1 /*
2 * Copyright (c) 2001, 2011, 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
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23 */
24
25 #ifndef SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
27
28 #include "gc_interface/gcCause.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/barrierSet.hpp"
31 #include "runtime/handles.hpp"
32 #include "runtime/perfData.hpp"
33 #include "runtime/safepoint.hpp"
34
35 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
36 // is an abstract class: there may be many different kinds of heaps. This
37 // class defines the functions that a heap must implement, and contains
38 // infrastructure common to all heaps.
39
40 class BarrierSet;
41 class ThreadClosure;
42 class AdaptiveSizePolicy;
43 class Thread;
44 class CollectorPolicy;
45
46 //
47 // CollectedHeap
48 // SharedHeap
49 // GenCollectedHeap
50 // G1CollectedHeap
51 // ParallelScavengeHeap
52 //
53 class CollectedHeap : public CHeapObj {
54 friend class VMStructs;
55 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
56 friend class constantPoolCacheKlass; // allocate() method inserts is_conc_safe
57
58 #ifdef ASSERT
59 static int _fire_out_of_memory_count;
60 #endif
61
62 // Used for filler objects (static, but initialized in ctor).
63 static size_t _filler_array_max_size;
64
65 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
66 bool _defer_initial_card_mark;
67
68 protected:
69 MemRegion _reserved;
70 BarrierSet* _barrier_set;
71 bool _is_gc_active;
72 int _n_par_threads;
73
74 unsigned int _total_collections; // ... started
75 unsigned int _total_full_collections; // ... started
76 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
77 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
78
79 // Reason for current garbage collection. Should be set to
80 // a value reflecting no collection between collections.
81 GCCause::Cause _gc_cause;
82 GCCause::Cause _gc_lastcause;
83 PerfStringVariable* _perf_gc_cause;
84 PerfStringVariable* _perf_gc_lastcause;
85
86 // Constructor
87 CollectedHeap();
88
89 // Do common initializations that must follow instance construction,
90 // for example, those needing virtual calls.
91 // This code could perhaps be moved into initialize() but would
92 // be slightly more awkward because we want the latter to be a
93 // pure virtual.
94 void pre_initialize();
95
96 // Create a new tlab. All TLAB allocations must go through this.
97 virtual HeapWord* allocate_new_tlab(size_t size);
98
99 // Accumulate statistics on all tlabs.
100 virtual void accumulate_statistics_all_tlabs();
101
102 // Reinitialize tlabs before resuming mutators.
103 virtual void resize_all_tlabs();
104
105 protected:
106 // Allocate from the current thread's TLAB, with broken-out slow path.
107 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
108 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
109
110 // Allocate an uninitialized block of the given size, or returns NULL if
111 // this is impossible.
112 inline static HeapWord* common_mem_allocate_noinit(size_t size, TRAPS);
113
114 // Like allocate_init, but the block returned by a successful allocation
115 // is guaranteed initialized to zeros.
116 inline static HeapWord* common_mem_allocate_init(size_t size, TRAPS);
117
118 // Same as common_mem version, except memory is allocated in the permanent area
119 // If there is no permanent area, revert to common_mem_allocate_noinit
120 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);
121
122 // Same as common_mem version, except memory is allocated in the permanent area
123 // If there is no permanent area, revert to common_mem_allocate_init
124 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);
125
126 // Helper functions for (VM) allocation.
127 inline static void post_allocation_setup_common(KlassHandle klass,
128 HeapWord* obj, size_t size);
129 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
130 HeapWord* objPtr,
131 size_t size);
132
133 inline static void post_allocation_setup_obj(KlassHandle klass,
134 HeapWord* obj, size_t size);
135
136 inline static void post_allocation_setup_array(KlassHandle klass,
137 HeapWord* obj, size_t size,
138 int length);
139
140 // Clears an allocated object.
141 inline static void init_obj(HeapWord* obj, size_t size);
142
143 // Filler object utilities.
144 static inline size_t filler_array_hdr_size();
145 static inline size_t filler_array_min_size();
146 static inline size_t filler_array_max_size();
147
148 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
149 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
150
151 // Fill with a single array; caller must ensure filler_array_min_size() <=
152 // words <= filler_array_max_size().
153 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
154
155 // Fill with a single object (either an int array or a java.lang.Object).
156 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
157
158 // Verification functions
159 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
160 PRODUCT_RETURN;
161 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
162 PRODUCT_RETURN;
163 debug_only(static void check_for_valid_allocation_state();)
164
165 public:
166 enum Name {
167 Abstract,
168 SharedHeap,
169 GenCollectedHeap,
170 ParallelScavengeHeap,
171 G1CollectedHeap
172 };
173
174 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
175
176 /**
177 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
178 * and JNI_OK on success.
179 */
180 virtual jint initialize() = 0;
181
182 // In many heaps, there will be a need to perform some initialization activities
183 // after the Universe is fully formed, but before general heap allocation is allowed.
184 // This is the correct place to place such initialization methods.
185 virtual void post_initialize() = 0;
186
187 MemRegion reserved_region() const { return _reserved; }
188 address base() const { return (address)reserved_region().start(); }
189
190 // Future cleanup here. The following functions should specify bytes or
191 // heapwords as part of their signature.
192 virtual size_t capacity() const = 0;
193 virtual size_t used() const = 0;
194
195 // Return "true" if the part of the heap that allocates Java
196 // objects has reached the maximal committed limit that it can
197 // reach, without a garbage collection.
198 virtual bool is_maximal_no_gc() const = 0;
199
200 virtual size_t permanent_capacity() const = 0;
201 virtual size_t permanent_used() const = 0;
202
203 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
204 // memory that the vm could make available for storing 'normal' java objects.
205 // This is based on the reserved address space, but should not include space
206 // that the vm uses internally for bookkeeping or temporary storage (e.g.,
207 // perm gen space or, in the case of the young gen, one of the survivor
208 // spaces).
209 virtual size_t max_capacity() const = 0;
210
211 // Returns "TRUE" if "p" points into the reserved area of the heap.
212 bool is_in_reserved(const void* p) const {
213 return _reserved.contains(p);
214 }
215
216 bool is_in_reserved_or_null(const void* p) const {
217 return p == NULL || is_in_reserved(p);
218 }
219
220 // Returns "TRUE" if "p" points to the head of an allocated object in the
221 // heap. Since this method can be expensive in general, we restrict its
222 // use to assertion checking only.
223 virtual bool is_in(const void* p) const = 0;
224
225 bool is_in_or_null(const void* p) const {
226 return p == NULL || is_in(p);
227 }
228
229 // Let's define some terms: a "closed" subset of a heap is one that
230 //
231 // 1) contains all currently-allocated objects, and
232 //
233 // 2) is closed under reference: no object in the closed subset
234 // references one outside the closed subset.
235 //
236 // Membership in a heap's closed subset is useful for assertions.
237 // Clearly, the entire heap is a closed subset, so the default
238 // implementation is to use "is_in_reserved". But this may not be too
239 // liberal to perform useful checking. Also, the "is_in" predicate
240 // defines a closed subset, but may be too expensive, since "is_in"
241 // verifies that its argument points to an object head. The
242 // "closed_subset" method allows a heap to define an intermediate
243 // predicate, allowing more precise checking than "is_in_reserved" at
244 // lower cost than "is_in."
245
246 // One important case is a heap composed of disjoint contiguous spaces,
247 // such as the Garbage-First collector. Such heaps have a convenient
248 // closed subset consisting of the allocated portions of those
249 // contiguous spaces.
250
251 // Return "TRUE" iff the given pointer points into the heap's defined
252 // closed subset (which defaults to the entire heap).
253 virtual bool is_in_closed_subset(const void* p) const {
254 return is_in_reserved(p);
255 }
256
257 bool is_in_closed_subset_or_null(const void* p) const {
258 return p == NULL || is_in_closed_subset(p);
259 }
260
261 // XXX is_permanent() and is_in_permanent() should be better named
262 // to distinguish one from the other.
263
264 // Returns "TRUE" if "p" is allocated as "permanent" data.
265 // If the heap does not use "permanent" data, returns the same
266 // value is_in_reserved() would return.
267 // NOTE: this actually returns true if "p" is in reserved space
268 // for the space not that it is actually allocated (i.e. in committed
269 // space). If you need the more conservative answer use is_permanent().
270 virtual bool is_in_permanent(const void *p) const = 0;
271
272
273 #ifdef ASSERT
274 // Returns true if "p" is in the part of the
275 // heap being collected.
276 virtual bool is_in_partial_collection(const void *p) = 0;
277 #endif
278
279 bool is_in_permanent_or_null(const void *p) const {
280 return p == NULL || is_in_permanent(p);
281 }
282
283 // Returns "TRUE" if "p" is in the committed area of "permanent" data.
284 // If the heap does not use "permanent" data, returns the same
285 // value is_in() would return.
286 virtual bool is_permanent(const void *p) const = 0;
287
288 bool is_permanent_or_null(const void *p) const {
289 return p == NULL || is_permanent(p);
290 }
291
292 // An object is scavengable if its location may move during a scavenge.
293 // (A scavenge is a GC which is not a full GC.)
294 virtual bool is_scavengable(const void *p) = 0;
295
296 // Returns "TRUE" if "p" is a method oop in the
297 // current heap, with high probability. This predicate
298 // is not stable, in general.
299 bool is_valid_method(oop p) const;
300
301 void set_gc_cause(GCCause::Cause v) {
302 if (UsePerfData) {
303 _gc_lastcause = _gc_cause;
304 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
305 _perf_gc_cause->set_value(GCCause::to_string(v));
306 }
307 _gc_cause = v;
308 }
309 GCCause::Cause gc_cause() { return _gc_cause; }
310
311 // Number of threads currently working on GC tasks.
312 int n_par_threads() { return _n_par_threads; }
313
314 // May be overridden to set additional parallelism.
315 virtual void set_par_threads(int t) { _n_par_threads = t; };
316
317 // Preload classes into the shared portion of the heap, and then dump
318 // that data to a file so that it can be loaded directly by another
319 // VM (then terminate).
320 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }
321
322 // General obj/array allocation facilities.
323 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
324 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
325
326 // Special obj/array allocation facilities.
327 // Some heaps may want to manage "permanent" data uniquely. These default
328 // to the general routines if the heap does not support such handling.
329 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
330 // permanent_obj_allocate_no_klass_install() does not do the installation of
331 // the klass pointer in the newly created object (as permanent_obj_allocate()
332 // above does). This allows for a delay in the installation of the klass
333 // pointer that is needed during the create of klassKlass's. The
334 // method post_allocation_install_obj_klass() is used to install the
335 // klass pointer.
336 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
337 int size,
338 TRAPS);
339 inline static void post_allocation_install_obj_klass(KlassHandle klass,
340 oop obj,
341 int size);
342 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
343
344 // Raw memory allocation facilities
345 // The obj and array allocate methods are covers for these methods.
346 // The permanent allocation method should default to mem_allocate if
347 // permanent memory isn't supported. mem_allocate() should never be
348 // called to allocate TLABs, only individual objects.
349 virtual HeapWord* mem_allocate(size_t size,
350 bool* gc_overhead_limit_was_exceeded) = 0;
351 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
352
353 // Utilities for turning raw memory into filler objects.
354 //
355 // min_fill_size() is the smallest region that can be filled.
356 // fill_with_objects() can fill arbitrary-sized regions of the heap using
357 // multiple objects. fill_with_object() is for regions known to be smaller
358 // than the largest array of integers; it uses a single object to fill the
359 // region and has slightly less overhead.
360 static size_t min_fill_size() {
361 return size_t(align_object_size(oopDesc::header_size()));
362 }
363
364 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
365
366 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
367 static void fill_with_object(MemRegion region, bool zap = true) {
368 fill_with_object(region.start(), region.word_size(), zap);
369 }
370 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
371 fill_with_object(start, pointer_delta(end, start), zap);
372 }
373
374 // Some heaps may offer a contiguous region for shared non-blocking
375 // allocation, via inlined code (by exporting the address of the top and
376 // end fields defining the extent of the contiguous allocation region.)
377
378 // This function returns "true" iff the heap supports this kind of
379 // allocation. (Default is "no".)
380 virtual bool supports_inline_contig_alloc() const {
381 return false;
382 }
383 // These functions return the addresses of the fields that define the
384 // boundaries of the contiguous allocation area. (These fields should be
385 // physically near to one another.)
386 virtual HeapWord** top_addr() const {
387 guarantee(false, "inline contiguous allocation not supported");
388 return NULL;
389 }
390 virtual HeapWord** end_addr() const {
391 guarantee(false, "inline contiguous allocation not supported");
392 return NULL;
393 }
394
395 // Some heaps may be in an unparseable state at certain times between
396 // collections. This may be necessary for efficient implementation of
397 // certain allocation-related activities. Calling this function before
398 // attempting to parse a heap ensures that the heap is in a parsable
399 // state (provided other concurrent activity does not introduce
400 // unparsability). It is normally expected, therefore, that this
401 // method is invoked with the world stopped.
402 // NOTE: if you override this method, make sure you call
403 // super::ensure_parsability so that the non-generational
404 // part of the work gets done. See implementation of
405 // CollectedHeap::ensure_parsability and, for instance,
406 // that of GenCollectedHeap::ensure_parsability().
407 // The argument "retire_tlabs" controls whether existing TLABs
408 // are merely filled or also retired, thus preventing further
409 // allocation from them and necessitating allocation of new TLABs.
410 virtual void ensure_parsability(bool retire_tlabs);
411
412 // Return an estimate of the maximum allocation that could be performed
413 // without triggering any collection or expansion activity. In a
414 // generational collector, for example, this is probably the largest
415 // allocation that could be supported (without expansion) in the youngest
416 // generation. It is "unsafe" because no locks are taken; the result
417 // should be treated as an approximation, not a guarantee, for use in
418 // heuristic resizing decisions.
419 virtual size_t unsafe_max_alloc() = 0;
420
421 // Section on thread-local allocation buffers (TLABs)
422 // If the heap supports thread-local allocation buffers, it should override
423 // the following methods:
424 // Returns "true" iff the heap supports thread-local allocation buffers.
425 // The default is "no".
426 virtual bool supports_tlab_allocation() const {
427 return false;
428 }
429 // The amount of space available for thread-local allocation buffers.
430 virtual size_t tlab_capacity(Thread *thr) const {
431 guarantee(false, "thread-local allocation buffers not supported");
432 return 0;
433 }
434 // An estimate of the maximum allocation that could be performed
435 // for thread-local allocation buffers without triggering any
436 // collection or expansion activity.
437 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
438 guarantee(false, "thread-local allocation buffers not supported");
439 return 0;
440 }
441
442 // Can a compiler initialize a new object without store barriers?
443 // This permission only extends from the creation of a new object
444 // via a TLAB up to the first subsequent safepoint. If such permission
445 // is granted for this heap type, the compiler promises to call
446 // defer_store_barrier() below on any slow path allocation of
447 // a new object for which such initializing store barriers will
448 // have been elided.
449 virtual bool can_elide_tlab_store_barriers() const = 0;
450
451 // If a compiler is eliding store barriers for TLAB-allocated objects,
452 // there is probably a corresponding slow path which can produce
453 // an object allocated anywhere. The compiler's runtime support
454 // promises to call this function on such a slow-path-allocated
455 // object before performing initializations that have elided
456 // store barriers. Returns new_obj, or maybe a safer copy thereof.
457 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
458
459 // Answers whether an initializing store to a new object currently
460 // allocated at the given address doesn't need a store
461 // barrier. Returns "true" if it doesn't need an initializing
462 // store barrier; answers "false" if it does.
463 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
464
465 // If a compiler is eliding store barriers for TLAB-allocated objects,
466 // we will be informed of a slow-path allocation by a call
467 // to new_store_pre_barrier() above. Such a call precedes the
468 // initialization of the object itself, and no post-store-barriers will
469 // be issued. Some heap types require that the barrier strictly follows
470 // the initializing stores. (This is currently implemented by deferring the
471 // barrier until the next slow-path allocation or gc-related safepoint.)
472 // This interface answers whether a particular heap type needs the card
473 // mark to be thus strictly sequenced after the stores.
474 virtual bool card_mark_must_follow_store() const = 0;
475
476 // If the CollectedHeap was asked to defer a store barrier above,
477 // this informs it to flush such a deferred store barrier to the
478 // remembered set.
479 virtual void flush_deferred_store_barrier(JavaThread* thread);
480
481 // Can a compiler elide a store barrier when it writes
482 // a permanent oop into the heap? Applies when the compiler
483 // is storing x to the heap, where x->is_perm() is true.
484 virtual bool can_elide_permanent_oop_store_barriers() const = 0;
485
486 // Does this heap support heap inspection (+PrintClassHistogram?)
487 virtual bool supports_heap_inspection() const = 0;
488
489 // Perform a collection of the heap; intended for use in implementing
490 // "System.gc". This probably implies as full a collection as the
491 // "CollectedHeap" supports.
492 virtual void collect(GCCause::Cause cause) = 0;
493
494 // This interface assumes that it's being called by the
495 // vm thread. It collects the heap assuming that the
496 // heap lock is already held and that we are executing in
497 // the context of the vm thread.
498 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
499
500 // Returns the barrier set for this heap
501 BarrierSet* barrier_set() { return _barrier_set; }
502
503 // Returns "true" iff there is a stop-world GC in progress. (I assume
504 // that it should answer "false" for the concurrent part of a concurrent
505 // collector -- dld).
506 bool is_gc_active() const { return _is_gc_active; }
507
508 // Total number of GC collections (started)
509 unsigned int total_collections() const { return _total_collections; }
510 unsigned int total_full_collections() const { return _total_full_collections;}
511
512 // Increment total number of GC collections (started)
513 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
514 void increment_total_collections(bool full = false) {
515 _total_collections++;
516 if (full) {
517 increment_total_full_collections();
518 }
519 }
520
521 void increment_total_full_collections() { _total_full_collections++; }
522
523 // Return the AdaptiveSizePolicy for the heap.
524 virtual AdaptiveSizePolicy* size_policy() = 0;
525
526 // Return the CollectorPolicy for the heap
527 virtual CollectorPolicy* collector_policy() const = 0;
528
529 // Iterate over all the ref-containing fields of all objects, calling
530 // "cl.do_oop" on each. This includes objects in permanent memory.
531 virtual void oop_iterate(OopClosure* cl) = 0;
532
533 // Iterate over all objects, calling "cl.do_object" on each.
534 // This includes objects in permanent memory.
535 virtual void object_iterate(ObjectClosure* cl) = 0;
536
537 // Similar to object_iterate() except iterates only
538 // over live objects.
539 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
540
541 // Behaves the same as oop_iterate, except only traverses
542 // interior pointers contained in permanent memory. If there
543 // is no permanent memory, does nothing.
544 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
545
546 // Behaves the same as object_iterate, except only traverses
547 // object contained in permanent memory. If there is no
548 // permanent memory, does nothing.
549 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
550
551 // NOTE! There is no requirement that a collector implement these
552 // functions.
553 //
554 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
555 // each address in the (reserved) heap is a member of exactly
556 // one block. The defining characteristic of a block is that it is
557 // possible to find its size, and thus to progress forward to the next
558 // block. (Blocks may be of different sizes.) Thus, blocks may
559 // represent Java objects, or they might be free blocks in a
560 // free-list-based heap (or subheap), as long as the two kinds are
561 // distinguishable and the size of each is determinable.
562
563 // Returns the address of the start of the "block" that contains the
564 // address "addr". We say "blocks" instead of "object" since some heaps
565 // may not pack objects densely; a chunk may either be an object or a
566 // non-object.
567 virtual HeapWord* block_start(const void* addr) const = 0;
568
569 // Requires "addr" to be the start of a chunk, and returns its size.
570 // "addr + size" is required to be the start of a new chunk, or the end
571 // of the active area of the heap.
572 virtual size_t block_size(const HeapWord* addr) const = 0;
573
574 // Requires "addr" to be the start of a block, and returns "TRUE" iff
575 // the block is an object.
576 virtual bool block_is_obj(const HeapWord* addr) const = 0;
577
578 // Returns the longest time (in ms) that has elapsed since the last
579 // time that any part of the heap was examined by a garbage collection.
580 virtual jlong millis_since_last_gc() = 0;
581
582 // Perform any cleanup actions necessary before allowing a verification.
583 virtual void prepare_for_verify() = 0;
584
585 // Generate any dumps preceding or following a full gc
586 void pre_full_gc_dump();
587 void post_full_gc_dump();
588
589 virtual void print() const = 0;
590 virtual void print_on(outputStream* st) const = 0;
591
592 // Print all GC threads (other than the VM thread)
593 // used by this heap.
594 virtual void print_gc_threads_on(outputStream* st) const = 0;
595 void print_gc_threads() { print_gc_threads_on(tty); }
596 // Iterator for all GC threads (other than VM thread)
597 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
598
599 // Print any relevant tracing info that flags imply.
600 // Default implementation does nothing.
601 virtual void print_tracing_info() const = 0;
602
603 // Heap verification
604 virtual void verify(bool allow_dirty, bool silent, VerifyOption option) = 0;
605
606 // Non product verification and debugging.
607 #ifndef PRODUCT
608 // Support for PromotionFailureALot. Return true if it's time to cause a
609 // promotion failure. The no-argument version uses
610 // this->_promotion_failure_alot_count as the counter.
611 inline bool promotion_should_fail(volatile size_t* count);
612 inline bool promotion_should_fail();
613
614 // Reset the PromotionFailureALot counters. Should be called at the end of a
615 // GC in which promotion failure ocurred.
616 inline void reset_promotion_should_fail(volatile size_t* count);
617 inline void reset_promotion_should_fail();
618 #endif // #ifndef PRODUCT
619
620 #ifdef ASSERT
621 static int fired_fake_oom() {
622 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
623 }
624 #endif
625
626 public:
627 // This is a convenience method that is used in cases where
628 // the actual number of GC worker threads is not pertinent but
629 // only whether there more than 0. Use of this method helps
630 // reduce the occurrence of ParallelGCThreads to uses where the
631 // actual number may be germane.
632 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
633 };
634
635 // Class to set and reset the GC cause for a CollectedHeap.
636
637 class GCCauseSetter : StackObj {
638 CollectedHeap* _heap;
639 GCCause::Cause _previous_cause;
640 public:
641 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
642 assert(SafepointSynchronize::is_at_safepoint(),
643 "This method manipulates heap state without locking");
644 _heap = heap;
645 _previous_cause = _heap->gc_cause();
646 _heap->set_gc_cause(cause);
647 }
648
649 ~GCCauseSetter() {
650 assert(SafepointSynchronize::is_at_safepoint(),
651 "This method manipulates heap state without locking");
652 _heap->set_gc_cause(_previous_cause);
653 }
654 };
655
656 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP