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 // Helper functions for allocation 116 HeapWord* attempt_allocation(size_t size, 117 bool is_tlab, 118 bool first_only); 119 120 // Helper function for two callbacks below. 121 // Considers collection of the first max_level+1 generations. 122 void do_collection(bool full, 123 bool clear_all_soft_refs, 124 size_t size, 125 bool is_tlab, 126 GenerationType max_generation); 127 128 // Callback from VM_GenCollectForAllocation operation. 129 // This function does everything necessary/possible to satisfy an 130 // allocation request that failed in the youngest generation that should 131 // have handled it (including collection, expansion, etc.) 132 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); 133 134 // Callback from VM_GenCollectFull operation. 135 // Perform a full collection of the first max_level+1 generations. 136 virtual void do_full_collection(bool clear_all_soft_refs); 137 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation); 138 139 // Does the "cause" of GC indicate that 140 // we absolutely __must__ clear soft refs? 141 bool must_clear_all_soft_refs(); 142 143 GenCollectedHeap(GenCollectorPolicy *policy); 144 145 virtual void check_gen_kinds() = 0; 146 147 public: 148 149 // Returns JNI_OK on success 150 virtual jint initialize(); 151 152 // Does operations required after initialization has been done. 153 void post_initialize(); 154 155 Generation* young_gen() const { return _young_gen; } 156 Generation* old_gen() const { return _old_gen; } 157 158 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; } 159 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; } 160 161 // The generational collector policy. 162 GenCollectorPolicy* gen_policy() const { return _gen_policy; } 163 164 virtual CollectorPolicy* collector_policy() const { return gen_policy(); } 165 166 // Adaptive size policy 167 virtual AdaptiveSizePolicy* size_policy() { 168 return gen_policy()->size_policy(); 169 } 170 171 // Return the (conservative) maximum heap alignment 172 static size_t conservative_max_heap_alignment() { 173 return Generation::GenGrain; 174 } 175 176 size_t capacity() const; 177 size_t used() const; 178 179 // Save the "used_region" for both generations. 180 void save_used_regions(); 181 182 size_t max_capacity() const; 183 184 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded); 185 186 // We may support a shared contiguous allocation area, if the youngest 187 // generation does. 188 bool supports_inline_contig_alloc() const; 189 HeapWord* volatile* top_addr() const; 190 HeapWord** end_addr() const; 191 192 // Perform a full collection of the heap; intended for use in implementing 193 // "System.gc". This implies as full a collection as the CollectedHeap 194 // supports. Caller does not hold the Heap_lock on entry. 195 virtual void collect(GCCause::Cause cause); 196 197 // The same as above but assume that the caller holds the Heap_lock. 198 void collect_locked(GCCause::Cause cause); 199 200 // Perform a full collection of generations up to and including max_generation. 201 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. 202 void collect(GCCause::Cause cause, GenerationType max_generation); 203 204 // Returns "TRUE" iff "p" points into the committed areas of the heap. 205 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may 206 // be expensive to compute in general, so, to prevent 207 // their inadvertent use in product jvm's, we restrict their use to 208 // assertion checking or verification only. 209 bool is_in(const void* p) const; 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(oop obj) { 221 return is_in_young(obj); 222 } 223 224 // Optimized nmethod scanning support routines 225 virtual void register_nmethod(nmethod* nm); 226 virtual void verify_nmethod(nmethod* nmethod); 227 228 // Iteration functions. 229 void oop_iterate_no_header(OopClosure* cl); 230 void oop_iterate(ExtendedOopClosure* cl); 231 void object_iterate(ObjectClosure* cl); 232 void safe_object_iterate(ObjectClosure* cl); 233 Space* space_containing(const void* addr) const; 234 235 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 236 // each address in the (reserved) heap is a member of exactly 237 // one block. The defining characteristic of a block is that it is 238 // possible to find its size, and thus to progress forward to the next 239 // block. (Blocks may be of different sizes.) Thus, blocks may 240 // represent Java objects, or they might be free blocks in a 241 // free-list-based heap (or subheap), as long as the two kinds are 242 // distinguishable and the size of each is determinable. 243 244 // Returns the address of the start of the "block" that contains the 245 // address "addr". We say "blocks" instead of "object" since some heaps 246 // may not pack objects densely; a chunk may either be an object or a 247 // non-object. 248 virtual HeapWord* block_start(const void* addr) const; 249 250 // Requires "addr" to be the start of a chunk, and returns its size. 251 // "addr + size" is required to be the start of a new chunk, or the end 252 // of the active area of the heap. Assumes (and verifies in non-product 253 // builds) that addr is in the allocated part of the heap and is 254 // the start of a chunk. 255 virtual size_t block_size(const HeapWord* addr) const; 256 257 // Requires "addr" to be the start of a block, and returns "TRUE" iff 258 // the block is an object. Assumes (and verifies in non-product 259 // builds) that addr is in the allocated part of the heap and is 260 // the start of a chunk. 261 virtual bool block_is_obj(const HeapWord* addr) const; 262 263 // Section on TLAB's. 264 virtual bool supports_tlab_allocation() const; 265 virtual size_t tlab_capacity(Thread* thr) const; 266 virtual size_t tlab_used(Thread* thr) const; 267 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; 268 virtual HeapWord* allocate_new_tlab(size_t size); 269 270 // Can a compiler initialize a new object without store barriers? 271 // This permission only extends from the creation of a new object 272 // via a TLAB up to the first subsequent safepoint. 273 virtual bool can_elide_tlab_store_barriers() const { 274 return true; 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(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; 340 341 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const; 342 343 // The functions below are helper functions that a subclass of 344 // "CollectedHeap" can use in the implementation of its virtual 345 // functions. 346 347 class GenClosure : public StackObj { 348 public: 349 virtual void do_generation(Generation* gen) = 0; 350 }; 351 352 // Apply "cl.do_generation" to all generations in the heap 353 // If "old_to_young" determines the order. 354 void generation_iterate(GenClosure* cl, bool old_to_young); 355 356 // Return "true" if all generations have reached the 357 // maximal committed limit that they can reach, without a garbage 358 // collection. 359 virtual bool is_maximal_no_gc() const; 360 361 // This function returns the CardTableRS object that allows us to scan 362 // generations in a fully generational heap. 363 CardTableRS* rem_set() { return _rem_set; } 364 365 // Convenience function to be used in situations where the heap type can be 366 // asserted to be this type. 367 static GenCollectedHeap* heap(); 368 369 // The ScanningOption determines which of the roots 370 // the closure is applied to: 371 // "SO_None" does none; 372 enum ScanningOption { 373 SO_None = 0x0, 374 SO_AllCodeCache = 0x8, 375 SO_ScavengeCodeCache = 0x10 376 }; 377 378 protected: 379 void process_roots(StrongRootsScope* scope, 380 ScanningOption so, 381 OopClosure* strong_roots, 382 OopClosure* weak_roots, 383 CLDClosure* strong_cld_closure, 384 CLDClosure* weak_cld_closure, 385 CodeBlobToOopClosure* code_roots); 386 387 void process_string_table_roots(StrongRootsScope* scope, 388 OopClosure* root_closure); 389 390 // Accessor for memory state verification support 391 NOT_PRODUCT( 392 virtual size_t skip_header_HeapWords() { return 0; } 393 ) 394 395 virtual void gc_prologue(bool full); 396 virtual void gc_epilogue(bool full); 397 398 public: 399 void young_process_roots(StrongRootsScope* scope, 400 OopsInGenClosure* root_closure, 401 OopsInGenClosure* old_gen_closure, 402 CLDClosure* cld_closure); 403 404 void full_process_roots(StrongRootsScope* scope, 405 bool is_adjust_phase, 406 ScanningOption so, 407 bool only_strong_roots, 408 OopsInGenClosure* root_closure, 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); 469 470 471 private: 472 // Override 473 void check_for_non_bad_heap_word_value(HeapWord* addr, 474 size_t size) PRODUCT_RETURN; 475 476 // For use by mark-sweep. As implemented, mark-sweep-compact is global 477 // in an essential way: compaction is performed across generations, by 478 // iterating over spaces. 479 void prepare_for_compaction(); 480 481 // Perform a full collection of the generations up to and including max_generation. 482 // This is the low level interface used by the public versions of 483 // collect() and collect_locked(). Caller holds the Heap_lock on entry. 484 void collect_locked(GCCause::Cause cause, GenerationType max_generation); 485 486 // Save the tops of the spaces in all generations 487 void record_gen_tops_before_GC() PRODUCT_RETURN; 488 }; 489 490 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP