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
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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 private:
89 #ifdef ASSERT
90 static int _fire_out_of_memory_count;
91 #endif
92
93 // Used for filler objects (static, but initialized in ctor).
94 static size_t _filler_array_max_size;
95
96 GCHeapLog* _gc_heap_log;
97
98 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 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 uint _n_par_threads;
107
108 unsigned int _total_collections; // ... started
109 unsigned int _total_full_collections; // ... started
110 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
111 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
112
113 // Reason for current garbage collection. Should be set to
114 // a value reflecting no collection between collections.
115 GCCause::Cause _gc_cause;
116 GCCause::Cause _gc_lastcause;
117 PerfStringVariable* _perf_gc_cause;
118 PerfStringVariable* _perf_gc_lastcause;
119
120 // Constructor
121 CollectedHeap();
122
123 // Do common initializations that must follow instance construction,
124 // for example, those needing virtual calls.
125 // This code could perhaps be moved into initialize() but would
126 // be slightly more awkward because we want the latter to be a
127 // pure virtual.
128 void pre_initialize();
129
130 // Create a new tlab. All TLAB allocations must go through this.
131 virtual HeapWord* allocate_new_tlab(size_t size);
132
133 // Accumulate statistics on all tlabs.
134 virtual void accumulate_statistics_all_tlabs();
135
136 // Reinitialize tlabs before resuming mutators.
137 virtual void resize_all_tlabs();
138
139 // Allocate from the current thread's TLAB, with broken-out slow path.
140 inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
141 static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
142
143 // Allocate an uninitialized block of the given size, or returns NULL if
144 // this is impossible.
145 inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
146
147 // Like allocate_init, but the block returned by a successful allocation
148 // is guaranteed initialized to zeros.
149 inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
150
151 // Helper functions for (VM) allocation.
152 inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
153 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
154 HeapWord* objPtr);
155
156 inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
157
158 inline static void post_allocation_setup_array(KlassHandle klass,
159 HeapWord* obj, int length);
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, 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 Abstract,
190 SharedHeap,
191 GenCollectedHeap,
192 ParallelScavengeHeap,
193 G1CollectedHeap
194 };
195
196 static inline size_t filler_array_max_size() {
197 return _filler_array_max_size;
198 }
199
200 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
201
202 /**
203 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
204 * and JNI_OK on success.
205 */
206 virtual jint initialize() = 0;
207
208 // In many heaps, there will be a need to perform some initialization activities
209 // after the Universe is fully formed, but before general heap allocation is allowed.
210 // This is the correct place to place such initialization methods.
211 virtual void post_initialize() = 0;
212
213 // Stop any onging concurrent work and prepare for exit.
214 virtual void stop() {}
215
216 void initialize_reserved_region(HeapWord *start, HeapWord *end);
217 MemRegion reserved_region() const { return _reserved; }
218 address base() const { return (address)reserved_region().start(); }
219
220 virtual size_t capacity() const = 0;
221 virtual size_t used() const = 0;
222
223 // Return "true" if the part of the heap that allocates Java
224 // objects has reached the maximal committed limit that it can
225 // reach, without a garbage collection.
226 virtual bool is_maximal_no_gc() const = 0;
227
228 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
229 // memory that the vm could make available for storing 'normal' java objects.
230 // This is based on the reserved address space, but should not include space
231 // that the vm uses internally for bookkeeping or temporary storage
232 // (e.g., in the case of the young gen, one of the survivor
233 // spaces).
234 virtual size_t max_capacity() const = 0;
235
236 // Returns "TRUE" if "p" points into the reserved area of the heap.
237 bool is_in_reserved(const void* p) const {
238 return _reserved.contains(p);
239 }
240
241 bool is_in_reserved_or_null(const void* p) const {
242 return p == NULL || is_in_reserved(p);
243 }
244
245 // Returns "TRUE" iff "p" points into the committed areas of the heap.
246 // Since this method can be expensive in general, we restrict its
247 // use to assertion checking only.
248 virtual bool is_in(const void* p) const = 0;
249
250 bool is_in_or_null(const void* p) const {
251 return p == NULL || is_in(p);
252 }
253
254 bool is_in_place(Metadata** p) {
255 return !Universe::heap()->is_in(p);
256 }
257 bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
258 bool is_in_place(narrowOop* p) {
259 oop o = oopDesc::load_decode_heap_oop_not_null(p);
260 return Universe::heap()->is_in((const void*)o);
261 }
262
263 // Let's define some terms: a "closed" subset of a heap is one that
264 //
265 // 1) contains all currently-allocated objects, and
266 //
267 // 2) is closed under reference: no object in the closed subset
268 // references one outside the closed subset.
269 //
270 // Membership in a heap's closed subset is useful for assertions.
271 // Clearly, the entire heap is a closed subset, so the default
272 // implementation is to use "is_in_reserved". But this may not be too
273 // liberal to perform useful checking. Also, the "is_in" predicate
274 // defines a closed subset, but may be too expensive, since "is_in"
275 // verifies that its argument points to an object head. The
276 // "closed_subset" method allows a heap to define an intermediate
277 // predicate, allowing more precise checking than "is_in_reserved" at
278 // lower cost than "is_in."
279
280 // One important case is a heap composed of disjoint contiguous spaces,
281 // such as the Garbage-First collector. Such heaps have a convenient
282 // closed subset consisting of the allocated portions of those
283 // contiguous spaces.
284
285 // Return "TRUE" iff the given pointer points into the heap's defined
286 // closed subset (which defaults to the entire heap).
287 virtual bool is_in_closed_subset(const void* p) const {
288 return is_in_reserved(p);
289 }
290
291 bool is_in_closed_subset_or_null(const void* p) const {
292 return p == NULL || is_in_closed_subset(p);
293 }
294
295 #ifdef ASSERT
296 // Returns true if "p" is in the part of the
297 // heap being collected.
298 virtual bool is_in_partial_collection(const void *p) = 0;
299 #endif
300
301 // An object is scavengable if its location may move during a scavenge.
302 // (A scavenge is a GC which is not a full GC.)
303 virtual bool is_scavengable(const void *p) = 0;
304
305 void set_gc_cause(GCCause::Cause v) {
306 if (UsePerfData) {
307 _gc_lastcause = _gc_cause;
308 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
309 _perf_gc_cause->set_value(GCCause::to_string(v));
310 }
311 _gc_cause = v;
312 }
313 GCCause::Cause gc_cause() { return _gc_cause; }
314
315 // Number of threads currently working on GC tasks.
316 uint n_par_threads() { return _n_par_threads; }
317
318 // May be overridden to set additional parallelism.
319 virtual void set_par_threads(uint t) { _n_par_threads = t; };
320
321 // General obj/array allocation facilities.
322 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
323 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
324 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
325
326 inline static void post_allocation_install_obj_klass(KlassHandle klass,
327 oop obj);
328
329 // Raw memory allocation facilities
330 // The obj and array allocate methods are covers for these methods.
331 // mem_allocate() should never be
332 // called to allocate TLABs, only individual objects.
333 virtual HeapWord* mem_allocate(size_t size,
334 bool* gc_overhead_limit_was_exceeded) = 0;
335
336 // Utilities for turning raw memory into filler objects.
337 //
338 // min_fill_size() is the smallest region that can be filled.
339 // fill_with_objects() can fill arbitrary-sized regions of the heap using
340 // multiple objects. fill_with_object() is for regions known to be smaller
341 // than the largest array of integers; it uses a single object to fill the
342 // region and has slightly less overhead.
343 static size_t min_fill_size() {
344 return size_t(align_object_size(oopDesc::header_size()));
345 }
346
347 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
348
349 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
350 static void fill_with_object(MemRegion region, bool zap = true) {
351 fill_with_object(region.start(), region.word_size(), zap);
352 }
353 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
354 fill_with_object(start, pointer_delta(end, start), zap);
355 }
356
357 // Return the address "addr" aligned by "alignment_in_bytes" if such
358 // an address is below "end". Return NULL otherwise.
359 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
360 HeapWord* end,
361 unsigned short alignment_in_bytes);
362
363 // Some heaps may offer a contiguous region for shared non-blocking
364 // allocation, via inlined code (by exporting the address of the top and
365 // end fields defining the extent of the contiguous allocation region.)
366
367 // This function returns "true" iff the heap supports this kind of
368 // allocation. (Default is "no".)
369 virtual bool supports_inline_contig_alloc() const {
370 return false;
371 }
372 // These functions return the addresses of the fields that define the
373 // boundaries of the contiguous allocation area. (These fields should be
374 // physically near to one another.)
375 virtual HeapWord** top_addr() const {
376 guarantee(false, "inline contiguous allocation not supported");
377 return NULL;
378 }
379 virtual HeapWord** end_addr() const {
380 guarantee(false, "inline contiguous allocation not supported");
381 return NULL;
382 }
383
384 // Some heaps may be in an unparseable state at certain times between
385 // collections. This may be necessary for efficient implementation of
386 // certain allocation-related activities. Calling this function before
387 // attempting to parse a heap ensures that the heap is in a parsable
388 // state (provided other concurrent activity does not introduce
389 // unparsability). It is normally expected, therefore, that this
390 // method is invoked with the world stopped.
391 // NOTE: if you override this method, make sure you call
392 // super::ensure_parsability so that the non-generational
393 // part of the work gets done. See implementation of
394 // CollectedHeap::ensure_parsability and, for instance,
395 // that of GenCollectedHeap::ensure_parsability().
396 // The argument "retire_tlabs" controls whether existing TLABs
397 // are merely filled or also retired, thus preventing further
398 // allocation from them and necessitating allocation of new TLABs.
399 virtual void ensure_parsability(bool retire_tlabs);
400
401 // Section on thread-local allocation buffers (TLABs)
402 // If the heap supports thread-local allocation buffers, it should override
403 // the following methods:
404 // Returns "true" iff the heap supports thread-local allocation buffers.
405 // The default is "no".
406 virtual bool supports_tlab_allocation() const = 0;
407
408 // The amount of space available for thread-local allocation buffers.
409 virtual size_t tlab_capacity(Thread *thr) const = 0;
410
411 // The amount of used space for thread-local allocation buffers for the given thread.
412 virtual size_t tlab_used(Thread *thr) const = 0;
413
414 virtual size_t max_tlab_size() const;
415
416 // An estimate of the maximum allocation that could be performed
417 // for thread-local allocation buffers without triggering any
418 // collection or expansion activity.
419 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
420 guarantee(false, "thread-local allocation buffers not supported");
421 return 0;
422 }
423
424 // Can a compiler initialize a new object without store barriers?
425 // This permission only extends from the creation of a new object
426 // via a TLAB up to the first subsequent safepoint. If such permission
427 // is granted for this heap type, the compiler promises to call
428 // defer_store_barrier() below on any slow path allocation of
429 // a new object for which such initializing store barriers will
430 // have been elided.
431 virtual bool can_elide_tlab_store_barriers() const = 0;
432
433 // If a compiler is eliding store barriers for TLAB-allocated objects,
434 // there is probably a corresponding slow path which can produce
435 // an object allocated anywhere. The compiler's runtime support
436 // promises to call this function on such a slow-path-allocated
437 // object before performing initializations that have elided
438 // store barriers. Returns new_obj, or maybe a safer copy thereof.
439 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
440
441 // Answers whether an initializing store to a new object currently
442 // allocated at the given address doesn't need a store
443 // barrier. Returns "true" if it doesn't need an initializing
444 // store barrier; answers "false" if it does.
445 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
446
447 // If a compiler is eliding store barriers for TLAB-allocated objects,
448 // we will be informed of a slow-path allocation by a call
449 // to new_store_pre_barrier() above. Such a call precedes the
450 // initialization of the object itself, and no post-store-barriers will
451 // be issued. Some heap types require that the barrier strictly follows
452 // the initializing stores. (This is currently implemented by deferring the
453 // barrier until the next slow-path allocation or gc-related safepoint.)
454 // This interface answers whether a particular heap type needs the card
455 // mark to be thus strictly sequenced after the stores.
456 virtual bool card_mark_must_follow_store() const = 0;
457
458 // If the CollectedHeap was asked to defer a store barrier above,
459 // this informs it to flush such a deferred store barrier to the
460 // remembered set.
461 virtual void flush_deferred_store_barrier(JavaThread* thread);
462
463 // Does this heap support heap inspection (+PrintClassHistogram?)
464 virtual bool supports_heap_inspection() const = 0;
465
466 // Perform a collection of the heap; intended for use in implementing
467 // "System.gc". This probably implies as full a collection as the
468 // "CollectedHeap" supports.
469 virtual void collect(GCCause::Cause cause) = 0;
470
471 // Perform a full collection
472 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
473
474 // This interface assumes that it's being called by the
475 // vm thread. It collects the heap assuming that the
476 // heap lock is already held and that we are executing in
477 // the context of the vm thread.
478 virtual void collect_as_vm_thread(GCCause::Cause cause);
479
480 // Returns the barrier set for this heap
481 BarrierSet* barrier_set() { return _barrier_set; }
482
483 // Returns "true" iff there is a stop-world GC in progress. (I assume
484 // that it should answer "false" for the concurrent part of a concurrent
485 // collector -- dld).
486 bool is_gc_active() const { return _is_gc_active; }
487
488 // Total number of GC collections (started)
489 unsigned int total_collections() const { return _total_collections; }
490 unsigned int total_full_collections() const { return _total_full_collections;}
491
492 // Increment total number of GC collections (started)
493 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
494 void increment_total_collections(bool full = false) {
495 _total_collections++;
496 if (full) {
497 increment_total_full_collections();
498 }
499 }
500
501 void increment_total_full_collections() { _total_full_collections++; }
502
503 // Return the AdaptiveSizePolicy for the heap.
504 virtual AdaptiveSizePolicy* size_policy() = 0;
505
506 // Return the CollectorPolicy for the heap
507 virtual CollectorPolicy* collector_policy() const = 0;
508
509 void oop_iterate_no_header(OopClosure* cl);
510
511 // Iterate over all the ref-containing fields of all objects, calling
512 // "cl.do_oop" on each.
513 virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
514
515 // Iterate over all objects, calling "cl.do_object" on each.
516 virtual void object_iterate(ObjectClosure* cl) = 0;
517
518 // Similar to object_iterate() except iterates only
519 // over live objects.
520 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
521
522 // NOTE! There is no requirement that a collector implement these
523 // functions.
524 //
525 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
526 // each address in the (reserved) heap is a member of exactly
527 // one block. The defining characteristic of a block is that it is
528 // possible to find its size, and thus to progress forward to the next
529 // block. (Blocks may be of different sizes.) Thus, blocks may
530 // represent Java objects, or they might be free blocks in a
531 // free-list-based heap (or subheap), as long as the two kinds are
532 // distinguishable and the size of each is determinable.
533
534 // Returns the address of the start of the "block" that contains the
535 // address "addr". We say "blocks" instead of "object" since some heaps
536 // may not pack objects densely; a chunk may either be an object or a
537 // non-object.
538 virtual HeapWord* block_start(const void* addr) const = 0;
539
540 // Requires "addr" to be the start of a chunk, and returns its size.
541 // "addr + size" is required to be the start of a new chunk, or the end
542 // of the active area of the heap.
543 virtual size_t block_size(const HeapWord* addr) const = 0;
544
545 // Requires "addr" to be the start of a block, and returns "TRUE" iff
546 // the block is an object.
547 virtual bool block_is_obj(const HeapWord* addr) const = 0;
548
549 // Returns the longest time (in ms) that has elapsed since the last
550 // time that any part of the heap was examined by a garbage collection.
551 virtual jlong millis_since_last_gc() = 0;
552
553 // Perform any cleanup actions necessary before allowing a verification.
554 virtual void prepare_for_verify() = 0;
555
556 // Generate any dumps preceding or following a full gc
557 void pre_full_gc_dump(GCTimer* timer);
558 void post_full_gc_dump(GCTimer* timer);
559
560 VirtualSpaceSummary create_heap_space_summary();
561 GCHeapSummary create_heap_summary();
562
563 MetaspaceSummary create_metaspace_summary();
564
565 // Print heap information on the given outputStream.
566 virtual void print_on(outputStream* st) const = 0;
567 // The default behavior is to call print_on() on tty.
568 virtual void print() const {
569 print_on(tty);
570 }
571 // Print more detailed heap information on the given
572 // outputStream. The default behavior is to call print_on(). It is
573 // up to each subclass to override it and add any additional output
574 // it needs.
575 virtual void print_extended_on(outputStream* st) const {
576 print_on(st);
577 }
578
579 virtual void print_on_error(outputStream* st) const {
580 st->print_cr("Heap:");
581 print_extended_on(st);
582 st->cr();
583
584 _barrier_set->print_on(st);
585 }
586
587 // Print all GC threads (other than the VM thread)
588 // used by this heap.
589 virtual void print_gc_threads_on(outputStream* st) const = 0;
590 // The default behavior is to call print_gc_threads_on() on tty.
591 void print_gc_threads() {
592 print_gc_threads_on(tty);
593 }
594 // Iterator for all GC threads (other than VM thread)
595 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
596
597 // Print any relevant tracing info that flags imply.
598 // Default implementation does nothing.
599 virtual void print_tracing_info() const = 0;
600
601 void print_heap_before_gc();
602 void print_heap_after_gc();
603
604 // Registering and unregistering an nmethod (compiled code) with the heap.
605 // Override with specific mechanism for each specialized heap type.
606 virtual void register_nmethod(nmethod* nm);
607 virtual void unregister_nmethod(nmethod* nm);
608
609 void trace_heap_before_gc(GCTracer* gc_tracer);
610 void trace_heap_after_gc(GCTracer* gc_tracer);
611
612 // Heap verification
613 virtual void verify(bool silent, VerifyOption option) = 0;
614
615 // Non product verification and debugging.
616 #ifndef PRODUCT
617 // Support for PromotionFailureALot. Return true if it's time to cause a
618 // promotion failure. The no-argument version uses
619 // this->_promotion_failure_alot_count as the counter.
620 inline bool promotion_should_fail(volatile size_t* count);
621 inline bool promotion_should_fail();
622
623 // Reset the PromotionFailureALot counters. Should be called at the end of a
624 // GC in which promotion failure occurred.
625 inline void reset_promotion_should_fail(volatile size_t* count);
626 inline void reset_promotion_should_fail();
627 #endif // #ifndef PRODUCT
628
629 #ifdef ASSERT
630 static int fired_fake_oom() {
631 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
632 }
633 #endif
634
635 public:
636 // This is a convenience method that is used in cases where
637 // the actual number of GC worker threads is not pertinent but
638 // only whether there more than 0. Use of this method helps
639 // reduce the occurrence of ParallelGCThreads to uses where the
640 // actual number may be germane.
641 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
642
643 // Copy the current allocation context statistics for the specified contexts.
644 // For each context in contexts, set the corresponding entries in the totals
645 // and accuracy arrays to the current values held by the statistics. Each
646 // array should be of length len.
647 // Returns true if there are more stats available.
648 virtual bool copy_allocation_context_stats(const jint* contexts,
649 jlong* totals,
650 jbyte* accuracy,
651 jint len) {
652 return false;
653 }
654
655 /////////////// Unit tests ///////////////
656
657 NOT_PRODUCT(static void test_is_in();)
658 };
659
660 // Class to set and reset the GC cause for a CollectedHeap.
661
662 class GCCauseSetter : StackObj {
663 CollectedHeap* _heap;
664 GCCause::Cause _previous_cause;
665 public:
666 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
667 assert(SafepointSynchronize::is_at_safepoint(),
668 "This method manipulates heap state without locking");
669 _heap = heap;
670 _previous_cause = _heap->gc_cause();
671 _heap->set_gc_cause(cause);
672 }
673
674 ~GCCauseSetter() {
675 assert(SafepointSynchronize::is_at_safepoint(),
676 "This method manipulates heap state without locking");
677 _heap->set_gc_cause(_previous_cause);
678 }
679 };
680
681 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP