Sat, 01 Sep 2012 13:25:18 -0400
6964458: Reimplement class meta-data storage to use native memory
Summary: Remove PermGen, allocate meta-data in metaspace linked to class loaders, rewrite GC walking, rewrite and rename metadata to be C++ classes
Reviewed-by: jmasa, stefank, never, coleenp, kvn, brutisso, mgerdin, dholmes, jrose, twisti, roland
Contributed-by: jmasa <jon.masamitsu@oracle.com>, stefank <stefan.karlsson@oracle.com>, mgerdin <mikael.gerdin@oracle.com>, never <tom.rodriguez@oracle.com>
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.
22 *
23 */
25 #ifndef SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
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"
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.
41 class BarrierSet;
42 class ThreadClosure;
43 class AdaptiveSizePolicy;
44 class Thread;
45 class CollectorPolicy;
47 class GCMessage : public FormatBuffer<1024> {
48 public:
49 bool is_before;
51 public:
52 GCMessage() {}
53 };
55 class GCHeapLog : public EventLogBase<GCMessage> {
56 private:
57 void log_heap(bool before);
59 public:
60 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
62 void log_heap_before() {
63 log_heap(true);
64 }
65 void log_heap_after() {
66 log_heap(false);
67 }
68 };
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
81 #ifdef ASSERT
82 static int _fire_out_of_memory_count;
83 #endif
85 // Used for filler objects (static, but initialized in ctor).
86 static size_t _filler_array_max_size;
88 GCHeapLog* _gc_heap_log;
90 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
91 bool _defer_initial_card_mark;
93 protected:
94 MemRegion _reserved;
95 BarrierSet* _barrier_set;
96 bool _is_gc_active;
97 uint _n_par_threads;
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;)
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;
111 // Constructor
112 CollectedHeap();
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();
121 // Create a new tlab. All TLAB allocations must go through this.
122 virtual HeapWord* allocate_new_tlab(size_t size);
124 // Accumulate statistics on all tlabs.
125 virtual void accumulate_statistics_all_tlabs();
127 // Reinitialize tlabs before resuming mutators.
128 virtual void resize_all_tlabs();
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);
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);
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);
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);
147 inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj);
149 inline static void post_allocation_setup_array(KlassHandle klass,
150 HeapWord* obj, int length);
152 // Clears an allocated object.
153 inline static void init_obj(HeapWord* obj, size_t size);
155 // Filler object utilities.
156 static inline size_t filler_array_hdr_size();
157 static inline size_t filler_array_min_size();
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);)
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);
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);
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();)
176 public:
177 enum Name {
178 Abstract,
179 SharedHeap,
180 GenCollectedHeap,
181 ParallelScavengeHeap,
182 G1CollectedHeap
183 };
185 static inline size_t filler_array_max_size() {
186 return _filler_array_max_size;
187 }
189 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
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;
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;
202 MemRegion reserved_region() const { return _reserved; }
203 address base() const { return (address)reserved_region().start(); }
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;
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;
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;
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 }
228 bool is_in_reserved_or_null(const void* p) const {
229 return p == NULL || is_in_reserved(p);
230 }
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;
237 bool is_in_or_null(const void* p) const {
238 return p == NULL || is_in(p);
239 }
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 }
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."
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.
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 }
278 bool is_in_closed_subset_or_null(const void* p) const {
279 return p == NULL || is_in_closed_subset(p);
280 }
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
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;
292 // Returns "TRUE" if "p" is a method oop in the
293 // current heap, with high probability. This predicate
294 // is not stable, in general.
295 bool is_valid_method(Method* p) const;
297 void set_gc_cause(GCCause::Cause v) {
298 if (UsePerfData) {
299 _gc_lastcause = _gc_cause;
300 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
301 _perf_gc_cause->set_value(GCCause::to_string(v));
302 }
303 _gc_cause = v;
304 }
305 GCCause::Cause gc_cause() { return _gc_cause; }
307 // Number of threads currently working on GC tasks.
308 uint n_par_threads() { return _n_par_threads; }
310 // May be overridden to set additional parallelism.
311 virtual void set_par_threads(uint t) { _n_par_threads = t; };
313 // Allocate and initialize instances of Class
314 static oop Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS);
316 // General obj/array allocation facilities.
317 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
318 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
319 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
321 inline static void post_allocation_install_obj_klass(KlassHandle klass,
322 oop obj);
324 // Raw memory allocation facilities
325 // The obj and array allocate methods are covers for these methods.
326 // mem_allocate() should never be
327 // called to allocate TLABs, only individual objects.
328 virtual HeapWord* mem_allocate(size_t size,
329 bool* gc_overhead_limit_was_exceeded) = 0;
331 // Utilities for turning raw memory into filler objects.
332 //
333 // min_fill_size() is the smallest region that can be filled.
334 // fill_with_objects() can fill arbitrary-sized regions of the heap using
335 // multiple objects. fill_with_object() is for regions known to be smaller
336 // than the largest array of integers; it uses a single object to fill the
337 // region and has slightly less overhead.
338 static size_t min_fill_size() {
339 return size_t(align_object_size(oopDesc::header_size()));
340 }
342 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
344 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
345 static void fill_with_object(MemRegion region, bool zap = true) {
346 fill_with_object(region.start(), region.word_size(), zap);
347 }
348 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
349 fill_with_object(start, pointer_delta(end, start), zap);
350 }
352 // Some heaps may offer a contiguous region for shared non-blocking
353 // allocation, via inlined code (by exporting the address of the top and
354 // end fields defining the extent of the contiguous allocation region.)
356 // This function returns "true" iff the heap supports this kind of
357 // allocation. (Default is "no".)
358 virtual bool supports_inline_contig_alloc() const {
359 return false;
360 }
361 // These functions return the addresses of the fields that define the
362 // boundaries of the contiguous allocation area. (These fields should be
363 // physically near to one another.)
364 virtual HeapWord** top_addr() const {
365 guarantee(false, "inline contiguous allocation not supported");
366 return NULL;
367 }
368 virtual HeapWord** end_addr() const {
369 guarantee(false, "inline contiguous allocation not supported");
370 return NULL;
371 }
373 // Some heaps may be in an unparseable state at certain times between
374 // collections. This may be necessary for efficient implementation of
375 // certain allocation-related activities. Calling this function before
376 // attempting to parse a heap ensures that the heap is in a parsable
377 // state (provided other concurrent activity does not introduce
378 // unparsability). It is normally expected, therefore, that this
379 // method is invoked with the world stopped.
380 // NOTE: if you override this method, make sure you call
381 // super::ensure_parsability so that the non-generational
382 // part of the work gets done. See implementation of
383 // CollectedHeap::ensure_parsability and, for instance,
384 // that of GenCollectedHeap::ensure_parsability().
385 // The argument "retire_tlabs" controls whether existing TLABs
386 // are merely filled or also retired, thus preventing further
387 // allocation from them and necessitating allocation of new TLABs.
388 virtual void ensure_parsability(bool retire_tlabs);
390 // Return an estimate of the maximum allocation that could be performed
391 // without triggering any collection or expansion activity. In a
392 // generational collector, for example, this is probably the largest
393 // allocation that could be supported (without expansion) in the youngest
394 // generation. It is "unsafe" because no locks are taken; the result
395 // should be treated as an approximation, not a guarantee, for use in
396 // heuristic resizing decisions.
397 virtual size_t unsafe_max_alloc() = 0;
399 // Section on thread-local allocation buffers (TLABs)
400 // If the heap supports thread-local allocation buffers, it should override
401 // the following methods:
402 // Returns "true" iff the heap supports thread-local allocation buffers.
403 // The default is "no".
404 virtual bool supports_tlab_allocation() const {
405 return false;
406 }
407 // The amount of space available for thread-local allocation buffers.
408 virtual size_t tlab_capacity(Thread *thr) const {
409 guarantee(false, "thread-local allocation buffers not supported");
410 return 0;
411 }
412 // An estimate of the maximum allocation that could be performed
413 // for thread-local allocation buffers without triggering any
414 // collection or expansion activity.
415 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
416 guarantee(false, "thread-local allocation buffers not supported");
417 return 0;
418 }
420 // Can a compiler initialize a new object without store barriers?
421 // This permission only extends from the creation of a new object
422 // via a TLAB up to the first subsequent safepoint. If such permission
423 // is granted for this heap type, the compiler promises to call
424 // defer_store_barrier() below on any slow path allocation of
425 // a new object for which such initializing store barriers will
426 // have been elided.
427 virtual bool can_elide_tlab_store_barriers() const = 0;
429 // If a compiler is eliding store barriers for TLAB-allocated objects,
430 // there is probably a corresponding slow path which can produce
431 // an object allocated anywhere. The compiler's runtime support
432 // promises to call this function on such a slow-path-allocated
433 // object before performing initializations that have elided
434 // store barriers. Returns new_obj, or maybe a safer copy thereof.
435 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
437 // Answers whether an initializing store to a new object currently
438 // allocated at the given address doesn't need a store
439 // barrier. Returns "true" if it doesn't need an initializing
440 // store barrier; answers "false" if it does.
441 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
443 // If a compiler is eliding store barriers for TLAB-allocated objects,
444 // we will be informed of a slow-path allocation by a call
445 // to new_store_pre_barrier() above. Such a call precedes the
446 // initialization of the object itself, and no post-store-barriers will
447 // be issued. Some heap types require that the barrier strictly follows
448 // the initializing stores. (This is currently implemented by deferring the
449 // barrier until the next slow-path allocation or gc-related safepoint.)
450 // This interface answers whether a particular heap type needs the card
451 // mark to be thus strictly sequenced after the stores.
452 virtual bool card_mark_must_follow_store() const = 0;
454 // If the CollectedHeap was asked to defer a store barrier above,
455 // this informs it to flush such a deferred store barrier to the
456 // remembered set.
457 virtual void flush_deferred_store_barrier(JavaThread* thread);
459 // Does this heap support heap inspection (+PrintClassHistogram?)
460 virtual bool supports_heap_inspection() const = 0;
462 // Perform a collection of the heap; intended for use in implementing
463 // "System.gc". This probably implies as full a collection as the
464 // "CollectedHeap" supports.
465 virtual void collect(GCCause::Cause cause) = 0;
467 // Perform a full collection
468 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
470 // This interface assumes that it's being called by the
471 // vm thread. It collects the heap assuming that the
472 // heap lock is already held and that we are executing in
473 // the context of the vm thread.
474 virtual void collect_as_vm_thread(GCCause::Cause cause);
476 // Callback from VM_CollectForMetadataAllocation operation.
477 MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
478 size_t size,
479 Metaspace::MetadataType mdtype);
481 // Returns the barrier set for this heap
482 BarrierSet* barrier_set() { return _barrier_set; }
484 // Returns "true" iff there is a stop-world GC in progress. (I assume
485 // that it should answer "false" for the concurrent part of a concurrent
486 // collector -- dld).
487 bool is_gc_active() const { return _is_gc_active; }
489 // Total number of GC collections (started)
490 unsigned int total_collections() const { return _total_collections; }
491 unsigned int total_full_collections() const { return _total_full_collections;}
493 // Increment total number of GC collections (started)
494 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
495 void increment_total_collections(bool full = false) {
496 _total_collections++;
497 if (full) {
498 increment_total_full_collections();
499 }
500 }
502 void increment_total_full_collections() { _total_full_collections++; }
504 // Return the AdaptiveSizePolicy for the heap.
505 virtual AdaptiveSizePolicy* size_policy() = 0;
507 // Return the CollectorPolicy for the heap
508 virtual CollectorPolicy* collector_policy() const = 0;
510 void oop_iterate_no_header(OopClosure* cl);
512 // Iterate over all the ref-containing fields of all objects, calling
513 // "cl.do_oop" on each.
514 virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
516 // Iterate over all objects, calling "cl.do_object" on each.
517 virtual void object_iterate(ObjectClosure* cl) = 0;
519 // Similar to object_iterate() except iterates only
520 // over live objects.
521 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
523 // NOTE! There is no requirement that a collector implement these
524 // functions.
525 //
526 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
527 // each address in the (reserved) heap is a member of exactly
528 // one block. The defining characteristic of a block is that it is
529 // possible to find its size, and thus to progress forward to the next
530 // block. (Blocks may be of different sizes.) Thus, blocks may
531 // represent Java objects, or they might be free blocks in a
532 // free-list-based heap (or subheap), as long as the two kinds are
533 // distinguishable and the size of each is determinable.
535 // Returns the address of the start of the "block" that contains the
536 // address "addr". We say "blocks" instead of "object" since some heaps
537 // may not pack objects densely; a chunk may either be an object or a
538 // non-object.
539 virtual HeapWord* block_start(const void* addr) const = 0;
541 // Requires "addr" to be the start of a chunk, and returns its size.
542 // "addr + size" is required to be the start of a new chunk, or the end
543 // of the active area of the heap.
544 virtual size_t block_size(const HeapWord* addr) const = 0;
546 // Requires "addr" to be the start of a block, and returns "TRUE" iff
547 // the block is an object.
548 virtual bool block_is_obj(const HeapWord* addr) const = 0;
550 // Returns the longest time (in ms) that has elapsed since the last
551 // time that any part of the heap was examined by a garbage collection.
552 virtual jlong millis_since_last_gc() = 0;
554 // Perform any cleanup actions necessary before allowing a verification.
555 virtual void prepare_for_verify() = 0;
557 // Generate any dumps preceding or following a full gc
558 void pre_full_gc_dump();
559 void post_full_gc_dump();
561 // Print heap information on the given outputStream.
562 virtual void print_on(outputStream* st) const = 0;
563 // The default behavior is to call print_on() on tty.
564 virtual void print() const {
565 print_on(tty);
566 }
567 // Print more detailed heap information on the given
568 // outputStream. The default behaviour is to call print_on(). It is
569 // up to each subclass to override it and add any additional output
570 // it needs.
571 virtual void print_extended_on(outputStream* st) const {
572 print_on(st);
573 }
575 // Print all GC threads (other than the VM thread)
576 // used by this heap.
577 virtual void print_gc_threads_on(outputStream* st) const = 0;
578 // The default behavior is to call print_gc_threads_on() on tty.
579 void print_gc_threads() {
580 print_gc_threads_on(tty);
581 }
582 // Iterator for all GC threads (other than VM thread)
583 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
585 // Print any relevant tracing info that flags imply.
586 // Default implementation does nothing.
587 virtual void print_tracing_info() const = 0;
589 // If PrintHeapAtGC is set call the appropriate routi
590 void print_heap_before_gc() {
591 if (PrintHeapAtGC) {
592 Universe::print_heap_before_gc();
593 }
594 if (_gc_heap_log != NULL) {
595 _gc_heap_log->log_heap_before();
596 }
597 }
598 void print_heap_after_gc() {
599 if (PrintHeapAtGC) {
600 Universe::print_heap_after_gc();
601 }
602 if (_gc_heap_log != NULL) {
603 _gc_heap_log->log_heap_after();
604 }
605 }
607 // Heap verification
608 virtual void verify(bool silent, VerifyOption option) = 0;
610 // Non product verification and debugging.
611 #ifndef PRODUCT
612 // Support for PromotionFailureALot. Return true if it's time to cause a
613 // promotion failure. The no-argument version uses
614 // this->_promotion_failure_alot_count as the counter.
615 inline bool promotion_should_fail(volatile size_t* count);
616 inline bool promotion_should_fail();
618 // Reset the PromotionFailureALot counters. Should be called at the end of a
619 // GC in which promotion failure ocurred.
620 inline void reset_promotion_should_fail(volatile size_t* count);
621 inline void reset_promotion_should_fail();
622 #endif // #ifndef PRODUCT
624 #ifdef ASSERT
625 static int fired_fake_oom() {
626 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
627 }
628 #endif
630 public:
631 // This is a convenience method that is used in cases where
632 // the actual number of GC worker threads is not pertinent but
633 // only whether there more than 0. Use of this method helps
634 // reduce the occurrence of ParallelGCThreads to uses where the
635 // actual number may be germane.
636 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
638 /////////////// Unit tests ///////////////
640 NOT_PRODUCT(static void test_is_in();)
641 };
643 // Class to set and reset the GC cause for a CollectedHeap.
645 class GCCauseSetter : StackObj {
646 CollectedHeap* _heap;
647 GCCause::Cause _previous_cause;
648 public:
649 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
650 assert(SafepointSynchronize::is_at_safepoint(),
651 "This method manipulates heap state without locking");
652 _heap = heap;
653 _previous_cause = _heap->gc_cause();
654 _heap->set_gc_cause(cause);
655 }
657 ~GCCauseSetter() {
658 assert(SafepointSynchronize::is_at_safepoint(),
659 "This method manipulates heap state without locking");
660 _heap->set_gc_cause(_previous_cause);
661 }
662 };
664 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP