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 GCServicabilitySupport;
48 class GCTimer;
49 class GCTracer;
50 class MetaspaceSummary;
51 class Thread;
52 class ThreadClosure;
53 class VirtualSpaceSummary;
54 class WorkGang;
55 class nmethod;
56
57 class GCMessage : public FormatBuffer<1024> {
58 public:
59 bool is_before;
60
61 public:
62 GCMessage() {}
63 };
64
65 class CollectedHeap;
66
67 class GCHeapLog : public EventLogBase<GCMessage> {
68 private:
69 void log_heap(CollectedHeap* heap, bool before);
70
71 public:
72 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
73
74 void log_heap_before(CollectedHeap* heap) {
75 log_heap(heap, true);
76 }
77 void log_heap_after(CollectedHeap* heap) {
78 log_heap(heap, false);
79 }
80 };
81
82 //
83 // CollectedHeap
84 // GenCollectedHeap
85 // SerialHeap
86 // CMSHeap
87 // G1CollectedHeap
88 // ParallelScavengeHeap
89 //
90 class CollectedHeap : public CHeapObj<mtInternal> {
91 friend class VMStructs;
92 friend class JVMCIVMStructs;
93 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
94
95 private:
96 #ifdef ASSERT
97 static int _fire_out_of_memory_count;
98 #endif
99
100 GCHeapLog* _gc_heap_log;
101
102 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
103 // or INCLUDE_JVMCI is being used
104 bool _defer_initial_card_mark;
105
106 MemRegion _reserved;
107
108 GCServicabilitySupport* _servicability;
109
110 virtual GCServicabilitySupport* create_servicability_support() = 0;
111
112 protected:
113 BarrierSet* _barrier_set;
114 bool _is_gc_active;
115
116 // Used for filler objects (static, but initialized in ctor).
117 static size_t _filler_array_max_size;
118
119 unsigned int _total_collections; // ... started
120 unsigned int _total_full_collections; // ... started
121 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
122 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
123
124 // Reason for current garbage collection. Should be set to
125 // a value reflecting no collection between collections.
126 GCCause::Cause _gc_cause;
127 GCCause::Cause _gc_lastcause;
128 PerfStringVariable* _perf_gc_cause;
129 PerfStringVariable* _perf_gc_lastcause;
130
131 // Constructor
132 CollectedHeap();
133
134 // Do common initializations that must follow instance construction,
135 // for example, those needing virtual calls.
136 // This code could perhaps be moved into initialize() but would
137 // be slightly more awkward because we want the latter to be a
138 // pure virtual.
139 void pre_initialize();
140
141 // Create a new tlab. All TLAB allocations must go through this.
142 virtual HeapWord* allocate_new_tlab(size_t size);
143
144 // Accumulate statistics on all tlabs.
145 virtual void accumulate_statistics_all_tlabs();
146
147 // Reinitialize tlabs before resuming mutators.
148 virtual void resize_all_tlabs();
149
150 // Allocate from the current thread's TLAB, with broken-out slow path.
151 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size);
152 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size);
153
154 // Allocate an uninitialized block of the given size, or returns NULL if
155 // this is impossible.
156 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);
157
158 // Like allocate_init, but the block returned by a successful allocation
159 // is guaranteed initialized to zeros.
160 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);
161
162 // Helper functions for (VM) allocation.
163 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);
164 inline static void post_allocation_setup_no_klass_install(Klass* klass,
165 HeapWord* objPtr);
166
167 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);
168
169 inline static void post_allocation_setup_array(Klass* klass,
170 HeapWord* obj, int length);
171
172 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);
173
174 // Clears an allocated object.
175 inline static void init_obj(HeapWord* obj, size_t size);
176
177 // Filler object utilities.
178 static inline size_t filler_array_hdr_size();
179 static inline size_t filler_array_min_size();
180
181 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
182 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
183
184 // Fill with a single array; caller must ensure filler_array_min_size() <=
185 // words <= filler_array_max_size().
186 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
187
188 // Fill with a single object (either an int array or a java.lang.Object).
189 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
190
191 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
192
193 // Verification functions
194 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
195 PRODUCT_RETURN;
196 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
197 PRODUCT_RETURN;
198 debug_only(static void check_for_valid_allocation_state();)
199
200 public:
201 enum Name {
202 SerialHeap,
203 ParallelScavengeHeap,
204 G1CollectedHeap,
205 CMSHeap
206 };
207
208 static inline size_t filler_array_max_size() {
209 return _filler_array_max_size;
210 }
211
212 virtual Name kind() const = 0;
213
214 virtual const char* name() const = 0;
215
216 /**
217 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
218 * and JNI_OK on success.
219 */
220 virtual jint initialize() = 0;
221
222 // In many heaps, there will be a need to perform some initialization activities
223 // after the Universe is fully formed, but before general heap allocation is allowed.
224 // This is the correct place to place such initialization methods.
225 virtual void post_initialize() = 0;
226
227 // Stop any onging concurrent work and prepare for exit.
228 virtual void stop() {}
229
230 // Stop and resume concurrent GC threads interfering with safepoint operations
231 virtual void safepoint_synchronize_begin() {}
232 virtual void safepoint_synchronize_end() {}
233
234 void initialize_reserved_region(HeapWord *start, HeapWord *end);
235 MemRegion reserved_region() const { return _reserved; }
236 address base() const { return (address)reserved_region().start(); }
237
238 virtual size_t capacity() const = 0;
239 virtual size_t used() const = 0;
240
241 // Return "true" if the part of the heap that allocates Java
242 // objects has reached the maximal committed limit that it can
243 // reach, without a garbage collection.
244 virtual bool is_maximal_no_gc() const = 0;
245
246 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
247 // memory that the vm could make available for storing 'normal' java objects.
248 // This is based on the reserved address space, but should not include space
249 // that the vm uses internally for bookkeeping or temporary storage
250 // (e.g., in the case of the young gen, one of the survivor
251 // spaces).
252 virtual size_t max_capacity() const = 0;
253
254 // Returns "TRUE" if "p" points into the reserved area of the heap.
255 bool is_in_reserved(const void* p) const {
256 return _reserved.contains(p);
257 }
258
259 bool is_in_reserved_or_null(const void* p) const {
260 return p == NULL || is_in_reserved(p);
261 }
262
263 // Returns "TRUE" iff "p" points into the committed areas of the heap.
264 // This method can be expensive so avoid using it in performance critical
265 // code.
266 virtual bool is_in(const void* p) const = 0;
267
268 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
269
270 // Let's define some terms: a "closed" subset of a heap is one that
271 //
272 // 1) contains all currently-allocated objects, and
273 //
274 // 2) is closed under reference: no object in the closed subset
275 // references one outside the closed subset.
276 //
277 // Membership in a heap's closed subset is useful for assertions.
278 // Clearly, the entire heap is a closed subset, so the default
279 // implementation is to use "is_in_reserved". But this may not be too
280 // liberal to perform useful checking. Also, the "is_in" predicate
281 // defines a closed subset, but may be too expensive, since "is_in"
282 // verifies that its argument points to an object head. The
283 // "closed_subset" method allows a heap to define an intermediate
284 // predicate, allowing more precise checking than "is_in_reserved" at
285 // lower cost than "is_in."
286
287 // One important case is a heap composed of disjoint contiguous spaces,
288 // such as the Garbage-First collector. Such heaps have a convenient
289 // closed subset consisting of the allocated portions of those
290 // contiguous spaces.
291
292 // Return "TRUE" iff the given pointer points into the heap's defined
293 // closed subset (which defaults to the entire heap).
294 virtual bool is_in_closed_subset(const void* p) const {
295 return is_in_reserved(p);
296 }
297
298 bool is_in_closed_subset_or_null(const void* p) const {
299 return p == NULL || is_in_closed_subset(p);
300 }
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 // General obj/array allocation facilities.
313 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
314 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
315 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
316 inline static oop class_allocate(Klass* klass, int size, TRAPS);
317
318 // Raw memory allocation facilities
319 // The obj and array allocate methods are covers for these methods.
320 // mem_allocate() should never be
321 // called to allocate TLABs, only individual objects.
322 virtual HeapWord* mem_allocate(size_t size,
323 bool* gc_overhead_limit_was_exceeded) = 0;
324
325 // Utilities for turning raw memory into filler objects.
326 //
327 // min_fill_size() is the smallest region that can be filled.
328 // fill_with_objects() can fill arbitrary-sized regions of the heap using
329 // multiple objects. fill_with_object() is for regions known to be smaller
330 // than the largest array of integers; it uses a single object to fill the
331 // region and has slightly less overhead.
332 static size_t min_fill_size() {
333 return size_t(align_object_size(oopDesc::header_size()));
334 }
335
336 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
337
338 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
339 static void fill_with_object(MemRegion region, bool zap = true) {
340 fill_with_object(region.start(), region.word_size(), zap);
341 }
342 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
343 fill_with_object(start, pointer_delta(end, start), zap);
344 }
345
346 // Return the address "addr" aligned by "alignment_in_bytes" if such
347 // an address is below "end". Return NULL otherwise.
348 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
349 HeapWord* end,
350 unsigned short alignment_in_bytes);
351
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.)
355
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* volatile* 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 }
372
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);
389
390 // Section on thread-local allocation buffers (TLABs)
391 // If the heap supports thread-local allocation buffers, it should override
392 // the following methods:
393 // Returns "true" iff the heap supports thread-local allocation buffers.
394 // The default is "no".
395 virtual bool supports_tlab_allocation() const = 0;
396
397 // The amount of space available for thread-local allocation buffers.
398 virtual size_t tlab_capacity(Thread *thr) const = 0;
399
400 // The amount of used space for thread-local allocation buffers for the given thread.
401 virtual size_t tlab_used(Thread *thr) const = 0;
402
403 virtual size_t max_tlab_size() const;
404
405 // An estimate of the maximum allocation that could be performed
406 // for thread-local allocation buffers without triggering any
407 // collection or expansion activity.
408 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
409 guarantee(false, "thread-local allocation buffers not supported");
410 return 0;
411 }
412
413 // Can a compiler initialize a new object without store barriers?
414 // This permission only extends from the creation of a new object
415 // via a TLAB up to the first subsequent safepoint. If such permission
416 // is granted for this heap type, the compiler promises to call
417 // defer_store_barrier() below on any slow path allocation of
418 // a new object for which such initializing store barriers will
419 // have been elided.
420 virtual bool can_elide_tlab_store_barriers() const = 0;
421
422 // If a compiler is eliding store barriers for TLAB-allocated objects,
423 // there is probably a corresponding slow path which can produce
424 // an object allocated anywhere. The compiler's runtime support
425 // promises to call this function on such a slow-path-allocated
426 // object before performing initializations that have elided
427 // store barriers. Returns new_obj, or maybe a safer copy thereof.
428 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
429
430 // Answers whether an initializing store to a new object currently
431 // allocated at the given address doesn't need a store
432 // barrier. Returns "true" if it doesn't need an initializing
433 // store barrier; answers "false" if it does.
434 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
435
436 // If a compiler is eliding store barriers for TLAB-allocated objects,
437 // we will be informed of a slow-path allocation by a call
438 // to new_store_pre_barrier() above. Such a call precedes the
439 // initialization of the object itself, and no post-store-barriers will
440 // be issued. Some heap types require that the barrier strictly follows
441 // the initializing stores. (This is currently implemented by deferring the
442 // barrier until the next slow-path allocation or gc-related safepoint.)
443 // This interface answers whether a particular heap type needs the card
444 // mark to be thus strictly sequenced after the stores.
445 virtual bool card_mark_must_follow_store() const = 0;
446
447 // If the CollectedHeap was asked to defer a store barrier above,
448 // this informs it to flush such a deferred store barrier to the
449 // remembered set.
450 virtual void flush_deferred_store_barrier(JavaThread* thread);
451
452 // Perform a collection of the heap; intended for use in implementing
453 // "System.gc". This probably implies as full a collection as the
454 // "CollectedHeap" supports.
455 virtual void collect(GCCause::Cause cause) = 0;
456
457 // Perform a full collection
458 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
459
460 // This interface assumes that it's being called by the
461 // vm thread. It collects the heap assuming that the
462 // heap lock is already held and that we are executing in
463 // the context of the vm thread.
464 virtual void collect_as_vm_thread(GCCause::Cause cause);
465
466 // Returns the barrier set for this heap
467 BarrierSet* barrier_set() { return _barrier_set; }
468 void set_barrier_set(BarrierSet* barrier_set);
469
470 GCServicabilitySupport* servicability_support();
471
472 // Returns "true" iff there is a stop-world GC in progress. (I assume
473 // that it should answer "false" for the concurrent part of a concurrent
474 // collector -- dld).
475 bool is_gc_active() const { return _is_gc_active; }
476
477 // Total number of GC collections (started)
478 unsigned int total_collections() const { return _total_collections; }
479 unsigned int total_full_collections() const { return _total_full_collections;}
480
481 // Increment total number of GC collections (started)
482 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
483 void increment_total_collections(bool full = false) {
484 _total_collections++;
485 if (full) {
486 increment_total_full_collections();
487 }
488 }
489
490 void increment_total_full_collections() { _total_full_collections++; }
491
492 // Return the CollectorPolicy for the heap
493 virtual CollectorPolicy* collector_policy() const = 0;
494
495 // Iterate over all objects, calling "cl.do_object" on each.
496 virtual void object_iterate(ObjectClosure* cl) = 0;
497
498 // Similar to object_iterate() except iterates only
499 // over live objects.
500 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
501
502 // NOTE! There is no requirement that a collector implement these
503 // functions.
504 //
505 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
506 // each address in the (reserved) heap is a member of exactly
507 // one block. The defining characteristic of a block is that it is
508 // possible to find its size, and thus to progress forward to the next
509 // block. (Blocks may be of different sizes.) Thus, blocks may
510 // represent Java objects, or they might be free blocks in a
511 // free-list-based heap (or subheap), as long as the two kinds are
512 // distinguishable and the size of each is determinable.
513
514 // Returns the address of the start of the "block" that contains the
515 // address "addr". We say "blocks" instead of "object" since some heaps
516 // may not pack objects densely; a chunk may either be an object or a
517 // non-object.
518 virtual HeapWord* block_start(const void* addr) const = 0;
519
520 // Requires "addr" to be the start of a chunk, and returns its size.
521 // "addr + size" is required to be the start of a new chunk, or the end
522 // of the active area of the heap.
523 virtual size_t block_size(const HeapWord* addr) const = 0;
524
525 // Requires "addr" to be the start of a block, and returns "TRUE" iff
526 // the block is an object.
527 virtual bool block_is_obj(const HeapWord* addr) const = 0;
528
529 // Returns the longest time (in ms) that has elapsed since the last
530 // time that any part of the heap was examined by a garbage collection.
531 virtual jlong millis_since_last_gc() = 0;
532
533 // Perform any cleanup actions necessary before allowing a verification.
534 virtual void prepare_for_verify() = 0;
535
536 // Generate any dumps preceding or following a full gc
537 private:
538 void full_gc_dump(GCTimer* timer, bool before);
539 public:
540 void pre_full_gc_dump(GCTimer* timer);
541 void post_full_gc_dump(GCTimer* timer);
542
543 VirtualSpaceSummary create_heap_space_summary();
544 GCHeapSummary create_heap_summary();
545
546 MetaspaceSummary create_metaspace_summary();
547
548 // Print heap information on the given outputStream.
549 virtual void print_on(outputStream* st) const = 0;
550 // The default behavior is to call print_on() on tty.
551 virtual void print() const {
552 print_on(tty);
553 }
554 // Print more detailed heap information on the given
555 // outputStream. The default behavior is to call print_on(). It is
556 // up to each subclass to override it and add any additional output
557 // it needs.
558 virtual void print_extended_on(outputStream* st) const {
559 print_on(st);
560 }
561
562 virtual void print_on_error(outputStream* st) const;
563
564 // Print all GC threads (other than the VM thread)
565 // used by this heap.
566 virtual void print_gc_threads_on(outputStream* st) const = 0;
567 // The default behavior is to call print_gc_threads_on() on tty.
568 void print_gc_threads() {
569 print_gc_threads_on(tty);
570 }
571 // Iterator for all GC threads (other than VM thread)
572 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
573
574 // Print any relevant tracing info that flags imply.
575 // Default implementation does nothing.
576 virtual void print_tracing_info() const = 0;
577
578 void print_heap_before_gc();
579 void print_heap_after_gc();
580
581 // An object is scavengable if its location may move during a scavenge.
582 // (A scavenge is a GC which is not a full GC.)
583 virtual bool is_scavengable(oop obj) = 0;
584 // Registering and unregistering an nmethod (compiled code) with the heap.
585 // Override with specific mechanism for each specialized heap type.
586 virtual void register_nmethod(nmethod* nm) {}
587 virtual void unregister_nmethod(nmethod* nm) {}
588 virtual void verify_nmethod(nmethod* nmethod) {}
589
590 void trace_heap_before_gc(const GCTracer* gc_tracer);
591 void trace_heap_after_gc(const GCTracer* gc_tracer);
592
593 // Heap verification
594 virtual void verify(VerifyOption option) = 0;
595
596 // Return true if concurrent phase control (via
597 // request_concurrent_phase_control) is supported by this collector.
598 // The default implementation returns false.
599 virtual bool supports_concurrent_phase_control() const;
600
601 // Return a NULL terminated array of concurrent phase names provided
602 // by this collector. Supports Whitebox testing. These are the
603 // names recognized by request_concurrent_phase(). The default
604 // implementation returns an array of one NULL element.
605 virtual const char* const* concurrent_phases() const;
606
607 // Request the collector enter the indicated concurrent phase, and
608 // wait until it does so. Supports WhiteBox testing. Only one
609 // request may be active at a time. Phases are designated by name;
610 // the set of names and their meaning is GC-specific. Once the
611 // requested phase has been reached, the collector will attempt to
612 // avoid transitioning to a new phase until a new request is made.
613 // [Note: A collector might not be able to remain in a given phase.
614 // For example, a full collection might cancel an in-progress
615 // concurrent collection.]
616 //
617 // Returns true when the phase is reached. Returns false for an
618 // unknown phase. The default implementation returns false.
619 virtual bool request_concurrent_phase(const char* phase);
620
621 // Provides a thread pool to SafepointSynchronize to use
622 // for parallel safepoint cleanup.
623 // GCs that use a GC worker thread pool may want to share
624 // it for use during safepoint cleanup. This is only possible
625 // if the GC can pause and resume concurrent work (e.g. G1
626 // concurrent marking) for an intermittent non-GC safepoint.
627 // If this method returns NULL, SafepointSynchronize will
628 // perform cleanup tasks serially in the VMThread.
629 virtual WorkGang* get_safepoint_workers() { return NULL; }
630
631 // Non product verification and debugging.
632 #ifndef PRODUCT
633 // Support for PromotionFailureALot. Return true if it's time to cause a
634 // promotion failure. The no-argument version uses
635 // this->_promotion_failure_alot_count as the counter.
636 inline bool promotion_should_fail(volatile size_t* count);
637 inline bool promotion_should_fail();
638
639 // Reset the PromotionFailureALot counters. Should be called at the end of a
640 // GC in which promotion failure occurred.
641 inline void reset_promotion_should_fail(volatile size_t* count);
642 inline void reset_promotion_should_fail();
643 #endif // #ifndef PRODUCT
644
645 #ifdef ASSERT
646 static int fired_fake_oom() {
647 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
648 }
649 #endif
650
651 public:
652 // Copy the current allocation context statistics for the specified contexts.
653 // For each context in contexts, set the corresponding entries in the totals
654 // and accuracy arrays to the current values held by the statistics. Each
655 // array should be of length len.
656 // Returns true if there are more stats available.
657 virtual bool copy_allocation_context_stats(const jint* contexts,
658 jlong* totals,
659 jbyte* accuracy,
660 jint len) {
661 return false;
662 }
663
664 };
665
666 // Class to set and reset the GC cause for a CollectedHeap.
667
668 class GCCauseSetter : StackObj {
669 CollectedHeap* _heap;
670 GCCause::Cause _previous_cause;
671 public:
672 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
673 assert(SafepointSynchronize::is_at_safepoint(),
674 "This method manipulates heap state without locking");
675 _heap = heap;
676 _previous_cause = _heap->gc_cause();
677 _heap->set_gc_cause(cause);
678 }
679
680 ~GCCauseSetter() {
681 assert(SafepointSynchronize::is_at_safepoint(),
682 "This method manipulates heap state without locking");
683 _heap->set_gc_cause(_previous_cause);
684 }
685 };
686
687 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP