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