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 friend class VM_PopulateDumpSharedSpace; 55 56 protected: 57 // Fields: 58 static GenCollectedHeap* _gch; 59 60 private: 61 Generation* _young_gen; 62 Generation* _old_gen; 63 64 // The singleton Gen Remembered Set. 65 GenRemSet* _rem_set; 66 67 // The generational collector policy. 68 GenCollectorPolicy* _gen_policy; 69 70 // Indicates that the most recent previous incremental collection failed. 71 // The flag is cleared when an action is taken that might clear the 72 // condition that caused that incremental collection to fail. 73 bool _incremental_collection_failed; 74 75 // In support of ExplicitGCInvokesConcurrent functionality 76 unsigned int _full_collections_completed; 77 78 // Data structure for claiming the (potentially) parallel tasks in 79 // (gen-specific) roots processing. 80 SubTasksDone* _process_strong_tasks; 81 82 // Collects the given generation. 83 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 84 bool run_verification, bool clear_soft_refs, 85 bool restore_marks_for_biased_locking); 86 87 // In block contents verification, the number of header words to skip 88 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 89 90 protected: 91 // Helper functions for allocation 92 HeapWord* attempt_allocation(size_t size, 93 bool is_tlab, 94 bool first_only); 95 96 // Helper function for two callbacks below. 97 // Considers collection of the first max_level+1 generations. 98 void do_collection(bool full, 99 bool clear_all_soft_refs, 100 size_t size, 101 bool is_tlab, 102 int max_level); 103 104 // Callback from VM_GenCollectForAllocation operation. 105 // This function does everything necessary/possible to satisfy an 106 // allocation request that failed in the youngest generation that should 107 // have handled it (including collection, expansion, etc.) 108 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 109 110 // Callback from VM_GenCollectFull operation. 111 // Perform a full collection of the first max_level+1 generations. 112 virtual void do_full_collection(bool clear_all_soft_refs); 113 void do_full_collection(bool clear_all_soft_refs, int max_level); 114 115 // Does the "cause" of GC indicate that 116 // we absolutely __must__ clear soft refs? 117 bool must_clear_all_soft_refs(); 118 119 public: 120 GenCollectedHeap(GenCollectorPolicy *policy); 121 122 GCStats* gc_stats(int level) const; 123 124 // Returns JNI_OK on success 125 virtual jint initialize(); 126 127 // Reserve aligned space for the heap as needed by the contained generations. 128 char* allocate(size_t alignment, ReservedSpace* heap_rs); 129 130 // Does operations required after initialization has been done. 131 void post_initialize(); 132 133 // Initialize ("weak") refs processing support 134 virtual void ref_processing_init(); 135 136 virtual CollectedHeap::Name kind() const { 137 return CollectedHeap::GenCollectedHeap; 138 } 139 140 Generation* young_gen() const { return _young_gen; } 141 Generation* old_gen() const { return _old_gen; } 142 143 // The generational collector policy. 144 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 145 146 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } 147 148 // Adaptive size policy 149 virtual AdaptiveSizePolicy* size_policy() { 150 return gen_policy()->size_policy(); 151 } 152 153 // Return the (conservative) maximum heap alignment 154 static size_t conservative_max_heap_alignment() { 155 return Generation::GenGrain; 156 } 157 158 size_t capacity() const; 159 size_t used() const; 160 161 // Save the "used_region" for generations level and lower. 162 void save_used_regions(int level); 163 164 size_t max_capacity() const; 165 166 HeapWord* mem_allocate(size_t size, 167 bool* gc_overhead_limit_was_exceeded); 168 169 // We may support a shared contiguous allocation area, if the youngest 170 // generation does. 171 bool supports_inline_contig_alloc() const; 172 HeapWord** top_addr() const; 173 HeapWord** end_addr() const; 174 175 // Does this heap support heap inspection? (+PrintClassHistogram) 176 virtual bool supports_heap_inspection() const { return true; } 177 178 // Perform a full collection of the heap; intended for use in implementing 179 // "System.gc". This implies as full a collection as the CollectedHeap 180 // supports. Caller does not hold the Heap_lock on entry. 181 void collect(GCCause::Cause cause); 182 183 // The same as above but assume that the caller holds the Heap_lock. 184 void collect_locked(GCCause::Cause cause); 185 186 // Perform a full collection of the first max_level+1 generations. 187 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 188 void collect(GCCause::Cause cause, int max_level); 189 190 // Returns "TRUE" iff "p" points into the committed areas of the heap. 191 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 192 // be expensive to compute in general, so, to prevent 193 // their inadvertent use in product jvm's, we restrict their use to 194 // assertion checking or verification only. 195 bool is_in(const void* p) const; 196 197 // override 198 bool is_in_closed_subset(const void* p) const { 199 if (UseConcMarkSweepGC) { 200 return is_in_reserved(p); 201 } else { 202 return is_in(p); 203 } 204 } 205 206 // Returns true if the reference is to an object in the reserved space 207 // for the young generation. 208 // Assumes the the young gen address range is less than that of the old gen. 209 bool is_in_young(oop p); 210 211 #ifdef ASSERT 212 virtual bool is_in_partial_collection(const void* p); 213 #endif 214 215 virtual bool is_scavengable(const void* addr) { 216 return is_in_young((oop)addr); 217 } 218 219 // Iteration functions. 220 void oop_iterate(ExtendedOopClosure* cl); 221 void object_iterate(ObjectClosure* cl); 222 void safe_object_iterate(ObjectClosure* cl); 223 Space* space_containing(const void* addr) const; 224 225 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 226 // each address in the (reserved) heap is a member of exactly 227 // one block. The defining characteristic of a block is that it is 228 // possible to find its size, and thus to progress forward to the next 229 // block. (Blocks may be of different sizes.) Thus, blocks may 230 // represent Java objects, or they might be free blocks in a 231 // free-list-based heap (or subheap), as long as the two kinds are 232 // distinguishable and the size of each is determinable. 233 234 // Returns the address of the start of the "block" that contains the 235 // address "addr". We say "blocks" instead of "object" since some heaps 236 // may not pack objects densely; a chunk may either be an object or a 237 // non-object. 238 virtual HeapWord* block_start(const void* addr) const; 239 240 // Requires "addr" to be the start of a chunk, and returns its size. 241 // "addr + size" is required to be the start of a new chunk, or the end 242 // of the active area of the heap. Assumes (and verifies in non-product 243 // builds) that addr is in the allocated part of the heap and is 244 // the start of a chunk. 245 virtual size_t block_size(const HeapWord* addr) const; 246 247 // Requires "addr" to be the start of a block, and returns "TRUE" iff 248 // the block is an object. Assumes (and verifies in non-product 249 // builds) that addr is in the allocated part of the heap and is 250 // the start of a chunk. 251 virtual bool block_is_obj(const HeapWord* addr) const; 252 253 // Section on TLAB's. 254 virtual bool supports_tlab_allocation() const; 255 virtual size_t tlab_capacity(Thread* thr) const; 256 virtual size_t tlab_used(Thread* thr) const; 257 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 258 virtual HeapWord* allocate_new_tlab(size_t size); 259 260 // Can a compiler initialize a new object without store barriers? 261 // This permission only extends from the creation of a new object 262 // via a TLAB up to the first subsequent safepoint. 263 virtual bool can_elide_tlab_store_barriers() const { 264 return true; 265 } 266 267 virtual bool card_mark_must_follow_store() const { 268 return UseConcMarkSweepGC; 269 } 270 271 // We don't need barriers for stores to objects in the 272 // young gen and, a fortiori, for initializing stores to 273 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 274 // only and may need to be re-examined in case other 275 // kinds of collectors are implemented in the future. 276 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 277 // We wanted to assert that:- 278 // assert(UseSerialGC || UseConcMarkSweepGC, 279 // "Check can_elide_initializing_store_barrier() for this collector"); 280 // but unfortunately the flag UseSerialGC need not necessarily always 281 // be set when DefNew+Tenured are being used. 282 return is_in_young(new_obj); 283 } 284 285 // The "requestor" generation is performing some garbage collection 286 // action for which it would be useful to have scratch space. The 287 // requestor promises to allocate no more than "max_alloc_words" in any 288 // older generation (via promotion say.) Any blocks of space that can 289 // be provided are returned as a list of ScratchBlocks, sorted by 290 // decreasing size. 291 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 292 // Allow each generation to reset any scratch space that it has 293 // contributed as it needs. 294 void release_scratch(); 295 296 // Ensure parsability: override 297 virtual void ensure_parsability(bool retire_tlabs); 298 299 // Time in ms since the longest time a collector ran in 300 // in any generation. 301 virtual jlong millis_since_last_gc(); 302 303 // Total number of full collections completed. 304 unsigned int total_full_collections_completed() { 305 assert(_full_collections_completed <= _total_full_collections, 306 "Can't complete more collections than were started"); 307 return _full_collections_completed; 308 } 309 310 // Update above counter, as appropriate, at the end of a stop-world GC cycle 311 unsigned int update_full_collections_completed(); 312 // Update above counter, as appropriate, at the end of a concurrent GC cycle 313 unsigned int update_full_collections_completed(unsigned int count); 314 315 // Update "time of last gc" for all generations to "now". 316 void update_time_of_last_gc(jlong now) { 317 _young_gen->update_time_of_last_gc(now); 318 _old_gen->update_time_of_last_gc(now); 319 } 320 321 // Update the gc statistics for each generation. 322 // "level" is the level of the latest collection. 323 void update_gc_stats(int current_level, bool full) { 324 _young_gen->update_gc_stats(current_level, full); 325 _old_gen->update_gc_stats(current_level, full); 326 } 327 328 // Override. 329 bool no_gc_in_progress() { return !is_gc_active(); } 330 331 // Override. 332 void prepare_for_verify(); 333 334 // Override. 335 void verify(bool silent, VerifyOption option); 336 337 // Override. 338 virtual void print_on(outputStream* st) const; 339 virtual void print_gc_threads_on(outputStream* st) const; 340 virtual void gc_threads_do(ThreadClosure* tc) const; 341 virtual void print_tracing_info() const; 342 virtual void print_on_error(outputStream* st) const; 343 344 // PrintGC, PrintGCDetails support 345 void print_heap_change(size_t prev_used) const; 346 347 // The functions below are helper functions that a subclass of 348 // "CollectedHeap" can use in the implementation of its virtual 349 // functions. 350 351 class GenClosure : public StackObj { 352 public: 353 virtual void do_generation(Generation* gen) = 0; 354 }; 355 356 // Apply "cl.do_generation" to all generations in the heap 357 // If "old_to_young" determines the order. 358 void generation_iterate(GenClosure* cl, bool old_to_young); 359 360 void space_iterate(SpaceClosure* cl); 361 362 // Return "true" if all generations have reached the 363 // maximal committed limit that they can reach, without a garbage 364 // collection. 365 virtual bool is_maximal_no_gc() const; 366 367 // This function returns the "GenRemSet" object that allows us to scan 368 // generations in a fully generational heap. 369 GenRemSet* rem_set() { return _rem_set; } 370 371 // Convenience function to be used in situations where the heap type can be 372 // asserted to be this type. 373 static GenCollectedHeap* heap(); 374 375 void set_par_threads(uint t); 376 void set_n_termination(uint t); 377 378 // Invoke the "do_oop" method of one of the closures "not_older_gens" 379 // or "older_gens" on root locations for the generation at 380 // "level". (The "older_gens" closure is used for scanning references 381 // from older generations; "not_older_gens" is used everywhere else.) 382 // If "younger_gens_as_roots" is false, younger generations are 383 // not scanned as roots; in this case, the caller must be arranging to 384 // scan the younger generations itself. (For example, a generation might 385 // explicitly mark reachable objects in younger generations, to avoid 386 // excess storage retention.) 387 // The "so" argument determines which of the roots 388 // the closure is applied to: 389 // "SO_None" does none; 390 enum ScanningOption { 391 SO_None = 0x0, 392 SO_AllCodeCache = 0x8, 393 SO_ScavengeCodeCache = 0x10 394 }; 395 396 private: 397 void process_roots(bool activate_scope, 398 ScanningOption so, 399 OopClosure* strong_roots, 400 OopClosure* weak_roots, 401 CLDClosure* strong_cld_closure, 402 CLDClosure* weak_cld_closure, 403 CodeBlobClosure* code_roots); 404 405 void gen_process_roots(int level, 406 bool younger_gens_as_roots, 407 bool activate_scope, 408 ScanningOption so, 409 OopsInGenClosure* not_older_gens, 410 OopsInGenClosure* weak_roots, 411 OopsInGenClosure* older_gens, 412 CLDClosure* cld_closure, 413 CLDClosure* weak_cld_closure, 414 CodeBlobClosure* code_closure); 415 416 public: 417 static const bool StrongAndWeakRoots = false; 418 static const bool StrongRootsOnly = true; 419 420 void gen_process_roots(int level, 421 bool younger_gens_as_roots, 422 bool activate_scope, 423 ScanningOption so, 424 bool only_strong_roots, 425 OopsInGenClosure* not_older_gens, 426 OopsInGenClosure* older_gens, 427 CLDClosure* cld_closure); 428 429 // Apply "root_closure" to all the weak roots of the system. 430 // These include JNI weak roots, string table, 431 // and referents of reachable weak refs. 432 void gen_process_weak_roots(OopClosure* root_closure); 433 434 // Set the saved marks of generations, if that makes sense. 435 // In particular, if any generation might iterate over the oops 436 // in other generations, it should call this method. 437 void save_marks(); 438 439 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 440 // allocated since the last call to save_marks in generations at or above 441 // "level". The "cur" closure is 442 // applied to references in the generation at "level", and the "older" 443 // closure to older generations. 444 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 445 void oop_since_save_marks_iterate(int level, \ 446 OopClosureType* cur, \ 447 OopClosureType* older); 448 449 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 450 451 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 452 453 // Returns "true" iff no allocations have occurred in any generation at 454 // "level" or above since the last 455 // call to "save_marks". 456 bool no_allocs_since_save_marks(int level); 457 458 // Returns true if an incremental collection is likely to fail. 459 // We optionally consult the young gen, if asked to do so; 460 // otherwise we base our answer on whether the previous incremental 461 // collection attempt failed with no corrective action as of yet. 462 bool incremental_collection_will_fail(bool consult_young) { 463 // Assumes a 2-generation system; the first disjunct remembers if an 464 // incremental collection failed, even when we thought (second disjunct) 465 // that it would not. 466 assert(heap()->collector_policy()->is_generation_policy(), 467 "the following definition may not be suitable for an n(>2)-generation system"); 468 return incremental_collection_failed() || 469 (consult_young && !_young_gen->collection_attempt_is_safe()); 470 } 471 472 // If a generation bails out of an incremental collection, 473 // it sets this flag. 474 bool incremental_collection_failed() const { 475 return _incremental_collection_failed; 476 } 477 void set_incremental_collection_failed() { 478 _incremental_collection_failed = true; 479 } 480 void clear_incremental_collection_failed() { 481 _incremental_collection_failed = false; 482 } 483 484 // Promotion of obj into gen failed. Try to promote obj to higher 485 // gens in ascending order; return the new location of obj if successful. 486 // Otherwise, try expand-and-allocate for obj in both the young and old 487 // generation; return the new location of obj if successful. Otherwise, return NULL. 488 oop handle_failed_promotion(Generation* old_gen, 489 oop obj, 490 size_t obj_size); 491 492 private: 493 // Accessor for memory state verification support 494 NOT_PRODUCT( 495 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 496 ) 497 498 // Override 499 void check_for_non_bad_heap_word_value(HeapWord* addr, 500 size_t size) PRODUCT_RETURN; 501 502 // For use by mark-sweep. As implemented, mark-sweep-compact is global 503 // in an essential way: compaction is performed across generations, by 504 // iterating over spaces. 505 void prepare_for_compaction(); 506 507 // Perform a full collection of the first max_level+1 generations. 508 // This is the low level interface used by the public versions of 509 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 510 void collect_locked(GCCause::Cause cause, int max_level); 511 512 // Returns success or failure. 513 bool create_cms_collector(); 514 515 // In support of ExplicitGCInvokesConcurrent functionality 516 bool should_do_concurrent_full_gc(GCCause::Cause cause); 517 void collect_mostly_concurrent(GCCause::Cause cause); 518 519 // Save the tops of the spaces in all generations 520 void record_gen_tops_before_GC() PRODUCT_RETURN; 521 522 protected: 523 virtual void gc_prologue(bool full); 524 virtual void gc_epilogue(bool full); 525 }; 526 527 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP