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_GC_SHARED_GENCOLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP 27 28 #include "gc/cms/concurrentMarkSweepThread.hpp" 29 #include "gc/shared/adaptiveSizePolicy.hpp" 30 #include "gc/shared/collectedHeap.hpp" 31 #include "gc/shared/collectorPolicy.hpp" 32 #include "gc/shared/generation.hpp" 33 34 class StrongRootsScope; 35 class SubTasksDone; 36 class WorkGang; 37 38 // A "GenCollectedHeap" is a CollectedHeap that uses generational 39 // collection. It has two generations, young and old. 40 class GenCollectedHeap : public CollectedHeap { 41 friend class GenCollectorPolicy; 42 friend class Generation; 43 friend class DefNewGeneration; 44 friend class TenuredGeneration; 45 friend class ConcurrentMarkSweepGeneration; 46 friend class CMSCollector; 47 friend class GenMarkSweep; 48 friend class VM_GenCollectForAllocation; 49 friend class VM_GenCollectFull; 50 friend class VM_GenCollectFullConcurrent; 51 friend class VM_GC_HeapInspection; 52 friend class VM_HeapDumper; 53 friend class HeapInspection; 54 friend class GCCauseSetter; 55 friend class VMStructs; 56 public: 57 friend class VM_PopulateDumpSharedSpace; 58 59 enum GenerationType { 60 YoungGen, 61 OldGen 62 }; 63 64 private: 65 Generation* _young_gen; 66 Generation* _old_gen; 67 68 // The singleton CardTable Remembered Set. 69 CardTableRS* _rem_set; 70 71 // The generational collector policy. 72 GenCollectorPolicy* _gen_policy; 73 74 // Indicates that the most recent previous incremental collection failed. 75 // The flag is cleared when an action is taken that might clear the 76 // condition that caused that incremental collection to fail. 77 bool _incremental_collection_failed; 78 79 // In support of ExplicitGCInvokesConcurrent functionality 80 unsigned int _full_collections_completed; 81 82 // Data structure for claiming the (potentially) parallel tasks in 83 // (gen-specific) roots processing. 84 SubTasksDone* _process_strong_tasks; 85 86 // Collects the given generation. 87 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 88 bool run_verification, bool clear_soft_refs, 89 bool restore_marks_for_biased_locking); 90 91 // In block contents verification, the number of header words to skip 92 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 93 94 WorkGang* _workers; 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 GenerationType max_generation); 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, GenerationType max_generation); 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 WorkGang* workers() const { return _workers; } 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 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 150 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 151 152 // The generational collector policy. 153 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 154 155 virtual CollectorPolicy* collector_policy() const { return gen_policy(); } 156 157 // Adaptive size policy 158 virtual AdaptiveSizePolicy* size_policy() { 159 return gen_policy()->size_policy(); 160 } 161 162 // Return the (conservative) maximum heap alignment 163 static size_t conservative_max_heap_alignment() { 164 return Generation::GenGrain; 165 } 166 167 size_t capacity() const; 168 size_t used() const; 169 170 // Save the "used_region" for both generations. 171 void save_used_regions(); 172 173 size_t max_capacity() const; 174 175 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 176 177 // We may support a shared contiguous allocation area, if the youngest 178 // generation does. 179 bool supports_inline_contig_alloc() const; 180 HeapWord** top_addr() const; 181 HeapWord** end_addr() const; 182 183 // Perform a full collection of the heap; intended for use in implementing 184 // "System.gc". This implies as full a collection as the CollectedHeap 185 // supports. Caller does not hold the Heap_lock on entry. 186 void collect(GCCause::Cause cause); 187 188 // The same as above but assume that the caller holds the Heap_lock. 189 void collect_locked(GCCause::Cause cause); 190 191 // Perform a full collection of generations up to and including max_generation. 192 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 193 void collect(GCCause::Cause cause, GenerationType max_generation); 194 195 // Returns "TRUE" iff "p" points into the committed areas of the heap. 196 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 197 // be expensive to compute in general, so, to prevent 198 // their inadvertent use in product jvm's, we restrict their use to 199 // assertion checking or verification only. 200 bool is_in(const void* p) const; 201 202 // override 203 bool is_in_closed_subset(const void* p) const { 204 if (UseConcMarkSweepGC) { 205 return is_in_reserved(p); 206 } else { 207 return is_in(p); 208 } 209 } 210 211 // Returns true if the reference is to an object in the reserved space 212 // for the young generation. 213 // Assumes the the young gen address range is less than that of the old gen. 214 bool is_in_young(oop p); 215 216 #ifdef ASSERT 217 bool is_in_partial_collection(const void* p); 218 #endif 219 220 virtual bool is_scavengable(const void* addr) { 221 return is_in_young((oop)addr); 222 } 223 224 // Iteration functions. 225 void oop_iterate_no_header(OopClosure* cl); 226 void oop_iterate(ExtendedOopClosure* cl); 227 void object_iterate(ObjectClosure* cl); 228 void safe_object_iterate(ObjectClosure* cl); 229 Space* space_containing(const void* addr) const; 230 231 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 232 // each address in the (reserved) heap is a member of exactly 233 // one block. The defining characteristic of a block is that it is 234 // possible to find its size, and thus to progress forward to the next 235 // block. (Blocks may be of different sizes.) Thus, blocks may 236 // represent Java objects, or they might be free blocks in a 237 // free-list-based heap (or subheap), as long as the two kinds are 238 // distinguishable and the size of each is determinable. 239 240 // Returns the address of the start of the "block" that contains the 241 // address "addr". We say "blocks" instead of "object" since some heaps 242 // may not pack objects densely; a chunk may either be an object or a 243 // non-object. 244 virtual HeapWord* block_start(const void* addr) const; 245 246 // Requires "addr" to be the start of a chunk, and returns its size. 247 // "addr + size" is required to be the start of a new chunk, or the end 248 // of the active area of the heap. 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 size_t block_size(const HeapWord* addr) const; 252 253 // Requires "addr" to be the start of a block, and returns "TRUE" iff 254 // the block is an object. 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 bool block_is_obj(const HeapWord* addr) const; 258 259 // Section on TLAB's. 260 virtual bool supports_tlab_allocation() const; 261 virtual size_t tlab_capacity(Thread* thr) const; 262 virtual size_t tlab_used(Thread* thr) const; 263 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 264 virtual HeapWord* allocate_new_tlab(size_t size); 265 266 // Can a compiler initialize a new object without store barriers? 267 // This permission only extends from the creation of a new object 268 // via a TLAB up to the first subsequent safepoint. 269 virtual bool can_elide_tlab_store_barriers() const { 270 return true; 271 } 272 273 virtual bool card_mark_must_follow_store() const { 274 return UseConcMarkSweepGC; 275 } 276 277 // We don't need barriers for stores to objects in the 278 // young gen and, a fortiori, for initializing stores to 279 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 280 // only and may need to be re-examined in case other 281 // kinds of collectors are implemented in the future. 282 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 283 return is_in_young(new_obj); 284 } 285 286 // The "requestor" generation is performing some garbage collection 287 // action for which it would be useful to have scratch space. The 288 // requestor promises to allocate no more than "max_alloc_words" in any 289 // older generation (via promotion say.) Any blocks of space that can 290 // be provided are returned as a list of ScratchBlocks, sorted by 291 // decreasing size. 292 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 293 // Allow each generation to reset any scratch space that it has 294 // contributed as it needs. 295 void release_scratch(); 296 297 // Ensure parsability: override 298 virtual void ensure_parsability(bool retire_tlabs); 299 300 // Time in ms since the longest time a collector ran in 301 // in any generation. 302 virtual jlong millis_since_last_gc(); 303 304 // Total number of full collections completed. 305 unsigned int total_full_collections_completed() { 306 assert(_full_collections_completed <= _total_full_collections, 307 "Can't complete more collections than were started"); 308 return _full_collections_completed; 309 } 310 311 // Update above counter, as appropriate, at the end of a stop-world GC cycle 312 unsigned int update_full_collections_completed(); 313 // Update above counter, as appropriate, at the end of a concurrent GC cycle 314 unsigned int update_full_collections_completed(unsigned int count); 315 316 // Update "time of last gc" for all generations to "now". 317 void update_time_of_last_gc(jlong now) { 318 _young_gen->update_time_of_last_gc(now); 319 _old_gen->update_time_of_last_gc(now); 320 } 321 322 // Update the gc statistics for each generation. 323 void update_gc_stats(Generation* current_generation, bool full) { 324 _old_gen->update_gc_stats(current_generation, full); 325 } 326 327 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 // Return "true" if all generations have reached the 359 // maximal committed limit that they can reach, without a garbage 360 // collection. 361 virtual bool is_maximal_no_gc() const; 362 363 // This function returns the CardTableRS object that allows us to scan 364 // generations in a fully generational heap. 365 CardTableRS* rem_set() { return _rem_set; } 366 367 // Convenience function to be used in situations where the heap type can be 368 // asserted to be this type. 369 static GenCollectedHeap* heap(); 370 371 // Invoke the "do_oop" method of one of the closures "not_older_gens" 372 // or "older_gens" on root locations for the generations depending on 373 // the type. (The "older_gens" closure is used for scanning references 374 // from older generations; "not_older_gens" is used everywhere else.) 375 // If "younger_gens_as_roots" is false, younger generations are 376 // not scanned as roots; in this case, the caller must be arranging to 377 // scan the younger generations itself. (For example, a generation might 378 // explicitly mark reachable objects in younger generations, to avoid 379 // excess storage retention.) 380 // The "so" argument determines which of the roots 381 // the closure is applied to: 382 // "SO_None" does none; 383 enum ScanningOption { 384 SO_None = 0x0, 385 SO_AllCodeCache = 0x8, 386 SO_ScavengeCodeCache = 0x10 387 }; 388 389 private: 390 void process_roots(StrongRootsScope* scope, 391 ScanningOption so, 392 OopClosure* strong_roots, 393 OopClosure* weak_roots, 394 CLDClosure* strong_cld_closure, 395 CLDClosure* weak_cld_closure, 396 CodeBlobClosure* code_roots); 397 398 public: 399 static const bool StrongAndWeakRoots = false; 400 static const bool StrongRootsOnly = true; 401 402 void gen_process_roots(StrongRootsScope* scope, 403 GenerationType type, 404 bool young_gen_as_roots, 405 ScanningOption so, 406 bool only_strong_roots, 407 OopsInGenClosure* not_older_gens, 408 OopsInGenClosure* older_gens, 409 CLDClosure* cld_closure); 410 411 // Apply "root_closure" to all the weak roots of the system. 412 // These include JNI weak roots, string table, 413 // and referents of reachable weak refs. 414 void gen_process_weak_roots(OopClosure* root_closure); 415 416 // Set the saved marks of generations, if that makes sense. 417 // In particular, if any generation might iterate over the oops 418 // in other generations, it should call this method. 419 void save_marks(); 420 421 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects 422 // allocated since the last call to save_marks in generations at or above 423 // "level". The "cur" closure is 424 // applied to references in the generation at "level", and the "older" 425 // closure to older generations. 426 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ 427 void oop_since_save_marks_iterate(GenerationType start_gen, \ 428 OopClosureType* cur, \ 429 OopClosureType* older); 430 431 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) 432 433 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL 434 435 // Returns "true" iff no allocations have occurred since the last 436 // call to "save_marks". 437 bool no_allocs_since_save_marks(); 438 439 // Returns true if an incremental collection is likely to fail. 440 // We optionally consult the young gen, if asked to do so; 441 // otherwise we base our answer on whether the previous incremental 442 // collection attempt failed with no corrective action as of yet. 443 bool incremental_collection_will_fail(bool consult_young) { 444 // The first disjunct remembers if an incremental collection failed, even 445 // when we thought (second disjunct) that it would not. 446 return incremental_collection_failed() || 447 (consult_young && !_young_gen->collection_attempt_is_safe()); 448 } 449 450 // If a generation bails out of an incremental collection, 451 // it sets this flag. 452 bool incremental_collection_failed() const { 453 return _incremental_collection_failed; 454 } 455 void set_incremental_collection_failed() { 456 _incremental_collection_failed = true; 457 } 458 void clear_incremental_collection_failed() { 459 _incremental_collection_failed = false; 460 } 461 462 // Promotion of obj into gen failed. Try to promote obj to higher 463 // gens in ascending order; return the new location of obj if successful. 464 // Otherwise, try expand-and-allocate for obj in both the young and old 465 // generation; return the new location of obj if successful. Otherwise, return NULL. 466 oop handle_failed_promotion(Generation* old_gen, 467 oop obj, 468 size_t obj_size); 469 470 private: 471 // Accessor for memory state verification support 472 NOT_PRODUCT( 473 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 474 ) 475 476 // Override 477 void check_for_non_bad_heap_word_value(HeapWord* addr, 478 size_t size) PRODUCT_RETURN; 479 480 // For use by mark-sweep. As implemented, mark-sweep-compact is global 481 // in an essential way: compaction is performed across generations, by 482 // iterating over spaces. 483 void prepare_for_compaction(); 484 485 // Perform a full collection of the generations up to and including max_generation. 486 // This is the low level interface used by the public versions of 487 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 488 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 489 490 // Returns success or failure. 491 bool create_cms_collector(); 492 493 // In support of ExplicitGCInvokesConcurrent functionality 494 bool should_do_concurrent_full_gc(GCCause::Cause cause); 495 void collect_mostly_concurrent(GCCause::Cause cause); 496 497 // Save the tops of the spaces in all generations 498 void record_gen_tops_before_GC() PRODUCT_RETURN; 499 500 protected: 501 void gc_prologue(bool full); 502 void gc_epilogue(bool full); 503 504 public: 505 void stop() { 506 if (UseConcMarkSweepGC) { 507 ConcurrentMarkSweepThread::stop(); 508 } 509 } 510 }; 511 512 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP