1 /*
2 * Copyright (c) 2001, 2017, 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.
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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_SHARED_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
27
28 #include "gc/shared/gcCause.hpp"
29 #include "gc/shared/gcWhen.hpp"
30 #include "memory/allocation.hpp"
31 #include "runtime/handles.hpp"
32 #include "runtime/perfData.hpp"
33 #include "runtime/safepoint.hpp"
34 #include "utilities/debug.hpp"
35 #include "utilities/events.hpp"
36 #include "utilities/formatBuffer.hpp"
37
38 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
39 // is an abstract class: there may be many different kinds of heaps. This
40 // class defines the functions that a heap must implement, and contains
41 // infrastructure common to all heaps.
42
43 class AdaptiveSizePolicy;
44 class BarrierSet;
45 class CollectorPolicy;
46 class GCHeapSummary;
47 class GCTimer;
48 class GCTracer;
49 class MetaspaceSummary;
50 class Thread;
51 class ThreadClosure;
52 class VirtualSpaceSummary;
53 class WorkGang;
54 class nmethod;
55
56 class GCMessage : public FormatBuffer<1024> {
57 public:
58 bool is_before;
59
60 public:
61 GCMessage() {}
62 };
63
64 class CollectedHeap;
65
66 class GCHeapLog : public EventLogBase<GCMessage> {
67 private:
68 void log_heap(CollectedHeap* heap, bool before);
69
70 public:
71 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
72
73 void log_heap_before(CollectedHeap* heap) {
74 log_heap(heap, true);
75 }
76 void log_heap_after(CollectedHeap* heap) {
77 log_heap(heap, false);
78 }
79 };
80
81 //
82 // CollectedHeap
83 // GenCollectedHeap
84 // G1CollectedHeap
85 // ParallelScavengeHeap
86 //
87 class CollectedHeap : public CHeapObj<mtInternal> {
88 friend class VMStructs;
89 friend class JVMCIVMStructs;
90 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
91
92 private:
93 #ifdef ASSERT
94 static int _fire_out_of_memory_count;
95 #endif
96
97 GCHeapLog* _gc_heap_log;
98
99 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
100 // or INCLUDE_JVMCI is being used
101 bool _defer_initial_card_mark;
102
103 MemRegion _reserved;
104
105 protected:
106 BarrierSet* _barrier_set;
107 bool _is_gc_active;
108
109 // Used for filler objects (static, but initialized in ctor).
110 static size_t _filler_array_max_size;
111
112 unsigned int _total_collections; // ... started
113 unsigned int _total_full_collections; // ... started
114 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
115 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
116
117 // Reason for current garbage collection. Should be set to
118 // a value reflecting no collection between collections.
119 GCCause::Cause _gc_cause;
120 GCCause::Cause _gc_lastcause;
121 PerfStringVariable* _perf_gc_cause;
122 PerfStringVariable* _perf_gc_lastcause;
123
124 // Constructor
125 CollectedHeap();
126
127 // Do common initializations that must follow instance construction,
128 // for example, those needing virtual calls.
129 // This code could perhaps be moved into initialize() but would
130 // be slightly more awkward because we want the latter to be a
131 // pure virtual.
132 void pre_initialize();
133
134 // Create a new tlab. All TLAB allocations must go through this.
135 virtual HeapWord* allocate_new_tlab(size_t size);
136
137 // Accumulate statistics on all tlabs.
138 virtual void accumulate_statistics_all_tlabs();
139
140 // Reinitialize tlabs before resuming mutators.
141 virtual void resize_all_tlabs();
142
143 // Allocate from the current thread's TLAB, with broken-out slow path.
144 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size);
145 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size);
146
147 // Handle if needed heap sampling.
148 static HeapWord* handle_heap_sampling(Thread* thread, HeapWord* obj, size_t size);
149
150 // Allocate an uninitialized block of the given size, or returns NULL if
151 // this is impossible.
152 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);
153
154 // Like allocate_init, but the block returned by a successful allocation
155 // is guaranteed initialized to zeros.
156 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);
157
158 // Helper functions for (VM) allocation.
159 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);
160 inline static void post_allocation_setup_no_klass_install(Klass* klass,
161 HeapWord* objPtr);
162
163 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);
164
165 inline static void post_allocation_setup_array(Klass* klass,
166 HeapWord* obj, int length);
167
168 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);
169
170 // Clears an allocated object.
171 inline static void init_obj(HeapWord* obj, size_t size);
172
173 // Filler object utilities.
174 static inline size_t filler_array_hdr_size();
175 static inline size_t filler_array_min_size();
176
177 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
178 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
179
180 // Fill with a single array; caller must ensure filler_array_min_size() <=
181 // words <= filler_array_max_size().
182 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
183
184 // Fill with a single object (either an int array or a java.lang.Object).
185 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
186
187 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
188
189 // Verification functions
190 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
191 PRODUCT_RETURN;
192 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
193 PRODUCT_RETURN;
194 debug_only(static void check_for_valid_allocation_state();)
195
196 public:
197 enum Name {
198 GenCollectedHeap,
199 ParallelScavengeHeap,
200 G1CollectedHeap
201 };
202
203 static inline size_t filler_array_max_size() {
204 return _filler_array_max_size;
205 }
206
207 virtual Name kind() const = 0;
208
209 virtual const char* name() const = 0;
210
211 /**
212 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
213 * and JNI_OK on success.
214 */
215 virtual jint initialize() = 0;
216
217 // In many heaps, there will be a need to perform some initialization activities
218 // after the Universe is fully formed, but before general heap allocation is allowed.
219 // This is the correct place to place such initialization methods.
220 virtual void post_initialize() = 0;
221
222 // Stop any onging concurrent work and prepare for exit.
223 virtual void stop() {}
224
225 void initialize_reserved_region(HeapWord *start, HeapWord *end);
226 MemRegion reserved_region() const { return _reserved; }
227 address base() const { return (address)reserved_region().start(); }
228
229 virtual size_t capacity() const = 0;
230 virtual size_t used() const = 0;
231
232 // Return "true" if the part of the heap that allocates Java
233 // objects has reached the maximal committed limit that it can
234 // reach, without a garbage collection.
235 virtual bool is_maximal_no_gc() const = 0;
236
237 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
238 // memory that the vm could make available for storing 'normal' java objects.
239 // This is based on the reserved address space, but should not include space
240 // that the vm uses internally for bookkeeping or temporary storage
241 // (e.g., in the case of the young gen, one of the survivor
242 // spaces).
243 virtual size_t max_capacity() const = 0;
244
245 // Returns "TRUE" if "p" points into the reserved area of the heap.
246 bool is_in_reserved(const void* p) const {
247 return _reserved.contains(p);
248 }
249
250 bool is_in_reserved_or_null(const void* p) const {
251 return p == NULL || is_in_reserved(p);
252 }
253
254 // Returns "TRUE" iff "p" points into the committed areas of the heap.
255 // This method can be expensive so avoid using it in performance critical
256 // code.
257 virtual bool is_in(const void* p) const = 0;
258
259 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
260
261 // Let's define some terms: a "closed" subset of a heap is one that
262 //
263 // 1) contains all currently-allocated objects, and
264 //
265 // 2) is closed under reference: no object in the closed subset
266 // references one outside the closed subset.
267 //
268 // Membership in a heap's closed subset is useful for assertions.
269 // Clearly, the entire heap is a closed subset, so the default
270 // implementation is to use "is_in_reserved". But this may not be too
271 // liberal to perform useful checking. Also, the "is_in" predicate
272 // defines a closed subset, but may be too expensive, since "is_in"
273 // verifies that its argument points to an object head. The
274 // "closed_subset" method allows a heap to define an intermediate
275 // predicate, allowing more precise checking than "is_in_reserved" at
276 // lower cost than "is_in."
277
278 // One important case is a heap composed of disjoint contiguous spaces,
279 // such as the Garbage-First collector. Such heaps have a convenient
280 // closed subset consisting of the allocated portions of those
281 // contiguous spaces.
282
283 // Return "TRUE" iff the given pointer points into the heap's defined
284 // closed subset (which defaults to the entire heap).
285 virtual bool is_in_closed_subset(const void* p) const {
286 return is_in_reserved(p);
287 }
288
289 bool is_in_closed_subset_or_null(const void* p) const {
290 return p == NULL || is_in_closed_subset(p);
291 }
292
293 // An object is scavengable if its location may move during a scavenge.
294 // (A scavenge is a GC which is not a full GC.)
295 virtual bool is_scavengable(const void *p) = 0;
296
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; }
306
307 // General obj/array allocation facilities.
308 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
309 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
310 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
311 inline static oop class_allocate(Klass* klass, int size, TRAPS);
312
313 // Raw memory allocation facilities
314 // The obj and array allocate methods are covers for these methods.
315 // mem_allocate() should never be
316 // called to allocate TLABs, only individual objects.
317 virtual HeapWord* mem_allocate(size_t size,
318 bool* gc_overhead_limit_was_exceeded) = 0;
319
320 // Utilities for turning raw memory into filler objects.
321 //
322 // min_fill_size() is the smallest region that can be filled.
323 // fill_with_objects() can fill arbitrary-sized regions of the heap using
324 // multiple objects. fill_with_object() is for regions known to be smaller
325 // than the largest array of integers; it uses a single object to fill the
326 // region and has slightly less overhead.
327 static size_t min_fill_size() {
328 return size_t(align_object_size(oopDesc::header_size()));
329 }
330
331 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
332
333 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
334 static void fill_with_object(MemRegion region, bool zap = true) {
335 fill_with_object(region.start(), region.word_size(), zap);
336 }
337 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
338 fill_with_object(start, pointer_delta(end, start), zap);
339 }
340
341 // Return the address "addr" aligned by "alignment_in_bytes" if such
342 // an address is below "end". Return NULL otherwise.
343 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
344 HeapWord* end,
345 unsigned short alignment_in_bytes);
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* volatile* 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 // Section on thread-local allocation buffers (TLABs)
386 // If the heap supports thread-local allocation buffers, it should override
387 // the following methods:
388 // Returns "true" iff the heap supports thread-local allocation buffers.
389 // The default is "no".
390 virtual bool supports_tlab_allocation() const = 0;
391
392 // The amount of space available for thread-local allocation buffers.
393 virtual size_t tlab_capacity(Thread *thr) const = 0;
394
395 // The amount of used space for thread-local allocation buffers for the given thread.
396 virtual size_t tlab_used(Thread *thr) const = 0;
397
398 virtual size_t max_tlab_size() const;
399
400 // An estimate of the maximum allocation that could be performed
401 // for thread-local allocation buffers without triggering any
402 // collection or expansion activity.
403 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
404 guarantee(false, "thread-local allocation buffers not supported");
405 return 0;
406 }
407
408 // Can a compiler initialize a new object without store barriers?
409 // This permission only extends from the creation of a new object
410 // via a TLAB up to the first subsequent safepoint. If such permission
411 // is granted for this heap type, the compiler promises to call
412 // defer_store_barrier() below on any slow path allocation of
413 // a new object for which such initializing store barriers will
414 // have been elided.
415 virtual bool can_elide_tlab_store_barriers() const = 0;
416
417 // If a compiler is eliding store barriers for TLAB-allocated objects,
418 // there is probably a corresponding slow path which can produce
419 // an object allocated anywhere. The compiler's runtime support
420 // promises to call this function on such a slow-path-allocated
421 // object before performing initializations that have elided
422 // store barriers. Returns new_obj, or maybe a safer copy thereof.
423 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
424
425 // Answers whether an initializing store to a new object currently
426 // allocated at the given address doesn't need a store
427 // barrier. Returns "true" if it doesn't need an initializing
428 // store barrier; answers "false" if it does.
429 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
430
431 // If a compiler is eliding store barriers for TLAB-allocated objects,
432 // we will be informed of a slow-path allocation by a call
433 // to new_store_pre_barrier() above. Such a call precedes the
434 // initialization of the object itself, and no post-store-barriers will
435 // be issued. Some heap types require that the barrier strictly follows
436 // the initializing stores. (This is currently implemented by deferring the
437 // barrier until the next slow-path allocation or gc-related safepoint.)
438 // This interface answers whether a particular heap type needs the card
439 // mark to be thus strictly sequenced after the stores.
440 virtual bool card_mark_must_follow_store() const = 0;
441
442 // If the CollectedHeap was asked to defer a store barrier above,
443 // this informs it to flush such a deferred store barrier to the
444 // remembered set.
445 virtual void flush_deferred_store_barrier(JavaThread* thread);
446
447 // Perform a collection of the heap; intended for use in implementing
448 // "System.gc". This probably implies as full a collection as the
449 // "CollectedHeap" supports.
450 virtual void collect(GCCause::Cause cause) = 0;
451
452 // Perform a full collection
453 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
454
455 // This interface assumes that it's being called by the
456 // vm thread. It collects the heap assuming that the
457 // heap lock is already held and that we are executing in
458 // the context of the vm thread.
459 virtual void collect_as_vm_thread(GCCause::Cause cause);
460
461 // Returns the barrier set for this heap
462 BarrierSet* barrier_set() { return _barrier_set; }
463 void set_barrier_set(BarrierSet* barrier_set);
464
465 // Returns "true" iff there is a stop-world GC in progress. (I assume
466 // that it should answer "false" for the concurrent part of a concurrent
467 // collector -- dld).
468 bool is_gc_active() const { return _is_gc_active; }
469
470 // Total number of GC collections (started)
471 unsigned int total_collections() const { return _total_collections; }
472 unsigned int total_full_collections() const { return _total_full_collections;}
473
474 // Increment total number of GC collections (started)
475 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
476 void increment_total_collections(bool full = false) {
477 _total_collections++;
478 if (full) {
479 increment_total_full_collections();
480 }
481 }
482
483 void increment_total_full_collections() { _total_full_collections++; }
484
485 // Return the CollectorPolicy for the heap
486 virtual CollectorPolicy* collector_policy() const = 0;
487
488 // Iterate over all objects, calling "cl.do_object" on each.
489 virtual void object_iterate(ObjectClosure* cl) = 0;
490
491 // Similar to object_iterate() except iterates only
492 // over live objects.
493 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
494
495 // NOTE! There is no requirement that a collector implement these
496 // functions.
497 //
498 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
499 // each address in the (reserved) heap is a member of exactly
500 // one block. The defining characteristic of a block is that it is
501 // possible to find its size, and thus to progress forward to the next
502 // block. (Blocks may be of different sizes.) Thus, blocks may
503 // represent Java objects, or they might be free blocks in a
504 // free-list-based heap (or subheap), as long as the two kinds are
505 // distinguishable and the size of each is determinable.
506
507 // Returns the address of the start of the "block" that contains the
508 // address "addr". We say "blocks" instead of "object" since some heaps
509 // may not pack objects densely; a chunk may either be an object or a
510 // non-object.
511 virtual HeapWord* block_start(const void* addr) const = 0;
512
513 // Requires "addr" to be the start of a chunk, and returns its size.
514 // "addr + size" is required to be the start of a new chunk, or the end
515 // of the active area of the heap.
516 virtual size_t block_size(const HeapWord* addr) const = 0;
517
518 // Requires "addr" to be the start of a block, and returns "TRUE" iff
519 // the block is an object.
520 virtual bool block_is_obj(const HeapWord* addr) const = 0;
521
522 // Returns the longest time (in ms) that has elapsed since the last
523 // time that any part of the heap was examined by a garbage collection.
524 virtual jlong millis_since_last_gc() = 0;
525
526 // Perform any cleanup actions necessary before allowing a verification.
527 virtual void prepare_for_verify() = 0;
528
529 // Generate any dumps preceding or following a full gc
530 private:
531 void full_gc_dump(GCTimer* timer, bool before);
532 public:
533 void pre_full_gc_dump(GCTimer* timer);
534 void post_full_gc_dump(GCTimer* timer);
535
536 VirtualSpaceSummary create_heap_space_summary();
537 GCHeapSummary create_heap_summary();
538
539 MetaspaceSummary create_metaspace_summary();
540
541 // Print heap information on the given outputStream.
542 virtual void print_on(outputStream* st) const = 0;
543 // The default behavior is to call print_on() on tty.
544 virtual void print() const {
545 print_on(tty);
546 }
547 // Print more detailed heap information on the given
548 // outputStream. The default behavior is to call print_on(). It is
549 // up to each subclass to override it and add any additional output
550 // it needs.
551 virtual void print_extended_on(outputStream* st) const {
552 print_on(st);
553 }
554
555 virtual void print_on_error(outputStream* st) const;
556
557 // Print all GC threads (other than the VM thread)
558 // used by this heap.
559 virtual void print_gc_threads_on(outputStream* st) const = 0;
560 // The default behavior is to call print_gc_threads_on() on tty.
561 void print_gc_threads() {
562 print_gc_threads_on(tty);
563 }
564 // Iterator for all GC threads (other than VM thread)
565 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
566
567 // Print any relevant tracing info that flags imply.
568 // Default implementation does nothing.
569 virtual void print_tracing_info() const = 0;
570
571 void print_heap_before_gc();
572 void print_heap_after_gc();
573
574 // Registering and unregistering an nmethod (compiled code) with the heap.
575 // Override with specific mechanism for each specialized heap type.
576 virtual void register_nmethod(nmethod* nm);
577 virtual void unregister_nmethod(nmethod* nm);
578
579 void trace_heap_before_gc(const GCTracer* gc_tracer);
580 void trace_heap_after_gc(const GCTracer* gc_tracer);
581
582 // Heap verification
583 virtual void verify(VerifyOption option) = 0;
584
585 // Return true if concurrent phase control (via
586 // request_concurrent_phase_control) is supported by this collector.
587 // The default implementation returns false.
588 virtual bool supports_concurrent_phase_control() const;
589
590 // Return a NULL terminated array of concurrent phase names provided
591 // by this collector. Supports Whitebox testing. These are the
592 // names recognized by request_concurrent_phase(). The default
593 // implementation returns an array of one NULL element.
594 virtual const char* const* concurrent_phases() const;
595
596 // Request the collector enter the indicated concurrent phase, and
597 // wait until it does so. Supports WhiteBox testing. Only one
598 // request may be active at a time. Phases are designated by name;
599 // the set of names and their meaning is GC-specific. Once the
600 // requested phase has been reached, the collector will attempt to
601 // avoid transitioning to a new phase until a new request is made.
602 // [Note: A collector might not be able to remain in a given phase.
603 // For example, a full collection might cancel an in-progress
604 // concurrent collection.]
605 //
606 // Returns true when the phase is reached. Returns false for an
607 // unknown phase. The default implementation returns false.
608 virtual bool request_concurrent_phase(const char* phase);
609
610 // Provides a thread pool to SafepointSynchronize to use
611 // for parallel safepoint cleanup.
612 // GCs that use a GC worker thread pool may want to share
613 // it for use during safepoint cleanup. This is only possible
614 // if the GC can pause and resume concurrent work (e.g. G1
615 // concurrent marking) for an intermittent non-GC safepoint.
616 // If this method returns NULL, SafepointSynchronize will
617 // perform cleanup tasks serially in the VMThread.
618 virtual WorkGang* get_safepoint_workers() { return NULL; }
619
620 // Non product verification and debugging.
621 #ifndef PRODUCT
622 // Support for PromotionFailureALot. Return true if it's time to cause a
623 // promotion failure. The no-argument version uses
624 // this->_promotion_failure_alot_count as the counter.
625 inline bool promotion_should_fail(volatile size_t* count);
626 inline bool promotion_should_fail();
627
628 // Reset the PromotionFailureALot counters. Should be called at the end of a
629 // GC in which promotion failure occurred.
630 inline void reset_promotion_should_fail(volatile size_t* count);
631 inline void reset_promotion_should_fail();
632 #endif // #ifndef PRODUCT
633
634 #ifdef ASSERT
635 static int fired_fake_oom() {
636 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
637 }
638 #endif
639
640 public:
641 // Copy the current allocation context statistics for the specified contexts.
642 // For each context in contexts, set the corresponding entries in the totals
643 // and accuracy arrays to the current values held by the statistics. Each
644 // array should be of length len.
645 // Returns true if there are more stats available.
646 virtual bool copy_allocation_context_stats(const jint* contexts,
647 jlong* totals,
648 jbyte* accuracy,
649 jint len) {
650 return false;
651 }
652
653 };
654
655 // Class to set and reset the GC cause for a CollectedHeap.
656
657 class GCCauseSetter : StackObj {
658 CollectedHeap* _heap;
659 GCCause::Cause _previous_cause;
660 public:
661 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
662 assert(SafepointSynchronize::is_at_safepoint(),
663 "This method manipulates heap state without locking");
664 _heap = heap;
665 _previous_cause = _heap->gc_cause();
666 _heap->set_gc_cause(cause);
667 }
668
669 ~GCCauseSetter() {
670 assert(SafepointSynchronize::is_at_safepoint(),
671 "This method manipulates heap state without locking");
672 _heap->set_gc_cause(_previous_cause);
673 }
674 };
675
676 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP