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/shared/adaptiveSizePolicy.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "gc/shared/collectorPolicy.hpp" 31 #include "gc/shared/generation.hpp" 32 33 class StrongRootsScope; 34 class SubTasksDone; 35 class WorkGang; 36 37 // A "GenCollectedHeap" is a CollectedHeap that uses generational 38 // collection. It has two generations, young and old. 39 class GenCollectedHeap : public CollectedHeap { 40 friend class GenCollectorPolicy; 41 friend class Generation; 42 friend class DefNewGeneration; 43 friend class TenuredGeneration; 44 friend class ConcurrentMarkSweepGeneration; 45 friend class CMSCollector; 46 friend class GenMarkSweep; 47 friend class VM_GenCollectForAllocation; 48 friend class VM_GenCollectFull; 49 friend class VM_GenCollectFullConcurrent; 50 friend class VM_GC_HeapInspection; 51 friend class VM_HeapDumper; 52 friend class HeapInspection; 53 friend class GCCauseSetter; 54 friend class VMStructs; 55 public: 56 friend class VM_PopulateDumpSharedSpace; 57 58 enum GenerationType { 59 YoungGen, 60 OldGen 61 }; 62 63 private: 64 Generation* _young_gen; 65 Generation* _old_gen; 66 67 // The singleton CardTable Remembered Set. 68 CardTableRS* _rem_set; 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* _process_strong_tasks; 84 85 // Collects the given generation. 86 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 87 bool run_verification, bool clear_soft_refs, 88 bool restore_marks_for_biased_locking); 89 90 // In block contents verification, the number of header words to skip 91 NOT_PRODUCT(static size_t _skip_header_HeapWords;) 92 93 WorkGang* _workers; 94 95 protected: 96 // Helper functions for allocation 97 HeapWord* attempt_allocation(size_t size, 98 bool is_tlab, 99 bool first_only); 100 101 // Helper function for two callbacks below. 102 // Considers collection of the first max_level+1 generations. 103 void do_collection(bool full, 104 bool clear_all_soft_refs, 105 size_t size, 106 bool is_tlab, 107 GenerationType max_generation); 108 109 // Callback from VM_GenCollectForAllocation operation. 110 // This function does everything necessary/possible to satisfy an 111 // allocation request that failed in the youngest generation that should 112 // have handled it (including collection, expansion, etc.) 113 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 114 115 // Callback from VM_GenCollectFull operation. 116 // Perform a full collection of the first max_level+1 generations. 117 virtual void do_full_collection(bool clear_all_soft_refs); 118 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 119 120 // Does the "cause" of GC indicate that 121 // we absolutely __must__ clear soft refs? 122 bool must_clear_all_soft_refs(); 123 124 public: 125 GenCollectedHeap(GenCollectorPolicy *policy); 126 127 WorkGang* workers() const { return _workers; } 128 129 // Returns JNI_OK on success 130 virtual jint initialize(); 131 132 // Reserve aligned space for the heap as needed by the contained generations. 133 char* allocate(size_t alignment, ReservedSpace* heap_rs); 134 135 // Does operations required after initialization has been done. 136 void post_initialize(); 137 138 // Initialize ("weak") refs processing support 139 virtual void ref_processing_init(); 140 141 virtual Name kind() const { 142 return CollectedHeap::GenCollectedHeap; 143 } 144 145 virtual const char* name() const { 146 if (UseConcMarkSweepGC) { 147 return "Concurrent Mark Sweep"; 148 } else { 149 return "Serial"; 150 } 151 } 152 153 Generation* young_gen() const { return _young_gen; } 154 Generation* old_gen() const { return _old_gen; } 155 156 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 157 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 158 159 // The generational collector policy. 160 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 161 162 virtual CollectorPolicy* collector_policy() const { return gen_policy(); } 163 164 // Adaptive size policy 165 virtual AdaptiveSizePolicy* size_policy() { 166 return gen_policy()->size_policy(); 167 } 168 169 // Return the (conservative) maximum heap alignment 170 static size_t conservative_max_heap_alignment() { 171 return Generation::GenGrain; 172 } 173 174 size_t capacity() const; 175 size_t used() const; 176 177 // Save the "used_region" for both generations. 178 void save_used_regions(); 179 180 size_t max_capacity() const; 181 182 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 183 184 // We may support a shared contiguous allocation area, if the youngest 185 // generation does. 186 bool supports_inline_contig_alloc() const; 187 HeapWord** top_addr() const; 188 HeapWord** end_addr() const; 189 190 // Perform a full collection of the heap; intended for use in implementing 191 // "System.gc". This implies as full a collection as the CollectedHeap 192 // supports. Caller does not hold the Heap_lock on entry. 193 void collect(GCCause::Cause cause); 194 195 // The same as above but assume that the caller holds the Heap_lock. 196 void collect_locked(GCCause::Cause cause); 197 198 // Perform a full collection of generations up to and including max_generation. 199 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 200 void collect(GCCause::Cause cause, GenerationType max_generation); 201 202 // Returns "TRUE" iff "p" points into the committed areas of the heap. 203 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 204 // be expensive to compute in general, so, to prevent 205 // their inadvertent use in product jvm's, we restrict their use to 206 // assertion checking or verification only. 207 bool is_in(const void* p) const; 208 209 // override 210 bool is_in_closed_subset(const void* p) const { 211 if (UseConcMarkSweepGC) { 212 return is_in_reserved(p); 213 } else { 214 return is_in(p); 215 } 216 } 217 218 // Returns true if the reference is to an object in the reserved space 219 // for the young generation. 220 // Assumes the the young gen address range is less than that of the old gen. 221 bool is_in_young(oop p); 222 223 #ifdef ASSERT 224 bool is_in_partial_collection(const void* p); 225 #endif 226 227 virtual bool is_scavengable(const void* addr) { 228 return is_in_young((oop)addr); 229 } 230 231 // Iteration functions. 232 void oop_iterate_no_header(OopClosure* cl); 233 void oop_iterate(ExtendedOopClosure* cl); 234 void object_iterate(ObjectClosure* cl); 235 void safe_object_iterate(ObjectClosure* cl); 236 Space* space_containing(const void* addr) const; 237 238 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 239 // each address in the (reserved) heap is a member of exactly 240 // one block. The defining characteristic of a block is that it is 241 // possible to find its size, and thus to progress forward to the next 242 // block. (Blocks may be of different sizes.) Thus, blocks may 243 // represent Java objects, or they might be free blocks in a 244 // free-list-based heap (or subheap), as long as the two kinds are 245 // distinguishable and the size of each is determinable. 246 247 // Returns the address of the start of the "block" that contains the 248 // address "addr". We say "blocks" instead of "object" since some heaps 249 // may not pack objects densely; a chunk may either be an object or a 250 // non-object. 251 virtual HeapWord* block_start(const void* addr) const; 252 253 // Requires "addr" to be the start of a chunk, and returns its size. 254 // "addr + size" is required to be the start of a new chunk, or the end 255 // of the active area of the heap. 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 size_t block_size(const HeapWord* addr) const; 259 260 // Requires "addr" to be the start of a block, and returns "TRUE" iff 261 // the block is an object. Assumes (and verifies in non-product 262 // builds) that addr is in the allocated part of the heap and is 263 // the start of a chunk. 264 virtual bool block_is_obj(const HeapWord* addr) const; 265 266 // Section on TLAB's. 267 virtual bool supports_tlab_allocation() const; 268 virtual size_t tlab_capacity(Thread* thr) const; 269 virtual size_t tlab_used(Thread* thr) const; 270 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 271 virtual HeapWord* allocate_new_tlab(size_t size); 272 273 // Can a compiler initialize a new object without store barriers? 274 // This permission only extends from the creation of a new object 275 // via a TLAB up to the first subsequent safepoint. 276 virtual bool can_elide_tlab_store_barriers() const { 277 return true; 278 } 279 280 virtual bool card_mark_must_follow_store() const { 281 return UseConcMarkSweepGC; 282 } 283 284 // We don't need barriers for stores to objects in the 285 // young gen and, a fortiori, for initializing stores to 286 // objects therein. This applies to DefNew+Tenured and ParNew+CMS 287 // only and may need to be re-examined in case other 288 // kinds of collectors are implemented in the future. 289 virtual bool can_elide_initializing_store_barrier(oop new_obj) { 290 return is_in_young(new_obj); 291 } 292 293 // The "requestor" generation is performing some garbage collection 294 // action for which it would be useful to have scratch space. The 295 // requestor promises to allocate no more than "max_alloc_words" in any 296 // older generation (via promotion say.) Any blocks of space that can 297 // be provided are returned as a list of ScratchBlocks, sorted by 298 // decreasing size. 299 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); 300 // Allow each generation to reset any scratch space that it has 301 // contributed as it needs. 302 void release_scratch(); 303 304 // Ensure parsability: override 305 virtual void ensure_parsability(bool retire_tlabs); 306 307 // Time in ms since the longest time a collector ran in 308 // in any generation. 309 virtual jlong millis_since_last_gc(); 310 311 // Total number of full collections completed. 312 unsigned int total_full_collections_completed() { 313 assert(_full_collections_completed <= _total_full_collections, 314 "Can't complete more collections than were started"); 315 return _full_collections_completed; 316 } 317 318 // Update above counter, as appropriate, at the end of a stop-world GC cycle 319 unsigned int update_full_collections_completed(); 320 // Update above counter, as appropriate, at the end of a concurrent GC cycle 321 unsigned int update_full_collections_completed(unsigned int count); 322 323 // Update "time of last gc" for all generations to "now". 324 void update_time_of_last_gc(jlong now) { 325 _young_gen->update_time_of_last_gc(now); 326 _old_gen->update_time_of_last_gc(now); 327 } 328 329 // Update the gc statistics for each generation. 330 void update_gc_stats(Generation* current_generation, bool full) { 331 _old_gen->update_gc_stats(current_generation, full); 332 } 333 334 bool no_gc_in_progress() { return !is_gc_active(); } 335 336 // Override. 337 void prepare_for_verify(); 338 339 // Override. 340 void verify(VerifyOption option); 341 342 // Override. 343 virtual void print_on(outputStream* st) const; 344 virtual void print_gc_threads_on(outputStream* st) const; 345 virtual void gc_threads_do(ThreadClosure* tc) const; 346 virtual void print_tracing_info() const; 347 virtual void print_on_error(outputStream* st) const; 348 349 // PrintGC, PrintGCDetails support 350 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const; 351 352 // The functions below are helper functions that a subclass of 353 // "CollectedHeap" can use in the implementation of its virtual 354 // functions. 355 356 class GenClosure : public StackObj { 357 public: 358 virtual void do_generation(Generation* gen) = 0; 359 }; 360 361 // Apply "cl.do_generation" to all generations in the heap 362 // If "old_to_young" determines the order. 363 void generation_iterate(GenClosure* cl, bool old_to_young); 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 // This function returns the CardTableRS object that allows us to scan 371 // generations in a fully generational heap. 372 CardTableRS* rem_set() { return _rem_set; } 373 374 // Convenience function to be used in situations where the heap type can be 375 // asserted to be this type. 376 static GenCollectedHeap* heap(); 377 378 // Invoke the "do_oop" method of one of the closures "not_older_gens" 379 // or "older_gens" on root locations for the generations depending on 380 // the type. (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(StrongRootsScope* 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 public: 406 static const bool StrongAndWeakRoots = false; 407 static const bool StrongRootsOnly = true; 408 409 void gen_process_roots(StrongRootsScope* scope, 410 GenerationType type, 411 bool young_gen_as_roots, 412 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(GenerationType start_gen, \ 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 since the last 443 // call to "save_marks". 444 bool no_allocs_since_save_marks(); 445 446 // Returns true if an incremental collection is likely to fail. 447 // We optionally consult the young gen, if asked to do so; 448 // otherwise we base our answer on whether the previous incremental 449 // collection attempt failed with no corrective action as of yet. 450 bool incremental_collection_will_fail(bool consult_young) { 451 // The first disjunct remembers if an incremental collection failed, even 452 // when we thought (second disjunct) that it would not. 453 return incremental_collection_failed() || 454 (consult_young && !_young_gen->collection_attempt_is_safe()); 455 } 456 457 // If a generation bails out of an incremental collection, 458 // it sets this flag. 459 bool incremental_collection_failed() const { 460 return _incremental_collection_failed; 461 } 462 void set_incremental_collection_failed() { 463 _incremental_collection_failed = true; 464 } 465 void clear_incremental_collection_failed() { 466 _incremental_collection_failed = false; 467 } 468 469 // Promotion of obj into gen failed. Try to promote obj to higher 470 // gens in ascending order; return the new location of obj if successful. 471 // Otherwise, try expand-and-allocate for obj in both the young and old 472 // generation; return the new location of obj if successful. Otherwise, return NULL. 473 oop handle_failed_promotion(Generation* old_gen, 474 oop obj, 475 size_t obj_size); 476 477 private: 478 // Accessor for memory state verification support 479 NOT_PRODUCT( 480 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } 481 ) 482 483 // Override 484 void check_for_non_bad_heap_word_value(HeapWord* addr, 485 size_t size) PRODUCT_RETURN; 486 487 // For use by mark-sweep. As implemented, mark-sweep-compact is global 488 // in an essential way: compaction is performed across generations, by 489 // iterating over spaces. 490 void prepare_for_compaction(); 491 492 // Perform a full collection of the generations up to and including max_generation. 493 // This is the low level interface used by the public versions of 494 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 495 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 496 497 // Returns success or failure. 498 bool create_cms_collector(); 499 500 // In support of ExplicitGCInvokesConcurrent functionality 501 bool should_do_concurrent_full_gc(GCCause::Cause cause); 502 void collect_mostly_concurrent(GCCause::Cause cause); 503 504 // Save the tops of the spaces in all generations 505 void record_gen_tops_before_GC() PRODUCT_RETURN; 506 507 protected: 508 void gc_prologue(bool full); 509 void gc_epilogue(bool full); 510 }; 511 512 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP