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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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 #include "utilities/growableArray.hpp"
38
39 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
40 // is an abstract class: there may be many different kinds of heaps. This
41 // class defines the functions that a heap must implement, and contains
42 // infrastructure common to all heaps.
43
44 class AdaptiveSizePolicy;
45 class BarrierSet;
46 class CollectorPolicy;
47 class GCHeapSummary;
48 class GCTimer;
49 class GCTracer;
50 class GCMemoryManager;
51 class MemoryPool;
52 class MetaspaceSummary;
53 class Thread;
54 class ThreadClosure;
55 class VirtualSpaceSummary;
56 class WorkGang;
57 class nmethod;
58
59 class GCMessage : public FormatBuffer<1024> {
60 public:
61 bool is_before;
62
63 public:
64 GCMessage() {}
65 };
66
67 class CollectedHeap;
68
69 class GCHeapLog : public EventLogBase<GCMessage> {
70 private:
71 void log_heap(CollectedHeap* heap, bool before);
72
73 public:
74 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
75
76 void log_heap_before(CollectedHeap* heap) {
77 log_heap(heap, true);
78 }
79 void log_heap_after(CollectedHeap* heap) {
80 log_heap(heap, false);
81 }
82 };
83
84 //
85 // CollectedHeap
86 // GenCollectedHeap
87 // SerialHeap
88 // CMSHeap
89 // G1CollectedHeap
90 // ParallelScavengeHeap
91 //
92 class CollectedHeap : public CHeapObj<mtInternal> {
93 friend class VMStructs;
94 friend class JVMCIVMStructs;
95 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
96
97 private:
98 #ifdef ASSERT
99 static int _fire_out_of_memory_count;
100 #endif
101
102 GCHeapLog* _gc_heap_log;
103
104 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
105 // or INCLUDE_JVMCI is being used
106 bool _defer_initial_card_mark;
107
108 MemRegion _reserved;
109
110 protected:
111 BarrierSet* _barrier_set;
112 bool _is_gc_active;
113
114 // Used for filler objects (static, but initialized in ctor).
115 static size_t _filler_array_max_size;
116
117 unsigned int _total_collections; // ... started
118 unsigned int _total_full_collections; // ... started
119 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
120 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
121
122 // Reason for current garbage collection. Should be set to
123 // a value reflecting no collection between collections.
124 GCCause::Cause _gc_cause;
125 GCCause::Cause _gc_lastcause;
126 PerfStringVariable* _perf_gc_cause;
127 PerfStringVariable* _perf_gc_lastcause;
128
129 // Constructor
130 CollectedHeap();
131
132 // Do common initializations that must follow instance construction,
133 // for example, those needing virtual calls.
134 // This code could perhaps be moved into initialize() but would
135 // be slightly more awkward because we want the latter to be a
136 // pure virtual.
137 void pre_initialize();
138
139 // Create a new tlab. All TLAB allocations must go through this.
140 virtual HeapWord* allocate_new_tlab(size_t size);
141
142 // Accumulate statistics on all tlabs.
143 virtual void accumulate_statistics_all_tlabs();
144
145 // Reinitialize tlabs before resuming mutators.
146 virtual void resize_all_tlabs();
147
148 // Allocate from the current thread's TLAB, with broken-out slow path.
149 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size);
150 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size);
151
152 // Allocate an uninitialized block of the given size, or returns NULL if
153 // this is impossible.
154 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);
155
156 // Like allocate_init, but the block returned by a successful allocation
157 // is guaranteed initialized to zeros.
158 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);
159
160 // Helper functions for (VM) allocation.
161 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);
162 inline static void post_allocation_setup_no_klass_install(Klass* klass,
163 HeapWord* objPtr);
164
165 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);
166
167 inline static void post_allocation_setup_array(Klass* klass,
168 HeapWord* obj, int length);
169
170 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);
171
172 // Clears an allocated object.
173 inline static void init_obj(HeapWord* obj, size_t size);
174
175 // Filler object utilities.
176 static inline size_t filler_array_hdr_size();
177 static inline size_t filler_array_min_size();
178
179 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
180 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
181
182 // Fill with a single array; caller must ensure filler_array_min_size() <=
183 // words <= filler_array_max_size().
184 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
185
186 // Fill with a single object (either an int array or a java.lang.Object).
187 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
188
189 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
190
191 // Verification functions
192 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
193 PRODUCT_RETURN;
194 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
195 PRODUCT_RETURN;
196 debug_only(static void check_for_valid_allocation_state();)
197
198 public:
199 enum Name {
200 SerialHeap,
201 ParallelScavengeHeap,
202 G1CollectedHeap,
203 CMSHeap
204 };
205
206 static inline size_t filler_array_max_size() {
207 return _filler_array_max_size;
208 }
209
210 virtual Name kind() const = 0;
211
212 virtual const char* name() const = 0;
213
214 /**
215 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
216 * and JNI_OK on success.
217 */
218 virtual jint initialize() = 0;
219
220 // In many heaps, there will be a need to perform some initialization activities
221 // after the Universe is fully formed, but before general heap allocation is allowed.
222 // This is the correct place to place such initialization methods.
223 virtual void post_initialize();
224
225 // Stop any onging concurrent work and prepare for exit.
226 virtual void stop() {}
227
228 // Stop and resume concurrent GC threads interfering with safepoint operations
229 virtual void safepoint_synchronize_begin() {}
230 virtual void safepoint_synchronize_end() {}
231
232 void initialize_reserved_region(HeapWord *start, HeapWord *end);
233 MemRegion reserved_region() const { return _reserved; }
234 address base() const { return (address)reserved_region().start(); }
235
236 virtual size_t capacity() const = 0;
237 virtual size_t used() const = 0;
238
239 // Return "true" if the part of the heap that allocates Java
240 // objects has reached the maximal committed limit that it can
241 // reach, without a garbage collection.
242 virtual bool is_maximal_no_gc() const = 0;
243
244 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
245 // memory that the vm could make available for storing 'normal' java objects.
246 // This is based on the reserved address space, but should not include space
247 // that the vm uses internally for bookkeeping or temporary storage
248 // (e.g., in the case of the young gen, one of the survivor
249 // spaces).
250 virtual size_t max_capacity() const = 0;
251
252 // Returns "TRUE" if "p" points into the reserved area of the heap.
253 bool is_in_reserved(const void* p) const {
254 return _reserved.contains(p);
255 }
256
257 bool is_in_reserved_or_null(const void* p) const {
258 return p == NULL || is_in_reserved(p);
259 }
260
261 // Returns "TRUE" iff "p" points into the committed areas of the heap.
262 // This method can be expensive so avoid using it in performance critical
263 // code.
264 virtual bool is_in(const void* p) const = 0;
265
266 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
267
268 // Let's define some terms: a "closed" subset of a heap is one that
269 //
270 // 1) contains all currently-allocated objects, and
271 //
272 // 2) is closed under reference: no object in the closed subset
273 // references one outside the closed subset.
274 //
275 // Membership in a heap's closed subset is useful for assertions.
276 // Clearly, the entire heap is a closed subset, so the default
277 // implementation is to use "is_in_reserved". But this may not be too
278 // liberal to perform useful checking. Also, the "is_in" predicate
279 // defines a closed subset, but may be too expensive, since "is_in"
280 // verifies that its argument points to an object head. The
281 // "closed_subset" method allows a heap to define an intermediate
282 // predicate, allowing more precise checking than "is_in_reserved" at
283 // lower cost than "is_in."
284
285 // One important case is a heap composed of disjoint contiguous spaces,
286 // such as the Garbage-First collector. Such heaps have a convenient
287 // closed subset consisting of the allocated portions of those
288 // contiguous spaces.
289
290 // Return "TRUE" iff the given pointer points into the heap's defined
291 // closed subset (which defaults to the entire heap).
292 virtual bool is_in_closed_subset(const void* p) const {
293 return is_in_reserved(p);
294 }
295
296 bool is_in_closed_subset_or_null(const void* p) const {
297 return p == NULL || is_in_closed_subset(p);
298 }
299
300 void set_gc_cause(GCCause::Cause v) {
301 if (UsePerfData) {
302 _gc_lastcause = _gc_cause;
303 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
304 _perf_gc_cause->set_value(GCCause::to_string(v));
305 }
306 _gc_cause = v;
307 }
308 GCCause::Cause gc_cause() { return _gc_cause; }
309
310 // General obj/array allocation facilities.
311 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
312 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
313 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
314 inline static oop class_allocate(Klass* klass, int size, TRAPS);
315
316 // Raw memory allocation facilities
317 // The obj and array allocate methods are covers for these methods.
318 // mem_allocate() should never be
319 // called to allocate TLABs, only individual objects.
320 virtual HeapWord* mem_allocate(size_t size,
321 bool* gc_overhead_limit_was_exceeded) = 0;
322
323 // Utilities for turning raw memory into filler objects.
324 //
325 // min_fill_size() is the smallest region that can be filled.
326 // fill_with_objects() can fill arbitrary-sized regions of the heap using
327 // multiple objects. fill_with_object() is for regions known to be smaller
328 // than the largest array of integers; it uses a single object to fill the
329 // region and has slightly less overhead.
330 static size_t min_fill_size() {
331 return size_t(align_object_size(oopDesc::header_size()));
332 }
333
334 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
335
336 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
337 static void fill_with_object(MemRegion region, bool zap = true) {
338 fill_with_object(region.start(), region.word_size(), zap);
339 }
340 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
341 fill_with_object(start, pointer_delta(end, start), zap);
342 }
343
344 // Return the address "addr" aligned by "alignment_in_bytes" if such
345 // an address is below "end". Return NULL otherwise.
346 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
347 HeapWord* end,
348 unsigned short alignment_in_bytes);
349
350 // Some heaps may offer a contiguous region for shared non-blocking
351 // allocation, via inlined code (by exporting the address of the top and
352 // end fields defining the extent of the contiguous allocation region.)
353
354 // This function returns "true" iff the heap supports this kind of
355 // allocation. (Default is "no".)
356 virtual bool supports_inline_contig_alloc() const {
357 return false;
358 }
359 // These functions return the addresses of the fields that define the
360 // boundaries of the contiguous allocation area. (These fields should be
361 // physically near to one another.)
362 virtual HeapWord* volatile* top_addr() const {
363 guarantee(false, "inline contiguous allocation not supported");
364 return NULL;
365 }
366 virtual HeapWord** end_addr() const {
367 guarantee(false, "inline contiguous allocation not supported");
368 return NULL;
369 }
370
371 // Some heaps may be in an unparseable state at certain times between
372 // collections. This may be necessary for efficient implementation of
373 // certain allocation-related activities. Calling this function before
374 // attempting to parse a heap ensures that the heap is in a parsable
375 // state (provided other concurrent activity does not introduce
376 // unparsability). It is normally expected, therefore, that this
377 // method is invoked with the world stopped.
378 // NOTE: if you override this method, make sure you call
379 // super::ensure_parsability so that the non-generational
380 // part of the work gets done. See implementation of
381 // CollectedHeap::ensure_parsability and, for instance,
382 // that of GenCollectedHeap::ensure_parsability().
383 // The argument "retire_tlabs" controls whether existing TLABs
384 // are merely filled or also retired, thus preventing further
385 // allocation from them and necessitating allocation of new TLABs.
386 virtual void ensure_parsability(bool retire_tlabs);
387
388 // Section on thread-local allocation buffers (TLABs)
389 // If the heap supports thread-local allocation buffers, it should override
390 // the following methods:
391 // Returns "true" iff the heap supports thread-local allocation buffers.
392 // The default is "no".
393 virtual bool supports_tlab_allocation() const = 0;
394
395 // The amount of space available for thread-local allocation buffers.
396 virtual size_t tlab_capacity(Thread *thr) const = 0;
397
398 // The amount of used space for thread-local allocation buffers for the given thread.
399 virtual size_t tlab_used(Thread *thr) const = 0;
400
401 virtual size_t max_tlab_size() const;
402
403 // An estimate of the maximum allocation that could be performed
404 // for thread-local allocation buffers without triggering any
405 // collection or expansion activity.
406 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
407 guarantee(false, "thread-local allocation buffers not supported");
408 return 0;
409 }
410
411 // Can a compiler initialize a new object without store barriers?
412 // This permission only extends from the creation of a new object
413 // via a TLAB up to the first subsequent safepoint. If such permission
414 // is granted for this heap type, the compiler promises to call
415 // defer_store_barrier() below on any slow path allocation of
416 // a new object for which such initializing store barriers will
417 // have been elided.
418 virtual bool can_elide_tlab_store_barriers() const = 0;
419
420 // If a compiler is eliding store barriers for TLAB-allocated objects,
421 // there is probably a corresponding slow path which can produce
422 // an object allocated anywhere. The compiler's runtime support
423 // promises to call this function on such a slow-path-allocated
424 // object before performing initializations that have elided
425 // store barriers. Returns new_obj, or maybe a safer copy thereof.
426 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
427
428 // Answers whether an initializing store to a new object currently
429 // allocated at the given address doesn't need a store
430 // barrier. Returns "true" if it doesn't need an initializing
431 // store barrier; answers "false" if it does.
432 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
433
434 // If a compiler is eliding store barriers for TLAB-allocated objects,
435 // we will be informed of a slow-path allocation by a call
436 // to new_store_pre_barrier() above. Such a call precedes the
437 // initialization of the object itself, and no post-store-barriers will
438 // be issued. Some heap types require that the barrier strictly follows
439 // the initializing stores. (This is currently implemented by deferring the
440 // barrier until the next slow-path allocation or gc-related safepoint.)
441 // This interface answers whether a particular heap type needs the card
442 // mark to be thus strictly sequenced after the stores.
443 virtual bool card_mark_must_follow_store() const = 0;
444
445 // If the CollectedHeap was asked to defer a store barrier above,
446 // this informs it to flush such a deferred store barrier to the
447 // remembered set.
448 virtual void flush_deferred_store_barrier(JavaThread* thread);
449
450 // Perform a collection of the heap; intended for use in implementing
451 // "System.gc". This probably implies as full a collection as the
452 // "CollectedHeap" supports.
453 virtual void collect(GCCause::Cause cause) = 0;
454
455 // Perform a full collection
456 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
457
458 // This interface assumes that it's being called by the
459 // vm thread. It collects the heap assuming that the
460 // heap lock is already held and that we are executing in
461 // the context of the vm thread.
462 virtual void collect_as_vm_thread(GCCause::Cause cause);
463
464 // Returns the barrier set for this heap
465 BarrierSet* barrier_set() { return _barrier_set; }
466 void set_barrier_set(BarrierSet* barrier_set);
467
468 // Returns "true" iff there is a stop-world GC in progress. (I assume
469 // that it should answer "false" for the concurrent part of a concurrent
470 // collector -- dld).
471 bool is_gc_active() const { return _is_gc_active; }
472
473 // Total number of GC collections (started)
474 unsigned int total_collections() const { return _total_collections; }
475 unsigned int total_full_collections() const { return _total_full_collections;}
476
477 // Increment total number of GC collections (started)
478 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
479 void increment_total_collections(bool full = false) {
480 _total_collections++;
481 if (full) {
482 increment_total_full_collections();
483 }
484 }
485
486 void increment_total_full_collections() { _total_full_collections++; }
487
488 // Return the CollectorPolicy for the heap
489 virtual CollectorPolicy* collector_policy() const = 0;
490
491 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
492 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
493
494 // Iterate over all objects, calling "cl.do_object" on each.
495 virtual void object_iterate(ObjectClosure* cl) = 0;
496
497 // Similar to object_iterate() except iterates only
498 // over live objects.
499 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
500
501 // NOTE! There is no requirement that a collector implement these
502 // functions.
503 //
504 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
505 // each address in the (reserved) heap is a member of exactly
506 // one block. The defining characteristic of a block is that it is
507 // possible to find its size, and thus to progress forward to the next
508 // block. (Blocks may be of different sizes.) Thus, blocks may
509 // represent Java objects, or they might be free blocks in a
510 // free-list-based heap (or subheap), as long as the two kinds are
511 // distinguishable and the size of each is determinable.
512
513 // Returns the address of the start of the "block" that contains the
514 // address "addr". We say "blocks" instead of "object" since some heaps
515 // may not pack objects densely; a chunk may either be an object or a
516 // non-object.
517 virtual HeapWord* block_start(const void* addr) const = 0;
518
519 // Requires "addr" to be the start of a chunk, and returns its size.
520 // "addr + size" is required to be the start of a new chunk, or the end
521 // of the active area of the heap.
522 virtual size_t block_size(const HeapWord* addr) const = 0;
523
524 // Requires "addr" to be the start of a block, and returns "TRUE" iff
525 // the block is an object.
526 virtual bool block_is_obj(const HeapWord* addr) const = 0;
527
528 // Returns the longest time (in ms) that has elapsed since the last
529 // time that any part of the heap was examined by a garbage collection.
530 virtual jlong millis_since_last_gc() = 0;
531
532 // Perform any cleanup actions necessary before allowing a verification.
533 virtual void prepare_for_verify() = 0;
534
535 // Generate any dumps preceding or following a full gc
536 private:
537 void full_gc_dump(GCTimer* timer, bool before);
538
539 virtual void initialize_serviceability() = 0;
540
541 public:
542 void pre_full_gc_dump(GCTimer* timer);
543 void post_full_gc_dump(GCTimer* timer);
544
545 VirtualSpaceSummary create_heap_space_summary();
546 GCHeapSummary create_heap_summary();
547
548 MetaspaceSummary create_metaspace_summary();
549
550 // Print heap information on the given outputStream.
551 virtual void print_on(outputStream* st) const = 0;
552 // The default behavior is to call print_on() on tty.
553 virtual void print() const {
554 print_on(tty);
555 }
556 // Print more detailed heap information on the given
557 // outputStream. The default behavior is to call print_on(). It is
558 // up to each subclass to override it and add any additional output
559 // it needs.
560 virtual void print_extended_on(outputStream* st) const {
561 print_on(st);
562 }
563
564 virtual void print_on_error(outputStream* st) const;
565
566 // Print all GC threads (other than the VM thread)
567 // used by this heap.
568 virtual void print_gc_threads_on(outputStream* st) const = 0;
569 // The default behavior is to call print_gc_threads_on() on tty.
570 void print_gc_threads() {
571 print_gc_threads_on(tty);
572 }
573 // Iterator for all GC threads (other than VM thread)
574 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
575
576 // Print any relevant tracing info that flags imply.
577 // Default implementation does nothing.
578 virtual void print_tracing_info() const = 0;
579
580 void print_heap_before_gc();
581 void print_heap_after_gc();
582
583 // An object is scavengable if its location may move during a scavenge.
584 // (A scavenge is a GC which is not a full GC.)
585 virtual bool is_scavengable(oop obj) = 0;
586 // Registering and unregistering an nmethod (compiled code) with the heap.
587 // Override with specific mechanism for each specialized heap type.
588 virtual void register_nmethod(nmethod* nm) {}
589 virtual void unregister_nmethod(nmethod* nm) {}
590 virtual void verify_nmethod(nmethod* nmethod) {}
591
592 void trace_heap_before_gc(const GCTracer* gc_tracer);
593 void trace_heap_after_gc(const GCTracer* gc_tracer);
594
595 // Heap verification
596 virtual void verify(VerifyOption option) = 0;
597
598 // Return true if concurrent phase control (via
599 // request_concurrent_phase_control) is supported by this collector.
600 // The default implementation returns false.
601 virtual bool supports_concurrent_phase_control() const;
602
603 // Return a NULL terminated array of concurrent phase names provided
604 // by this collector. Supports Whitebox testing. These are the
605 // names recognized by request_concurrent_phase(). The default
606 // implementation returns an array of one NULL element.
607 virtual const char* const* concurrent_phases() const;
608
609 // Request the collector enter the indicated concurrent phase, and
610 // wait until it does so. Supports WhiteBox testing. Only one
611 // request may be active at a time. Phases are designated by name;
612 // the set of names and their meaning is GC-specific. Once the
613 // requested phase has been reached, the collector will attempt to
614 // avoid transitioning to a new phase until a new request is made.
615 // [Note: A collector might not be able to remain in a given phase.
616 // For example, a full collection might cancel an in-progress
617 // concurrent collection.]
618 //
619 // Returns true when the phase is reached. Returns false for an
620 // unknown phase. The default implementation returns false.
621 virtual bool request_concurrent_phase(const char* phase);
622
623 // Provides a thread pool to SafepointSynchronize to use
624 // for parallel safepoint cleanup.
625 // GCs that use a GC worker thread pool may want to share
626 // it for use during safepoint cleanup. This is only possible
627 // if the GC can pause and resume concurrent work (e.g. G1
628 // concurrent marking) for an intermittent non-GC safepoint.
629 // If this method returns NULL, SafepointSynchronize will
630 // perform cleanup tasks serially in the VMThread.
631 virtual WorkGang* get_safepoint_workers() { return NULL; }
632
633 // Non product verification and debugging.
634 #ifndef PRODUCT
635 // Support for PromotionFailureALot. Return true if it's time to cause a
636 // promotion failure. The no-argument version uses
637 // this->_promotion_failure_alot_count as the counter.
638 inline bool promotion_should_fail(volatile size_t* count);
639 inline bool promotion_should_fail();
640
641 // Reset the PromotionFailureALot counters. Should be called at the end of a
642 // GC in which promotion failure occurred.
643 inline void reset_promotion_should_fail(volatile size_t* count);
644 inline void reset_promotion_should_fail();
645 #endif // #ifndef PRODUCT
646
647 #ifdef ASSERT
648 static int fired_fake_oom() {
649 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
650 }
651 #endif
652
653 public:
654 // Copy the current allocation context statistics for the specified contexts.
655 // For each context in contexts, set the corresponding entries in the totals
656 // and accuracy arrays to the current values held by the statistics. Each
657 // array should be of length len.
658 // Returns true if there are more stats available.
659 virtual bool copy_allocation_context_stats(const jint* contexts,
660 jlong* totals,
661 jbyte* accuracy,
662 jint len) {
663 return false;
664 }
665
666 };
667
668 // Class to set and reset the GC cause for a CollectedHeap.
669
670 class GCCauseSetter : StackObj {
671 CollectedHeap* _heap;
672 GCCause::Cause _previous_cause;
673 public:
674 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
675 assert(SafepointSynchronize::is_at_safepoint(),
676 "This method manipulates heap state without locking");
677 _heap = heap;
678 _previous_cause = _heap->gc_cause();
679 _heap->set_gc_cause(cause);
680 }
681
682 ~GCCauseSetter() {
683 assert(SafepointSynchronize::is_at_safepoint(),
684 "This method manipulates heap state without locking");
685 _heap->set_gc_cause(_previous_cause);
686 }
687 };
688
689 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP