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.
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20 * or visit www.oracle.com if you need additional information or have any
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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 SoftRefPolicy;
54 class Thread;
55 class ThreadClosure;
56 class VirtualSpaceSummary;
57 class WorkGang;
58 class nmethod;
59
60 class GCMessage : public FormatBuffer<1024> {
61 public:
62 bool is_before;
63
64 public:
65 GCMessage() {}
66 };
67
68 class CollectedHeap;
69
70 class GCHeapLog : public EventLogBase<GCMessage> {
71 private:
72 void log_heap(CollectedHeap* heap, bool before);
73
74 public:
75 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
76
77 void log_heap_before(CollectedHeap* heap) {
78 log_heap(heap, true);
79 }
80 void log_heap_after(CollectedHeap* heap) {
81 log_heap(heap, false);
82 }
83 };
84
85 //
86 // CollectedHeap
87 // GenCollectedHeap
88 // SerialHeap
89 // CMSHeap
90 // G1CollectedHeap
91 // ParallelScavengeHeap
92 //
93 class CollectedHeap : public CHeapObj<mtInternal> {
94 friend class VMStructs;
95 friend class JVMCIVMStructs;
96 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
97
98 private:
99 #ifdef ASSERT
100 static int _fire_out_of_memory_count;
101 #endif
102
103 GCHeapLog* _gc_heap_log;
104
105 MemRegion _reserved;
106
107 protected:
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 None,
190 Serial,
191 Parallel,
192 CMS,
193 G1
194 };
195
196 static inline size_t filler_array_max_size() {
197 return _filler_array_max_size;
198 }
199
200 virtual Name kind() const = 0;
201
202 virtual const char* name() const = 0;
203
204 /**
205 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
206 * and JNI_OK on success.
207 */
208 virtual jint initialize() = 0;
209
210 // In many heaps, there will be a need to perform some initialization activities
211 // after the Universe is fully formed, but before general heap allocation is allowed.
212 // This is the correct place to place such initialization methods.
213 virtual void post_initialize();
214
215 // Stop any onging concurrent work and prepare for exit.
216 virtual void stop() {}
217
218 // Stop and resume concurrent GC threads interfering with safepoint operations
219 virtual void safepoint_synchronize_begin() {}
220 virtual void safepoint_synchronize_end() {}
221
222 void initialize_reserved_region(HeapWord *start, HeapWord *end);
223 MemRegion reserved_region() const { return _reserved; }
224 address base() const { return (address)reserved_region().start(); }
225
226 virtual size_t capacity() const = 0;
227 virtual size_t used() const = 0;
228
229 // Return "true" if the part of the heap that allocates Java
230 // objects has reached the maximal committed limit that it can
231 // reach, without a garbage collection.
232 virtual bool is_maximal_no_gc() const = 0;
233
234 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
235 // memory that the vm could make available for storing 'normal' java objects.
236 // This is based on the reserved address space, but should not include space
237 // that the vm uses internally for bookkeeping or temporary storage
238 // (e.g., in the case of the young gen, one of the survivor
239 // spaces).
240 virtual size_t max_capacity() const = 0;
241
242 // Returns "TRUE" if "p" points into the reserved area of the heap.
243 bool is_in_reserved(const void* p) const {
244 return _reserved.contains(p);
245 }
246
247 bool is_in_reserved_or_null(const void* p) const {
248 return p == NULL || is_in_reserved(p);
249 }
250
251 // Returns "TRUE" iff "p" points into the committed areas of the heap.
252 // This method can be expensive so avoid using it in performance critical
253 // code.
254 virtual bool is_in(const void* p) const = 0;
255
256 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
257
258 // Let's define some terms: a "closed" subset of a heap is one that
259 //
260 // 1) contains all currently-allocated objects, and
261 //
262 // 2) is closed under reference: no object in the closed subset
263 // references one outside the closed subset.
264 //
265 // Membership in a heap's closed subset is useful for assertions.
266 // Clearly, the entire heap is a closed subset, so the default
267 // implementation is to use "is_in_reserved". But this may not be too
268 // liberal to perform useful checking. Also, the "is_in" predicate
269 // defines a closed subset, but may be too expensive, since "is_in"
270 // verifies that its argument points to an object head. The
271 // "closed_subset" method allows a heap to define an intermediate
272 // predicate, allowing more precise checking than "is_in_reserved" at
273 // lower cost than "is_in."
274
275 // One important case is a heap composed of disjoint contiguous spaces,
276 // such as the Garbage-First collector. Such heaps have a convenient
277 // closed subset consisting of the allocated portions of those
278 // contiguous spaces.
279
280 // Return "TRUE" iff the given pointer points into the heap's defined
281 // closed subset (which defaults to the entire heap).
282 virtual bool is_in_closed_subset(const void* p) const {
283 return is_in_reserved(p);
284 }
285
286 bool is_in_closed_subset_or_null(const void* p) const {
287 return p == NULL || is_in_closed_subset(p);
288 }
289
290 void set_gc_cause(GCCause::Cause v) {
291 if (UsePerfData) {
292 _gc_lastcause = _gc_cause;
293 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
294 _perf_gc_cause->set_value(GCCause::to_string(v));
295 }
296 _gc_cause = v;
297 }
298 GCCause::Cause gc_cause() { return _gc_cause; }
299
300 // General obj/array allocation facilities.
301 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
302 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
303 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
304 inline static oop class_allocate(Klass* klass, int size, TRAPS);
305
306 // Raw memory allocation facilities
307 // The obj and array allocate methods are covers for these methods.
308 // mem_allocate() should never be
309 // called to allocate TLABs, only individual objects.
310 virtual HeapWord* mem_allocate(size_t size,
311 bool* gc_overhead_limit_was_exceeded) = 0;
312
313 // Utilities for turning raw memory into filler objects.
314 //
315 // min_fill_size() is the smallest region that can be filled.
316 // fill_with_objects() can fill arbitrary-sized regions of the heap using
317 // multiple objects. fill_with_object() is for regions known to be smaller
318 // than the largest array of integers; it uses a single object to fill the
319 // region and has slightly less overhead.
320 static size_t min_fill_size() {
321 return size_t(align_object_size(oopDesc::header_size()));
322 }
323
324 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
325
326 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
327 static void fill_with_object(MemRegion region, bool zap = true) {
328 fill_with_object(region.start(), region.word_size(), zap);
329 }
330 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
331 fill_with_object(start, pointer_delta(end, start), zap);
332 }
333
334 // Return the address "addr" aligned by "alignment_in_bytes" if such
335 // an address is below "end". Return NULL otherwise.
336 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
337 HeapWord* end,
338 unsigned short alignment_in_bytes);
339
340 // Some heaps may offer a contiguous region for shared non-blocking
341 // allocation, via inlined code (by exporting the address of the top and
342 // end fields defining the extent of the contiguous allocation region.)
343
344 // This function returns "true" iff the heap supports this kind of
345 // allocation. (Default is "no".)
346 virtual bool supports_inline_contig_alloc() const {
347 return false;
348 }
349 // These functions return the addresses of the fields that define the
350 // boundaries of the contiguous allocation area. (These fields should be
351 // physically near to one another.)
352 virtual HeapWord* volatile* top_addr() const {
353 guarantee(false, "inline contiguous allocation not supported");
354 return NULL;
355 }
356 virtual HeapWord** end_addr() const {
357 guarantee(false, "inline contiguous allocation not supported");
358 return NULL;
359 }
360
361 // Some heaps may be in an unparseable state at certain times between
362 // collections. This may be necessary for efficient implementation of
363 // certain allocation-related activities. Calling this function before
364 // attempting to parse a heap ensures that the heap is in a parsable
365 // state (provided other concurrent activity does not introduce
366 // unparsability). It is normally expected, therefore, that this
367 // method is invoked with the world stopped.
368 // NOTE: if you override this method, make sure you call
369 // super::ensure_parsability so that the non-generational
370 // part of the work gets done. See implementation of
371 // CollectedHeap::ensure_parsability and, for instance,
372 // that of GenCollectedHeap::ensure_parsability().
373 // The argument "retire_tlabs" controls whether existing TLABs
374 // are merely filled or also retired, thus preventing further
375 // allocation from them and necessitating allocation of new TLABs.
376 virtual void ensure_parsability(bool retire_tlabs);
377
378 // Section on thread-local allocation buffers (TLABs)
379 // If the heap supports thread-local allocation buffers, it should override
380 // the following methods:
381 // Returns "true" iff the heap supports thread-local allocation buffers.
382 // The default is "no".
383 virtual bool supports_tlab_allocation() const = 0;
384
385 // The amount of space available for thread-local allocation buffers.
386 virtual size_t tlab_capacity(Thread *thr) const = 0;
387
388 // The amount of used space for thread-local allocation buffers for the given thread.
389 virtual size_t tlab_used(Thread *thr) const = 0;
390
391 virtual size_t max_tlab_size() const;
392
393 // An estimate of the maximum allocation that could be performed
394 // for thread-local allocation buffers without triggering any
395 // collection or expansion activity.
396 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
397 guarantee(false, "thread-local allocation buffers not supported");
398 return 0;
399 }
400
401 // Perform a collection of the heap; intended for use in implementing
402 // "System.gc". This probably implies as full a collection as the
403 // "CollectedHeap" supports.
404 virtual void collect(GCCause::Cause cause) = 0;
405
406 // Perform a full collection
407 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
408
409 // This interface assumes that it's being called by the
410 // vm thread. It collects the heap assuming that the
411 // heap lock is already held and that we are executing in
412 // the context of the vm thread.
413 virtual void collect_as_vm_thread(GCCause::Cause cause);
414
415 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
416 size_t size,
417 Metaspace::MetadataType mdtype);
418
419 // Returns "true" iff there is a stop-world GC in progress. (I assume
420 // that it should answer "false" for the concurrent part of a concurrent
421 // collector -- dld).
422 bool is_gc_active() const { return _is_gc_active; }
423
424 // Total number of GC collections (started)
425 unsigned int total_collections() const { return _total_collections; }
426 unsigned int total_full_collections() const { return _total_full_collections;}
427
428 // Increment total number of GC collections (started)
429 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
430 void increment_total_collections(bool full = false) {
431 _total_collections++;
432 if (full) {
433 increment_total_full_collections();
434 }
435 }
436
437 void increment_total_full_collections() { _total_full_collections++; }
438
439 // Return the CollectorPolicy for the heap
440 virtual CollectorPolicy* collector_policy() const = 0;
441
442 // Return the SoftRefPolicy for the heap;
443 virtual SoftRefPolicy* soft_ref_policy() = 0;
444
445 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
446 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
447
448 // Iterate over all objects, calling "cl.do_object" on each.
449 virtual void object_iterate(ObjectClosure* cl) = 0;
450
451 // Similar to object_iterate() except iterates only
452 // over live objects.
453 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
454
455 // NOTE! There is no requirement that a collector implement these
456 // functions.
457 //
458 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
459 // each address in the (reserved) heap is a member of exactly
460 // one block. The defining characteristic of a block is that it is
461 // possible to find its size, and thus to progress forward to the next
462 // block. (Blocks may be of different sizes.) Thus, blocks may
463 // represent Java objects, or they might be free blocks in a
464 // free-list-based heap (or subheap), as long as the two kinds are
465 // distinguishable and the size of each is determinable.
466
467 // Returns the address of the start of the "block" that contains the
468 // address "addr". We say "blocks" instead of "object" since some heaps
469 // may not pack objects densely; a chunk may either be an object or a
470 // non-object.
471 virtual HeapWord* block_start(const void* addr) const = 0;
472
473 // Requires "addr" to be the start of a chunk, and returns its size.
474 // "addr + size" is required to be the start of a new chunk, or the end
475 // of the active area of the heap.
476 virtual size_t block_size(const HeapWord* addr) const = 0;
477
478 // Requires "addr" to be the start of a block, and returns "TRUE" iff
479 // the block is an object.
480 virtual bool block_is_obj(const HeapWord* addr) const = 0;
481
482 // Returns the longest time (in ms) that has elapsed since the last
483 // time that any part of the heap was examined by a garbage collection.
484 virtual jlong millis_since_last_gc() = 0;
485
486 // Perform any cleanup actions necessary before allowing a verification.
487 virtual void prepare_for_verify() = 0;
488
489 // Generate any dumps preceding or following a full gc
490 private:
491 void full_gc_dump(GCTimer* timer, bool before);
492
493 virtual void initialize_serviceability() = 0;
494
495 public:
496 void pre_full_gc_dump(GCTimer* timer);
497 void post_full_gc_dump(GCTimer* timer);
498
499 virtual VirtualSpaceSummary create_heap_space_summary();
500 GCHeapSummary create_heap_summary();
501
502 MetaspaceSummary create_metaspace_summary();
503
504 // Print heap information on the given outputStream.
505 virtual void print_on(outputStream* st) const = 0;
506 // The default behavior is to call print_on() on tty.
507 virtual void print() const {
508 print_on(tty);
509 }
510 // Print more detailed heap information on the given
511 // outputStream. The default behavior is to call print_on(). It is
512 // up to each subclass to override it and add any additional output
513 // it needs.
514 virtual void print_extended_on(outputStream* st) const {
515 print_on(st);
516 }
517
518 virtual void print_on_error(outputStream* st) const;
519
520 // Print all GC threads (other than the VM thread)
521 // used by this heap.
522 virtual void print_gc_threads_on(outputStream* st) const = 0;
523 // The default behavior is to call print_gc_threads_on() on tty.
524 void print_gc_threads() {
525 print_gc_threads_on(tty);
526 }
527 // Iterator for all GC threads (other than VM thread)
528 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
529
530 // Print any relevant tracing info that flags imply.
531 // Default implementation does nothing.
532 virtual void print_tracing_info() const = 0;
533
534 void print_heap_before_gc();
535 void print_heap_after_gc();
536
537 // An object is scavengable if its location may move during a scavenge.
538 // (A scavenge is a GC which is not a full GC.)
539 virtual bool is_scavengable(oop obj) = 0;
540 // Registering and unregistering an nmethod (compiled code) with the heap.
541 // Override with specific mechanism for each specialized heap type.
542 virtual void register_nmethod(nmethod* nm) {}
543 virtual void unregister_nmethod(nmethod* nm) {}
544 virtual void verify_nmethod(nmethod* nmethod) {}
545
546 void trace_heap_before_gc(const GCTracer* gc_tracer);
547 void trace_heap_after_gc(const GCTracer* gc_tracer);
548
549 // Heap verification
550 virtual void verify(VerifyOption option) = 0;
551
552 // Return true if concurrent phase control (via
553 // request_concurrent_phase_control) is supported by this collector.
554 // The default implementation returns false.
555 virtual bool supports_concurrent_phase_control() const;
556
557 // Return a NULL terminated array of concurrent phase names provided
558 // by this collector. Supports Whitebox testing. These are the
559 // names recognized by request_concurrent_phase(). The default
560 // implementation returns an array of one NULL element.
561 virtual const char* const* concurrent_phases() const;
562
563 // Request the collector enter the indicated concurrent phase, and
564 // wait until it does so. Supports WhiteBox testing. Only one
565 // request may be active at a time. Phases are designated by name;
566 // the set of names and their meaning is GC-specific. Once the
567 // requested phase has been reached, the collector will attempt to
568 // avoid transitioning to a new phase until a new request is made.
569 // [Note: A collector might not be able to remain in a given phase.
570 // For example, a full collection might cancel an in-progress
571 // concurrent collection.]
572 //
573 // Returns true when the phase is reached. Returns false for an
574 // unknown phase. The default implementation returns false.
575 virtual bool request_concurrent_phase(const char* phase);
576
577 // Provides a thread pool to SafepointSynchronize to use
578 // for parallel safepoint cleanup.
579 // GCs that use a GC worker thread pool may want to share
580 // it for use during safepoint cleanup. This is only possible
581 // if the GC can pause and resume concurrent work (e.g. G1
582 // concurrent marking) for an intermittent non-GC safepoint.
583 // If this method returns NULL, SafepointSynchronize will
584 // perform cleanup tasks serially in the VMThread.
585 virtual WorkGang* get_safepoint_workers() { return NULL; }
586
587 // Support for object pinning. This is used by JNI Get*Critical()
588 // and Release*Critical() family of functions. If supported, the GC
589 // must guarantee that pinned objects never move.
590 virtual bool supports_object_pinning() const;
591 virtual oop pin_object(JavaThread* thread, oop obj);
592 virtual void unpin_object(JavaThread* thread, oop obj);
593
594 virtual bool is_oop(oop object) const;
595
596 // Non product verification and debugging.
597 #ifndef PRODUCT
598 // Support for PromotionFailureALot. Return true if it's time to cause a
599 // promotion failure. The no-argument version uses
600 // this->_promotion_failure_alot_count as the counter.
601 bool promotion_should_fail(volatile size_t* count);
602 bool promotion_should_fail();
603
604 // Reset the PromotionFailureALot counters. Should be called at the end of a
605 // GC in which promotion failure occurred.
606 void reset_promotion_should_fail(volatile size_t* count);
607 void reset_promotion_should_fail();
608 #endif // #ifndef PRODUCT
609
610 #ifdef ASSERT
611 static int fired_fake_oom() {
612 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
613 }
614 #endif
615 };
616
617 // Class to set and reset the GC cause for a CollectedHeap.
618
619 class GCCauseSetter : StackObj {
620 CollectedHeap* _heap;
621 GCCause::Cause _previous_cause;
622 public:
623 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
624 _heap = heap;
625 _previous_cause = _heap->gc_cause();
626 _heap->set_gc_cause(cause);
627 }
628
629 ~GCCauseSetter() {
630 _heap->set_gc_cause(_previous_cause);
631 }
632 };
633
634 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP