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 SoftRefPolicy;
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 virtual size_t space_alignment() const = 0;
242 virtual size_t heap_alignment() const = 0;
243
244 // Returns "TRUE" if "p" points into the reserved area of the heap.
245 bool is_in_reserved(const void* p) const {
246 return _reserved.contains(p);
247 }
248
249 bool is_in_reserved_or_null(const void* p) const {
250 return p == NULL || is_in_reserved(p);
251 }
252
253 // Returns "TRUE" iff "p" points into the committed areas of the heap.
254 // This method can be expensive so avoid using it in performance critical
255 // code.
256 virtual bool is_in(const void* p) const = 0;
257
258 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
259
260 // Let's define some terms: a "closed" subset of a heap is one that
261 //
262 // 1) contains all currently-allocated objects, and
263 //
264 // 2) is closed under reference: no object in the closed subset
265 // references one outside the closed subset.
266 //
267 // Membership in a heap's closed subset is useful for assertions.
268 // Clearly, the entire heap is a closed subset, so the default
269 // implementation is to use "is_in_reserved". But this may not be too
270 // liberal to perform useful checking. Also, the "is_in" predicate
271 // defines a closed subset, but may be too expensive, since "is_in"
272 // verifies that its argument points to an object head. The
273 // "closed_subset" method allows a heap to define an intermediate
274 // predicate, allowing more precise checking than "is_in_reserved" at
275 // lower cost than "is_in."
276
277 // One important case is a heap composed of disjoint contiguous spaces,
278 // such as the Garbage-First collector. Such heaps have a convenient
279 // closed subset consisting of the allocated portions of those
280 // contiguous spaces.
281
282 // Return "TRUE" iff the given pointer points into the heap's defined
283 // closed subset (which defaults to the entire heap).
284 virtual bool is_in_closed_subset(const void* p) const {
285 return is_in_reserved(p);
286 }
287
288 bool is_in_closed_subset_or_null(const void* p) const {
289 return p == NULL || is_in_closed_subset(p);
290 }
291
292 void set_gc_cause(GCCause::Cause v) {
293 if (UsePerfData) {
294 _gc_lastcause = _gc_cause;
295 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
296 _perf_gc_cause->set_value(GCCause::to_string(v));
297 }
298 _gc_cause = v;
299 }
300 GCCause::Cause gc_cause() { return _gc_cause; }
301
302 // General obj/array allocation facilities.
303 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
304 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
305 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
306 inline static oop class_allocate(Klass* klass, int size, TRAPS);
307
308 // Raw memory allocation facilities
309 // The obj and array allocate methods are covers for these methods.
310 // mem_allocate() should never be
311 // called to allocate TLABs, only individual objects.
312 virtual HeapWord* mem_allocate(size_t size,
313 bool* gc_overhead_limit_was_exceeded) = 0;
314
315 // Utilities for turning raw memory into filler objects.
316 //
317 // min_fill_size() is the smallest region that can be filled.
318 // fill_with_objects() can fill arbitrary-sized regions of the heap using
319 // multiple objects. fill_with_object() is for regions known to be smaller
320 // than the largest array of integers; it uses a single object to fill the
321 // region and has slightly less overhead.
322 static size_t min_fill_size() {
323 return size_t(align_object_size(oopDesc::header_size()));
324 }
325
326 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
327
328 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
329 static void fill_with_object(MemRegion region, bool zap = true) {
330 fill_with_object(region.start(), region.word_size(), zap);
331 }
332 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
333 fill_with_object(start, pointer_delta(end, start), zap);
334 }
335
336 // Return the address "addr" aligned by "alignment_in_bytes" if such
337 // an address is below "end". Return NULL otherwise.
338 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
339 HeapWord* end,
340 unsigned short alignment_in_bytes);
341
342 // Some heaps may offer a contiguous region for shared non-blocking
343 // allocation, via inlined code (by exporting the address of the top and
344 // end fields defining the extent of the contiguous allocation region.)
345
346 // This function returns "true" iff the heap supports this kind of
347 // allocation. (Default is "no".)
348 virtual bool supports_inline_contig_alloc() const {
349 return false;
350 }
351 // These functions return the addresses of the fields that define the
352 // boundaries of the contiguous allocation area. (These fields should be
353 // physically near to one another.)
354 virtual HeapWord* volatile* top_addr() const {
355 guarantee(false, "inline contiguous allocation not supported");
356 return NULL;
357 }
358 virtual HeapWord** end_addr() const {
359 guarantee(false, "inline contiguous allocation not supported");
360 return NULL;
361 }
362
363 // Some heaps may be in an unparseable state at certain times between
364 // collections. This may be necessary for efficient implementation of
365 // certain allocation-related activities. Calling this function before
366 // attempting to parse a heap ensures that the heap is in a parsable
367 // state (provided other concurrent activity does not introduce
368 // unparsability). It is normally expected, therefore, that this
369 // method is invoked with the world stopped.
370 // NOTE: if you override this method, make sure you call
371 // super::ensure_parsability so that the non-generational
372 // part of the work gets done. See implementation of
373 // CollectedHeap::ensure_parsability and, for instance,
374 // that of GenCollectedHeap::ensure_parsability().
375 // The argument "retire_tlabs" controls whether existing TLABs
376 // are merely filled or also retired, thus preventing further
377 // allocation from them and necessitating allocation of new TLABs.
378 virtual void ensure_parsability(bool retire_tlabs);
379
380 // Section on thread-local allocation buffers (TLABs)
381 // If the heap supports thread-local allocation buffers, it should override
382 // the following methods:
383 // Returns "true" iff the heap supports thread-local allocation buffers.
384 // The default is "no".
385 virtual bool supports_tlab_allocation() const = 0;
386
387 // The amount of space available for thread-local allocation buffers.
388 virtual size_t tlab_capacity(Thread *thr) const = 0;
389
390 // The amount of used space for thread-local allocation buffers for the given thread.
391 virtual size_t tlab_used(Thread *thr) const = 0;
392
393 virtual size_t max_tlab_size() const;
394
395 // An estimate of the maximum allocation that could be performed
396 // for thread-local allocation buffers without triggering any
397 // collection or expansion activity.
398 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
399 guarantee(false, "thread-local allocation buffers not supported");
400 return 0;
401 }
402
403 // Perform a collection of the heap; intended for use in implementing
404 // "System.gc". This probably implies as full a collection as the
405 // "CollectedHeap" supports.
406 virtual void collect(GCCause::Cause cause) = 0;
407
408 // Perform a full collection
409 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
410
411 // This interface assumes that it's being called by the
412 // vm thread. It collects the heap assuming that the
413 // heap lock is already held and that we are executing in
414 // the context of the vm thread.
415 virtual void collect_as_vm_thread(GCCause::Cause cause);
416
417 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
418 size_t size,
419 Metaspace::MetadataType mdtype);
420
421 // Returns the barrier set for this heap
422 BarrierSet* barrier_set() { return _barrier_set; }
423 void set_barrier_set(BarrierSet* barrier_set);
424
425 // Returns "true" iff there is a stop-world GC in progress. (I assume
426 // that it should answer "false" for the concurrent part of a concurrent
427 // collector -- dld).
428 bool is_gc_active() const { return _is_gc_active; }
429
430 // Total number of GC collections (started)
431 unsigned int total_collections() const { return _total_collections; }
432 unsigned int total_full_collections() const { return _total_full_collections;}
433
434 // Increment total number of GC collections (started)
435 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
436 void increment_total_collections(bool full = false) {
437 _total_collections++;
438 if (full) {
439 increment_total_full_collections();
440 }
441 }
442
443 void increment_total_full_collections() { _total_full_collections++; }
444
445 virtual SoftRefPolicy* soft_ref_policy() = 0;
446
447 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
448 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
449
450 // Iterate over all objects, calling "cl.do_object" on each.
451 virtual void object_iterate(ObjectClosure* cl) = 0;
452
453 // Similar to object_iterate() except iterates only
454 // over live objects.
455 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
456
457 // NOTE! There is no requirement that a collector implement these
458 // functions.
459 //
460 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
461 // each address in the (reserved) heap is a member of exactly
462 // one block. The defining characteristic of a block is that it is
463 // possible to find its size, and thus to progress forward to the next
464 // block. (Blocks may be of different sizes.) Thus, blocks may
465 // represent Java objects, or they might be free blocks in a
466 // free-list-based heap (or subheap), as long as the two kinds are
467 // distinguishable and the size of each is determinable.
468
469 // Returns the address of the start of the "block" that contains the
470 // address "addr". We say "blocks" instead of "object" since some heaps
471 // may not pack objects densely; a chunk may either be an object or a
472 // non-object.
473 virtual HeapWord* block_start(const void* addr) const = 0;
474
475 // Requires "addr" to be the start of a chunk, and returns its size.
476 // "addr + size" is required to be the start of a new chunk, or the end
477 // of the active area of the heap.
478 virtual size_t block_size(const HeapWord* addr) const = 0;
479
480 // Requires "addr" to be the start of a block, and returns "TRUE" iff
481 // the block is an object.
482 virtual bool block_is_obj(const HeapWord* addr) const = 0;
483
484 // Returns the longest time (in ms) that has elapsed since the last
485 // time that any part of the heap was examined by a garbage collection.
486 virtual jlong millis_since_last_gc() = 0;
487
488 // Perform any cleanup actions necessary before allowing a verification.
489 virtual void prepare_for_verify() = 0;
490
491 // Generate any dumps preceding or following a full gc
492 private:
493 void full_gc_dump(GCTimer* timer, bool before);
494
495 virtual void initialize_serviceability() = 0;
496
497 public:
498 void pre_full_gc_dump(GCTimer* timer);
499 void post_full_gc_dump(GCTimer* timer);
500
501 virtual VirtualSpaceSummary create_heap_space_summary();
502 GCHeapSummary create_heap_summary();
503
504 MetaspaceSummary create_metaspace_summary();
505
506 // Print heap information on the given outputStream.
507 virtual void print_on(outputStream* st) const = 0;
508 // The default behavior is to call print_on() on tty.
509 virtual void print() const {
510 print_on(tty);
511 }
512 // Print more detailed heap information on the given
513 // outputStream. The default behavior is to call print_on(). It is
514 // up to each subclass to override it and add any additional output
515 // it needs.
516 virtual void print_extended_on(outputStream* st) const {
517 print_on(st);
518 }
519
520 virtual void print_on_error(outputStream* st) const;
521
522 // Print all GC threads (other than the VM thread)
523 // used by this heap.
524 virtual void print_gc_threads_on(outputStream* st) const = 0;
525 // The default behavior is to call print_gc_threads_on() on tty.
526 void print_gc_threads() {
527 print_gc_threads_on(tty);
528 }
529 // Iterator for all GC threads (other than VM thread)
530 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
531
532 // Print any relevant tracing info that flags imply.
533 // Default implementation does nothing.
534 virtual void print_tracing_info() const = 0;
535
536 void print_heap_before_gc();
537 void print_heap_after_gc();
538
539 // An object is scavengable if its location may move during a scavenge.
540 // (A scavenge is a GC which is not a full GC.)
541 virtual bool is_scavengable(oop obj) = 0;
542 // Registering and unregistering an nmethod (compiled code) with the heap.
543 // Override with specific mechanism for each specialized heap type.
544 virtual void register_nmethod(nmethod* nm) {}
545 virtual void unregister_nmethod(nmethod* nm) {}
546 virtual void verify_nmethod(nmethod* nmethod) {}
547
548 void trace_heap_before_gc(const GCTracer* gc_tracer);
549 void trace_heap_after_gc(const GCTracer* gc_tracer);
550
551 // Heap verification
552 virtual void verify(VerifyOption option) = 0;
553
554 // Return true if concurrent phase control (via
555 // request_concurrent_phase_control) is supported by this collector.
556 // The default implementation returns false.
557 virtual bool supports_concurrent_phase_control() const;
558
559 // Return a NULL terminated array of concurrent phase names provided
560 // by this collector. Supports Whitebox testing. These are the
561 // names recognized by request_concurrent_phase(). The default
562 // implementation returns an array of one NULL element.
563 virtual const char* const* concurrent_phases() const;
564
565 // Request the collector enter the indicated concurrent phase, and
566 // wait until it does so. Supports WhiteBox testing. Only one
567 // request may be active at a time. Phases are designated by name;
568 // the set of names and their meaning is GC-specific. Once the
569 // requested phase has been reached, the collector will attempt to
570 // avoid transitioning to a new phase until a new request is made.
571 // [Note: A collector might not be able to remain in a given phase.
572 // For example, a full collection might cancel an in-progress
573 // concurrent collection.]
574 //
575 // Returns true when the phase is reached. Returns false for an
576 // unknown phase. The default implementation returns false.
577 virtual bool request_concurrent_phase(const char* phase);
578
579 // Provides a thread pool to SafepointSynchronize to use
580 // for parallel safepoint cleanup.
581 // GCs that use a GC worker thread pool may want to share
582 // it for use during safepoint cleanup. This is only possible
583 // if the GC can pause and resume concurrent work (e.g. G1
584 // concurrent marking) for an intermittent non-GC safepoint.
585 // If this method returns NULL, SafepointSynchronize will
586 // perform cleanup tasks serially in the VMThread.
587 virtual WorkGang* get_safepoint_workers() { return NULL; }
588
589 // Non product verification and debugging.
590 #ifndef PRODUCT
591 // Support for PromotionFailureALot. Return true if it's time to cause a
592 // promotion failure. The no-argument version uses
593 // this->_promotion_failure_alot_count as the counter.
594 inline bool promotion_should_fail(volatile size_t* count);
595 inline bool promotion_should_fail();
596
597 // Reset the PromotionFailureALot counters. Should be called at the end of a
598 // GC in which promotion failure occurred.
599 inline void reset_promotion_should_fail(volatile size_t* count);
600 inline void reset_promotion_should_fail();
601 #endif // #ifndef PRODUCT
602
603 #ifdef ASSERT
604 static int fired_fake_oom() {
605 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
606 }
607 #endif
608
609 public:
610 // Copy the current allocation context statistics for the specified contexts.
611 // For each context in contexts, set the corresponding entries in the totals
612 // and accuracy arrays to the current values held by the statistics. Each
613 // array should be of length len.
614 // Returns true if there are more stats available.
615 virtual bool copy_allocation_context_stats(const jint* contexts,
616 jlong* totals,
617 jbyte* accuracy,
618 jint len) {
619 return false;
620 }
621
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 assert(SafepointSynchronize::is_at_safepoint(),
632 "This method manipulates heap state without locking");
633 _heap = heap;
634 _previous_cause = _heap->gc_cause();
635 _heap->set_gc_cause(cause);
636 }
637
638 ~GCCauseSetter() {
639 assert(SafepointSynchronize::is_at_safepoint(),
640 "This method manipulates heap state without locking");
641 _heap->set_gc_cause(_previous_cause);
642 }
643 };
644
645 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP