1 /*
2 * Copyright (c) 2001, 2014, 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 "gc_implementation/shared/gcWhen.hpp"
30 #include "memory/allocation.hpp"
31 #include "memory/barrierSet.hpp"
32 #include "runtime/handles.hpp"
33 #include "runtime/perfData.hpp"
34 #include "runtime/safepoint.hpp"
35 #include "utilities/events.hpp"
36
37 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
38 // is an abstract class: there may be many different kinds of heaps. This
39 // class defines the functions that a heap must implement, and contains
40 // infrastructure common to all heaps.
41
42 class AdaptiveSizePolicy;
43 class BarrierSet;
44 class CollectorPolicy;
45 class GCHeapSummary;
46 class GCTimer;
47 class GCTracer;
48 class MetaspaceSummary;
49 class Thread;
50 class ThreadClosure;
51 class VirtualSpaceSummary;
52 class nmethod;
53
54 class GCMessage : public FormatBuffer<1024> {
55 public:
56 bool is_before;
57
58 public:
59 GCMessage() {}
60 };
61
62 class GCHeapLog : public EventLogBase<GCMessage> {
63 private:
64 void log_heap(bool before);
65
66 public:
67 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
68
69 void log_heap_before() {
70 log_heap(true);
71 }
72 void log_heap_after() {
73 log_heap(false);
74 }
75 };
76
77 //
78 // CollectedHeap
79 // SharedHeap
80 // GenCollectedHeap
81 // G1CollectedHeap
82 // ParallelScavengeHeap
83 //
84 class CollectedHeap : public CHeapObj<mtInternal> {
85 friend class VMStructs;
86 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
87
88 #ifdef ASSERT
89 static int _fire_out_of_memory_count;
90 #endif
91
92 // Used for filler objects (static, but initialized in ctor).
93 static size_t _filler_array_max_size;
94
95 GCHeapLog* _gc_heap_log;
96
97 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
98 bool _defer_initial_card_mark;
99
100 protected:
101 MemRegion _reserved;
102 BarrierSet* _barrier_set;
103 bool _is_gc_active;
104 uint _n_par_threads;
105
106 unsigned int _total_collections; // ... started
107 unsigned int _total_full_collections; // ... started
108 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
109 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
110
111 // Reason for current garbage collection. Should be set to
112 // a value reflecting no collection between collections.
113 GCCause::Cause _gc_cause;
114 GCCause::Cause _gc_lastcause;
115 PerfStringVariable* _perf_gc_cause;
116 PerfStringVariable* _perf_gc_lastcause;
117
118 // Constructor
119 CollectedHeap();
120
121 // Do common initializations that must follow instance construction,
122 // for example, those needing virtual calls.
123 // This code could perhaps be moved into initialize() but would
124 // be slightly more awkward because we want the latter to be a
125 // pure virtual.
126 void pre_initialize();
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(KlassHandle klass, Thread* thread, size_t size);
139 static HeapWord* allocate_from_tlab_slow(KlassHandle 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(KlassHandle 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(KlassHandle klass, size_t size, TRAPS);
148
149 // Helper functions for (VM) allocation.
150 inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
151 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
152 HeapWord* objPtr);
153
154 inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
155
156 inline static void post_allocation_setup_array(KlassHandle klass,
157 HeapWord* obj, int length);
158
159 // Clears an allocated object.
160 inline static void init_obj(HeapWord* obj, size_t size);
161
162 // Filler object utilities.
163 static inline size_t filler_array_hdr_size();
164 static inline size_t filler_array_min_size();
165
166 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
167 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
168
169 // Fill with a single array; caller must ensure filler_array_min_size() <=
170 // words <= filler_array_max_size().
171 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
172
173 // Fill with a single object (either an int array or a java.lang.Object).
174 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
175
176 virtual void trace_heap(GCWhen::Type when, GCTracer* tracer);
177
178 // Verification functions
179 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
180 PRODUCT_RETURN;
181 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
182 PRODUCT_RETURN;
183 debug_only(static void check_for_valid_allocation_state();)
184
185 public:
186 enum Name {
187 Abstract,
188 SharedHeap,
189 GenCollectedHeap,
190 ParallelScavengeHeap,
191 G1CollectedHeap
192 };
193
194 static inline size_t filler_array_max_size() {
195 return _filler_array_max_size;
196 }
197
198 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
199
200 /**
201 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
202 * and JNI_OK on success.
203 */
204 virtual jint initialize() = 0;
205
206 // In many heaps, there will be a need to perform some initialization activities
207 // after the Universe is fully formed, but before general heap allocation is allowed.
208 // This is the correct place to place such initialization methods.
209 virtual void post_initialize() = 0;
210
211 // Stop any onging concurrent work and prepare for exit.
212 virtual void stop() {}
213
214 MemRegion reserved_region() const { return _reserved; }
215 address base() const { return (address)reserved_region().start(); }
216
217 virtual size_t capacity() const = 0;
218 virtual size_t used() const = 0;
219
220 // Return "true" if the part of the heap that allocates Java
221 // objects has reached the maximal committed limit that it can
222 // reach, without a garbage collection.
223 virtual bool is_maximal_no_gc() const = 0;
224
225 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
226 // memory that the vm could make available for storing 'normal' java objects.
227 // This is based on the reserved address space, but should not include space
228 // that the vm uses internally for bookkeeping or temporary storage
229 // (e.g., in the case of the young gen, one of the survivor
230 // spaces).
231 virtual size_t max_capacity() const = 0;
232
233 // Returns "TRUE" if "p" points into the reserved area of the heap.
234 bool is_in_reserved(const void* p) const {
235 return _reserved.contains(p);
236 }
237
238 bool is_in_reserved_or_null(const void* p) const {
239 return p == NULL || is_in_reserved(p);
240 }
241
242 // Returns "TRUE" iff "p" points into the committed areas of the heap.
243 // Since this method can be expensive in general, we restrict its
244 // use to assertion checking only.
245 virtual bool is_in(const void* p) const = 0;
246
247 bool is_in_or_null(const void* p) const {
248 return p == NULL || is_in(p);
249 }
250
251 bool is_in_place(Metadata** p) {
252 return !Universe::heap()->is_in(p);
253 }
254 bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
255 bool is_in_place(narrowOop* p) {
256 oop o = oopDesc::load_decode_heap_oop_not_null(p);
257 return Universe::heap()->is_in((const void*)o);
258 }
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 #ifdef ASSERT
293 // Returns true if "p" is in the part of the
294 // heap being collected.
295 virtual bool is_in_partial_collection(const void *p) = 0;
296 #endif
297
298 // An object is scavengable if its location may move during a scavenge.
299 // (A scavenge is a GC which is not a full GC.)
300 virtual bool is_scavengable(const void *p) = 0;
301
302 void set_gc_cause(GCCause::Cause v) {
303 if (UsePerfData) {
304 _gc_lastcause = _gc_cause;
305 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
306 _perf_gc_cause->set_value(GCCause::to_string(v));
307 }
308 _gc_cause = v;
309 }
310 GCCause::Cause gc_cause() { return _gc_cause; }
311
312 // Number of threads currently working on GC tasks.
313 uint n_par_threads() { return _n_par_threads; }
314
315 // May be overridden to set additional parallelism.
316 virtual void set_par_threads(uint t) { _n_par_threads = t; };
317
318 // General obj/array allocation facilities.
319 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
320 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
321 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
322
323 inline static void post_allocation_install_obj_klass(KlassHandle klass,
324 oop obj);
325
326 // Raw memory allocation facilities
327 // The obj and array allocate methods are covers for these methods.
328 // mem_allocate() should never be
329 // called to allocate TLABs, only individual objects.
330 virtual HeapWord* mem_allocate(size_t size,
331 bool* gc_overhead_limit_was_exceeded) = 0;
332
333 // Utilities for turning raw memory into filler objects.
334 //
335 // min_fill_size() is the smallest region that can be filled.
336 // fill_with_objects() can fill arbitrary-sized regions of the heap using
337 // multiple objects. fill_with_object() is for regions known to be smaller
338 // than the largest array of integers; it uses a single object to fill the
339 // region and has slightly less overhead.
340 static size_t min_fill_size() {
341 return size_t(align_object_size(oopDesc::header_size()));
342 }
343
344 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
345
346 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
347 static void fill_with_object(MemRegion region, bool zap = true) {
348 fill_with_object(region.start(), region.word_size(), zap);
349 }
350 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
351 fill_with_object(start, pointer_delta(end, start), zap);
352 }
353
354 // Return the address "addr" aligned by "alignment_in_bytes" if such
355 // an address is below "end". Return NULL otherwise.
356 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
357 HeapWord* end,
358 unsigned short alignment_in_bytes);
359
360 // Some heaps may offer a contiguous region for shared non-blocking
361 // allocation, via inlined code (by exporting the address of the top and
362 // end fields defining the extent of the contiguous allocation region.)
363
364 // This function returns "true" iff the heap supports this kind of
365 // allocation. (Default is "no".)
366 virtual bool supports_inline_contig_alloc() const {
367 return false;
368 }
369 // These functions return the addresses of the fields that define the
370 // boundaries of the contiguous allocation area. (These fields should be
371 // physically near to one another.)
372 virtual HeapWord** top_addr() const {
373 guarantee(false, "inline contiguous allocation not supported");
374 return NULL;
375 }
376 virtual HeapWord** end_addr() const {
377 guarantee(false, "inline contiguous allocation not supported");
378 return NULL;
379 }
380
381 // Some heaps may be in an unparseable state at certain times between
382 // collections. This may be necessary for efficient implementation of
383 // certain allocation-related activities. Calling this function before
384 // attempting to parse a heap ensures that the heap is in a parsable
385 // state (provided other concurrent activity does not introduce
386 // unparsability). It is normally expected, therefore, that this
387 // method is invoked with the world stopped.
388 // NOTE: if you override this method, make sure you call
389 // super::ensure_parsability so that the non-generational
390 // part of the work gets done. See implementation of
391 // CollectedHeap::ensure_parsability and, for instance,
392 // that of GenCollectedHeap::ensure_parsability().
393 // The argument "retire_tlabs" controls whether existing TLABs
394 // are merely filled or also retired, thus preventing further
395 // allocation from them and necessitating allocation of new TLABs.
396 virtual void ensure_parsability(bool retire_tlabs);
397
398 // Section on thread-local allocation buffers (TLABs)
399 // If the heap supports thread-local allocation buffers, it should override
400 // the following methods:
401 // Returns "true" iff the heap supports thread-local allocation buffers.
402 // The default is "no".
403 virtual bool supports_tlab_allocation() const = 0;
404
405 // The amount of space available for thread-local allocation buffers.
406 virtual size_t tlab_capacity(Thread *thr) const = 0;
407
408 // The amount of used space for thread-local allocation buffers for the given thread.
409 virtual size_t tlab_used(Thread *thr) const = 0;
410
411 virtual size_t max_tlab_size() const;
412
413 // An estimate of the maximum allocation that could be performed
414 // for thread-local allocation buffers without triggering any
415 // collection or expansion activity.
416 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
417 guarantee(false, "thread-local allocation buffers not supported");
418 return 0;
419 }
420
421 // Can a compiler initialize a new object without store barriers?
422 // This permission only extends from the creation of a new object
423 // via a TLAB up to the first subsequent safepoint. If such permission
424 // is granted for this heap type, the compiler promises to call
425 // defer_store_barrier() below on any slow path allocation of
426 // a new object for which such initializing store barriers will
427 // have been elided.
428 virtual bool can_elide_tlab_store_barriers() const = 0;
429
430 // If a compiler is eliding store barriers for TLAB-allocated objects,
431 // there is probably a corresponding slow path which can produce
432 // an object allocated anywhere. The compiler's runtime support
433 // promises to call this function on such a slow-path-allocated
434 // object before performing initializations that have elided
435 // store barriers. Returns new_obj, or maybe a safer copy thereof.
436 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
437
438 // Answers whether an initializing store to a new object currently
439 // allocated at the given address doesn't need a store
440 // barrier. Returns "true" if it doesn't need an initializing
441 // store barrier; answers "false" if it does.
442 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
443
444 // If a compiler is eliding store barriers for TLAB-allocated objects,
445 // we will be informed of a slow-path allocation by a call
446 // to new_store_pre_barrier() above. Such a call precedes the
447 // initialization of the object itself, and no post-store-barriers will
448 // be issued. Some heap types require that the barrier strictly follows
449 // the initializing stores. (This is currently implemented by deferring the
450 // barrier until the next slow-path allocation or gc-related safepoint.)
451 // This interface answers whether a particular heap type needs the card
452 // mark to be thus strictly sequenced after the stores.
453 virtual bool card_mark_must_follow_store() const = 0;
454
455 // If the CollectedHeap was asked to defer a store barrier above,
456 // this informs it to flush such a deferred store barrier to the
457 // remembered set.
458 virtual void flush_deferred_store_barrier(JavaThread* thread);
459
460 // Does this heap support heap inspection (+PrintClassHistogram?)
461 virtual bool supports_heap_inspection() const = 0;
462
463 // Perform a collection of the heap; intended for use in implementing
464 // "System.gc". This probably implies as full a collection as the
465 // "CollectedHeap" supports.
466 virtual void collect(GCCause::Cause cause) = 0;
467
468 // Perform a full collection
469 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
470
471 // This interface assumes that it's being called by the
472 // vm thread. It collects the heap assuming that the
473 // heap lock is already held and that we are executing in
474 // the context of the vm thread.
475 virtual void collect_as_vm_thread(GCCause::Cause cause);
476
477 // Returns the barrier set for this heap
478 BarrierSet* barrier_set() { return _barrier_set; }
479
480 // Returns "true" iff there is a stop-world GC in progress. (I assume
481 // that it should answer "false" for the concurrent part of a concurrent
482 // collector -- dld).
483 bool is_gc_active() const { return _is_gc_active; }
484
485 // Total number of GC collections (started)
486 unsigned int total_collections() const { return _total_collections; }
487 unsigned int total_full_collections() const { return _total_full_collections;}
488
489 // Increment total number of GC collections (started)
490 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
491 void increment_total_collections(bool full = false) {
492 _total_collections++;
493 if (full) {
494 increment_total_full_collections();
495 }
496 }
497
498 void increment_total_full_collections() { _total_full_collections++; }
499
500 // Return the AdaptiveSizePolicy for the heap.
501 virtual AdaptiveSizePolicy* size_policy() = 0;
502
503 // Return the CollectorPolicy for the heap
504 virtual CollectorPolicy* collector_policy() const = 0;
505
506 void oop_iterate_no_header(OopClosure* cl);
507
508 // Iterate over all the ref-containing fields of all objects, calling
509 // "cl.do_oop" on each.
510 virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
511
512 // Iterate over all objects, calling "cl.do_object" on each.
513 virtual void object_iterate(ObjectClosure* cl) = 0;
514
515 // Similar to object_iterate() except iterates only
516 // over live objects.
517 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
518
519 // NOTE! There is no requirement that a collector implement these
520 // functions.
521 //
522 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
523 // each address in the (reserved) heap is a member of exactly
524 // one block. The defining characteristic of a block is that it is
525 // possible to find its size, and thus to progress forward to the next
526 // block. (Blocks may be of different sizes.) Thus, blocks may
527 // represent Java objects, or they might be free blocks in a
528 // free-list-based heap (or subheap), as long as the two kinds are
529 // distinguishable and the size of each is determinable.
530
531 // Returns the address of the start of the "block" that contains the
532 // address "addr". We say "blocks" instead of "object" since some heaps
533 // may not pack objects densely; a chunk may either be an object or a
534 // non-object.
535 virtual HeapWord* block_start(const void* addr) const = 0;
536
537 // Requires "addr" to be the start of a chunk, and returns its size.
538 // "addr + size" is required to be the start of a new chunk, or the end
539 // of the active area of the heap.
540 virtual size_t block_size(const HeapWord* addr) const = 0;
541
542 // Requires "addr" to be the start of a block, and returns "TRUE" iff
543 // the block is an object.
544 virtual bool block_is_obj(const HeapWord* addr) const = 0;
545
546 // Returns the longest time (in ms) that has elapsed since the last
547 // time that any part of the heap was examined by a garbage collection.
548 virtual jlong millis_since_last_gc() = 0;
549
550 // Perform any cleanup actions necessary before allowing a verification.
551 virtual void prepare_for_verify() = 0;
552
553 // Generate any dumps preceding or following a full gc
554 void pre_full_gc_dump(GCTimer* timer);
555 void post_full_gc_dump(GCTimer* timer);
556
557 VirtualSpaceSummary create_heap_space_summary();
558 GCHeapSummary create_heap_summary();
559
560 MetaspaceSummary create_metaspace_summary();
561
562 // Print heap information on the given outputStream.
563 virtual void print_on(outputStream* st) const = 0;
564 // The default behavior is to call print_on() on tty.
565 virtual void print() const {
566 print_on(tty);
567 }
568 // Print more detailed heap information on the given
569 // outputStream. The default behavior is to call print_on(). It is
570 // up to each subclass to override it and add any additional output
571 // it needs.
572 virtual void print_extended_on(outputStream* st) const {
573 print_on(st);
574 }
575
576 virtual void print_on_error(outputStream* st) const {
577 st->print_cr("Heap:");
578 print_extended_on(st);
579 st->cr();
580
581 _barrier_set->print_on(st);
582 }
583
584 // Print all GC threads (other than the VM thread)
585 // used by this heap.
586 virtual void print_gc_threads_on(outputStream* st) const = 0;
587 // The default behavior is to call print_gc_threads_on() on tty.
588 void print_gc_threads() {
589 print_gc_threads_on(tty);
590 }
591 // Iterator for all GC threads (other than VM thread)
592 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
593
594 // Print any relevant tracing info that flags imply.
595 // Default implementation does nothing.
596 virtual void print_tracing_info() const = 0;
597
598 void print_heap_before_gc();
599 void print_heap_after_gc();
600
601 // Registering and unregistering an nmethod (compiled code) with the heap.
602 // Override with specific mechanism for each specialized heap type.
603 virtual void register_nmethod(nmethod* nm);
604 virtual void unregister_nmethod(nmethod* nm);
605
606 void trace_heap_before_gc(GCTracer* gc_tracer);
607 void trace_heap_after_gc(GCTracer* gc_tracer);
608
609 // Heap verification
610 virtual void verify(bool silent, VerifyOption option) = 0;
611
612 // Non product verification and debugging.
613 #ifndef PRODUCT
614 // Support for PromotionFailureALot. Return true if it's time to cause a
615 // promotion failure. The no-argument version uses
616 // this->_promotion_failure_alot_count as the counter.
617 inline bool promotion_should_fail(volatile size_t* count);
618 inline bool promotion_should_fail();
619
620 // Reset the PromotionFailureALot counters. Should be called at the end of a
621 // GC in which promotion failure occurred.
622 inline void reset_promotion_should_fail(volatile size_t* count);
623 inline void reset_promotion_should_fail();
624 #endif // #ifndef PRODUCT
625
626 #ifdef ASSERT
627 static int fired_fake_oom() {
628 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
629 }
630 #endif
631
632 public:
633 // This is a convenience method that is used in cases where
634 // the actual number of GC worker threads is not pertinent but
635 // only whether there more than 0. Use of this method helps
636 // reduce the occurrence of ParallelGCThreads to uses where the
637 // actual number may be germane.
638 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
639
640 // Copy the current allocation context statistics for the specified contexts.
641 // For each context in contexts, set the corresponding entries in the totals
642 // and accuracy arrays to the current values held by the statistics. Each
643 // array should be of length len.
644 // Returns true if there are more stats available.
645 virtual bool copy_allocation_context_stats(const jint* contexts,
646 jlong* totals,
647 jbyte* accuracy,
648 jint len) {
649 return false;
650 }
651
652 /////////////// Unit tests ///////////////
653
654 NOT_PRODUCT(static void test_is_in();)
655 };
656
657 // Class to set and reset the GC cause for a CollectedHeap.
658
659 class GCCauseSetter : StackObj {
660 CollectedHeap* _heap;
661 GCCause::Cause _previous_cause;
662 public:
663 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
664 assert(SafepointSynchronize::is_at_safepoint(),
665 "This method manipulates heap state without locking");
666 _heap = heap;
667 _previous_cause = _heap->gc_cause();
668 _heap->set_gc_cause(cause);
669 }
670
671 ~GCCauseSetter() {
672 assert(SafepointSynchronize::is_at_safepoint(),
673 "This method manipulates heap state without locking");
674 _heap->set_gc_cause(_previous_cause);
675 }
676 };
677
678 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP