1 /* 2 * Copyright (c) 2001, 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_COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP 27 28 #include "gc/shared/gcCause.hpp" 29 #include "gc/shared/gcWhen.hpp" 30 #include "memory/allocation.hpp" 31 #include "runtime/handles.hpp" 32 #include "runtime/perfData.hpp" 33 #include "runtime/safepoint.hpp" 34 #include "utilities/debug.hpp" 35 #include "utilities/events.hpp" 36 #include "utilities/formatBuffer.hpp" 37 38 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This 39 // is an abstract class: there may be many different kinds of heaps. This 40 // class defines the functions that a heap must implement, and contains 41 // infrastructure common to all heaps. 42 43 class AdaptiveSizePolicy; 44 class BarrierSet; 45 class CollectorPolicy; 46 class GCHeapSummary; 47 class GCTimer; 48 class GCTracer; 49 class MetaspaceSummary; 50 class Thread; 51 class ThreadClosure; 52 class VirtualSpaceSummary; 53 class WorkGang; 54 class nmethod; 55 56 class GCMessage : public FormatBuffer<1024> { 57 public: 58 bool is_before; 59 60 public: 61 GCMessage() {} 62 }; 63 64 class CollectedHeap; 65 66 class GCHeapLog : public EventLogBase<GCMessage> { 67 private: 68 void log_heap(CollectedHeap* heap, bool before); 69 70 public: 71 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {} 72 73 void log_heap_before(CollectedHeap* heap) { 74 log_heap(heap, true); 75 } 76 void log_heap_after(CollectedHeap* heap) { 77 log_heap(heap, false); 78 } 79 }; 80 81 // 82 // CollectedHeap 83 // GenCollectedHeap 84 // SerialHeap 85 // CMSHeap 86 // G1CollectedHeap 87 // ParallelScavengeHeap 88 // 89 class CollectedHeap : public CHeapObj<mtInternal> { 90 friend class VMStructs; 91 friend class JVMCIVMStructs; 92 friend class IsGCActiveMark; // Block structured external access to _is_gc_active 93 94 private: 95 #ifdef ASSERT 96 static int _fire_out_of_memory_count; 97 #endif 98 99 GCHeapLog* _gc_heap_log; 100 101 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 102 // or INCLUDE_JVMCI is being used 103 bool _defer_initial_card_mark; 104 105 MemRegion _reserved; 106 107 protected: 108 BarrierSet* _barrier_set; 109 bool _is_gc_active; 110 111 // Used for filler objects (static, but initialized in ctor). 112 static size_t _filler_array_max_size; 113 114 unsigned int _total_collections; // ... started 115 unsigned int _total_full_collections; // ... started 116 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;) 117 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;) 118 119 // Reason for current garbage collection. Should be set to 120 // a value reflecting no collection between collections. 121 GCCause::Cause _gc_cause; 122 GCCause::Cause _gc_lastcause; 123 PerfStringVariable* _perf_gc_cause; 124 PerfStringVariable* _perf_gc_lastcause; 125 126 // Constructor 127 CollectedHeap(); 128 129 // Do common initializations that must follow instance construction, 130 // for example, those needing virtual calls. 131 // This code could perhaps be moved into initialize() but would 132 // be slightly more awkward because we want the latter to be a 133 // pure virtual. 134 void pre_initialize(); 135 136 // Create a new tlab. All TLAB allocations must go through this. 137 virtual HeapWord* allocate_new_tlab(size_t size); 138 139 // Accumulate statistics on all tlabs. 140 virtual void accumulate_statistics_all_tlabs(); 141 142 // Reinitialize tlabs before resuming mutators. 143 virtual void resize_all_tlabs(); 144 145 // Allocate from the current thread's TLAB, with broken-out slow path. 146 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size); 147 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size); 148 149 // Allocate an uninitialized block of the given size, or returns NULL if 150 // this is impossible. 151 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS); 152 153 // Like allocate_init, but the block returned by a successful allocation 154 // is guaranteed initialized to zeros. 155 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS); 156 157 // Helper functions for (VM) allocation. 158 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj); 159 inline static void post_allocation_setup_no_klass_install(Klass* klass, 160 HeapWord* objPtr); 161 162 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size); 163 164 inline static void post_allocation_setup_array(Klass* klass, 165 HeapWord* obj, int length); 166 167 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size); 168 169 // Clears an allocated object. 170 inline static void init_obj(HeapWord* obj, size_t size); 171 172 // Filler object utilities. 173 static inline size_t filler_array_hdr_size(); 174 static inline size_t filler_array_min_size(); 175 176 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);) 177 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);) 178 179 // Fill with a single array; caller must ensure filler_array_min_size() <= 180 // words <= filler_array_max_size(). 181 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true); 182 183 // Fill with a single object (either an int array or a java.lang.Object). 184 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true); 185 186 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer); 187 188 // Verification functions 189 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size) 190 PRODUCT_RETURN; 191 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) 192 PRODUCT_RETURN; 193 debug_only(static void check_for_valid_allocation_state();) 194 195 public: 196 enum Name { 197 SerialHeap, 198 ParallelScavengeHeap, 199 G1CollectedHeap, 200 CMSHeap 201 }; 202 203 static inline size_t filler_array_max_size() { 204 return _filler_array_max_size; 205 } 206 207 virtual Name kind() const = 0; 208 209 virtual const char* name() const = 0; 210 211 /** 212 * Returns JNI error code JNI_ENOMEM if memory could not be allocated, 213 * and JNI_OK on success. 214 */ 215 virtual jint initialize() = 0; 216 217 // In many heaps, there will be a need to perform some initialization activities 218 // after the Universe is fully formed, but before general heap allocation is allowed. 219 // This is the correct place to place such initialization methods. 220 virtual void post_initialize() = 0; 221 222 // Stop any onging concurrent work and prepare for exit. 223 virtual void stop() {} 224 225 // Stop and resume concurrent GC threads interfering with safepoint operations 226 virtual void safepoint_synchronize_begin() {} 227 virtual void safepoint_synchronize_end() {} 228 229 void initialize_reserved_region(HeapWord *start, HeapWord *end); 230 MemRegion reserved_region() const { return _reserved; } 231 address base() const { return (address)reserved_region().start(); } 232 233 virtual size_t capacity() const = 0; 234 virtual size_t used() const = 0; 235 236 // Return "true" if the part of the heap that allocates Java 237 // objects has reached the maximal committed limit that it can 238 // reach, without a garbage collection. 239 virtual bool is_maximal_no_gc() const = 0; 240 241 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of 242 // memory that the vm could make available for storing 'normal' java objects. 243 // This is based on the reserved address space, but should not include space 244 // that the vm uses internally for bookkeeping or temporary storage 245 // (e.g., in the case of the young gen, one of the survivor 246 // spaces). 247 virtual size_t max_capacity() const = 0; 248 249 // Returns "TRUE" if "p" points into the reserved area of the heap. 250 bool is_in_reserved(const void* p) const { 251 return _reserved.contains(p); 252 } 253 254 bool is_in_reserved_or_null(const void* p) const { 255 return p == NULL || is_in_reserved(p); 256 } 257 258 // Returns "TRUE" iff "p" points into the committed areas of the heap. 259 // This method can be expensive so avoid using it in performance critical 260 // code. 261 virtual bool is_in(const void* p) const = 0; 262 263 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); }) 264 265 // Let's define some terms: a "closed" subset of a heap is one that 266 // 267 // 1) contains all currently-allocated objects, and 268 // 269 // 2) is closed under reference: no object in the closed subset 270 // references one outside the closed subset. 271 // 272 // Membership in a heap's closed subset is useful for assertions. 273 // Clearly, the entire heap is a closed subset, so the default 274 // implementation is to use "is_in_reserved". But this may not be too 275 // liberal to perform useful checking. Also, the "is_in" predicate 276 // defines a closed subset, but may be too expensive, since "is_in" 277 // verifies that its argument points to an object head. The 278 // "closed_subset" method allows a heap to define an intermediate 279 // predicate, allowing more precise checking than "is_in_reserved" at 280 // lower cost than "is_in." 281 282 // One important case is a heap composed of disjoint contiguous spaces, 283 // such as the Garbage-First collector. Such heaps have a convenient 284 // closed subset consisting of the allocated portions of those 285 // contiguous spaces. 286 287 // Return "TRUE" iff the given pointer points into the heap's defined 288 // closed subset (which defaults to the entire heap). 289 virtual bool is_in_closed_subset(const void* p) const { 290 return is_in_reserved(p); 291 } 292 293 bool is_in_closed_subset_or_null(const void* p) const { 294 return p == NULL || is_in_closed_subset(p); 295 } 296 297 void set_gc_cause(GCCause::Cause v) { 298 if (UsePerfData) { 299 _gc_lastcause = _gc_cause; 300 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause)); 301 _perf_gc_cause->set_value(GCCause::to_string(v)); 302 } 303 _gc_cause = v; 304 } 305 GCCause::Cause gc_cause() { return _gc_cause; } 306 307 // General obj/array allocation facilities. 308 inline static oop obj_allocate(Klass* klass, int size, TRAPS); 309 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS); 310 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS); 311 inline static oop class_allocate(Klass* klass, int size, TRAPS); 312 313 // Raw memory allocation facilities 314 // The obj and array allocate methods are covers for these methods. 315 // mem_allocate() should never be 316 // called to allocate TLABs, only individual objects. 317 virtual HeapWord* mem_allocate(size_t size, 318 bool* gc_overhead_limit_was_exceeded) = 0; 319 320 // Utilities for turning raw memory into filler objects. 321 // 322 // min_fill_size() is the smallest region that can be filled. 323 // fill_with_objects() can fill arbitrary-sized regions of the heap using 324 // multiple objects. fill_with_object() is for regions known to be smaller 325 // than the largest array of integers; it uses a single object to fill the 326 // region and has slightly less overhead. 327 static size_t min_fill_size() { 328 return size_t(align_object_size(oopDesc::header_size())); 329 } 330 331 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true); 332 333 static void fill_with_object(HeapWord* start, size_t words, bool zap = true); 334 static void fill_with_object(MemRegion region, bool zap = true) { 335 fill_with_object(region.start(), region.word_size(), zap); 336 } 337 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) { 338 fill_with_object(start, pointer_delta(end, start), zap); 339 } 340 341 // Return the address "addr" aligned by "alignment_in_bytes" if such 342 // an address is below "end". Return NULL otherwise. 343 inline static HeapWord* align_allocation_or_fail(HeapWord* addr, 344 HeapWord* end, 345 unsigned short alignment_in_bytes); 346 347 // Some heaps may offer a contiguous region for shared non-blocking 348 // allocation, via inlined code (by exporting the address of the top and 349 // end fields defining the extent of the contiguous allocation region.) 350 351 // This function returns "true" iff the heap supports this kind of 352 // allocation. (Default is "no".) 353 virtual bool supports_inline_contig_alloc() const { 354 return false; 355 } 356 // These functions return the addresses of the fields that define the 357 // boundaries of the contiguous allocation area. (These fields should be 358 // physically near to one another.) 359 virtual HeapWord* volatile* top_addr() const { 360 guarantee(false, "inline contiguous allocation not supported"); 361 return NULL; 362 } 363 virtual HeapWord** end_addr() const { 364 guarantee(false, "inline contiguous allocation not supported"); 365 return NULL; 366 } 367 368 // Some heaps may be in an unparseable state at certain times between 369 // collections. This may be necessary for efficient implementation of 370 // certain allocation-related activities. Calling this function before 371 // attempting to parse a heap ensures that the heap is in a parsable 372 // state (provided other concurrent activity does not introduce 373 // unparsability). It is normally expected, therefore, that this 374 // method is invoked with the world stopped. 375 // NOTE: if you override this method, make sure you call 376 // super::ensure_parsability so that the non-generational 377 // part of the work gets done. See implementation of 378 // CollectedHeap::ensure_parsability and, for instance, 379 // that of GenCollectedHeap::ensure_parsability(). 380 // The argument "retire_tlabs" controls whether existing TLABs 381 // are merely filled or also retired, thus preventing further 382 // allocation from them and necessitating allocation of new TLABs. 383 virtual void ensure_parsability(bool retire_tlabs); 384 385 // Section on thread-local allocation buffers (TLABs) 386 // If the heap supports thread-local allocation buffers, it should override 387 // the following methods: 388 // Returns "true" iff the heap supports thread-local allocation buffers. 389 // The default is "no". 390 virtual bool supports_tlab_allocation() const = 0; 391 392 // The amount of space available for thread-local allocation buffers. 393 virtual size_t tlab_capacity(Thread *thr) const = 0; 394 395 // The amount of used space for thread-local allocation buffers for the given thread. 396 virtual size_t tlab_used(Thread *thr) const = 0; 397 398 virtual size_t max_tlab_size() const; 399 400 // An estimate of the maximum allocation that could be performed 401 // for thread-local allocation buffers without triggering any 402 // collection or expansion activity. 403 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const { 404 guarantee(false, "thread-local allocation buffers not supported"); 405 return 0; 406 } 407 408 // Can a compiler initialize a new object without store barriers? 409 // This permission only extends from the creation of a new object 410 // via a TLAB up to the first subsequent safepoint. If such permission 411 // is granted for this heap type, the compiler promises to call 412 // defer_store_barrier() below on any slow path allocation of 413 // a new object for which such initializing store barriers will 414 // have been elided. 415 virtual bool can_elide_tlab_store_barriers() const = 0; 416 417 // If a compiler is eliding store barriers for TLAB-allocated objects, 418 // there is probably a corresponding slow path which can produce 419 // an object allocated anywhere. The compiler's runtime support 420 // promises to call this function on such a slow-path-allocated 421 // object before performing initializations that have elided 422 // store barriers. Returns new_obj, or maybe a safer copy thereof. 423 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj); 424 425 // Answers whether an initializing store to a new object currently 426 // allocated at the given address doesn't need a store 427 // barrier. Returns "true" if it doesn't need an initializing 428 // store barrier; answers "false" if it does. 429 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0; 430 431 // If a compiler is eliding store barriers for TLAB-allocated objects, 432 // we will be informed of a slow-path allocation by a call 433 // to new_store_pre_barrier() above. Such a call precedes the 434 // initialization of the object itself, and no post-store-barriers will 435 // be issued. Some heap types require that the barrier strictly follows 436 // the initializing stores. (This is currently implemented by deferring the 437 // barrier until the next slow-path allocation or gc-related safepoint.) 438 // This interface answers whether a particular heap type needs the card 439 // mark to be thus strictly sequenced after the stores. 440 virtual bool card_mark_must_follow_store() const = 0; 441 442 // If the CollectedHeap was asked to defer a store barrier above, 443 // this informs it to flush such a deferred store barrier to the 444 // remembered set. 445 virtual void flush_deferred_store_barrier(JavaThread* thread); 446 447 // Perform a collection of the heap; intended for use in implementing 448 // "System.gc". This probably implies as full a collection as the 449 // "CollectedHeap" supports. 450 virtual void collect(GCCause::Cause cause) = 0; 451 452 // Perform a full collection 453 virtual void do_full_collection(bool clear_all_soft_refs) = 0; 454 455 // This interface assumes that it's being called by the 456 // vm thread. It collects the heap assuming that the 457 // heap lock is already held and that we are executing in 458 // the context of the vm thread. 459 virtual void collect_as_vm_thread(GCCause::Cause cause); 460 461 // Returns the barrier set for this heap 462 BarrierSet* barrier_set() { return _barrier_set; } 463 void set_barrier_set(BarrierSet* barrier_set); 464 465 // Returns "true" iff there is a stop-world GC in progress. (I assume 466 // that it should answer "false" for the concurrent part of a concurrent 467 // collector -- dld). 468 bool is_gc_active() const { return _is_gc_active; } 469 470 // Total number of GC collections (started) 471 unsigned int total_collections() const { return _total_collections; } 472 unsigned int total_full_collections() const { return _total_full_collections;} 473 474 // Increment total number of GC collections (started) 475 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2 476 void increment_total_collections(bool full = false) { 477 _total_collections++; 478 if (full) { 479 increment_total_full_collections(); 480 } 481 } 482 483 void increment_total_full_collections() { _total_full_collections++; } 484 485 // Return the CollectorPolicy for the heap 486 virtual CollectorPolicy* collector_policy() const = 0; 487 488 // Iterate over all objects, calling "cl.do_object" on each. 489 virtual void object_iterate(ObjectClosure* cl) = 0; 490 491 // Similar to object_iterate() except iterates only 492 // over live objects. 493 virtual void safe_object_iterate(ObjectClosure* cl) = 0; 494 495 // NOTE! There is no requirement that a collector implement these 496 // functions. 497 // 498 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 499 // each address in the (reserved) heap is a member of exactly 500 // one block. The defining characteristic of a block is that it is 501 // possible to find its size, and thus to progress forward to the next 502 // block. (Blocks may be of different sizes.) Thus, blocks may 503 // represent Java objects, or they might be free blocks in a 504 // free-list-based heap (or subheap), as long as the two kinds are 505 // distinguishable and the size of each is determinable. 506 507 // Returns the address of the start of the "block" that contains the 508 // address "addr". We say "blocks" instead of "object" since some heaps 509 // may not pack objects densely; a chunk may either be an object or a 510 // non-object. 511 virtual HeapWord* block_start(const void* addr) const = 0; 512 513 // Requires "addr" to be the start of a chunk, and returns its size. 514 // "addr + size" is required to be the start of a new chunk, or the end 515 // of the active area of the heap. 516 virtual size_t block_size(const HeapWord* addr) const = 0; 517 518 // Requires "addr" to be the start of a block, and returns "TRUE" iff 519 // the block is an object. 520 virtual bool block_is_obj(const HeapWord* addr) const = 0; 521 522 // Returns the longest time (in ms) that has elapsed since the last 523 // time that any part of the heap was examined by a garbage collection. 524 virtual jlong millis_since_last_gc() = 0; 525 526 // Perform any cleanup actions necessary before allowing a verification. 527 virtual void prepare_for_verify() = 0; 528 529 // Generate any dumps preceding or following a full gc 530 private: 531 void full_gc_dump(GCTimer* timer, bool before); 532 public: 533 void pre_full_gc_dump(GCTimer* timer); 534 void post_full_gc_dump(GCTimer* timer); 535 536 VirtualSpaceSummary create_heap_space_summary(); 537 GCHeapSummary create_heap_summary(); 538 539 MetaspaceSummary create_metaspace_summary(); 540 541 // Print heap information on the given outputStream. 542 virtual void print_on(outputStream* st) const = 0; 543 // The default behavior is to call print_on() on tty. 544 virtual void print() const { 545 print_on(tty); 546 } 547 // Print more detailed heap information on the given 548 // outputStream. The default behavior is to call print_on(). It is 549 // up to each subclass to override it and add any additional output 550 // it needs. 551 virtual void print_extended_on(outputStream* st) const { 552 print_on(st); 553 } 554 555 virtual void print_on_error(outputStream* st) const; 556 557 // Print all GC threads (other than the VM thread) 558 // used by this heap. 559 virtual void print_gc_threads_on(outputStream* st) const = 0; 560 // The default behavior is to call print_gc_threads_on() on tty. 561 void print_gc_threads() { 562 print_gc_threads_on(tty); 563 } 564 // Iterator for all GC threads (other than VM thread) 565 virtual void gc_threads_do(ThreadClosure* tc) const = 0; 566 567 // Print any relevant tracing info that flags imply. 568 // Default implementation does nothing. 569 virtual void print_tracing_info() const = 0; 570 571 void print_heap_before_gc(); 572 void print_heap_after_gc(); 573 574 // An object is scavengable if its location may move during a scavenge. 575 // (A scavenge is a GC which is not a full GC.) 576 virtual bool is_scavengable(oop obj) = 0; 577 // Registering and unregistering an nmethod (compiled code) with the heap. 578 // Override with specific mechanism for each specialized heap type. 579 virtual void register_nmethod(nmethod* nm) {} 580 virtual void unregister_nmethod(nmethod* nm) {} 581 virtual void verify_nmethod(nmethod* nmethod) {} 582 583 void trace_heap_before_gc(const GCTracer* gc_tracer); 584 void trace_heap_after_gc(const GCTracer* gc_tracer); 585 586 // Heap verification 587 virtual void verify(VerifyOption option) = 0; 588 589 // Return true if concurrent phase control (via 590 // request_concurrent_phase_control) is supported by this collector. 591 // The default implementation returns false. 592 virtual bool supports_concurrent_phase_control() const; 593 594 // Return a NULL terminated array of concurrent phase names provided 595 // by this collector. Supports Whitebox testing. These are the 596 // names recognized by request_concurrent_phase(). The default 597 // implementation returns an array of one NULL element. 598 virtual const char* const* concurrent_phases() const; 599 600 // Request the collector enter the indicated concurrent phase, and 601 // wait until it does so. Supports WhiteBox testing. Only one 602 // request may be active at a time. Phases are designated by name; 603 // the set of names and their meaning is GC-specific. Once the 604 // requested phase has been reached, the collector will attempt to 605 // avoid transitioning to a new phase until a new request is made. 606 // [Note: A collector might not be able to remain in a given phase. 607 // For example, a full collection might cancel an in-progress 608 // concurrent collection.] 609 // 610 // Returns true when the phase is reached. Returns false for an 611 // unknown phase. The default implementation returns false. 612 virtual bool request_concurrent_phase(const char* phase); 613 614 // Provides a thread pool to SafepointSynchronize to use 615 // for parallel safepoint cleanup. 616 // GCs that use a GC worker thread pool may want to share 617 // it for use during safepoint cleanup. This is only possible 618 // if the GC can pause and resume concurrent work (e.g. G1 619 // concurrent marking) for an intermittent non-GC safepoint. 620 // If this method returns NULL, SafepointSynchronize will 621 // perform cleanup tasks serially in the VMThread. 622 virtual WorkGang* get_safepoint_workers() { return NULL; } 623 624 // Non product verification and debugging. 625 #ifndef PRODUCT 626 // Support for PromotionFailureALot. Return true if it's time to cause a 627 // promotion failure. The no-argument version uses 628 // this->_promotion_failure_alot_count as the counter. 629 inline bool promotion_should_fail(volatile size_t* count); 630 inline bool promotion_should_fail(); 631 632 // Reset the PromotionFailureALot counters. Should be called at the end of a 633 // GC in which promotion failure occurred. 634 inline void reset_promotion_should_fail(volatile size_t* count); 635 inline void reset_promotion_should_fail(); 636 #endif // #ifndef PRODUCT 637 638 #ifdef ASSERT 639 static int fired_fake_oom() { 640 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt); 641 } 642 #endif 643 644 public: 645 // Copy the current allocation context statistics for the specified contexts. 646 // For each context in contexts, set the corresponding entries in the totals 647 // and accuracy arrays to the current values held by the statistics. Each 648 // array should be of length len. 649 // Returns true if there are more stats available. 650 virtual bool copy_allocation_context_stats(const jint* contexts, 651 jlong* totals, 652 jbyte* accuracy, 653 jint len) { 654 return false; 655 } 656 657 }; 658 659 // Class to set and reset the GC cause for a CollectedHeap. 660 661 class GCCauseSetter : StackObj { 662 CollectedHeap* _heap; 663 GCCause::Cause _previous_cause; 664 public: 665 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) { 666 assert(SafepointSynchronize::is_at_safepoint(), 667 "This method manipulates heap state without locking"); 668 _heap = heap; 669 _previous_cause = _heap->gc_cause(); 670 _heap->set_gc_cause(cause); 671 } 672 673 ~GCCauseSetter() { 674 assert(SafepointSynchronize::is_at_safepoint(), 675 "This method manipulates heap state without locking"); 676 _heap->set_gc_cause(_previous_cause); 677 } 678 }; 679 680 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP