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