1 /* 2 * Copyright (c) 2001, 2018, 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 #include "utilities/growableArray.hpp" 38 39 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This 40 // is an abstract class: there may be many different kinds of heaps. This 41 // class defines the functions that a heap must implement, and contains 42 // infrastructure common to all heaps. 43 44 class AdaptiveSizePolicy; 45 class BarrierSet; 46 class CollectorPolicy; 47 class GCHeapSummary; 48 class GCTimer; 49 class GCTracer; 50 class GCMemoryManager; 51 class MemoryPool; 52 class MetaspaceSummary; 53 class Thread; 54 class ThreadClosure; 55 class VirtualSpaceSummary; 56 class WorkGang; 57 class nmethod; 58 59 class GCMessage : public FormatBuffer<1024> { 60 public: 61 bool is_before; 62 63 public: 64 GCMessage() {} 65 }; 66 67 class CollectedHeap; 68 69 class GCHeapLog : public EventLogBase<GCMessage> { 70 private: 71 void log_heap(CollectedHeap* heap, bool before); 72 73 public: 74 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {} 75 76 void log_heap_before(CollectedHeap* heap) { 77 log_heap(heap, true); 78 } 79 void log_heap_after(CollectedHeap* heap) { 80 log_heap(heap, false); 81 } 82 }; 83 84 // 85 // CollectedHeap 86 // GenCollectedHeap 87 // SerialHeap 88 // CMSHeap 89 // G1CollectedHeap 90 // ParallelScavengeHeap 91 // 92 class CollectedHeap : public CHeapObj<mtInternal> { 93 friend class VMStructs; 94 friend class JVMCIVMStructs; 95 friend class IsGCActiveMark; // Block structured external access to _is_gc_active 96 97 private: 98 #ifdef ASSERT 99 static int _fire_out_of_memory_count; 100 #endif 101 102 GCHeapLog* _gc_heap_log; 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 // Create a new tlab. All TLAB allocations must go through this. 129 virtual HeapWord* allocate_new_tlab(size_t size); 130 131 // Accumulate statistics on all tlabs. 132 virtual void accumulate_statistics_all_tlabs(); 133 134 // Reinitialize tlabs before resuming mutators. 135 virtual void resize_all_tlabs(); 136 137 // Allocate from the current thread's TLAB, with broken-out slow path. 138 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size); 139 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size); 140 141 // Allocate an uninitialized block of the given size, or returns NULL if 142 // this is impossible. 143 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS); 144 145 // Like allocate_init, but the block returned by a successful allocation 146 // is guaranteed initialized to zeros. 147 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS); 148 149 // Helper functions for (VM) allocation. 150 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj); 151 inline static void post_allocation_setup_no_klass_install(Klass* klass, 152 HeapWord* objPtr); 153 154 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size); 155 156 inline static void post_allocation_setup_array(Klass* klass, 157 HeapWord* obj, int length); 158 159 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size); 160 161 // Clears an allocated object. 162 inline static void init_obj(HeapWord* obj, size_t size); 163 164 // Filler object utilities. 165 static inline size_t filler_array_hdr_size(); 166 static inline size_t filler_array_min_size(); 167 168 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);) 169 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);) 170 171 // Fill with a single array; caller must ensure filler_array_min_size() <= 172 // words <= filler_array_max_size(). 173 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true); 174 175 // Fill with a single object (either an int array or a java.lang.Object). 176 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true); 177 178 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer); 179 180 // Verification functions 181 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size) 182 PRODUCT_RETURN; 183 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) 184 PRODUCT_RETURN; 185 debug_only(static void check_for_valid_allocation_state();) 186 187 public: 188 enum Name { 189 SerialHeap, 190 ParallelScavengeHeap, 191 G1CollectedHeap, 192 CMSHeap 193 }; 194 195 static inline size_t filler_array_max_size() { 196 return _filler_array_max_size; 197 } 198 199 virtual Name kind() const = 0; 200 201 virtual const char* name() const = 0; 202 203 /** 204 * Returns JNI error code JNI_ENOMEM if memory could not be allocated, 205 * and JNI_OK on success. 206 */ 207 virtual jint initialize() = 0; 208 209 // In many heaps, there will be a need to perform some initialization activities 210 // after the Universe is fully formed, but before general heap allocation is allowed. 211 // This is the correct place to place such initialization methods. 212 virtual void post_initialize(); 213 214 // Stop any onging concurrent work and prepare for exit. 215 virtual void stop() {} 216 217 // Stop and resume concurrent GC threads interfering with safepoint operations 218 virtual void safepoint_synchronize_begin() {} 219 virtual void safepoint_synchronize_end() {} 220 221 void initialize_reserved_region(HeapWord *start, HeapWord *end); 222 MemRegion reserved_region() const { return _reserved; } 223 address base() const { return (address)reserved_region().start(); } 224 225 virtual size_t capacity() const = 0; 226 virtual size_t used() const = 0; 227 228 // Return "true" if the part of the heap that allocates Java 229 // objects has reached the maximal committed limit that it can 230 // reach, without a garbage collection. 231 virtual bool is_maximal_no_gc() const = 0; 232 233 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of 234 // memory that the vm could make available for storing 'normal' java objects. 235 // This is based on the reserved address space, but should not include space 236 // that the vm uses internally for bookkeeping or temporary storage 237 // (e.g., in the case of the young gen, one of the survivor 238 // spaces). 239 virtual size_t max_capacity() const = 0; 240 241 // Returns "TRUE" if "p" points into the reserved area of the heap. 242 bool is_in_reserved(const void* p) const { 243 return _reserved.contains(p); 244 } 245 246 bool is_in_reserved_or_null(const void* p) const { 247 return p == NULL || is_in_reserved(p); 248 } 249 250 // Returns "TRUE" iff "p" points into the committed areas of the heap. 251 // This method can be expensive so avoid using it in performance critical 252 // code. 253 virtual bool is_in(const void* p) const = 0; 254 255 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); }) 256 257 // Let's define some terms: a "closed" subset of a heap is one that 258 // 259 // 1) contains all currently-allocated objects, and 260 // 261 // 2) is closed under reference: no object in the closed subset 262 // references one outside the closed subset. 263 // 264 // Membership in a heap's closed subset is useful for assertions. 265 // Clearly, the entire heap is a closed subset, so the default 266 // implementation is to use "is_in_reserved". But this may not be too 267 // liberal to perform useful checking. Also, the "is_in" predicate 268 // defines a closed subset, but may be too expensive, since "is_in" 269 // verifies that its argument points to an object head. The 270 // "closed_subset" method allows a heap to define an intermediate 271 // predicate, allowing more precise checking than "is_in_reserved" at 272 // lower cost than "is_in." 273 274 // One important case is a heap composed of disjoint contiguous spaces, 275 // such as the Garbage-First collector. Such heaps have a convenient 276 // closed subset consisting of the allocated portions of those 277 // contiguous spaces. 278 279 // Return "TRUE" iff the given pointer points into the heap's defined 280 // closed subset (which defaults to the entire heap). 281 virtual bool is_in_closed_subset(const void* p) const { 282 return is_in_reserved(p); 283 } 284 285 bool is_in_closed_subset_or_null(const void* p) const { 286 return p == NULL || is_in_closed_subset(p); 287 } 288 289 void set_gc_cause(GCCause::Cause v) { 290 if (UsePerfData) { 291 _gc_lastcause = _gc_cause; 292 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause)); 293 _perf_gc_cause->set_value(GCCause::to_string(v)); 294 } 295 _gc_cause = v; 296 } 297 GCCause::Cause gc_cause() { return _gc_cause; } 298 299 // General obj/array allocation facilities. 300 inline static oop obj_allocate(Klass* klass, int size, TRAPS); 301 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS); 302 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS); 303 inline static oop class_allocate(Klass* klass, int size, TRAPS); 304 305 // Raw memory allocation facilities 306 // The obj and array allocate methods are covers for these methods. 307 // mem_allocate() should never be 308 // called to allocate TLABs, only individual objects. 309 virtual HeapWord* mem_allocate(size_t size, 310 bool* gc_overhead_limit_was_exceeded) = 0; 311 312 // Utilities for turning raw memory into filler objects. 313 // 314 // min_fill_size() is the smallest region that can be filled. 315 // fill_with_objects() can fill arbitrary-sized regions of the heap using 316 // multiple objects. fill_with_object() is for regions known to be smaller 317 // than the largest array of integers; it uses a single object to fill the 318 // region and has slightly less overhead. 319 static size_t min_fill_size() { 320 return size_t(align_object_size(oopDesc::header_size())); 321 } 322 323 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true); 324 325 static void fill_with_object(HeapWord* start, size_t words, bool zap = true); 326 static void fill_with_object(MemRegion region, bool zap = true) { 327 fill_with_object(region.start(), region.word_size(), zap); 328 } 329 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) { 330 fill_with_object(start, pointer_delta(end, start), zap); 331 } 332 333 // Return the address "addr" aligned by "alignment_in_bytes" if such 334 // an address is below "end". Return NULL otherwise. 335 inline static HeapWord* align_allocation_or_fail(HeapWord* addr, 336 HeapWord* end, 337 unsigned short alignment_in_bytes); 338 339 // Some heaps may offer a contiguous region for shared non-blocking 340 // allocation, via inlined code (by exporting the address of the top and 341 // end fields defining the extent of the contiguous allocation region.) 342 343 // This function returns "true" iff the heap supports this kind of 344 // allocation. (Default is "no".) 345 virtual bool supports_inline_contig_alloc() const { 346 return false; 347 } 348 // These functions return the addresses of the fields that define the 349 // boundaries of the contiguous allocation area. (These fields should be 350 // physically near to one another.) 351 virtual HeapWord* volatile* top_addr() const { 352 guarantee(false, "inline contiguous allocation not supported"); 353 return NULL; 354 } 355 virtual HeapWord** end_addr() const { 356 guarantee(false, "inline contiguous allocation not supported"); 357 return NULL; 358 } 359 360 // Some heaps may be in an unparseable state at certain times between 361 // collections. This may be necessary for efficient implementation of 362 // certain allocation-related activities. Calling this function before 363 // attempting to parse a heap ensures that the heap is in a parsable 364 // state (provided other concurrent activity does not introduce 365 // unparsability). It is normally expected, therefore, that this 366 // method is invoked with the world stopped. 367 // NOTE: if you override this method, make sure you call 368 // super::ensure_parsability so that the non-generational 369 // part of the work gets done. See implementation of 370 // CollectedHeap::ensure_parsability and, for instance, 371 // that of GenCollectedHeap::ensure_parsability(). 372 // The argument "retire_tlabs" controls whether existing TLABs 373 // are merely filled or also retired, thus preventing further 374 // allocation from them and necessitating allocation of new TLABs. 375 virtual void ensure_parsability(bool retire_tlabs); 376 377 // Section on thread-local allocation buffers (TLABs) 378 // If the heap supports thread-local allocation buffers, it should override 379 // the following methods: 380 // Returns "true" iff the heap supports thread-local allocation buffers. 381 // The default is "no". 382 virtual bool supports_tlab_allocation() const = 0; 383 384 // The amount of space available for thread-local allocation buffers. 385 virtual size_t tlab_capacity(Thread *thr) const = 0; 386 387 // The amount of used space for thread-local allocation buffers for the given thread. 388 virtual size_t tlab_used(Thread *thr) const = 0; 389 390 virtual size_t max_tlab_size() const; 391 392 // An estimate of the maximum allocation that could be performed 393 // for thread-local allocation buffers without triggering any 394 // collection or expansion activity. 395 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const { 396 guarantee(false, "thread-local allocation buffers not supported"); 397 return 0; 398 } 399 400 // Perform a collection of the heap; intended for use in implementing 401 // "System.gc". This probably implies as full a collection as the 402 // "CollectedHeap" supports. 403 virtual void collect(GCCause::Cause cause) = 0; 404 405 // Perform a full collection 406 virtual void do_full_collection(bool clear_all_soft_refs) = 0; 407 408 // This interface assumes that it's being called by the 409 // vm thread. It collects the heap assuming that the 410 // heap lock is already held and that we are executing in 411 // the context of the vm thread. 412 virtual void collect_as_vm_thread(GCCause::Cause cause); 413 414 // Returns the barrier set for this heap 415 BarrierSet* barrier_set() { return _barrier_set; } 416 void set_barrier_set(BarrierSet* barrier_set); 417 418 // Returns "true" iff there is a stop-world GC in progress. (I assume 419 // that it should answer "false" for the concurrent part of a concurrent 420 // collector -- dld). 421 bool is_gc_active() const { return _is_gc_active; } 422 423 // Total number of GC collections (started) 424 unsigned int total_collections() const { return _total_collections; } 425 unsigned int total_full_collections() const { return _total_full_collections;} 426 427 // Increment total number of GC collections (started) 428 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2 429 void increment_total_collections(bool full = false) { 430 _total_collections++; 431 if (full) { 432 increment_total_full_collections(); 433 } 434 } 435 436 void increment_total_full_collections() { _total_full_collections++; } 437 438 // Return the CollectorPolicy for the heap 439 virtual CollectorPolicy* collector_policy() const = 0; 440 441 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0; 442 virtual GrowableArray<MemoryPool*> memory_pools() = 0; 443 444 // Iterate over all objects, calling "cl.do_object" on each. 445 virtual void object_iterate(ObjectClosure* cl) = 0; 446 447 // Similar to object_iterate() except iterates only 448 // over live objects. 449 virtual void safe_object_iterate(ObjectClosure* cl) = 0; 450 451 // NOTE! There is no requirement that a collector implement these 452 // functions. 453 // 454 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 455 // each address in the (reserved) heap is a member of exactly 456 // one block. The defining characteristic of a block is that it is 457 // possible to find its size, and thus to progress forward to the next 458 // block. (Blocks may be of different sizes.) Thus, blocks may 459 // represent Java objects, or they might be free blocks in a 460 // free-list-based heap (or subheap), as long as the two kinds are 461 // distinguishable and the size of each is determinable. 462 463 // Returns the address of the start of the "block" that contains the 464 // address "addr". We say "blocks" instead of "object" since some heaps 465 // may not pack objects densely; a chunk may either be an object or a 466 // non-object. 467 virtual HeapWord* block_start(const void* addr) const = 0; 468 469 // Requires "addr" to be the start of a chunk, and returns its size. 470 // "addr + size" is required to be the start of a new chunk, or the end 471 // of the active area of the heap. 472 virtual size_t block_size(const HeapWord* addr) const = 0; 473 474 // Requires "addr" to be the start of a block, and returns "TRUE" iff 475 // the block is an object. 476 virtual bool block_is_obj(const HeapWord* addr) const = 0; 477 478 // Returns the longest time (in ms) that has elapsed since the last 479 // time that any part of the heap was examined by a garbage collection. 480 virtual jlong millis_since_last_gc() = 0; 481 482 // Perform any cleanup actions necessary before allowing a verification. 483 virtual void prepare_for_verify() = 0; 484 485 // Generate any dumps preceding or following a full gc 486 private: 487 void full_gc_dump(GCTimer* timer, bool before); 488 489 virtual void initialize_serviceability() = 0; 490 491 public: 492 void pre_full_gc_dump(GCTimer* timer); 493 void post_full_gc_dump(GCTimer* timer); 494 495 virtual VirtualSpaceSummary create_heap_space_summary(); 496 GCHeapSummary create_heap_summary(); 497 498 MetaspaceSummary create_metaspace_summary(); 499 500 // Print heap information on the given outputStream. 501 virtual void print_on(outputStream* st) const = 0; 502 // The default behavior is to call print_on() on tty. 503 virtual void print() const { 504 print_on(tty); 505 } 506 // Print more detailed heap information on the given 507 // outputStream. The default behavior is to call print_on(). It is 508 // up to each subclass to override it and add any additional output 509 // it needs. 510 virtual void print_extended_on(outputStream* st) const { 511 print_on(st); 512 } 513 514 virtual void print_on_error(outputStream* st) const; 515 516 // Print all GC threads (other than the VM thread) 517 // used by this heap. 518 virtual void print_gc_threads_on(outputStream* st) const = 0; 519 // The default behavior is to call print_gc_threads_on() on tty. 520 void print_gc_threads() { 521 print_gc_threads_on(tty); 522 } 523 // Iterator for all GC threads (other than VM thread) 524 virtual void gc_threads_do(ThreadClosure* tc) const = 0; 525 526 // Print any relevant tracing info that flags imply. 527 // Default implementation does nothing. 528 virtual void print_tracing_info() const = 0; 529 530 void print_heap_before_gc(); 531 void print_heap_after_gc(); 532 533 // An object is scavengable if its location may move during a scavenge. 534 // (A scavenge is a GC which is not a full GC.) 535 virtual bool is_scavengable(oop obj) = 0; 536 // Registering and unregistering an nmethod (compiled code) with the heap. 537 // Override with specific mechanism for each specialized heap type. 538 virtual void register_nmethod(nmethod* nm) {} 539 virtual void unregister_nmethod(nmethod* nm) {} 540 virtual void verify_nmethod(nmethod* nmethod) {} 541 542 void trace_heap_before_gc(const GCTracer* gc_tracer); 543 void trace_heap_after_gc(const GCTracer* gc_tracer); 544 545 // Heap verification 546 virtual void verify(VerifyOption option) = 0; 547 548 // Return true if concurrent phase control (via 549 // request_concurrent_phase_control) is supported by this collector. 550 // The default implementation returns false. 551 virtual bool supports_concurrent_phase_control() const; 552 553 // Return a NULL terminated array of concurrent phase names provided 554 // by this collector. Supports Whitebox testing. These are the 555 // names recognized by request_concurrent_phase(). The default 556 // implementation returns an array of one NULL element. 557 virtual const char* const* concurrent_phases() const; 558 559 // Request the collector enter the indicated concurrent phase, and 560 // wait until it does so. Supports WhiteBox testing. Only one 561 // request may be active at a time. Phases are designated by name; 562 // the set of names and their meaning is GC-specific. Once the 563 // requested phase has been reached, the collector will attempt to 564 // avoid transitioning to a new phase until a new request is made. 565 // [Note: A collector might not be able to remain in a given phase. 566 // For example, a full collection might cancel an in-progress 567 // concurrent collection.] 568 // 569 // Returns true when the phase is reached. Returns false for an 570 // unknown phase. The default implementation returns false. 571 virtual bool request_concurrent_phase(const char* phase); 572 573 // Provides a thread pool to SafepointSynchronize to use 574 // for parallel safepoint cleanup. 575 // GCs that use a GC worker thread pool may want to share 576 // it for use during safepoint cleanup. This is only possible 577 // if the GC can pause and resume concurrent work (e.g. G1 578 // concurrent marking) for an intermittent non-GC safepoint. 579 // If this method returns NULL, SafepointSynchronize will 580 // perform cleanup tasks serially in the VMThread. 581 virtual WorkGang* get_safepoint_workers() { return NULL; } 582 583 // Non product verification and debugging. 584 #ifndef PRODUCT 585 // Support for PromotionFailureALot. Return true if it's time to cause a 586 // promotion failure. The no-argument version uses 587 // this->_promotion_failure_alot_count as the counter. 588 inline bool promotion_should_fail(volatile size_t* count); 589 inline bool promotion_should_fail(); 590 591 // Reset the PromotionFailureALot counters. Should be called at the end of a 592 // GC in which promotion failure occurred. 593 inline void reset_promotion_should_fail(volatile size_t* count); 594 inline void reset_promotion_should_fail(); 595 #endif // #ifndef PRODUCT 596 597 #ifdef ASSERT 598 static int fired_fake_oom() { 599 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt); 600 } 601 #endif 602 603 public: 604 // Copy the current allocation context statistics for the specified contexts. 605 // For each context in contexts, set the corresponding entries in the totals 606 // and accuracy arrays to the current values held by the statistics. Each 607 // array should be of length len. 608 // Returns true if there are more stats available. 609 virtual bool copy_allocation_context_stats(const jint* contexts, 610 jlong* totals, 611 jbyte* accuracy, 612 jint len) { 613 return false; 614 } 615 616 }; 617 618 // Class to set and reset the GC cause for a CollectedHeap. 619 620 class GCCauseSetter : StackObj { 621 CollectedHeap* _heap; 622 GCCause::Cause _previous_cause; 623 public: 624 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) { 625 assert(SafepointSynchronize::is_at_safepoint(), 626 "This method manipulates heap state without locking"); 627 _heap = heap; 628 _previous_cause = _heap->gc_cause(); 629 _heap->set_gc_cause(cause); 630 } 631 632 ~GCCauseSetter() { 633 assert(SafepointSynchronize::is_at_safepoint(), 634 "This method manipulates heap state without locking"); 635 _heap->set_gc_cause(_previous_cause); 636 } 637 }; 638 639 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP