // Initialize ("weak") refs processing support 137 virtual void ref_processing_init(); 138 139 virtual CollectedHeap::Name kind() const { 140 return CollectedHeap::GenCollectedHeap; 141 } 142 143 Generation* young_gen() const { return _young_gen; } 144 Generation* old_gen() const { return _old_gen; } 145 146 // The generational collector policy. 147 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 148 149 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 150 151 // Adaptive size policy 152 virtual AdaptiveSizePolicy* size_policy() { 153 return gen_policy()->size_policy(); 154 } 155 156 // Return the (conservative) maximum heap alignment 157 static size_t conservative_max_heap_alignment() { 158 return Generation::GenGrain; 159 } 160 161 size_t capacity() const; 162 size_t used() const; 163 164 // Save the "used_region" for generations level and lower. 165 void save_used_regions(int level); 166 167 size_t max_capacity() const; 168 169 HeapWord* mem_allocate(size_t size, 170 bool* gc_overhead_limit_was_exceeded); 171 172 // We may support a shared contiguous allocation area, if the youngest 173 // generation does. 174 bool supports_inline_contig_alloc() const; 175 HeapWord** top_addr() const; 176 HeapWord** end_addr() const; 177 178 // Does this heap support heap inspection? (+PrintClassHistogram) 179 virtual bool supports_heap_inspection() const { return true; } 180 181 // Perform a full collection of the heap; intended for use in implementing 182 // "System.gc". This implies as full a collection as the CollectedHeap 183 // supports. Caller does not hold the Heap_lock on entry. 184 void collect(GCCause::Cause cause); 185 186 // The same as above but assume that the caller holds the Heap_lock. 187 void collect_locked(GCCause::Cause cause); 188 189 // Perform a full collection of the first max_level+1 generations. 190 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 191 void collect(GCCause::Cause cause, int max_level); 192 193 // Returns "TRUE" iff "p" points into the committed areas of the heap. 194 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 195 // be expensive to compute in general, so, to prevent 196 // their inadvertent use in product jvm's, we restrict their use to 197 // assertion checking or verification only. 198 bool is_in(const void* p) const; 199 200 // override 201 bool is_in_closed_subset(const void* p) const { 202 if (UseConcMarkSweepGC) { 203 return is_in_reserved(p); 204 } else { 205 return is_in(p); 206 } 207 } 208 209 // Returns true if the reference is to an object in the reserved space 210 // for the young generation. 211 // Assumes the the young gen address range is less than that of the old gen. 212 bool is_in_young(oop p); 213 214 #ifdef ASSERT 215 virtual bool is_in_partial_collection(const void* p); 216 #endif 217 218 virtual bool is_scavengable(const void* addr) { 219 return is_in_young((oop)addr); 220 } 221 222 // Iteration functions. 223 void oop_iterate(ExtendedOopClosure* cl); 224 void object_iterate(ObjectClosure* cl); 225 void safe_object_iterate(ObjectClosure* cl); 226 Space* space_containing(const void* addr) const; 227 228 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 229 // each address in the (reserved) heap is a member of exactly 230 // one block. The defining characteristic of a block is that it is 231 // possible to find its size, and thus to progress forward to the next 232 // block. (Blocks may be of different sizes.) Thus, blocks may 233 // represent Java objects, or they might be free blocks in a 234 // free-list-based heap (or subheap), as long as the two kinds are 235 // distinguishable and the size of each is determinable. 236 237 // Returns the address of the start of the "block" that contains the 238 // address "addr". We say "blocks" instead of "object" since some heaps 239 // may not pack objects densely; a chunk may either be an object or a 240 // non-object. 241 virtual HeapWord* block_start(const void* addr) const; 242 243 // Requires "addr" to be the start of a chunk, and returns its size. 244 // "addr + size" is required to be the start of a new chunk, or the end 245 // of the active area of the heap. Assumes (and verifies in non-product 246 // builds) that addr is in the allocated part of the heap and is 247 // the start of a chunk. 248 virtual size_t block_size(const HeapWord* addr) const; 249 250 // Requires "addr" to be the start of a block, and returns "TRUE" iff 251 // the block is an object. 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 bool block_is_obj(const HeapWord* addr) const; 255 256 // Section on TLAB's. 257 virtual bool supports_tlab_allocation() const; 258 virtual size_t tlab_capacity(Thread* thr) const; 259 virtual size_t tlab_used(Thread* thr) const; 260 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 261 virtual HeapWord* allocate_new_tlab(size_t size); 262 263 // Can a compiler initialize a new object without store barriers? 264 // This permission only extends from the creation of a new object 265 // via a TLAB up to the first subsequent safepoint. 266 virtual bool can_elide_tlab_store_barriers() const { 267 return true; 268 } 269 270 virtual bool card_mark_must_follow_store() const { 271 return UseConcMarkSweepGC; 272 } 273 274 // We don't need barriers for stores to objects in the 275 // young gen and, a fortiori, for initializing stores to 276 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS} 277 // only and may need to be re-examined in case other 278 // kinds of collectors are implemented in the future. 279 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 280 // We wanted to assert that:- 281 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC, 282 // "Check can_elide_initializing_store_barrier() for this collector"); 283 // but unfortunately the flag UseSerialGC need not necessarily always 284 // be set when DefNew+Tenured are being used. 285 return is_in_young(new_obj); 286 } 287 288 // The "requestor" generation is performing some garbage collection 289 // action for which it would be useful to have scratch space. The 290 // requestor promises to allocate no more than "max_alloc_words" in any 291 // older generation (via promotion say.) Any blocks of space that can 292 // be provided are returned as a list of ScratchBlocks, sorted by 293 // decreasing size. 294 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 295 // Allow each generation to reset any scratch space that it has 296 // contributed as it needs. 297 void release_scratch(); 298 299 // Ensure parsability: override 300 virtual void ensure_parsability(bool retire_tlabs); 301 302 // Time in ms since the longest time a collector ran in 303 // in any generation. 304 virtual jlong millis_since_last_gc(); 305 306 // Total number of full collections completed. 307 unsigned int total_full_collections_completed() { 308 assert(_full_collections_completed <= _total_full_collections, 309 "Can't complete more collections than were started"); 310 return _full_collections_completed; 311 } 312 313 // Update above counter, as appropriate, at the end of a stop-world GC cycle 314 unsigned int update_full_collections_completed(); 315 // Update above counter, as appropriate, at the end of a concurrent GC cycle 316 unsigned int update_full_collections_completed(unsigned int count); 317 318 // Update "time of last gc" for all generations to "now". 319 void update_time_of_last_gc(jlong now) { 320 _young_gen->update_time_of_last_gc(now); 321 _old_gen->update_time_of_last_gc(now); 322 } 323 324 // Update the gc statistics for each generation. 325 // "level" is the level of the latest collection. 326 void update_gc_stats(int current_level, bool full) { 327 _young_gen->update_gc_stats(current_level, full); 328 _old_gen->update_gc_stats(current_level, full); 329 } 330 331 // Override. 332 bool no_gc_in_progress() { return !is_gc_active(); } 333 334 // Override. 335 void prepare_for_verify(); 336 337 // Override. 338 void verify(bool silent, VerifyOption option); 339 340 // Override. 341 virtual void print_on(outputStream* st) const; 342 virtual void print_gc_threads_on(outputStream* st) const; 343 virtual void gc_threads_do(ThreadClosure* tc) const; 344 virtual void print_tracing_info() const; 345 virtual void print_on_error(outputStream* st) const; 346 347 // PrintGC, PrintGCDetails support 348 void print_heap_change(size_t prev_used) const; 349 350 // The functions below are helper functions that a subclass of 351 // "CollectedHeap" can use in the implementation of its virtual 352 // functions. 353 354 class GenClosure : public StackObj { 355 public: 356 virtual void do_generation(Generation* gen) = 0; 357 }; 358 359 // Apply "cl.do_generation" to all generations in the heap 360 // If "old_to_young" determines the order. 361 void generation_iterate(GenClosure* cl, bool old_to_young); 362 363 void space_iterate(SpaceClosure* cl); 364 365 // Return "true" if all generations have reached the 366 // maximal committed limit that they can reach, without a garbage 367 // collection. 368 virtual bool is_maximal_no_gc() const; 369 370 int n_gens() const { 371 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity"); 372 return _n_gens; 373 } 374 375 // Convenience function to be used in situations where the heap type can be 376 // asserted to be this type. 377 static GenCollectedHeap* heap(); 378 379 void set_par_threads(uint t); 380 381 // Invoke the "do_oop" method of one of the closures "not_older_gens" 382 // or "older_gens" on root locations for the generation at 383 // "level". (The "older_gens" closure is used for scanning references 384 // from older generations; "not_older_gens" is used everywhere else.) 385 // If "younger_gens_as_roots" is false, younger generations are 386 // not scanned as roots; in this case, the caller must be arranging to 387 // scan the younger generations itself. (For example, a generation might 388 // explicitly mark reachable objects in younger generations, to avoid 389 // excess storage retention.) 390 // The "so" argument determines which of the roots 391 // the closure is applied to: 392 // "SO_None" does none; 393 private: 394 void gen_process_roots(int level, 395 bool younger_gens_as_roots, 396 bool activate_scope, 397 SharedHeap::ScanningOption so, 398 OopsInGenClosure* not_older_gens, 399 OopsInGenClosure* weak_roots, 400 OopsInGenClosure* older_gens, 401 CLDClosure* cld_closure, 402 CLDClosure* weak_cld_closure, 403 CodeBlobClosure* code_closure); 404 405 public: 406 static const bool StrongAndWeakRoots = false; 407 static const bool StrongRootsOnly = true; 408 409 void gen_process_roots(int level, 410 bool younger_gens_as_roots, 411 bool activate_scope, 412 SharedHeap::ScanningOption so, 413 bool only_strong_roots, 414 OopsInGenClosure* not_older_gens, 415 OopsInGenClosure* older_gens, 416 CLDClosure* cld_closure); 417 418 // Apply "root_closure" to all the weak roots of the system. 419 // These include JNI weak roots, string table, 420 // and referents of reachable weak refs. 421 void gen_process_weak_roots(OopClosure* root_closure); 422 423 // Set the saved marks of generations, if that makes sense. 424 // In particular, if any generation might iterate over the oops 425 // in other generations, it should call this method. 426 void save_marks(); 427 428 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 429 // allocated since the last call to save_marks in generations at or above 430 // "level". The "cur" closure is 431 // applied to references in the generation at "level", and the "older" 432 // closure to older generations. 433 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 434 void oop_since_save_marks_iterate(int level, \ 435 OopClosureType* cur, \ 436 OopClosureType* older); 437 438 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 439 440 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 441 442 // Returns "true" iff no allocations have occurred in any generation at 443 // "level" or above since the last 444 // call to "save_marks". 445 bool no_allocs_since_save_marks(int level); 446 447 // Returns true if an incremental collection is likely to fail. 448 // We optionally consult the young gen, if asked to do so; 449 // otherwise we base our answer on whether the previous incremental 450 // collection attempt failed with no corrective action as of yet. 451 bool incremental_collection_will_fail(bool consult_young) { 452 // Assumes a 2-generation system; the first disjunct remembers if an 453 // incremental collection failed, even when we thought (second disjunct) 454 // that it would not. 455 assert(heap()->collector_policy()->is_generation_policy(), 456 "the following definition may not be suitable for an n(>2)-generation system"); 457 return incremental_collection_failed() || 458 (consult_young && !_young_gen->collection_attempt_is_safe()); 459 } 460 461 // If a generation bails out of an incremental collection, 462 // it sets this flag. 463 bool incremental_collection_failed() const { 464 return _incremental_collection_failed; 465 } 466 void set_incremental_collection_failed() { 467 _incremental_collection_failed = true; 468 } 469 void clear_incremental_collection_failed() { 470 _incremental_collection_failed = false; 471 } 472 473 // Promotion of obj into gen failed. Try to promote obj to higher 474 // gens in ascending order; return the new location of obj if successful. 475 // Otherwise, try expand-and-allocate for obj in both the young and old 476 // generation; return the new location of obj if successful. Otherwise, return NULL. 477 oop handle_failed_promotion(Generation* old_gen, 478 oop obj, 479 size_t obj_size); 480 481 private: 482 // Accessor for memory state verification support 483 NOT_PRODUCT( 484 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 485 ) 486 487 // Override 488 void check_for_non_bad_heap_word_value(HeapWord* addr, 489 size_t size) PRODUCT_RETURN; 490 491 // For use by mark-sweep. As implemented, mark-sweep-compact is global 492 // in an essential way: compaction is performed across generations, by 493 // iterating over spaces. 494 void prepare_for_compaction(); 495 496 // Perform a full collection of the first max_level+1 generations. 497 // This is the low level interface used by the public versions of 498 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 499 void collect_locked(GCCause::Cause cause, int max_level); 500 501 // Returns success or failure. 502 bool create_cms_collector(); 503 504 // In support of ExplicitGCInvokesConcurrent functionality 505 bool should_do_concurrent_full_gc(GCCause::Cause cause); 506 void collect_mostly_concurrent(GCCause::Cause cause); 507 508 // Save the tops of the spaces in all generations 509 void record_gen_tops_before_GC() PRODUCT_RETURN; 510 511 protected: 512 virtual void gc_prologue(bool full); 513 virtual void gc_epilogue(bool full); 514 }; 515 516 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP