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