1 /* 2 * Copyright (c) 2000, 2017, 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 // Collects the given generation. 82 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab, 83 bool run_verification, bool clear_soft_refs, 84 bool restore_marks_for_biased_locking); 85 86 // Reserve aligned space for the heap as needed by the contained generations. 87 char* allocate(size_t alignment, ReservedSpace* heap_rs); 88 89 // Initialize ("weak") refs processing support 90 void ref_processing_init(); 91 92 protected: 93 94 // The set of potentially parallel tasks in root scanning. 95 enum GCH_strong_roots_tasks { 96 GCH_PS_Universe_oops_do, 97 GCH_PS_JNIHandles_oops_do, 98 GCH_PS_ObjectSynchronizer_oops_do, 99 GCH_PS_FlatProfiler_oops_do, 100 GCH_PS_Management_oops_do, 101 GCH_PS_SystemDictionary_oops_do, 102 GCH_PS_ClassLoaderDataGraph_oops_do, 103 GCH_PS_jvmti_oops_do, 104 GCH_PS_CodeCache_oops_do, 105 GCH_PS_aot_oops_do, 106 GCH_PS_younger_gens, 107 // Leave this one last. 108 GCH_PS_NumElements 109 }; 110 111 // Data structure for claiming the (potentially) parallel tasks in 112 // (gen-specific) roots processing. 113 SubTasksDone* _process_strong_tasks; 114 115 GCMemoryManager* _minor_mgr; 116 GCMemoryManager* _major_mgr; 117 118 // Helper functions for allocation 119 HeapWord* attempt_allocation(size_t size, 120 bool is_tlab, 121 bool first_only); 122 123 // Helper function for two callbacks below. 124 // Considers collection of the first max_level+1 generations. 125 void do_collection(bool full, 126 bool clear_all_soft_refs, 127 size_t size, 128 bool is_tlab, 129 GenerationType max_generation); 130 131 // Callback from VM_GenCollectForAllocation operation. 132 // This function does everything necessary/possible to satisfy an 133 // allocation request that failed in the youngest generation that should 134 // have handled it (including collection, expansion, etc.) 135 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 136 137 // Callback from VM_GenCollectFull operation. 138 // Perform a full collection of the first max_level+1 generations. 139 virtual void do_full_collection(bool clear_all_soft_refs); 140 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 141 142 // Does the "cause" of GC indicate that 143 // we absolutely __must__ clear soft refs? 144 bool must_clear_all_soft_refs(); 145 146 GenCollectedHeap(GenCollectorPolicy *policy); 147 148 virtual void check_gen_kinds() = 0; 149 150 public: 151 152 // Returns JNI_OK on success 153 virtual jint initialize(); 154 155 virtual void init_memory_managers() = 0; 156 GCMemoryManager* major_mgr() { return _major_mgr; } 157 GCMemoryManager* minor_mgr() { return _minor_mgr; } 158 159 // Does operations required after initialization has been done. 160 void post_initialize(); 161 162 Generation* young_gen() const { return _young_gen; } 163 Generation* old_gen() const { return _old_gen; } 164 165 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 166 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 167 168 // The generational collector policy. 169 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 170 171 virtual CollectorPolicy* collector_policy() const { return gen_policy(); } 172 173 // Adaptive size policy 174 virtual AdaptiveSizePolicy* size_policy() { 175 return gen_policy()->size_policy(); 176 } 177 178 // Return the (conservative) maximum heap alignment 179 static size_t conservative_max_heap_alignment() { 180 return Generation::GenGrain; 181 } 182 183 size_t capacity() const; 184 size_t used() const; 185 186 // Save the "used_region" for both generations. 187 void save_used_regions(); 188 189 size_t max_capacity() const; 190 191 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 192 193 // We may support a shared contiguous allocation area, if the youngest 194 // generation does. 195 bool supports_inline_contig_alloc() const; 196 HeapWord* volatile* top_addr() const; 197 HeapWord** end_addr() const; 198 199 // Perform a full collection of the heap; intended for use in implementing 200 // "System.gc". This implies as full a collection as the CollectedHeap 201 // supports. Caller does not hold the Heap_lock on entry. 202 virtual void collect(GCCause::Cause cause); 203 204 // The same as above but assume that the caller holds the Heap_lock. 205 void collect_locked(GCCause::Cause cause); 206 207 // Perform a full collection of generations up to and including max_generation. 208 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 209 void collect(GCCause::Cause cause, GenerationType max_generation); 210 211 // Returns "TRUE" iff "p" points into the committed areas of the heap. 212 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 213 // be expensive to compute in general, so, to prevent 214 // their inadvertent use in product jvm's, we restrict their use to 215 // assertion checking or verification only. 216 bool is_in(const void* p) const; 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(oop obj) { 228 return is_in_young(obj); 229 } 230 231 // Optimized nmethod scanning support routines 232 virtual void register_nmethod(nmethod* nm); 233 virtual void verify_nmethod(nmethod* nmethod); 234 235 // Iteration functions. 236 void oop_iterate_no_header(OopClosure* cl); 237 void oop_iterate(ExtendedOopClosure* cl); 238 void object_iterate(ObjectClosure* cl); 239 void safe_object_iterate(ObjectClosure* cl); 240 Space* space_containing(const void* addr) const; 241 242 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 243 // each address in the (reserved) heap is a member of exactly 244 // one block. The defining characteristic of a block is that it is 245 // possible to find its size, and thus to progress forward to the next 246 // block. (Blocks may be of different sizes.) Thus, blocks may 247 // represent Java objects, or they might be free blocks in a 248 // free-list-based heap (or subheap), as long as the two kinds are 249 // distinguishable and the size of each is determinable. 250 251 // Returns the address of the start of the "block" that contains the 252 // address "addr". We say "blocks" instead of "object" since some heaps 253 // may not pack objects densely; a chunk may either be an object or a 254 // non-object. 255 virtual HeapWord* block_start(const void* addr) const; 256 257 // Requires "addr" to be the start of a chunk, and returns its size. 258 // "addr + size" is required to be the start of a new chunk, or the end 259 // of the active area of the heap. Assumes (and verifies in non-product 260 // builds) that addr is in the allocated part of the heap and is 261 // the start of a chunk. 262 virtual size_t block_size(const HeapWord* addr) const; 263 264 // Requires "addr" to be the start of a block, and returns "TRUE" iff 265 // the block is an object. Assumes (and verifies in non-product 266 // builds) that addr is in the allocated part of the heap and is 267 // the start of a chunk. 268 virtual bool block_is_obj(const HeapWord* addr) const; 269 270 // Section on TLAB's. 271 virtual bool supports_tlab_allocation() const; 272 virtual size_t tlab_capacity(Thread* thr) const; 273 virtual size_t tlab_used(Thread* thr) const; 274 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 275 virtual HeapWord* allocate_new_tlab(size_t size); 276 277 // Can a compiler initialize a new object without store barriers? 278 // This permission only extends from the creation of a new object 279 // via a TLAB up to the first subsequent safepoint. 280 virtual bool can_elide_tlab_store_barriers() const { 281 return true; 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; 347 348 void print_heap_change(size_t young_prev_used, size_t old_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 // Return "true" if all generations have reached the 364 // maximal committed limit that they can reach, without a garbage 365 // collection. 366 virtual bool is_maximal_no_gc() const; 367 368 // This function returns the CardTableRS object that allows us to scan 369 // generations in a fully generational heap. 370 CardTableRS* rem_set() { return _rem_set; } 371 372 // Convenience function to be used in situations where the heap type can be 373 // asserted to be this type. 374 static GenCollectedHeap* heap(); 375 376 // The ScanningOption determines which of the roots 377 // the closure is applied to: 378 // "SO_None" does none; 379 enum ScanningOption { 380 SO_None = 0x0, 381 SO_AllCodeCache = 0x8, 382 SO_ScavengeCodeCache = 0x10 383 }; 384 385 protected: 386 void process_roots(StrongRootsScope* scope, 387 ScanningOption so, 388 OopClosure* strong_roots, 389 OopClosure* weak_roots, 390 CLDClosure* strong_cld_closure, 391 CLDClosure* weak_cld_closure, 392 CodeBlobToOopClosure* code_roots); 393 394 void process_string_table_roots(StrongRootsScope* scope, 395 OopClosure* root_closure); 396 397 // Accessor for memory state verification support 398 NOT_PRODUCT( 399 virtual size_t skip_header_HeapWords() { return 0; } 400 ) 401 402 virtual void gc_prologue(bool full); 403 virtual void gc_epilogue(bool full); 404 405 public: 406 void young_process_roots(StrongRootsScope* scope, 407 OopsInGenClosure* root_closure, 408 OopsInGenClosure* old_gen_closure, 409 CLDClosure* cld_closure); 410 411 void full_process_roots(StrongRootsScope* scope, 412 bool is_adjust_phase, 413 ScanningOption so, 414 bool only_strong_roots, 415 OopsInGenClosure* root_closure, 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); 476 477 478 private: 479 // Override 480 void check_for_non_bad_heap_word_value(HeapWord* addr, 481 size_t size) PRODUCT_RETURN; 482 483 // For use by mark-sweep. As implemented, mark-sweep-compact is global 484 // in an essential way: compaction is performed across generations, by 485 // iterating over spaces. 486 void prepare_for_compaction(); 487 488 // Perform a full collection of the generations up to and including max_generation. 489 // This is the low level interface used by the public versions of 490 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 491 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 492 493 // Save the tops of the spaces in all generations 494 void record_gen_tops_before_GC() PRODUCT_RETURN; 495 }; 496 497 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP