1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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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/events.hpp"
35
36 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
37 // is an abstract class: there may be many different kinds of heaps. This
38 // class defines the functions that a heap must implement, and contains
39 // infrastructure common to all heaps.
40
41 class AdaptiveSizePolicy;
42 class BarrierSet;
43 class CollectorPolicy;
44 class GCHeapSummary;
45 class GCTimer;
46 class GCTracer;
47 class MetaspaceSummary;
48 class Thread;
49 class ThreadClosure;
50 class VirtualSpaceSummary;
51 class nmethod;
52
53 class GCMessage : public FormatBuffer<1024> {
54 public:
55 bool is_before;
56
57 public:
58 GCMessage() {}
59 };
60
61 class CollectedHeap;
62
63 class GCHeapLog : public EventLogBase<GCMessage> {
64 private:
65 void log_heap(CollectedHeap* heap, bool before);
66
67 public:
68 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
69
70 void log_heap_before(CollectedHeap* heap) {
71 log_heap(heap, true);
72 }
73 void log_heap_after(CollectedHeap* heap) {
74 log_heap(heap, false);
75 }
76 };
77
78 //
79 // CollectedHeap
80 // GenCollectedHeap
81 // G1CollectedHeap
82 // ShenandoahHeap
83 // ParallelScavengeHeap
84 //
85 class CollectedHeap : public CHeapObj<mtInternal> {
86 friend class VMStructs;
87 friend class JVMCIVMStructs;
88 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
89
90 private:
91 #ifdef ASSERT
92 static int _fire_out_of_memory_count;
93 #endif
94
95 GCHeapLog* _gc_heap_log;
96
97 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
98 // or INCLUDE_JVMCI is being used
99 bool _defer_initial_card_mark;
100
101 MemRegion _reserved;
102
103 protected:
104 BarrierSet* _barrier_set;
105 bool _is_gc_active;
106
107 // Used for filler objects (static, but initialized in ctor).
108 static size_t _filler_array_max_size;
109
110 unsigned int _total_collections; // ... started
111 unsigned int _total_full_collections; // ... started
112 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
113 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
114
115 // Reason for current garbage collection. Should be set to
116 // a value reflecting no collection between collections.
117 GCCause::Cause _gc_cause;
118 GCCause::Cause _gc_lastcause;
119 PerfStringVariable* _perf_gc_cause;
120 PerfStringVariable* _perf_gc_lastcause;
121
122 // Constructor
123 CollectedHeap();
124
125 // Do common initializations that must follow instance construction,
126 // for example, those needing virtual calls.
127 // This code could perhaps be moved into initialize() but would
128 // be slightly more awkward because we want the latter to be a
129 // pure virtual.
130 void pre_initialize();
131
132 // Create a new tlab. All TLAB allocations must go through this.
133 virtual HeapWord* allocate_new_tlab(size_t size);
134
135 // Accumulate statistics on all tlabs.
136 virtual void accumulate_statistics_all_tlabs();
137
138 // Reinitialize tlabs before resuming mutators.
139 virtual void resize_all_tlabs();
140
141 // Allocate from the current thread's TLAB, with broken-out slow path.
142 inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
143 static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
144
145 // Allocate an uninitialized block of the given size, or returns NULL if
146 // this is impossible.
147 inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
148
149 // Like allocate_init, but the block returned by a successful allocation
150 // is guaranteed initialized to zeros.
151 inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
152
153 // Helper functions for (VM) allocation.
154 inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
155 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
156 HeapWord* objPtr);
157
158 inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
159
160 inline static void post_allocation_setup_array(KlassHandle klass,
161 HeapWord* obj, int length);
162
163 inline static void post_allocation_setup_class(KlassHandle klass, HeapWord* obj, int size);
164
165 // Clears an allocated object.
166 inline static void init_obj(HeapWord* obj, size_t size);
167
168 // Filler object utilities.
169 static inline size_t filler_array_hdr_size();
170 static inline size_t filler_array_min_size();
171
172 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
173 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
174
175 // Fill with a single array; caller must ensure filler_array_min_size() <=
176 // words <= filler_array_max_size().
177 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
178
179 // Fill with a single object (either an int array or a java.lang.Object).
180 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
181
182 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
183
184 // Verification functions
185 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
186 PRODUCT_RETURN;
187 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
188 PRODUCT_RETURN;
189 debug_only(static void check_for_valid_allocation_state();)
190
191 public:
192 enum Name {
193 GenCollectedHeap,
194 ParallelScavengeHeap,
195 G1CollectedHeap,
196 ShenandoahHeap
197 };
198
199 static inline size_t filler_array_max_size() {
200 return _filler_array_max_size;
201 }
202
203 virtual Name kind() const = 0;
204
205 virtual HeapWord* tlab_post_allocation_setup(HeapWord* obj);
206
207 virtual const char* name() const = 0;
208
209 /**
210 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
211 * and JNI_OK on success.
212 */
213 virtual jint initialize() = 0;
214
215 // In many heaps, there will be a need to perform some initialization activities
216 // after the Universe is fully formed, but before general heap allocation is allowed.
217 // This is the correct place to place such initialization methods.
218 virtual void post_initialize() = 0;
219
220 // Stop any onging concurrent work and prepare for exit.
221 virtual void stop() {}
222
223 void initialize_reserved_region(HeapWord *start, HeapWord *end);
224 MemRegion reserved_region() const { return _reserved; }
225 address base() const { return (address)reserved_region().start(); }
226
227 virtual size_t capacity() const = 0;
228 virtual size_t used() const = 0;
229
230 // Return "true" if the part of the heap that allocates Java
231 // objects has reached the maximal committed limit that it can
232 // reach, without a garbage collection.
233 virtual bool is_maximal_no_gc() const = 0;
234
235 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
236 // memory that the vm could make available for storing 'normal' java objects.
237 // This is based on the reserved address space, but should not include space
238 // that the vm uses internally for bookkeeping or temporary storage
239 // (e.g., in the case of the young gen, one of the survivor
240 // spaces).
241 virtual size_t max_capacity() const = 0;
242
243 // Returns "TRUE" if "p" points into the reserved area of the heap.
244 bool is_in_reserved(const void* p) const {
245 return _reserved.contains(p);
246 }
247
248 bool is_in_reserved_or_null(const void* p) const {
249 return p == NULL || is_in_reserved(p);
250 }
251
252 // Returns "TRUE" iff "p" points into the committed areas of the heap.
253 // This method can be expensive so avoid using it in performance critical
254 // code.
255 virtual bool is_in(const void* p) const = 0;
256
257 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
258
259 // Let's define some terms: a "closed" subset of a heap is one that
260 //
261 // 1) contains all currently-allocated objects, and
262 //
263 // 2) is closed under reference: no object in the closed subset
264 // references one outside the closed subset.
265 //
266 // Membership in a heap's closed subset is useful for assertions.
267 // Clearly, the entire heap is a closed subset, so the default
268 // implementation is to use "is_in_reserved". But this may not be too
269 // liberal to perform useful checking. Also, the "is_in" predicate
270 // defines a closed subset, but may be too expensive, since "is_in"
271 // verifies that its argument points to an object head. The
272 // "closed_subset" method allows a heap to define an intermediate
273 // predicate, allowing more precise checking than "is_in_reserved" at
274 // lower cost than "is_in."
275
276 // One important case is a heap composed of disjoint contiguous spaces,
277 // such as the Garbage-First collector. Such heaps have a convenient
278 // closed subset consisting of the allocated portions of those
279 // contiguous spaces.
280
281 // Return "TRUE" iff the given pointer points into the heap's defined
282 // closed subset (which defaults to the entire heap).
283 virtual bool is_in_closed_subset(const void* p) const {
284 return is_in_reserved(p);
285 }
286
287 bool is_in_closed_subset_or_null(const void* p) const {
288 return p == NULL || is_in_closed_subset(p);
289 }
290
291 // An object is scavengable if its location may move during a scavenge.
292 // (A scavenge is a GC which is not a full GC.)
293 virtual bool is_scavengable(const void *p) = 0;
294
295 void set_gc_cause(GCCause::Cause v) {
296 if (UsePerfData) {
297 _gc_lastcause = _gc_cause;
298 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
299 _perf_gc_cause->set_value(GCCause::to_string(v));
300 }
301 _gc_cause = v;
302 }
303 GCCause::Cause gc_cause() { return _gc_cause; }
304
305 // General obj/array allocation facilities.
306 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
307 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
308 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
309 inline static oop class_allocate(KlassHandle klass, int size, TRAPS);
310
311 virtual uint oop_extra_words();
312
313 #ifndef CC_INTERP
314 virtual void compile_prepare_oop(MacroAssembler* masm, Register obj);
315 #endif
316
317 // Raw memory allocation facilities
318 // The obj and array allocate methods are covers for these methods.
319 // mem_allocate() should never be
320 // called to allocate TLABs, only individual objects.
321 virtual HeapWord* mem_allocate(size_t size,
322 bool* gc_overhead_limit_was_exceeded) = 0;
323
324 // Utilities for turning raw memory into filler objects.
325 //
326 // min_fill_size() is the smallest region that can be filled.
327 // fill_with_objects() can fill arbitrary-sized regions of the heap using
328 // multiple objects. fill_with_object() is for regions known to be smaller
329 // than the largest array of integers; it uses a single object to fill the
330 // region and has slightly less overhead.
331 static size_t min_fill_size() {
332 return size_t(align_object_size(oopDesc::header_size()));
333 }
334
335 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
336
337 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
338 static void fill_with_object(MemRegion region, bool zap = true) {
339 fill_with_object(region.start(), region.word_size(), zap);
340 }
341 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
342 fill_with_object(start, pointer_delta(end, start), zap);
343 }
344
345 // Return the address "addr" aligned by "alignment_in_bytes" if such
346 // an address is below "end". Return NULL otherwise.
347 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
348 HeapWord* end,
349 unsigned short alignment_in_bytes);
350
351 // Some heaps may offer a contiguous region for shared non-blocking
352 // allocation, via inlined code (by exporting the address of the top and
353 // end fields defining the extent of the contiguous allocation region.)
354
355 // This function returns "true" iff the heap supports this kind of
356 // allocation. (Default is "no".)
357 virtual bool supports_inline_contig_alloc() const {
358 return false;
359 }
360 // These functions return the addresses of the fields that define the
361 // boundaries of the contiguous allocation area. (These fields should be
362 // physically near to one another.)
363 virtual HeapWord* volatile* top_addr() const {
364 guarantee(false, "inline contiguous allocation not supported");
365 return NULL;
366 }
367 virtual HeapWord** end_addr() const {
368 guarantee(false, "inline contiguous allocation not supported");
369 return NULL;
370 }
371
372 // Some heaps may be in an unparseable state at certain times between
373 // collections. This may be necessary for efficient implementation of
374 // certain allocation-related activities. Calling this function before
375 // attempting to parse a heap ensures that the heap is in a parsable
376 // state (provided other concurrent activity does not introduce
377 // unparsability). It is normally expected, therefore, that this
378 // method is invoked with the world stopped.
379 // NOTE: if you override this method, make sure you call
380 // super::ensure_parsability so that the non-generational
381 // part of the work gets done. See implementation of
382 // CollectedHeap::ensure_parsability and, for instance,
383 // that of GenCollectedHeap::ensure_parsability().
384 // The argument "retire_tlabs" controls whether existing TLABs
385 // are merely filled or also retired, thus preventing further
386 // allocation from them and necessitating allocation of new TLABs.
387 virtual void ensure_parsability(bool retire_tlabs);
388
389 // Section on thread-local allocation buffers (TLABs)
390 // If the heap supports thread-local allocation buffers, it should override
391 // the following methods:
392 // Returns "true" iff the heap supports thread-local allocation buffers.
393 // The default is "no".
394 virtual bool supports_tlab_allocation() const = 0;
395
396 // The amount of space available for thread-local allocation buffers.
397 virtual size_t tlab_capacity(Thread *thr) const = 0;
398
399 // The amount of used space for thread-local allocation buffers for the given thread.
400 virtual size_t tlab_used(Thread *thr) const = 0;
401
402 virtual size_t max_tlab_size() const;
403
404 // An estimate of the maximum allocation that could be performed
405 // for thread-local allocation buffers without triggering any
406 // collection or expansion activity.
407 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
408 guarantee(false, "thread-local allocation buffers not supported");
409 return 0;
410 }
411
412 // Can a compiler initialize a new object without store barriers?
413 // This permission only extends from the creation of a new object
414 // via a TLAB up to the first subsequent safepoint. If such permission
415 // is granted for this heap type, the compiler promises to call
416 // defer_store_barrier() below on any slow path allocation of
417 // a new object for which such initializing store barriers will
418 // have been elided.
419 virtual bool can_elide_tlab_store_barriers() const = 0;
420
421 // If a compiler is eliding store barriers for TLAB-allocated objects,
422 // there is probably a corresponding slow path which can produce
423 // an object allocated anywhere. The compiler's runtime support
424 // promises to call this function on such a slow-path-allocated
425 // object before performing initializations that have elided
426 // store barriers. Returns new_obj, or maybe a safer copy thereof.
427 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
428
429 // Answers whether an initializing store to a new object currently
430 // allocated at the given address doesn't need a store
431 // barrier. Returns "true" if it doesn't need an initializing
432 // store barrier; answers "false" if it does.
433 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
434
435 // If a compiler is eliding store barriers for TLAB-allocated objects,
436 // we will be informed of a slow-path allocation by a call
437 // to new_store_pre_barrier() above. Such a call precedes the
438 // initialization of the object itself, and no post-store-barriers will
439 // be issued. Some heap types require that the barrier strictly follows
440 // the initializing stores. (This is currently implemented by deferring the
441 // barrier until the next slow-path allocation or gc-related safepoint.)
442 // This interface answers whether a particular heap type needs the card
443 // mark to be thus strictly sequenced after the stores.
444 virtual bool card_mark_must_follow_store() const = 0;
445
446 // If the CollectedHeap was asked to defer a store barrier above,
447 // this informs it to flush such a deferred store barrier to the
448 // remembered set.
449 virtual void flush_deferred_store_barrier(JavaThread* thread);
450
451 // Perform a collection of the heap; intended for use in implementing
452 // "System.gc". This probably implies as full a collection as the
453 // "CollectedHeap" supports.
454 virtual void collect(GCCause::Cause cause) = 0;
455
456 // Perform a full collection
457 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
458
459 // This interface assumes that it's being called by the
460 // vm thread. It collects the heap assuming that the
461 // heap lock is already held and that we are executing in
462 // the context of the vm thread.
463 virtual void collect_as_vm_thread(GCCause::Cause cause);
464
465 // Returns the barrier set for this heap
466 BarrierSet* barrier_set() { return _barrier_set; }
467 void set_barrier_set(BarrierSet* barrier_set);
468
469 // Returns "true" iff there is a stop-world GC in progress. (I assume
470 // that it should answer "false" for the concurrent part of a concurrent
471 // collector -- dld).
472 bool is_gc_active() const { return _is_gc_active; }
473
474 // Total number of GC collections (started)
475 unsigned int total_collections() const { return _total_collections; }
476 unsigned int total_full_collections() const { return _total_full_collections;}
477
478 // Increment total number of GC collections (started)
479 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
480 void increment_total_collections(bool full = false) {
481 _total_collections++;
482 if (full) {
483 increment_total_full_collections();
484 }
485 }
486
487 void increment_total_full_collections() { _total_full_collections++; }
488
489 // Return the AdaptiveSizePolicy for the heap.
490 virtual AdaptiveSizePolicy* size_policy() = 0;
491
492 // Return the CollectorPolicy for the heap
493 virtual CollectorPolicy* collector_policy() const = 0;
494
495 // Iterate over all objects, calling "cl.do_object" on each.
496 virtual void object_iterate(ObjectClosure* cl) = 0;
497
498 // Similar to object_iterate() except iterates only
499 // over live objects.
500 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
501
502 // NOTE! There is no requirement that a collector implement these
503 // functions.
504 //
505 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
506 // each address in the (reserved) heap is a member of exactly
507 // one block. The defining characteristic of a block is that it is
508 // possible to find its size, and thus to progress forward to the next
509 // block. (Blocks may be of different sizes.) Thus, blocks may
510 // represent Java objects, or they might be free blocks in a
511 // free-list-based heap (or subheap), as long as the two kinds are
512 // distinguishable and the size of each is determinable.
513
514 // Returns the address of the start of the "block" that contains the
515 // address "addr". We say "blocks" instead of "object" since some heaps
516 // may not pack objects densely; a chunk may either be an object or a
517 // non-object.
518 virtual HeapWord* block_start(const void* addr) const = 0;
519
520 // Requires "addr" to be the start of a chunk, and returns its size.
521 // "addr + size" is required to be the start of a new chunk, or the end
522 // of the active area of the heap.
523 virtual size_t block_size(const HeapWord* addr) const = 0;
524
525 // Requires "addr" to be the start of a block, and returns "TRUE" iff
526 // the block is an object.
527 virtual bool block_is_obj(const HeapWord* addr) const = 0;
528
529 // Returns the longest time (in ms) that has elapsed since the last
530 // time that any part of the heap was examined by a garbage collection.
531 virtual jlong millis_since_last_gc() = 0;
532
533 // Perform any cleanup actions necessary before allowing a verification.
534 virtual void prepare_for_verify() = 0;
535
536 // Generate any dumps preceding or following a full gc
537 private:
538 void full_gc_dump(GCTimer* timer, bool before);
539 public:
540 void pre_full_gc_dump(GCTimer* timer);
541 void post_full_gc_dump(GCTimer* timer);
542
543 VirtualSpaceSummary create_heap_space_summary();
544 GCHeapSummary create_heap_summary();
545
546 MetaspaceSummary create_metaspace_summary();
547
548 // Print heap information on the given outputStream.
549 virtual void print_on(outputStream* st) const = 0;
550 // The default behavior is to call print_on() on tty.
551 virtual void print() const {
552 print_on(tty);
553 }
554 // Print more detailed heap information on the given
555 // outputStream. The default behavior is to call print_on(). It is
556 // up to each subclass to override it and add any additional output
557 // it needs.
558 virtual void print_extended_on(outputStream* st) const {
559 print_on(st);
560 }
561
562 virtual void print_on_error(outputStream* st) const;
563
564 // Print all GC threads (other than the VM thread)
565 // used by this heap.
566 virtual void print_gc_threads_on(outputStream* st) const = 0;
567 // The default behavior is to call print_gc_threads_on() on tty.
568 void print_gc_threads() {
569 print_gc_threads_on(tty);
570 }
571 // Iterator for all GC threads (other than VM thread)
572 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
573
574 // Print any relevant tracing info that flags imply.
575 // Default implementation does nothing.
576 virtual void print_tracing_info() const = 0;
577
578 void print_heap_before_gc();
579 void print_heap_after_gc();
580
581 // Registering and unregistering an nmethod (compiled code) with the heap.
582 // Override with specific mechanism for each specialized heap type.
583 virtual void register_nmethod(nmethod* nm);
584 virtual void unregister_nmethod(nmethod* nm);
585
586 // The following two methods are there to support object pinning for JNI critical
587 // regions. They are called whenever a thread enters or leaves a JNI critical
588 // region and requires an object not to move. Notice that there's another
589 // mechanism for GCs to implement critical region (see gcLocker.hpp). The default
590 // implementation does nothing.
591 virtual void pin_object(oop o);
592 virtual void unpin_object(oop o);
593
594 void trace_heap_before_gc(const GCTracer* gc_tracer);
595 void trace_heap_after_gc(const GCTracer* gc_tracer);
596
597 // Heap verification
598 virtual void verify(VerifyOption option) = 0;
599
600 // Accumulate additional statistics from GCLABs.
601 virtual void accumulate_statistics_all_gclabs();
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 inline bool promotion_should_fail(volatile size_t* count);
609 inline 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 inline void reset_promotion_should_fail(volatile size_t* count);
614 inline 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 public:
624 // Copy the current allocation context statistics for the specified contexts.
625 // For each context in contexts, set the corresponding entries in the totals
626 // and accuracy arrays to the current values held by the statistics. Each
627 // array should be of length len.
628 // Returns true if there are more stats available.
629 virtual bool copy_allocation_context_stats(const jint* contexts,
630 jlong* totals,
631 jbyte* accuracy,
632 jint len) {
633 return false;
634 }
635
636 };
637
638 // Class to set and reset the GC cause for a CollectedHeap.
639
640 class GCCauseSetter : StackObj {
641 CollectedHeap* _heap;
642 GCCause::Cause _previous_cause;
643 public:
644 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
645 assert(SafepointSynchronize::is_at_safepoint(),
646 "This method manipulates heap state without locking");
647 _heap = heap;
648 _previous_cause = _heap->gc_cause();
649 _heap->set_gc_cause(cause);
650 }
651
652 ~GCCauseSetter() {
653 assert(SafepointSynchronize::is_at_safepoint(),
654 "This method manipulates heap state without locking");
655 _heap->set_gc_cause(_previous_cause);
656 }
657 };
658
659 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP