Mon, 26 Sep 2011 10:24:05 -0700
7081933: Use zeroing elimination optimization for large array
Summary: Don't zero new typeArray during runtime call if the allocation is followed by arraycopy into it.
Reviewed-by: twisti
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.
18 *
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
21 * questions.
22 *
23 */
25 #ifndef SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
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"
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.
40 class BarrierSet;
41 class ThreadClosure;
42 class AdaptiveSizePolicy;
43 class Thread;
44 class CollectorPolicy;
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
58 #ifdef ASSERT
59 static int _fire_out_of_memory_count;
60 #endif
62 // Used for filler objects (static, but initialized in ctor).
63 static size_t _filler_array_max_size;
65 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
66 bool _defer_initial_card_mark;
68 protected:
69 MemRegion _reserved;
70 BarrierSet* _barrier_set;
71 bool _is_gc_active;
72 int _n_par_threads;
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;)
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;
86 // Constructor
87 CollectedHeap();
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();
96 // Create a new tlab. All TLAB allocations must go through this.
97 virtual HeapWord* allocate_new_tlab(size_t size);
99 // Accumulate statistics on all tlabs.
100 virtual void accumulate_statistics_all_tlabs();
102 // Reinitialize tlabs before resuming mutators.
103 virtual void resize_all_tlabs();
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);
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);
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);
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);
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);
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);
133 inline static void post_allocation_setup_obj(KlassHandle klass,
134 HeapWord* obj, size_t size);
136 inline static void post_allocation_setup_array(KlassHandle klass,
137 HeapWord* obj, size_t size,
138 int length);
140 // Clears an allocated object.
141 inline static void init_obj(HeapWord* obj, size_t size);
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();
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);)
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);
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);
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();)
165 public:
166 enum Name {
167 Abstract,
168 SharedHeap,
169 GenCollectedHeap,
170 ParallelScavengeHeap,
171 G1CollectedHeap
172 };
174 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
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;
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;
187 MemRegion reserved_region() const { return _reserved; }
188 address base() const { return (address)reserved_region().start(); }
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;
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;
200 virtual size_t permanent_capacity() const = 0;
201 virtual size_t permanent_used() const = 0;
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;
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 }
216 bool is_in_reserved_or_null(const void* p) const {
217 return p == NULL || is_in_reserved(p);
218 }
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;
225 bool is_in_or_null(const void* p) const {
226 return p == NULL || is_in(p);
227 }
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."
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.
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 }
257 bool is_in_closed_subset_or_null(const void* p) const {
258 return p == NULL || is_in_closed_subset(p);
259 }
261 // XXX is_permanent() and is_in_permanent() should be better named
262 // to distinguish one from the other.
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;
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
279 bool is_in_permanent_or_null(const void *p) const {
280 return p == NULL || is_in_permanent(p);
281 }
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;
288 bool is_permanent_or_null(const void *p) const {
289 return p == NULL || is_permanent(p);
290 }
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;
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;
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; }
311 // Number of threads currently working on GC tasks.
312 int n_par_threads() { return _n_par_threads; }
314 // May be overridden to set additional parallelism.
315 virtual void set_par_threads(int t) { _n_par_threads = t; };
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(); }
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 inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
327 // Special obj/array allocation facilities.
328 // Some heaps may want to manage "permanent" data uniquely. These default
329 // to the general routines if the heap does not support such handling.
330 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
331 // permanent_obj_allocate_no_klass_install() does not do the installation of
332 // the klass pointer in the newly created object (as permanent_obj_allocate()
333 // above does). This allows for a delay in the installation of the klass
334 // pointer that is needed during the create of klassKlass's. The
335 // method post_allocation_install_obj_klass() is used to install the
336 // klass pointer.
337 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
338 int size,
339 TRAPS);
340 inline static void post_allocation_install_obj_klass(KlassHandle klass,
341 oop obj,
342 int size);
343 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
345 // Raw memory allocation facilities
346 // The obj and array allocate methods are covers for these methods.
347 // The permanent allocation method should default to mem_allocate if
348 // permanent memory isn't supported. mem_allocate() should never be
349 // called to allocate TLABs, only individual objects.
350 virtual HeapWord* mem_allocate(size_t size,
351 bool* gc_overhead_limit_was_exceeded) = 0;
352 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
354 // Utilities for turning raw memory into filler objects.
355 //
356 // min_fill_size() is the smallest region that can be filled.
357 // fill_with_objects() can fill arbitrary-sized regions of the heap using
358 // multiple objects. fill_with_object() is for regions known to be smaller
359 // than the largest array of integers; it uses a single object to fill the
360 // region and has slightly less overhead.
361 static size_t min_fill_size() {
362 return size_t(align_object_size(oopDesc::header_size()));
363 }
365 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
367 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
368 static void fill_with_object(MemRegion region, bool zap = true) {
369 fill_with_object(region.start(), region.word_size(), zap);
370 }
371 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
372 fill_with_object(start, pointer_delta(end, start), zap);
373 }
375 // Some heaps may offer a contiguous region for shared non-blocking
376 // allocation, via inlined code (by exporting the address of the top and
377 // end fields defining the extent of the contiguous allocation region.)
379 // This function returns "true" iff the heap supports this kind of
380 // allocation. (Default is "no".)
381 virtual bool supports_inline_contig_alloc() const {
382 return false;
383 }
384 // These functions return the addresses of the fields that define the
385 // boundaries of the contiguous allocation area. (These fields should be
386 // physically near to one another.)
387 virtual HeapWord** top_addr() const {
388 guarantee(false, "inline contiguous allocation not supported");
389 return NULL;
390 }
391 virtual HeapWord** end_addr() const {
392 guarantee(false, "inline contiguous allocation not supported");
393 return NULL;
394 }
396 // Some heaps may be in an unparseable state at certain times between
397 // collections. This may be necessary for efficient implementation of
398 // certain allocation-related activities. Calling this function before
399 // attempting to parse a heap ensures that the heap is in a parsable
400 // state (provided other concurrent activity does not introduce
401 // unparsability). It is normally expected, therefore, that this
402 // method is invoked with the world stopped.
403 // NOTE: if you override this method, make sure you call
404 // super::ensure_parsability so that the non-generational
405 // part of the work gets done. See implementation of
406 // CollectedHeap::ensure_parsability and, for instance,
407 // that of GenCollectedHeap::ensure_parsability().
408 // The argument "retire_tlabs" controls whether existing TLABs
409 // are merely filled or also retired, thus preventing further
410 // allocation from them and necessitating allocation of new TLABs.
411 virtual void ensure_parsability(bool retire_tlabs);
413 // Return an estimate of the maximum allocation that could be performed
414 // without triggering any collection or expansion activity. In a
415 // generational collector, for example, this is probably the largest
416 // allocation that could be supported (without expansion) in the youngest
417 // generation. It is "unsafe" because no locks are taken; the result
418 // should be treated as an approximation, not a guarantee, for use in
419 // heuristic resizing decisions.
420 virtual size_t unsafe_max_alloc() = 0;
422 // Section on thread-local allocation buffers (TLABs)
423 // If the heap supports thread-local allocation buffers, it should override
424 // the following methods:
425 // Returns "true" iff the heap supports thread-local allocation buffers.
426 // The default is "no".
427 virtual bool supports_tlab_allocation() const {
428 return false;
429 }
430 // The amount of space available for thread-local allocation buffers.
431 virtual size_t tlab_capacity(Thread *thr) const {
432 guarantee(false, "thread-local allocation buffers not supported");
433 return 0;
434 }
435 // An estimate of the maximum allocation that could be performed
436 // for thread-local allocation buffers without triggering any
437 // collection or expansion activity.
438 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
439 guarantee(false, "thread-local allocation buffers not supported");
440 return 0;
441 }
443 // Can a compiler initialize a new object without store barriers?
444 // This permission only extends from the creation of a new object
445 // via a TLAB up to the first subsequent safepoint. If such permission
446 // is granted for this heap type, the compiler promises to call
447 // defer_store_barrier() below on any slow path allocation of
448 // a new object for which such initializing store barriers will
449 // have been elided.
450 virtual bool can_elide_tlab_store_barriers() const = 0;
452 // If a compiler is eliding store barriers for TLAB-allocated objects,
453 // there is probably a corresponding slow path which can produce
454 // an object allocated anywhere. The compiler's runtime support
455 // promises to call this function on such a slow-path-allocated
456 // object before performing initializations that have elided
457 // store barriers. Returns new_obj, or maybe a safer copy thereof.
458 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
460 // Answers whether an initializing store to a new object currently
461 // allocated at the given address doesn't need a store
462 // barrier. Returns "true" if it doesn't need an initializing
463 // store barrier; answers "false" if it does.
464 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
466 // If a compiler is eliding store barriers for TLAB-allocated objects,
467 // we will be informed of a slow-path allocation by a call
468 // to new_store_pre_barrier() above. Such a call precedes the
469 // initialization of the object itself, and no post-store-barriers will
470 // be issued. Some heap types require that the barrier strictly follows
471 // the initializing stores. (This is currently implemented by deferring the
472 // barrier until the next slow-path allocation or gc-related safepoint.)
473 // This interface answers whether a particular heap type needs the card
474 // mark to be thus strictly sequenced after the stores.
475 virtual bool card_mark_must_follow_store() const = 0;
477 // If the CollectedHeap was asked to defer a store barrier above,
478 // this informs it to flush such a deferred store barrier to the
479 // remembered set.
480 virtual void flush_deferred_store_barrier(JavaThread* thread);
482 // Can a compiler elide a store barrier when it writes
483 // a permanent oop into the heap? Applies when the compiler
484 // is storing x to the heap, where x->is_perm() is true.
485 virtual bool can_elide_permanent_oop_store_barriers() const = 0;
487 // Does this heap support heap inspection (+PrintClassHistogram?)
488 virtual bool supports_heap_inspection() const = 0;
490 // Perform a collection of the heap; intended for use in implementing
491 // "System.gc". This probably implies as full a collection as the
492 // "CollectedHeap" supports.
493 virtual void collect(GCCause::Cause cause) = 0;
495 // This interface assumes that it's being called by the
496 // vm thread. It collects the heap assuming that the
497 // heap lock is already held and that we are executing in
498 // the context of the vm thread.
499 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
501 // Returns the barrier set for this heap
502 BarrierSet* barrier_set() { return _barrier_set; }
504 // Returns "true" iff there is a stop-world GC in progress. (I assume
505 // that it should answer "false" for the concurrent part of a concurrent
506 // collector -- dld).
507 bool is_gc_active() const { return _is_gc_active; }
509 // Total number of GC collections (started)
510 unsigned int total_collections() const { return _total_collections; }
511 unsigned int total_full_collections() const { return _total_full_collections;}
513 // Increment total number of GC collections (started)
514 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
515 void increment_total_collections(bool full = false) {
516 _total_collections++;
517 if (full) {
518 increment_total_full_collections();
519 }
520 }
522 void increment_total_full_collections() { _total_full_collections++; }
524 // Return the AdaptiveSizePolicy for the heap.
525 virtual AdaptiveSizePolicy* size_policy() = 0;
527 // Return the CollectorPolicy for the heap
528 virtual CollectorPolicy* collector_policy() const = 0;
530 // Iterate over all the ref-containing fields of all objects, calling
531 // "cl.do_oop" on each. This includes objects in permanent memory.
532 virtual void oop_iterate(OopClosure* cl) = 0;
534 // Iterate over all objects, calling "cl.do_object" on each.
535 // This includes objects in permanent memory.
536 virtual void object_iterate(ObjectClosure* cl) = 0;
538 // Similar to object_iterate() except iterates only
539 // over live objects.
540 virtual void safe_object_iterate(ObjectClosure* cl) = 0;
542 // Behaves the same as oop_iterate, except only traverses
543 // interior pointers contained in permanent memory. If there
544 // is no permanent memory, does nothing.
545 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
547 // Behaves the same as object_iterate, except only traverses
548 // object contained in permanent memory. If there is no
549 // permanent memory, does nothing.
550 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
552 // NOTE! There is no requirement that a collector implement these
553 // functions.
554 //
555 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
556 // each address in the (reserved) heap is a member of exactly
557 // one block. The defining characteristic of a block is that it is
558 // possible to find its size, and thus to progress forward to the next
559 // block. (Blocks may be of different sizes.) Thus, blocks may
560 // represent Java objects, or they might be free blocks in a
561 // free-list-based heap (or subheap), as long as the two kinds are
562 // distinguishable and the size of each is determinable.
564 // Returns the address of the start of the "block" that contains the
565 // address "addr". We say "blocks" instead of "object" since some heaps
566 // may not pack objects densely; a chunk may either be an object or a
567 // non-object.
568 virtual HeapWord* block_start(const void* addr) const = 0;
570 // Requires "addr" to be the start of a chunk, and returns its size.
571 // "addr + size" is required to be the start of a new chunk, or the end
572 // of the active area of the heap.
573 virtual size_t block_size(const HeapWord* addr) const = 0;
575 // Requires "addr" to be the start of a block, and returns "TRUE" iff
576 // the block is an object.
577 virtual bool block_is_obj(const HeapWord* addr) const = 0;
579 // Returns the longest time (in ms) that has elapsed since the last
580 // time that any part of the heap was examined by a garbage collection.
581 virtual jlong millis_since_last_gc() = 0;
583 // Perform any cleanup actions necessary before allowing a verification.
584 virtual void prepare_for_verify() = 0;
586 // Generate any dumps preceding or following a full gc
587 void pre_full_gc_dump();
588 void post_full_gc_dump();
590 virtual void print() const = 0;
591 virtual void print_on(outputStream* st) const = 0;
593 // Print all GC threads (other than the VM thread)
594 // used by this heap.
595 virtual void print_gc_threads_on(outputStream* st) const = 0;
596 void print_gc_threads() { print_gc_threads_on(tty); }
597 // Iterator for all GC threads (other than VM thread)
598 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
600 // Print any relevant tracing info that flags imply.
601 // Default implementation does nothing.
602 virtual void print_tracing_info() const = 0;
604 // Heap verification
605 virtual void verify(bool allow_dirty, bool silent, VerifyOption option) = 0;
607 // Non product verification and debugging.
608 #ifndef PRODUCT
609 // Support for PromotionFailureALot. Return true if it's time to cause a
610 // promotion failure. The no-argument version uses
611 // this->_promotion_failure_alot_count as the counter.
612 inline bool promotion_should_fail(volatile size_t* count);
613 inline bool promotion_should_fail();
615 // Reset the PromotionFailureALot counters. Should be called at the end of a
616 // GC in which promotion failure ocurred.
617 inline void reset_promotion_should_fail(volatile size_t* count);
618 inline void reset_promotion_should_fail();
619 #endif // #ifndef PRODUCT
621 #ifdef ASSERT
622 static int fired_fake_oom() {
623 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
624 }
625 #endif
627 public:
628 // This is a convenience method that is used in cases where
629 // the actual number of GC worker threads is not pertinent but
630 // only whether there more than 0. Use of this method helps
631 // reduce the occurrence of ParallelGCThreads to uses where the
632 // actual number may be germane.
633 static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
634 };
636 // Class to set and reset the GC cause for a CollectedHeap.
638 class GCCauseSetter : StackObj {
639 CollectedHeap* _heap;
640 GCCause::Cause _previous_cause;
641 public:
642 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
643 assert(SafepointSynchronize::is_at_safepoint(),
644 "This method manipulates heap state without locking");
645 _heap = heap;
646 _previous_cause = _heap->gc_cause();
647 _heap->set_gc_cause(cause);
648 }
650 ~GCCauseSetter() {
651 assert(SafepointSynchronize::is_at_safepoint(),
652 "This method manipulates heap state without locking");
653 _heap->set_gc_cause(_previous_cause);
654 }
655 };
657 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP