Mercurial > hg > graal-jvmci-8
annotate src/share/vm/gc_interface/collectedHeap.hpp @ 113:ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
Summary: Compressed oops in instances, arrays, and headers. Code contributors are coleenp, phh, never, swamyv
Reviewed-by: jmasa, kamg, acorn, tbell, kvn, rasbold
author | coleenp |
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date | Sun, 13 Apr 2008 17:43:42 -0400 |
parents | a61af66fc99e |
children | d1605aabd0a1 37f87013dfd8 |
rev | line source |
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0 | 1 /* |
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This | |
26 // is an abstract class: there may be many different kinds of heaps. This | |
27 // class defines the functions that a heap must implement, and contains | |
28 // infrastructure common to all heaps. | |
29 | |
30 class BarrierSet; | |
31 class ThreadClosure; | |
32 class AdaptiveSizePolicy; | |
33 class Thread; | |
34 | |
35 // | |
36 // CollectedHeap | |
37 // SharedHeap | |
38 // GenCollectedHeap | |
39 // G1CollectedHeap | |
40 // ParallelScavengeHeap | |
41 // | |
42 class CollectedHeap : public CHeapObj { | |
43 friend class VMStructs; | |
44 friend class IsGCActiveMark; // Block structured external access to _is_gc_active | |
45 | |
46 #ifdef ASSERT | |
47 static int _fire_out_of_memory_count; | |
48 #endif | |
49 | |
50 protected: | |
51 MemRegion _reserved; | |
52 BarrierSet* _barrier_set; | |
53 bool _is_gc_active; | |
54 unsigned int _total_collections; // ... started | |
55 unsigned int _total_full_collections; // ... started | |
56 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;) | |
57 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;) | |
58 | |
59 // Reason for current garbage collection. Should be set to | |
60 // a value reflecting no collection between collections. | |
61 GCCause::Cause _gc_cause; | |
62 GCCause::Cause _gc_lastcause; | |
63 PerfStringVariable* _perf_gc_cause; | |
64 PerfStringVariable* _perf_gc_lastcause; | |
65 | |
66 // Constructor | |
67 CollectedHeap(); | |
68 | |
69 // Create a new tlab | |
70 virtual HeapWord* allocate_new_tlab(size_t size); | |
71 | |
72 // Fix up tlabs to make the heap well-formed again, | |
73 // optionally retiring the tlabs. | |
74 virtual void fill_all_tlabs(bool retire); | |
75 | |
76 // Accumulate statistics on all tlabs. | |
77 virtual void accumulate_statistics_all_tlabs(); | |
78 | |
79 // Reinitialize tlabs before resuming mutators. | |
80 virtual void resize_all_tlabs(); | |
81 | |
82 debug_only(static void check_for_valid_allocation_state();) | |
83 | |
84 protected: | |
85 // Allocate from the current thread's TLAB, with broken-out slow path. | |
86 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size); | |
87 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size); | |
88 | |
89 // Allocate an uninitialized block of the given size, or returns NULL if | |
90 // this is impossible. | |
91 inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS); | |
92 | |
93 // Like allocate_init, but the block returned by a successful allocation | |
94 // is guaranteed initialized to zeros. | |
95 inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS); | |
96 | |
97 // Same as common_mem version, except memory is allocated in the permanent area | |
98 // If there is no permanent area, revert to common_mem_allocate_noinit | |
99 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS); | |
100 | |
101 // Same as common_mem version, except memory is allocated in the permanent area | |
102 // If there is no permanent area, revert to common_mem_allocate_init | |
103 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS); | |
104 | |
105 // Helper functions for (VM) allocation. | |
106 inline static void post_allocation_setup_common(KlassHandle klass, | |
107 HeapWord* obj, size_t size); | |
108 inline static void post_allocation_setup_no_klass_install(KlassHandle klass, | |
109 HeapWord* objPtr, | |
110 size_t size); | |
111 | |
112 inline static void post_allocation_setup_obj(KlassHandle klass, | |
113 HeapWord* obj, size_t size); | |
114 | |
115 inline static void post_allocation_setup_array(KlassHandle klass, | |
116 HeapWord* obj, size_t size, | |
117 int length); | |
118 | |
119 // Clears an allocated object. | |
120 inline static void init_obj(HeapWord* obj, size_t size); | |
121 | |
122 // Verification functions | |
123 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size) | |
124 PRODUCT_RETURN; | |
125 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) | |
126 PRODUCT_RETURN; | |
127 | |
128 public: | |
129 enum Name { | |
130 Abstract, | |
131 SharedHeap, | |
132 GenCollectedHeap, | |
133 ParallelScavengeHeap, | |
134 G1CollectedHeap | |
135 }; | |
136 | |
137 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; } | |
138 | |
139 /** | |
140 * Returns JNI error code JNI_ENOMEM if memory could not be allocated, | |
141 * and JNI_OK on success. | |
142 */ | |
143 virtual jint initialize() = 0; | |
144 | |
145 // In many heaps, there will be a need to perform some initialization activities | |
146 // after the Universe is fully formed, but before general heap allocation is allowed. | |
147 // This is the correct place to place such initialization methods. | |
148 virtual void post_initialize() = 0; | |
149 | |
150 MemRegion reserved_region() const { return _reserved; } | |
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
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changeset
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151 address base() const { return (address)reserved_region().start(); } |
0 | 152 |
153 // Future cleanup here. The following functions should specify bytes or | |
154 // heapwords as part of their signature. | |
155 virtual size_t capacity() const = 0; | |
156 virtual size_t used() const = 0; | |
157 | |
158 // Return "true" if the part of the heap that allocates Java | |
159 // objects has reached the maximal committed limit that it can | |
160 // reach, without a garbage collection. | |
161 virtual bool is_maximal_no_gc() const = 0; | |
162 | |
163 virtual size_t permanent_capacity() const = 0; | |
164 virtual size_t permanent_used() const = 0; | |
165 | |
166 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of | |
167 // memory that the vm could make available for storing 'normal' java objects. | |
168 // This is based on the reserved address space, but should not include space | |
169 // that the vm uses internally for bookkeeping or temporary storage (e.g., | |
170 // perm gen space or, in the case of the young gen, one of the survivor | |
171 // spaces). | |
172 virtual size_t max_capacity() const = 0; | |
173 | |
174 // Returns "TRUE" if "p" points into the reserved area of the heap. | |
175 bool is_in_reserved(const void* p) const { | |
176 return _reserved.contains(p); | |
177 } | |
178 | |
179 bool is_in_reserved_or_null(const void* p) const { | |
180 return p == NULL || is_in_reserved(p); | |
181 } | |
182 | |
183 // Returns "TRUE" if "p" points to the head of an allocated object in the | |
184 // heap. Since this method can be expensive in general, we restrict its | |
185 // use to assertion checking only. | |
186 virtual bool is_in(const void* p) const = 0; | |
187 | |
188 bool is_in_or_null(const void* p) const { | |
189 return p == NULL || is_in(p); | |
190 } | |
191 | |
192 // Let's define some terms: a "closed" subset of a heap is one that | |
193 // | |
194 // 1) contains all currently-allocated objects, and | |
195 // | |
196 // 2) is closed under reference: no object in the closed subset | |
197 // references one outside the closed subset. | |
198 // | |
199 // Membership in a heap's closed subset is useful for assertions. | |
200 // Clearly, the entire heap is a closed subset, so the default | |
201 // implementation is to use "is_in_reserved". But this may not be too | |
202 // liberal to perform useful checking. Also, the "is_in" predicate | |
203 // defines a closed subset, but may be too expensive, since "is_in" | |
204 // verifies that its argument points to an object head. The | |
205 // "closed_subset" method allows a heap to define an intermediate | |
206 // predicate, allowing more precise checking than "is_in_reserved" at | |
207 // lower cost than "is_in." | |
208 | |
209 // One important case is a heap composed of disjoint contiguous spaces, | |
210 // such as the Garbage-First collector. Such heaps have a convenient | |
211 // closed subset consisting of the allocated portions of those | |
212 // contiguous spaces. | |
213 | |
214 // Return "TRUE" iff the given pointer points into the heap's defined | |
215 // closed subset (which defaults to the entire heap). | |
216 virtual bool is_in_closed_subset(const void* p) const { | |
217 return is_in_reserved(p); | |
218 } | |
219 | |
220 bool is_in_closed_subset_or_null(const void* p) const { | |
221 return p == NULL || is_in_closed_subset(p); | |
222 } | |
223 | |
224 // Returns "TRUE" if "p" is allocated as "permanent" data. | |
225 // If the heap does not use "permanent" data, returns the same | |
226 // value is_in_reserved() would return. | |
227 // NOTE: this actually returns true if "p" is in reserved space | |
228 // for the space not that it is actually allocated (i.e. in committed | |
229 // space). If you need the more conservative answer use is_permanent(). | |
230 virtual bool is_in_permanent(const void *p) const = 0; | |
231 | |
232 // Returns "TRUE" if "p" is in the committed area of "permanent" data. | |
233 // If the heap does not use "permanent" data, returns the same | |
234 // value is_in() would return. | |
235 virtual bool is_permanent(const void *p) const = 0; | |
236 | |
237 bool is_in_permanent_or_null(const void *p) const { | |
238 return p == NULL || is_in_permanent(p); | |
239 } | |
240 | |
241 // Returns "TRUE" if "p" is a method oop in the | |
242 // current heap, with high probability. This predicate | |
243 // is not stable, in general. | |
244 bool is_valid_method(oop p) const; | |
245 | |
246 void set_gc_cause(GCCause::Cause v) { | |
247 if (UsePerfData) { | |
248 _gc_lastcause = _gc_cause; | |
249 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause)); | |
250 _perf_gc_cause->set_value(GCCause::to_string(v)); | |
251 } | |
252 _gc_cause = v; | |
253 } | |
254 GCCause::Cause gc_cause() { return _gc_cause; } | |
255 | |
256 // Preload classes into the shared portion of the heap, and then dump | |
257 // that data to a file so that it can be loaded directly by another | |
258 // VM (then terminate). | |
259 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); } | |
260 | |
261 // General obj/array allocation facilities. | |
262 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS); | |
263 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS); | |
264 inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS); | |
265 | |
266 // Special obj/array allocation facilities. | |
267 // Some heaps may want to manage "permanent" data uniquely. These default | |
268 // to the general routines if the heap does not support such handling. | |
269 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS); | |
270 // permanent_obj_allocate_no_klass_install() does not do the installation of | |
271 // the klass pointer in the newly created object (as permanent_obj_allocate() | |
272 // above does). This allows for a delay in the installation of the klass | |
273 // pointer that is needed during the create of klassKlass's. The | |
274 // method post_allocation_install_obj_klass() is used to install the | |
275 // klass pointer. | |
276 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass, | |
277 int size, | |
278 TRAPS); | |
279 inline static void post_allocation_install_obj_klass(KlassHandle klass, | |
280 oop obj, | |
281 int size); | |
282 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS); | |
283 | |
284 // Raw memory allocation facilities | |
285 // The obj and array allocate methods are covers for these methods. | |
286 // The permanent allocation method should default to mem_allocate if | |
287 // permanent memory isn't supported. | |
288 virtual HeapWord* mem_allocate(size_t size, | |
289 bool is_noref, | |
290 bool is_tlab, | |
291 bool* gc_overhead_limit_was_exceeded) = 0; | |
292 virtual HeapWord* permanent_mem_allocate(size_t size) = 0; | |
293 | |
294 // The boundary between a "large" and "small" array of primitives, in words. | |
295 virtual size_t large_typearray_limit() = 0; | |
296 | |
297 // Some heaps may offer a contiguous region for shared non-blocking | |
298 // allocation, via inlined code (by exporting the address of the top and | |
299 // end fields defining the extent of the contiguous allocation region.) | |
300 | |
301 // This function returns "true" iff the heap supports this kind of | |
302 // allocation. (Default is "no".) | |
303 virtual bool supports_inline_contig_alloc() const { | |
304 return false; | |
305 } | |
306 // These functions return the addresses of the fields that define the | |
307 // boundaries of the contiguous allocation area. (These fields should be | |
308 // physically near to one another.) | |
309 virtual HeapWord** top_addr() const { | |
310 guarantee(false, "inline contiguous allocation not supported"); | |
311 return NULL; | |
312 } | |
313 virtual HeapWord** end_addr() const { | |
314 guarantee(false, "inline contiguous allocation not supported"); | |
315 return NULL; | |
316 } | |
317 | |
318 // Some heaps may be in an unparseable state at certain times between | |
319 // collections. This may be necessary for efficient implementation of | |
320 // certain allocation-related activities. Calling this function before | |
321 // attempting to parse a heap ensures that the heap is in a parsable | |
322 // state (provided other concurrent activity does not introduce | |
323 // unparsability). It is normally expected, therefore, that this | |
324 // method is invoked with the world stopped. | |
325 // NOTE: if you override this method, make sure you call | |
326 // super::ensure_parsability so that the non-generational | |
327 // part of the work gets done. See implementation of | |
328 // CollectedHeap::ensure_parsability and, for instance, | |
329 // that of GenCollectedHeap::ensure_parsability(). | |
330 // The argument "retire_tlabs" controls whether existing TLABs | |
331 // are merely filled or also retired, thus preventing further | |
332 // allocation from them and necessitating allocation of new TLABs. | |
333 virtual void ensure_parsability(bool retire_tlabs); | |
334 | |
335 // Return an estimate of the maximum allocation that could be performed | |
336 // without triggering any collection or expansion activity. In a | |
337 // generational collector, for example, this is probably the largest | |
338 // allocation that could be supported (without expansion) in the youngest | |
339 // generation. It is "unsafe" because no locks are taken; the result | |
340 // should be treated as an approximation, not a guarantee, for use in | |
341 // heuristic resizing decisions. | |
342 virtual size_t unsafe_max_alloc() = 0; | |
343 | |
344 // Section on thread-local allocation buffers (TLABs) | |
345 // If the heap supports thread-local allocation buffers, it should override | |
346 // the following methods: | |
347 // Returns "true" iff the heap supports thread-local allocation buffers. | |
348 // The default is "no". | |
349 virtual bool supports_tlab_allocation() const { | |
350 return false; | |
351 } | |
352 // The amount of space available for thread-local allocation buffers. | |
353 virtual size_t tlab_capacity(Thread *thr) const { | |
354 guarantee(false, "thread-local allocation buffers not supported"); | |
355 return 0; | |
356 } | |
357 // An estimate of the maximum allocation that could be performed | |
358 // for thread-local allocation buffers without triggering any | |
359 // collection or expansion activity. | |
360 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const { | |
361 guarantee(false, "thread-local allocation buffers not supported"); | |
362 return 0; | |
363 } | |
364 // Can a compiler initialize a new object without store barriers? | |
365 // This permission only extends from the creation of a new object | |
366 // via a TLAB up to the first subsequent safepoint. | |
367 virtual bool can_elide_tlab_store_barriers() const { | |
368 guarantee(kind() < CollectedHeap::G1CollectedHeap, "else change or refactor this"); | |
369 return true; | |
370 } | |
371 // If a compiler is eliding store barriers for TLAB-allocated objects, | |
372 // there is probably a corresponding slow path which can produce | |
373 // an object allocated anywhere. The compiler's runtime support | |
374 // promises to call this function on such a slow-path-allocated | |
375 // object before performing initializations that have elided | |
376 // store barriers. Returns new_obj, or maybe a safer copy thereof. | |
377 virtual oop new_store_barrier(oop new_obj); | |
378 | |
379 // Can a compiler elide a store barrier when it writes | |
380 // a permanent oop into the heap? Applies when the compiler | |
381 // is storing x to the heap, where x->is_perm() is true. | |
382 virtual bool can_elide_permanent_oop_store_barriers() const; | |
383 | |
384 // Does this heap support heap inspection (+PrintClassHistogram?) | |
385 virtual bool supports_heap_inspection() const { | |
386 return false; // Until RFE 5023697 is implemented | |
387 } | |
388 | |
389 // Perform a collection of the heap; intended for use in implementing | |
390 // "System.gc". This probably implies as full a collection as the | |
391 // "CollectedHeap" supports. | |
392 virtual void collect(GCCause::Cause cause) = 0; | |
393 | |
394 // This interface assumes that it's being called by the | |
395 // vm thread. It collects the heap assuming that the | |
396 // heap lock is already held and that we are executing in | |
397 // the context of the vm thread. | |
398 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0; | |
399 | |
400 // Returns the barrier set for this heap | |
401 BarrierSet* barrier_set() { return _barrier_set; } | |
402 | |
403 // Returns "true" iff there is a stop-world GC in progress. (I assume | |
404 // that it should answer "false" for the concurrent part of a concurrent | |
405 // collector -- dld). | |
406 bool is_gc_active() const { return _is_gc_active; } | |
407 | |
408 // Total number of GC collections (started) | |
409 unsigned int total_collections() const { return _total_collections; } | |
410 unsigned int total_full_collections() const { return _total_full_collections;} | |
411 | |
412 // Increment total number of GC collections (started) | |
413 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2 | |
414 void increment_total_collections(bool full = false) { | |
415 _total_collections++; | |
416 if (full) { | |
417 increment_total_full_collections(); | |
418 } | |
419 } | |
420 | |
421 void increment_total_full_collections() { _total_full_collections++; } | |
422 | |
423 // Return the AdaptiveSizePolicy for the heap. | |
424 virtual AdaptiveSizePolicy* size_policy() = 0; | |
425 | |
426 // Iterate over all the ref-containing fields of all objects, calling | |
427 // "cl.do_oop" on each. This includes objects in permanent memory. | |
428 virtual void oop_iterate(OopClosure* cl) = 0; | |
429 | |
430 // Iterate over all objects, calling "cl.do_object" on each. | |
431 // This includes objects in permanent memory. | |
432 virtual void object_iterate(ObjectClosure* cl) = 0; | |
433 | |
434 // Behaves the same as oop_iterate, except only traverses | |
435 // interior pointers contained in permanent memory. If there | |
436 // is no permanent memory, does nothing. | |
437 virtual void permanent_oop_iterate(OopClosure* cl) = 0; | |
438 | |
439 // Behaves the same as object_iterate, except only traverses | |
440 // object contained in permanent memory. If there is no | |
441 // permanent memory, does nothing. | |
442 virtual void permanent_object_iterate(ObjectClosure* cl) = 0; | |
443 | |
444 // NOTE! There is no requirement that a collector implement these | |
445 // functions. | |
446 // | |
447 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, | |
448 // each address in the (reserved) heap is a member of exactly | |
449 // one block. The defining characteristic of a block is that it is | |
450 // possible to find its size, and thus to progress forward to the next | |
451 // block. (Blocks may be of different sizes.) Thus, blocks may | |
452 // represent Java objects, or they might be free blocks in a | |
453 // free-list-based heap (or subheap), as long as the two kinds are | |
454 // distinguishable and the size of each is determinable. | |
455 | |
456 // Returns the address of the start of the "block" that contains the | |
457 // address "addr". We say "blocks" instead of "object" since some heaps | |
458 // may not pack objects densely; a chunk may either be an object or a | |
459 // non-object. | |
460 virtual HeapWord* block_start(const void* addr) const = 0; | |
461 | |
462 // Requires "addr" to be the start of a chunk, and returns its size. | |
463 // "addr + size" is required to be the start of a new chunk, or the end | |
464 // of the active area of the heap. | |
465 virtual size_t block_size(const HeapWord* addr) const = 0; | |
466 | |
467 // Requires "addr" to be the start of a block, and returns "TRUE" iff | |
468 // the block is an object. | |
469 virtual bool block_is_obj(const HeapWord* addr) const = 0; | |
470 | |
471 // Returns the longest time (in ms) that has elapsed since the last | |
472 // time that any part of the heap was examined by a garbage collection. | |
473 virtual jlong millis_since_last_gc() = 0; | |
474 | |
475 // Perform any cleanup actions necessary before allowing a verification. | |
476 virtual void prepare_for_verify() = 0; | |
477 | |
478 virtual void print() const = 0; | |
479 virtual void print_on(outputStream* st) const = 0; | |
480 | |
481 // Print all GC threads (other than the VM thread) | |
482 // used by this heap. | |
483 virtual void print_gc_threads_on(outputStream* st) const = 0; | |
484 void print_gc_threads() { print_gc_threads_on(tty); } | |
485 // Iterator for all GC threads (other than VM thread) | |
486 virtual void gc_threads_do(ThreadClosure* tc) const = 0; | |
487 | |
488 // Print any relevant tracing info that flags imply. | |
489 // Default implementation does nothing. | |
490 virtual void print_tracing_info() const = 0; | |
491 | |
492 // Heap verification | |
493 virtual void verify(bool allow_dirty, bool silent) = 0; | |
494 | |
495 // Non product verification and debugging. | |
496 #ifndef PRODUCT | |
497 // Support for PromotionFailureALot. Return true if it's time to cause a | |
498 // promotion failure. The no-argument version uses | |
499 // this->_promotion_failure_alot_count as the counter. | |
500 inline bool promotion_should_fail(volatile size_t* count); | |
501 inline bool promotion_should_fail(); | |
502 | |
503 // Reset the PromotionFailureALot counters. Should be called at the end of a | |
504 // GC in which promotion failure ocurred. | |
505 inline void reset_promotion_should_fail(volatile size_t* count); | |
506 inline void reset_promotion_should_fail(); | |
507 #endif // #ifndef PRODUCT | |
508 | |
509 #ifdef ASSERT | |
510 static int fired_fake_oom() { | |
511 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt); | |
512 } | |
513 #endif | |
514 }; | |
515 | |
516 // Class to set and reset the GC cause for a CollectedHeap. | |
517 | |
518 class GCCauseSetter : StackObj { | |
519 CollectedHeap* _heap; | |
520 GCCause::Cause _previous_cause; | |
521 public: | |
522 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) { | |
523 assert(SafepointSynchronize::is_at_safepoint(), | |
524 "This method manipulates heap state without locking"); | |
525 _heap = heap; | |
526 _previous_cause = _heap->gc_cause(); | |
527 _heap->set_gc_cause(cause); | |
528 } | |
529 | |
530 ~GCCauseSetter() { | |
531 assert(SafepointSynchronize::is_at_safepoint(), | |
532 "This method manipulates heap state without locking"); | |
533 _heap->set_gc_cause(_previous_cause); | |
534 } | |
535 }; |