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