1 /*
2 * Copyright (c) 2001, 2012, 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_INTERFACE_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
27
28 #include "gc_interface/gcCause.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/barrierSet.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 BarrierSet;
42 class ThreadClosure;
43 class AdaptiveSizePolicy;
44 class Thread;
45 class CollectorPolicy;
46
47 class GCMessage : public FormatBuffer<1024> {
48 public:
49 bool is_before;
50
51 public:
52 GCMessage() {}
53 };
54
55 class GCHeapLog : public EventLogBase<GCMessage> {
56 private:
57 void log_heap(bool before);
58
59 public:
60 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
61
62 void log_heap_before() {
63 log_heap(true);
64 }
65 void log_heap_after() {
66 log_heap(false);
67 }
68 };
69
70 //
71 // CollectedHeap
72 // SharedHeap
73 // GenCollectedHeap
74 // G1CollectedHeap
75 // ParallelScavengeHeap
76 //
77 class CollectedHeap : public CHeapObj<mtInternal> {
78 friend class VMStructs;
79 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
80
81 #ifdef ASSERT
82 static int _fire_out_of_memory_count;
83 #endif
84
85 // Used for filler objects (static, but initialized in ctor).
86 static size_t _filler_array_max_size;
87
88 GCHeapLog* _gc_heap_log;
89
90 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
91 bool _defer_initial_card_mark;
92
93 protected:
94 MemRegion _reserved;
95 BarrierSet* _barrier_set;
96 bool _is_gc_active;
97 uint _n_par_threads;
98
99 unsigned int _total_collections; // ... started
100 unsigned int _total_full_collections; // ... started
101 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
102 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
103
104 // Reason for current garbage collection. Should be set to
105 // a value reflecting no collection between collections.
106 GCCause::Cause _gc_cause;
107 GCCause::Cause _gc_lastcause;
108 PerfStringVariable* _perf_gc_cause;
109 PerfStringVariable* _perf_gc_lastcause;
110
111 // Constructor
112 CollectedHeap();
113
114 // Do common initializations that must follow instance construction,
115 // for example, those needing virtual calls.
116 // This code could perhaps be moved into initialize() but would
117 // be slightly more awkward because we want the latter to be a
118 // pure virtual.
119 void pre_initialize();
120
121 // Create a new tlab. All TLAB allocations must go through this.
122 virtual HeapWord* allocate_new_tlab(size_t size);
123
124 // Accumulate statistics on all tlabs.
125 virtual void accumulate_statistics_all_tlabs();
126
127 // Reinitialize tlabs before resuming mutators.
128 virtual void resize_all_tlabs();
129
130 // Allocate from the current thread's TLAB, with broken-out slow path.
131 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
132 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
133
134 // Allocate an uninitialized block of the given size, or returns NULL if
135 // this is impossible.
136 inline static HeapWord* common_mem_allocate_noinit(size_t size, TRAPS);
137
138 // Like allocate_init, but the block returned by a successful allocation
139 // is guaranteed initialized to zeros.
140 inline static HeapWord* common_mem_allocate_init(size_t size, TRAPS);
141
142 // Helper functions for (VM) allocation.
143 inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
144 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
145 HeapWord* objPtr);
146
147 inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj);
148
149 inline static void post_allocation_setup_array(KlassHandle klass,
150 HeapWord* obj, int length);
151
152 // Clears an allocated object.
153 inline static void init_obj(HeapWord* obj, size_t size);
154
155 // Filler object utilities.
156 static inline size_t filler_array_hdr_size();
157 static inline size_t filler_array_min_size();
158
159 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
160 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
161
162 // Fill with a single array; caller must ensure filler_array_min_size() <=
163 // words <= filler_array_max_size().
164 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
165
166 // Fill with a single object (either an int array or a java.lang.Object).
167 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
168
169 // Verification functions
170 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
171 PRODUCT_RETURN;
172 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
173 PRODUCT_RETURN;
174 debug_only(static void check_for_valid_allocation_state();)
175
176 public:
177 enum Name {
178 Abstract,
179 SharedHeap,
180 GenCollectedHeap,
181 ParallelScavengeHeap,
182 G1CollectedHeap
183 };
184
185 static inline size_t filler_array_max_size() {
186 return _filler_array_max_size;
187 }
188
189 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
190
191 /**
192 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
193 * and JNI_OK on success.
194 */
195 virtual jint initialize() = 0;
196
197 // In many heaps, there will be a need to perform some initialization activities
198 // after the Universe is fully formed, but before general heap allocation is allowed.
199 // This is the correct place to place such initialization methods.
200 virtual void post_initialize() = 0;
201
202 MemRegion reserved_region() const { return _reserved; }
203 address base() const { return (address)reserved_region().start(); }
204
205 // Future cleanup here. The following functions should specify bytes or
206 // heapwords as part of their signature.
207 virtual size_t capacity() const = 0;
208 virtual size_t used() const = 0;
209
210 // Return "true" if the part of the heap that allocates Java
211 // objects has reached the maximal committed limit that it can
212 // reach, without a garbage collection.
213 virtual bool is_maximal_no_gc() const = 0;
214
215 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
216 // memory that the vm could make available for storing 'normal' java objects.
217 // This is based on the reserved address space, but should not include space
218 // that the vm uses internally for bookkeeping or temporary storage
219 // (e.g., in the case of the young gen, one of the survivor
220 // spaces).
221 virtual size_t max_capacity() const = 0;
222
223 // Returns "TRUE" if "p" points into the reserved area of the heap.
224 bool is_in_reserved(const void* p) const {
225 return _reserved.contains(p);
226 }
227
228 bool is_in_reserved_or_null(const void* p) const {
229 return p == NULL || is_in_reserved(p);
230 }
231
232 // Returns "TRUE" iff "p" points into the committed areas of the heap.
233 // Since this method can be expensive in general, we restrict its
234 // use to assertion checking only.
235 virtual bool is_in(const void* p) const = 0;
236
237 bool is_in_or_null(const void* p) const {
238 return p == NULL || is_in(p);
239 }
240
241 bool is_in_place(Metadata** p) {
242 return !Universe::heap()->is_in(p);
243 }
244 bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
245 bool is_in_place(narrowOop* p) {
246 oop o = oopDesc::load_decode_heap_oop_not_null(p);
247 return Universe::heap()->is_in((const void*)o);
248 }
249
250 // Let's define some terms: a "closed" subset of a heap is one that
251 //
252 // 1) contains all currently-allocated objects, and
253 //
254 // 2) is closed under reference: no object in the closed subset
255 // references one outside the closed subset.
256 //
257 // Membership in a heap's closed subset is useful for assertions.
258 // Clearly, the entire heap is a closed subset, so the default
259 // implementation is to use "is_in_reserved". But this may not be too
260 // liberal to perform useful checking. Also, the "is_in" predicate
261 // defines a closed subset, but may be too expensive, since "is_in"
262 // verifies that its argument points to an object head. The
263 // "closed_subset" method allows a heap to define an intermediate
264 // predicate, allowing more precise checking than "is_in_reserved" at
265 // lower cost than "is_in."
266
267 // One important case is a heap composed of disjoint contiguous spaces,
268 // such as the Garbage-First collector. Such heaps have a convenient
269 // closed subset consisting of the allocated portions of those
270 // contiguous spaces.
271
272 // Return "TRUE" iff the given pointer points into the heap's defined
273 // closed subset (which defaults to the entire heap).
274 virtual bool is_in_closed_subset(const void* p) const {
275 return is_in_reserved(p);
276 }
277
278 bool is_in_closed_subset_or_null(const void* p) const {
279 return p == NULL || is_in_closed_subset(p);
280 }
281
282 #ifdef ASSERT
283 // Returns true if "p" is in the part of the
284 // heap being collected.
285 virtual bool is_in_partial_collection(const void *p) = 0;
286 #endif
287
288 // An object is scavengable if its location may move during a scavenge.
289 // (A scavenge is a GC which is not a full GC.)
290 virtual bool is_scavengable(const void *p) = 0;
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 // Number of threads currently working on GC tasks.
303 uint n_par_threads() { return _n_par_threads; }
304
305 // May be overridden to set additional parallelism.
306 virtual void set_par_threads(uint t) { _n_par_threads = t; };
307
308 // Allocate and initialize instances of Class
309 static oop Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS);
310
311 // General obj/array allocation facilities.
312 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
313 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
314 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
315
316 inline static void post_allocation_install_obj_klass(KlassHandle klass,
317 oop obj);
318
319 // Raw memory allocation facilities
320 // The obj and array allocate methods are covers for these methods.
321 // mem_allocate() should never be
322 // called to allocate TLABs, only individual objects.
323 virtual HeapWord* mem_allocate(size_t size,
324 bool* gc_overhead_limit_was_exceeded) = 0;
325
326 // Utilities for turning raw memory into filler objects.
327 //
328 // min_fill_size() is the smallest region that can be filled.
329 // fill_with_objects() can fill arbitrary-sized regions of the heap using
330 // multiple objects. fill_with_object() is for regions known to be smaller
331 // than the largest array of integers; it uses a single object to fill the
332 // region and has slightly less overhead.
333 static size_t min_fill_size() {
334 return size_t(align_object_size(oopDesc::header_size()));
335 }
336
337 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
338
339 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
340 static void fill_with_object(MemRegion region, bool zap = true) {
341 fill_with_object(region.start(), region.word_size(), zap);
342 }
343 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
344 fill_with_object(start, pointer_delta(end, start), zap);
345 }
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** 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 // Return an estimate of the maximum allocation that could be performed
386 // without triggering any collection or expansion activity. In a
387 // generational collector, for example, this is probably the largest
388 // allocation that could be supported (without expansion) in the youngest
389 // generation. It is "unsafe" because no locks are taken; the result
390 // should be treated as an approximation, not a guarantee, for use in
391 // heuristic resizing decisions.
392 virtual size_t unsafe_max_alloc() = 0;
393
394 // Section on thread-local allocation buffers (TLABs)
395 // If the heap supports thread-local allocation buffers, it should override
396 // the following methods:
397 // Returns "true" iff the heap supports thread-local allocation buffers.
398 // The default is "no".
399 virtual bool supports_tlab_allocation() const {
400 return false;
401 }
402 // The amount of space available for thread-local allocation buffers.
403 virtual size_t tlab_capacity(Thread *thr) const {
404 guarantee(false, "thread-local allocation buffers not supported");
405 return 0;
406 }
407 // An estimate of the maximum allocation that could be performed
408 // for thread-local allocation buffers without triggering any
409 // collection or expansion activity.
410 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
411 guarantee(false, "thread-local allocation buffers not supported");
412 return 0;
413 }
414
415 // Can a compiler initialize a new object without store barriers?
416 // This permission only extends from the creation of a new object
417 // via a TLAB up to the first subsequent safepoint. If such permission
418 // is granted for this heap type, the compiler promises to call
419 // defer_store_barrier() below on any slow path allocation of
420 // a new object for which such initializing store barriers will
421 // have been elided.
422 virtual bool can_elide_tlab_store_barriers() const = 0;
423
424 // If a compiler is eliding store barriers for TLAB-allocated objects,
425 // there is probably a corresponding slow path which can produce
426 // an object allocated anywhere. The compiler's runtime support
427 // promises to call this function on such a slow-path-allocated
428 // object before performing initializations that have elided
429 // store barriers. Returns new_obj, or maybe a safer copy thereof.
430 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
431
432 // Answers whether an initializing store to a new object currently
433 // allocated at the given address doesn't need a store
434 // barrier. Returns "true" if it doesn't need an initializing
435 // store barrier; answers "false" if it does.
436 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
437
438 // If a compiler is eliding store barriers for TLAB-allocated objects,
439 // we will be informed of a slow-path allocation by a call
440 // to new_store_pre_barrier() above. Such a call precedes the
441 // initialization of the object itself, and no post-store-barriers will
442 // be issued. Some heap types require that the barrier strictly follows
443 // the initializing stores. (This is currently implemented by deferring the
444 // barrier until the next slow-path allocation or gc-related safepoint.)
445 // This interface answers whether a particular heap type needs the card
446 // mark to be thus strictly sequenced after the stores.
447 virtual bool card_mark_must_follow_store() const = 0;
448
449 // If the CollectedHeap was asked to defer a store barrier above,
450 // this informs it to flush such a deferred store barrier to the
451 // remembered set.
452 virtual void flush_deferred_store_barrier(JavaThread* thread);
453
454 // Does this heap support heap inspection (+PrintClassHistogram?)
455 virtual bool supports_heap_inspection() const = 0;
456
457 // Perform a collection of the heap; intended for use in implementing
458 // "System.gc". This probably implies as full a collection as the
459 // "CollectedHeap" supports.
460 virtual void collect(GCCause::Cause cause) = 0;
461
462 // Perform a full collection
463 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
464
465 // This interface assumes that it's being called by the
466 // vm thread. It collects the heap assuming that the
467 // heap lock is already held and that we are executing in
468 // the context of the vm thread.
469 virtual void collect_as_vm_thread(GCCause::Cause cause);
470
471 // Callback from VM_CollectForMetadataAllocation operation.
472 MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
473 size_t size,
474 Metaspace::MetadataType mdtype);
475
476 // Returns the barrier set for this heap
477 BarrierSet* barrier_set() { return _barrier_set; }
478
479 // Returns "true" iff there is a stop-world GC in progress. (I assume
480 // that it should answer "false" for the concurrent part of a concurrent
481 // collector -- dld).
482 bool is_gc_active() const { return _is_gc_active; }
483
484 // Total number of GC collections (started)
485 unsigned int total_collections() const { return _total_collections; }
486 unsigned int total_full_collections() const { return _total_full_collections;}
487
488 // Increment total number of GC collections (started)
489 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
490 void increment_total_collections(bool full = false) {
491 _total_collections++;
492 if (full) {
493 increment_total_full_collections();
494 }
495 }
496
497 void increment_total_full_collections() { _total_full_collections++; }
498
499 // Return the AdaptiveSizePolicy for the heap.
500 virtual AdaptiveSizePolicy* size_policy() = 0;
501
502 // Return the CollectorPolicy for the heap
503 virtual CollectorPolicy* collector_policy() const = 0;
504
505 void oop_iterate_no_header(OopClosure* cl);
506
507 // Iterate over all the ref-containing fields of all objects, calling
508 // "cl.do_oop" on each.
509 virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
510
511 // Iterate over all objects, calling "cl.do_object" on each.
512 virtual void object_iterate(ObjectClosure* cl) = 0;
513
514 // Similar to object_iterate() except iterates only
515 // over live objects.
516 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
517
518 // NOTE! There is no requirement that a collector implement these
519 // functions.
520 //
521 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
522 // each address in the (reserved) heap is a member of exactly
523 // one block. The defining characteristic of a block is that it is
524 // possible to find its size, and thus to progress forward to the next
525 // block. (Blocks may be of different sizes.) Thus, blocks may
526 // represent Java objects, or they might be free blocks in a
527 // free-list-based heap (or subheap), as long as the two kinds are
528 // distinguishable and the size of each is determinable.
529
530 // Returns the address of the start of the "block" that contains the
531 // address "addr". We say "blocks" instead of "object" since some heaps
532 // may not pack objects densely; a chunk may either be an object or a
533 // non-object.
534 virtual HeapWord* block_start(const void* addr) const = 0;
535
536 // Requires "addr" to be the start of a chunk, and returns its size.
537 // "addr + size" is required to be the start of a new chunk, or the end
538 // of the active area of the heap.
539 virtual size_t block_size(const HeapWord* addr) const = 0;
540
541 // Requires "addr" to be the start of a block, and returns "TRUE" iff
542 // the block is an object.
543 virtual bool block_is_obj(const HeapWord* addr) const = 0;
544
545 // Returns the longest time (in ms) that has elapsed since the last
546 // time that any part of the heap was examined by a garbage collection.
547 virtual jlong millis_since_last_gc() = 0;
548
549 // Perform any cleanup actions necessary before allowing a verification.
550 virtual void prepare_for_verify() = 0;
551
552 // Generate any dumps preceding or following a full gc
553 void pre_full_gc_dump();
554 void post_full_gc_dump();
555
556 // Print heap information on the given outputStream.
557 virtual void print_on(outputStream* st) const = 0;
558 // The default behavior is to call print_on() on tty.
559 virtual void print() const {
560 print_on(tty);
561 }
562 // Print more detailed heap information on the given
563 // outputStream. The default behaviour is to call print_on(). It is
564 // up to each subclass to override it and add any additional output
565 // it needs.
566 virtual void print_extended_on(outputStream* st) const {
567 print_on(st);
568 }
569
570 virtual void print_on_error(outputStream* st) const {
571 st->print_cr("Heap:");
572 print_extended_on(st);
573 st->cr();
574
575 _barrier_set->print_on(st);
576 }
577
578 // Print all GC threads (other than the VM thread)
579 // used by this heap.
580 virtual void print_gc_threads_on(outputStream* st) const = 0;
581 // The default behavior is to call print_gc_threads_on() on tty.
582 void print_gc_threads() {
583 print_gc_threads_on(tty);
584 }
585 // Iterator for all GC threads (other than VM thread)
586 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
587
588 // Print any relevant tracing info that flags imply.
589 // Default implementation does nothing.
590 virtual void print_tracing_info() const = 0;
591
592 // If PrintHeapAtGC is set call the appropriate routi
593 void print_heap_before_gc() {
594 if (PrintHeapAtGC) {
595 Universe::print_heap_before_gc();
596 }
597 if (_gc_heap_log != NULL) {
598 _gc_heap_log->log_heap_before();
599 }
600 }
601 void print_heap_after_gc() {
602 if (PrintHeapAtGC) {
603 Universe::print_heap_after_gc();
604 }
605 if (_gc_heap_log != NULL) {
606 _gc_heap_log->log_heap_after();
607 }
608 }
609
610 // Heap verification
611 virtual void verify(bool silent, VerifyOption option) = 0;
612
613 // Non product verification and debugging.
614 #ifndef PRODUCT
615 // Support for PromotionFailureALot. Return true if it's time to cause a
616 // promotion failure. The no-argument version uses
617 // this->_promotion_failure_alot_count as the counter.
618 inline bool promotion_should_fail(volatile size_t* count);
619 inline bool promotion_should_fail();
620
621 // Reset the PromotionFailureALot counters. Should be called at the end of a
622 // GC in which promotion failure ocurred.
623 inline void reset_promotion_should_fail(volatile size_t* count);
624 inline void reset_promotion_should_fail();
625 #endif // #ifndef PRODUCT
626
627 #ifdef ASSERT
628 static int fired_fake_oom() {
629 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
630 }
631 #endif
632
633 public:
634 // This is a convenience method that is used in cases where
635 // the actual number of GC worker threads is not pertinent but
636 // only whether there more than 0. Use of this method helps
637 // reduce the occurrence of ParallelGCThreads to uses where the
638 // actual number may be germane.
639 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
640
641 /////////////// Unit tests ///////////////
642
643 NOT_PRODUCT(static void test_is_in();)
644 };
645
646 // Class to set and reset the GC cause for a CollectedHeap.
647
648 class GCCauseSetter : StackObj {
649 CollectedHeap* _heap;
650 GCCause::Cause _previous_cause;
651 public:
652 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
653 assert(SafepointSynchronize::is_at_safepoint(),
654 "This method manipulates heap state without locking");
655 _heap = heap;
656 _previous_cause = _heap->gc_cause();
657 _heap->set_gc_cause(cause);
658 }
659
660 ~GCCauseSetter() {
661 assert(SafepointSynchronize::is_at_safepoint(),
662 "This method manipulates heap state without locking");
663 _heap->set_gc_cause(_previous_cause);
664 }
665 };
666
667 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP