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 #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 // Sample the allocation via HeapMonitoring.
153 // overflowed_words represents the number of HeapWords that went past the
154 // sampling boundary. This is used to fix the next sampling rate.
155 static void sample_allocation(Thread* thread, HeapWord* obj, size_t size,
156 size_t overflowed_words = 0);
157 // Try to allocate the object we want to sample in this tlab, returns NULL if
158 // fails to allocate.
159 static HeapWord* allocate_sampled_object(Thread* thread, size_t size);
160
161 // Allocate an uninitialized block of the given size, or returns NULL if
162 // this is impossible.
163 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);
164
165 // Like allocate_init, but the block returned by a successful allocation
166 // is guaranteed initialized to zeros.
167 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);
168
169 // Helper functions for (VM) allocation.
170 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);
171 inline static void post_allocation_setup_no_klass_install(Klass* klass,
172 HeapWord* objPtr);
173
174 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);
175
176 inline static void post_allocation_setup_array(Klass* klass,
177 HeapWord* obj, int length);
178
179 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);
180
181 // Clears an allocated object.
182 inline static void init_obj(HeapWord* obj, size_t size);
183
184 // Filler object utilities.
185 static inline size_t filler_array_hdr_size();
186 static inline size_t filler_array_min_size();
187
188 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
189 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
190
191 // Fill with a single array; caller must ensure filler_array_min_size() <=
192 // words <= filler_array_max_size().
193 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
194
195 // Fill with a single object (either an int array or a java.lang.Object).
196 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
197
198 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
199
200 // Verification functions
201 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
202 PRODUCT_RETURN;
203 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
204 PRODUCT_RETURN;
205 debug_only(static void check_for_valid_allocation_state();)
206
207 public:
208 enum Name {
209 SerialHeap,
210 ParallelScavengeHeap,
211 G1CollectedHeap,
212 CMSHeap
213 };
214
215 static inline size_t filler_array_max_size() {
216 return _filler_array_max_size;
217 }
218
219 virtual Name kind() const = 0;
220
221 virtual const char* name() const = 0;
222
223 /**
224 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
225 * and JNI_OK on success.
226 */
227 virtual jint initialize() = 0;
228
229 // In many heaps, there will be a need to perform some initialization activities
230 // after the Universe is fully formed, but before general heap allocation is allowed.
231 // This is the correct place to place such initialization methods.
232 virtual void post_initialize();
233
234 // Stop any onging concurrent work and prepare for exit.
235 virtual void stop() {}
236
237 // Stop and resume concurrent GC threads interfering with safepoint operations
238 virtual void safepoint_synchronize_begin() {}
239 virtual void safepoint_synchronize_end() {}
240
241 void initialize_reserved_region(HeapWord *start, HeapWord *end);
242 MemRegion reserved_region() const { return _reserved; }
243 address base() const { return (address)reserved_region().start(); }
244
245 virtual size_t capacity() const = 0;
246 virtual size_t used() const = 0;
247
248 // Return "true" if the part of the heap that allocates Java
249 // objects has reached the maximal committed limit that it can
250 // reach, without a garbage collection.
251 virtual bool is_maximal_no_gc() const = 0;
252
253 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
254 // memory that the vm could make available for storing 'normal' java objects.
255 // This is based on the reserved address space, but should not include space
256 // that the vm uses internally for bookkeeping or temporary storage
257 // (e.g., in the case of the young gen, one of the survivor
258 // spaces).
259 virtual size_t max_capacity() const = 0;
260
261 // Returns "TRUE" if "p" points into the reserved area of the heap.
262 bool is_in_reserved(const void* p) const {
263 return _reserved.contains(p);
264 }
265
266 bool is_in_reserved_or_null(const void* p) const {
267 return p == NULL || is_in_reserved(p);
268 }
269
270 // Returns "TRUE" iff "p" points into the committed areas of the heap.
271 // This method can be expensive so avoid using it in performance critical
272 // code.
273 virtual bool is_in(const void* p) const = 0;
274
275 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
276
277 // Let's define some terms: a "closed" subset of a heap is one that
278 //
279 // 1) contains all currently-allocated objects, and
280 //
281 // 2) is closed under reference: no object in the closed subset
282 // references one outside the closed subset.
283 //
284 // Membership in a heap's closed subset is useful for assertions.
285 // Clearly, the entire heap is a closed subset, so the default
286 // implementation is to use "is_in_reserved". But this may not be too
287 // liberal to perform useful checking. Also, the "is_in" predicate
288 // defines a closed subset, but may be too expensive, since "is_in"
289 // verifies that its argument points to an object head. The
290 // "closed_subset" method allows a heap to define an intermediate
291 // predicate, allowing more precise checking than "is_in_reserved" at
292 // lower cost than "is_in."
293
294 // One important case is a heap composed of disjoint contiguous spaces,
295 // such as the Garbage-First collector. Such heaps have a convenient
296 // closed subset consisting of the allocated portions of those
297 // contiguous spaces.
298
299 // Return "TRUE" iff the given pointer points into the heap's defined
300 // closed subset (which defaults to the entire heap).
301 virtual bool is_in_closed_subset(const void* p) const {
302 return is_in_reserved(p);
303 }
304
305 bool is_in_closed_subset_or_null(const void* p) const {
306 return p == NULL || is_in_closed_subset(p);
307 }
308
309 void set_gc_cause(GCCause::Cause v) {
310 if (UsePerfData) {
311 _gc_lastcause = _gc_cause;
312 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
313 _perf_gc_cause->set_value(GCCause::to_string(v));
314 }
315 _gc_cause = v;
316 }
317 GCCause::Cause gc_cause() { return _gc_cause; }
318
319 // General obj/array allocation facilities.
320 inline static oop obj_allocate(Klass* klass, int size, TRAPS);
321 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
322 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
323 inline static oop class_allocate(Klass* klass, int size, TRAPS);
324
325 // Raw memory allocation facilities
326 // The obj and array allocate methods are covers for these methods.
327 // mem_allocate() should never be
328 // called to allocate TLABs, only individual objects.
329 virtual HeapWord* mem_allocate(size_t size,
330 bool* gc_overhead_limit_was_exceeded) = 0;
331
332 // Utilities for turning raw memory into filler objects.
333 //
334 // min_fill_size() is the smallest region that can be filled.
335 // fill_with_objects() can fill arbitrary-sized regions of the heap using
336 // multiple objects. fill_with_object() is for regions known to be smaller
337 // than the largest array of integers; it uses a single object to fill the
338 // region and has slightly less overhead.
339 static size_t min_fill_size() {
340 return size_t(align_object_size(oopDesc::header_size()));
341 }
342
343 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
344
345 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
346 static void fill_with_object(MemRegion region, bool zap = true) {
347 fill_with_object(region.start(), region.word_size(), zap);
348 }
349 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
350 fill_with_object(start, pointer_delta(end, start), zap);
351 }
352
353 // Return the address "addr" aligned by "alignment_in_bytes" if such
354 // an address is below "end". Return NULL otherwise.
355 inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
356 HeapWord* end,
357 unsigned short alignment_in_bytes);
358
359 // Some heaps may offer a contiguous region for shared non-blocking
360 // allocation, via inlined code (by exporting the address of the top and
361 // end fields defining the extent of the contiguous allocation region.)
362
363 // This function returns "true" iff the heap supports this kind of
364 // allocation. (Default is "no".)
365 virtual bool supports_inline_contig_alloc() const {
366 return false;
367 }
368 // These functions return the addresses of the fields that define the
369 // boundaries of the contiguous allocation area. (These fields should be
370 // physically near to one another.)
371 virtual HeapWord* volatile* top_addr() const {
372 guarantee(false, "inline contiguous allocation not supported");
373 return NULL;
374 }
375 virtual HeapWord** end_addr() const {
376 guarantee(false, "inline contiguous allocation not supported");
377 return NULL;
378 }
379
380 // Some heaps may be in an unparseable state at certain times between
381 // collections. This may be necessary for efficient implementation of
382 // certain allocation-related activities. Calling this function before
383 // attempting to parse a heap ensures that the heap is in a parsable
384 // state (provided other concurrent activity does not introduce
385 // unparsability). It is normally expected, therefore, that this
386 // method is invoked with the world stopped.
387 // NOTE: if you override this method, make sure you call
388 // super::ensure_parsability so that the non-generational
389 // part of the work gets done. See implementation of
390 // CollectedHeap::ensure_parsability and, for instance,
391 // that of GenCollectedHeap::ensure_parsability().
392 // The argument "retire_tlabs" controls whether existing TLABs
393 // are merely filled or also retired, thus preventing further
394 // allocation from them and necessitating allocation of new TLABs.
395 virtual void ensure_parsability(bool retire_tlabs);
396
397 // Section on thread-local allocation buffers (TLABs)
398 // If the heap supports thread-local allocation buffers, it should override
399 // the following methods:
400 // Returns "true" iff the heap supports thread-local allocation buffers.
401 // The default is "no".
402 virtual bool supports_tlab_allocation() const = 0;
403
404 // The amount of space available for thread-local allocation buffers.
405 virtual size_t tlab_capacity(Thread *thr) const = 0;
406
407 // The amount of used space for thread-local allocation buffers for the given thread.
408 virtual size_t tlab_used(Thread *thr) const = 0;
409
410 virtual size_t max_tlab_size() const;
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 }
419
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;
428
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);
436
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;
442
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;
453
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);
458
459 // Perform a collection of the heap; intended for use in implementing
460 // "System.gc". This probably implies as full a collection as the
461 // "CollectedHeap" supports.
462 virtual void collect(GCCause::Cause cause) = 0;
463
464 // Perform a full collection
465 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
466
467 // This interface assumes that it's being called by the
468 // vm thread. It collects the heap assuming that the
469 // heap lock is already held and that we are executing in
470 // the context of the vm thread.
471 virtual void collect_as_vm_thread(GCCause::Cause cause);
472
473 // Returns the barrier set for this heap
474 BarrierSet* barrier_set() { return _barrier_set; }
475 void set_barrier_set(BarrierSet* barrier_set);
476
477 // Returns "true" iff there is a stop-world GC in progress. (I assume
478 // that it should answer "false" for the concurrent part of a concurrent
479 // collector -- dld).
480 bool is_gc_active() const { return _is_gc_active; }
481
482 // Total number of GC collections (started)
483 unsigned int total_collections() const { return _total_collections; }
484 unsigned int total_full_collections() const { return _total_full_collections;}
485
486 // Increment total number of GC collections (started)
487 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
488 void increment_total_collections(bool full = false) {
489 _total_collections++;
490 if (full) {
491 increment_total_full_collections();
492 }
493 }
494
495 void increment_total_full_collections() { _total_full_collections++; }
496
497 // Return the CollectorPolicy for the heap
498 virtual CollectorPolicy* collector_policy() const = 0;
499
500 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
501 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
502
503 // Iterate over all objects, calling "cl.do_object" on each.
504 virtual void object_iterate(ObjectClosure* cl) = 0;
505
506 // Similar to object_iterate() except iterates only
507 // over live objects.
508 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
509
510 // NOTE! There is no requirement that a collector implement these
511 // functions.
512 //
513 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
514 // each address in the (reserved) heap is a member of exactly
515 // one block. The defining characteristic of a block is that it is
516 // possible to find its size, and thus to progress forward to the next
517 // block. (Blocks may be of different sizes.) Thus, blocks may
518 // represent Java objects, or they might be free blocks in a
519 // free-list-based heap (or subheap), as long as the two kinds are
520 // distinguishable and the size of each is determinable.
521
522 // Returns the address of the start of the "block" that contains the
523 // address "addr". We say "blocks" instead of "object" since some heaps
524 // may not pack objects densely; a chunk may either be an object or a
525 // non-object.
526 virtual HeapWord* block_start(const void* addr) const = 0;
527
528 // Requires "addr" to be the start of a chunk, and returns its size.
529 // "addr + size" is required to be the start of a new chunk, or the end
530 // of the active area of the heap.
531 virtual size_t block_size(const HeapWord* addr) const = 0;
532
533 // Requires "addr" to be the start of a block, and returns "TRUE" iff
534 // the block is an object.
535 virtual bool block_is_obj(const HeapWord* addr) const = 0;
536
537 // Returns the longest time (in ms) that has elapsed since the last
538 // time that any part of the heap was examined by a garbage collection.
539 virtual jlong millis_since_last_gc() = 0;
540
541 // Perform any cleanup actions necessary before allowing a verification.
542 virtual void prepare_for_verify() = 0;
543
544 // Generate any dumps preceding or following a full gc
545 private:
546 void full_gc_dump(GCTimer* timer, bool before);
547
548 virtual void initialize_serviceability() = 0;
549
550 public:
551 void pre_full_gc_dump(GCTimer* timer);
552 void post_full_gc_dump(GCTimer* timer);
553
554 VirtualSpaceSummary create_heap_space_summary();
555 GCHeapSummary create_heap_summary();
556
557 MetaspaceSummary create_metaspace_summary();
558
559 // Print heap information on the given outputStream.
560 virtual void print_on(outputStream* st) const = 0;
561 // The default behavior is to call print_on() on tty.
562 virtual void print() const {
563 print_on(tty);
564 }
565 // Print more detailed heap information on the given
566 // outputStream. The default behavior is to call print_on(). It is
567 // up to each subclass to override it and add any additional output
568 // it needs.
569 virtual void print_extended_on(outputStream* st) const {
570 print_on(st);
571 }
572
573 virtual void print_on_error(outputStream* st) const;
574
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;
584
585 // Print any relevant tracing info that flags imply.
586 // Default implementation does nothing.
587 virtual void print_tracing_info() const = 0;
588
589 void print_heap_before_gc();
590 void print_heap_after_gc();
591
592 // An object is scavengable if its location may move during a scavenge.
593 // (A scavenge is a GC which is not a full GC.)
594 virtual bool is_scavengable(oop obj) = 0;
595 // Registering and unregistering an nmethod (compiled code) with the heap.
596 // Override with specific mechanism for each specialized heap type.
597 virtual void register_nmethod(nmethod* nm) {}
598 virtual void unregister_nmethod(nmethod* nm) {}
599 virtual void verify_nmethod(nmethod* nmethod) {}
600
601 void trace_heap_before_gc(const GCTracer* gc_tracer);
602 void trace_heap_after_gc(const GCTracer* gc_tracer);
603
604 // Heap verification
605 virtual void verify(VerifyOption option) = 0;
606
607 // Return true if concurrent phase control (via
608 // request_concurrent_phase_control) is supported by this collector.
609 // The default implementation returns false.
610 virtual bool supports_concurrent_phase_control() const;
611
612 // Return a NULL terminated array of concurrent phase names provided
613 // by this collector. Supports Whitebox testing. These are the
614 // names recognized by request_concurrent_phase(). The default
615 // implementation returns an array of one NULL element.
616 virtual const char* const* concurrent_phases() const;
617
618 // Request the collector enter the indicated concurrent phase, and
619 // wait until it does so. Supports WhiteBox testing. Only one
620 // request may be active at a time. Phases are designated by name;
621 // the set of names and their meaning is GC-specific. Once the
622 // requested phase has been reached, the collector will attempt to
623 // avoid transitioning to a new phase until a new request is made.
624 // [Note: A collector might not be able to remain in a given phase.
625 // For example, a full collection might cancel an in-progress
626 // concurrent collection.]
627 //
628 // Returns true when the phase is reached. Returns false for an
629 // unknown phase. The default implementation returns false.
630 virtual bool request_concurrent_phase(const char* phase);
631
632 // Provides a thread pool to SafepointSynchronize to use
633 // for parallel safepoint cleanup.
634 // GCs that use a GC worker thread pool may want to share
635 // it for use during safepoint cleanup. This is only possible
636 // if the GC can pause and resume concurrent work (e.g. G1
637 // concurrent marking) for an intermittent non-GC safepoint.
638 // If this method returns NULL, SafepointSynchronize will
639 // perform cleanup tasks serially in the VMThread.
640 virtual WorkGang* get_safepoint_workers() { return NULL; }
641
642 // Non product verification and debugging.
643 #ifndef PRODUCT
644 // Support for PromotionFailureALot. Return true if it's time to cause a
645 // promotion failure. The no-argument version uses
646 // this->_promotion_failure_alot_count as the counter.
647 inline bool promotion_should_fail(volatile size_t* count);
648 inline bool promotion_should_fail();
649
650 // Reset the PromotionFailureALot counters. Should be called at the end of a
651 // GC in which promotion failure occurred.
652 inline void reset_promotion_should_fail(volatile size_t* count);
653 inline void reset_promotion_should_fail();
654 #endif // #ifndef PRODUCT
655
656 #ifdef ASSERT
657 static int fired_fake_oom() {
658 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
659 }
660 #endif
661
662 public:
663 // Copy the current allocation context statistics for the specified contexts.
664 // For each context in contexts, set the corresponding entries in the totals
665 // and accuracy arrays to the current values held by the statistics. Each
666 // array should be of length len.
667 // Returns true if there are more stats available.
668 virtual bool copy_allocation_context_stats(const jint* contexts,
669 jlong* totals,
670 jbyte* accuracy,
671 jint len) {
672 return false;
673 }
674
675 };
676
677 // Class to set and reset the GC cause for a CollectedHeap.
678
679 class GCCauseSetter : StackObj {
680 CollectedHeap* _heap;
681 GCCause::Cause _previous_cause;
682 public:
683 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
684 assert(SafepointSynchronize::is_at_safepoint(),
685 "This method manipulates heap state without locking");
686 _heap = heap;
687 _previous_cause = _heap->gc_cause();
688 _heap->set_gc_cause(cause);
689 }
690
691 ~GCCauseSetter() {
692 assert(SafepointSynchronize::is_at_safepoint(),
693 "This method manipulates heap state without locking");
694 _heap->set_gc_cause(_previous_cause);
695 }
696 };
697
698 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP