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annotate src/share/vm/memory/genCollectedHeap.hpp @ 3109:3664989976e2
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author | Gilles Duboscq <gilles.duboscq@oracle.com> |
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date | Fri, 01 Jul 2011 12:57:10 +0200 |
parents | 6cd6d394f280 |
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0 | 1 /* |
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2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP |
26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP | |
27 | |
28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp" | |
29 #include "memory/collectorPolicy.hpp" | |
30 #include "memory/generation.hpp" | |
31 #include "memory/sharedHeap.hpp" | |
32 | |
0 | 33 class SubTasksDone; |
34 | |
35 // A "GenCollectedHeap" is a SharedHeap that uses generational | |
36 // collection. It is represented with a sequence of Generation's. | |
37 class GenCollectedHeap : public SharedHeap { | |
38 friend class GenCollectorPolicy; | |
39 friend class Generation; | |
40 friend class DefNewGeneration; | |
41 friend class TenuredGeneration; | |
42 friend class ConcurrentMarkSweepGeneration; | |
43 friend class CMSCollector; | |
44 friend class GenMarkSweep; | |
45 friend class VM_GenCollectForAllocation; | |
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46 friend class VM_GenCollectForPermanentAllocation; |
0 | 47 friend class VM_GenCollectFull; |
48 friend class VM_GenCollectFullConcurrent; | |
49 friend class VM_GC_HeapInspection; | |
50 friend class VM_HeapDumper; | |
51 friend class HeapInspection; | |
52 friend class GCCauseSetter; | |
53 friend class VMStructs; | |
54 public: | |
55 enum SomeConstants { | |
56 max_gens = 10 | |
57 }; | |
58 | |
59 friend class VM_PopulateDumpSharedSpace; | |
60 | |
61 protected: | |
62 // Fields: | |
63 static GenCollectedHeap* _gch; | |
64 | |
65 private: | |
66 int _n_gens; | |
67 Generation* _gens[max_gens]; | |
68 GenerationSpec** _gen_specs; | |
69 | |
70 // The generational collector policy. | |
71 GenCollectorPolicy* _gen_policy; | |
72 | |
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73 // Indicates that the most recent previous incremental collection failed. |
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74 // The flag is cleared when an action is taken that might clear the |
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75 // condition that caused that incremental collection to fail. |
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76 bool _incremental_collection_failed; |
0 | 77 |
78 // In support of ExplicitGCInvokesConcurrent functionality | |
79 unsigned int _full_collections_completed; | |
80 | |
81 // Data structure for claiming the (potentially) parallel tasks in | |
82 // (gen-specific) strong roots processing. | |
83 SubTasksDone* _gen_process_strong_tasks; | |
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84 SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_tasks; } |
0 | 85 |
86 // In block contents verification, the number of header words to skip | |
87 NOT_PRODUCT(static size_t _skip_header_HeapWords;) | |
88 | |
89 // GC is not allowed during the dump of the shared classes. Keep track | |
90 // of this in order to provide an reasonable error message when terminating. | |
91 bool _preloading_shared_classes; | |
92 | |
93 protected: | |
94 // Directs each generation up to and including "collectedGen" to recompute | |
95 // its desired size. | |
96 void compute_new_generation_sizes(int collectedGen); | |
97 | |
98 // Helper functions for allocation | |
99 HeapWord* attempt_allocation(size_t size, | |
100 bool is_tlab, | |
101 bool first_only); | |
102 | |
103 // Helper function for two callbacks below. | |
104 // Considers collection of the first max_level+1 generations. | |
105 void do_collection(bool full, | |
106 bool clear_all_soft_refs, | |
107 size_t size, | |
108 bool is_tlab, | |
109 int max_level); | |
110 | |
111 // Callback from VM_GenCollectForAllocation operation. | |
112 // This function does everything necessary/possible to satisfy an | |
113 // allocation request that failed in the youngest generation that should | |
114 // have handled it (including collection, expansion, etc.) | |
115 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab); | |
116 | |
117 // Callback from VM_GenCollectFull operation. | |
118 // Perform a full collection of the first max_level+1 generations. | |
119 void do_full_collection(bool clear_all_soft_refs, int max_level); | |
120 | |
121 // Does the "cause" of GC indicate that | |
122 // we absolutely __must__ clear soft refs? | |
123 bool must_clear_all_soft_refs(); | |
124 | |
125 public: | |
126 GenCollectedHeap(GenCollectorPolicy *policy); | |
127 | |
128 GCStats* gc_stats(int level) const; | |
129 | |
130 // Returns JNI_OK on success | |
131 virtual jint initialize(); | |
132 char* allocate(size_t alignment, PermanentGenerationSpec* perm_gen_spec, | |
133 size_t* _total_reserved, int* _n_covered_regions, | |
134 ReservedSpace* heap_rs); | |
135 | |
136 // Does operations required after initialization has been done. | |
137 void post_initialize(); | |
138 | |
139 // Initialize ("weak") refs processing support | |
140 virtual void ref_processing_init(); | |
141 | |
142 virtual CollectedHeap::Name kind() const { | |
143 return CollectedHeap::GenCollectedHeap; | |
144 } | |
145 | |
146 // The generational collector policy. | |
147 GenCollectorPolicy* gen_policy() const { return _gen_policy; } | |
148 | |
149 // Adaptive size policy | |
150 virtual AdaptiveSizePolicy* size_policy() { | |
151 return gen_policy()->size_policy(); | |
152 } | |
153 | |
154 size_t capacity() const; | |
155 size_t used() const; | |
156 | |
157 // Save the "used_region" for generations level and lower, | |
158 // and, if perm is true, for perm gen. | |
159 void save_used_regions(int level, bool perm); | |
160 | |
161 size_t max_capacity() const; | |
162 | |
163 HeapWord* mem_allocate(size_t size, | |
164 bool is_large_noref, | |
165 bool is_tlab, | |
166 bool* gc_overhead_limit_was_exceeded); | |
167 | |
168 // We may support a shared contiguous allocation area, if the youngest | |
169 // generation does. | |
170 bool supports_inline_contig_alloc() const; | |
171 HeapWord** top_addr() const; | |
172 HeapWord** end_addr() const; | |
173 | |
174 // Return an estimate of the maximum allocation that could be performed | |
175 // without triggering any collection activity. In a generational | |
176 // collector, for example, this is probably the largest allocation that | |
177 // could be supported in the youngest generation. It is "unsafe" because | |
178 // no locks are taken; the result should be treated as an approximation, | |
179 // not a guarantee. | |
180 size_t unsafe_max_alloc(); | |
181 | |
182 // Does this heap support heap inspection? (+PrintClassHistogram) | |
183 virtual bool supports_heap_inspection() const { return true; } | |
184 | |
185 // Perform a full collection of the heap; intended for use in implementing | |
186 // "System.gc". This implies as full a collection as the CollectedHeap | |
187 // supports. Caller does not hold the Heap_lock on entry. | |
188 void collect(GCCause::Cause cause); | |
189 | |
190 // This interface assumes that it's being called by the | |
191 // vm thread. It collects the heap assuming that the | |
192 // heap lock is already held and that we are executing in | |
193 // the context of the vm thread. | |
194 void collect_as_vm_thread(GCCause::Cause cause); | |
195 | |
196 // The same as above but assume that the caller holds the Heap_lock. | |
197 void collect_locked(GCCause::Cause cause); | |
198 | |
199 // Perform a full collection of the first max_level+1 generations. | |
200 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry. | |
201 void collect(GCCause::Cause cause, int max_level); | |
202 | |
203 // Returns "TRUE" iff "p" points into the allocated area of the heap. | |
204 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may | |
205 // be expensive to compute in general, so, to prevent | |
206 // their inadvertent use in product jvm's, we restrict their use to | |
207 // assertion checking or verification only. | |
208 bool is_in(const void* p) const; | |
209 | |
210 // override | |
211 bool is_in_closed_subset(const void* p) const { | |
212 if (UseConcMarkSweepGC) { | |
213 return is_in_reserved(p); | |
214 } else { | |
215 return is_in(p); | |
216 } | |
217 } | |
218 | |
219 // Returns "TRUE" iff "p" points into the youngest generation. | |
220 bool is_in_youngest(void* p); | |
221 | |
222 // Iteration functions. | |
223 void oop_iterate(OopClosure* cl); | |
224 void oop_iterate(MemRegion mr, OopClosure* cl); | |
225 void object_iterate(ObjectClosure* cl); | |
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226 void safe_object_iterate(ObjectClosure* cl); |
0 | 227 void object_iterate_since_last_GC(ObjectClosure* cl); |
228 Space* space_containing(const void* addr) const; | |
229 | |
230 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, | |
231 // each address in the (reserved) heap is a member of exactly | |
232 // one block. The defining characteristic of a block is that it is | |
233 // possible to find its size, and thus to progress forward to the next | |
234 // block. (Blocks may be of different sizes.) Thus, blocks may | |
235 // represent Java objects, or they might be free blocks in a | |
236 // free-list-based heap (or subheap), as long as the two kinds are | |
237 // distinguishable and the size of each is determinable. | |
238 | |
239 // Returns the address of the start of the "block" that contains the | |
240 // address "addr". We say "blocks" instead of "object" since some heaps | |
241 // may not pack objects densely; a chunk may either be an object or a | |
242 // non-object. | |
243 virtual HeapWord* block_start(const void* addr) const; | |
244 | |
245 // Requires "addr" to be the start of a chunk, and returns its size. | |
246 // "addr + size" is required to be the start of a new chunk, or the end | |
247 // of the active area of the heap. Assumes (and verifies in non-product | |
248 // builds) that addr is in the allocated part of the heap and is | |
249 // the start of a chunk. | |
250 virtual size_t block_size(const HeapWord* addr) const; | |
251 | |
252 // Requires "addr" to be the start of a block, and returns "TRUE" iff | |
253 // the block is an object. Assumes (and verifies in non-product | |
254 // builds) that addr is in the allocated part of the heap and is | |
255 // the start of a chunk. | |
256 virtual bool block_is_obj(const HeapWord* addr) const; | |
257 | |
258 // Section on TLAB's. | |
259 virtual bool supports_tlab_allocation() const; | |
260 virtual size_t tlab_capacity(Thread* thr) const; | |
261 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; | |
262 virtual HeapWord* allocate_new_tlab(size_t size); | |
263 | |
342
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264 // Can a compiler initialize a new object without store barriers? |
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265 // This permission only extends from the creation of a new object |
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266 // via a TLAB up to the first subsequent safepoint. |
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267 virtual bool can_elide_tlab_store_barriers() const { |
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268 return true; |
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269 } |
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270 |
1166 | 271 virtual bool card_mark_must_follow_store() const { |
272 return UseConcMarkSweepGC; | |
273 } | |
274 | |
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275 // We don't need barriers for stores to objects in the |
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276 // young gen and, a fortiori, for initializing stores to |
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277 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS} |
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278 // only and may need to be re-examined in case other |
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279 // kinds of collectors are implemented in the future. |
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280 virtual bool can_elide_initializing_store_barrier(oop new_obj) { |
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281 // We wanted to assert that:- |
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282 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC, |
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283 // "Check can_elide_initializing_store_barrier() for this collector"); |
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284 // but unfortunately the flag UseSerialGC need not necessarily always |
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285 // be set when DefNew+Tenured are being used. |
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286 return is_in_youngest((void*)new_obj); |
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287 } |
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288 |
342
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289 // Can a compiler elide a store barrier when it writes |
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290 // a permanent oop into the heap? Applies when the compiler |
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291 // is storing x to the heap, where x->is_perm() is true. |
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292 virtual bool can_elide_permanent_oop_store_barriers() const { |
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293 // CMS needs to see all, even intra-generational, ref updates. |
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294 return !UseConcMarkSweepGC; |
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295 } |
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296 |
0 | 297 // The "requestor" generation is performing some garbage collection |
298 // action for which it would be useful to have scratch space. The | |
299 // requestor promises to allocate no more than "max_alloc_words" in any | |
300 // older generation (via promotion say.) Any blocks of space that can | |
301 // be provided are returned as a list of ScratchBlocks, sorted by | |
302 // decreasing size. | |
303 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words); | |
263
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304 // Allow each generation to reset any scratch space that it has |
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305 // contributed as it needs. |
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306 void release_scratch(); |
0 | 307 |
308 size_t large_typearray_limit(); | |
309 | |
310 // Ensure parsability: override | |
311 virtual void ensure_parsability(bool retire_tlabs); | |
312 | |
313 // Time in ms since the longest time a collector ran in | |
314 // in any generation. | |
315 virtual jlong millis_since_last_gc(); | |
316 | |
317 // Total number of full collections completed. | |
318 unsigned int total_full_collections_completed() { | |
319 assert(_full_collections_completed <= _total_full_collections, | |
320 "Can't complete more collections than were started"); | |
321 return _full_collections_completed; | |
322 } | |
323 | |
324 // Update above counter, as appropriate, at the end of a stop-world GC cycle | |
325 unsigned int update_full_collections_completed(); | |
326 // Update above counter, as appropriate, at the end of a concurrent GC cycle | |
327 unsigned int update_full_collections_completed(unsigned int count); | |
328 | |
329 // Update "time of last gc" for all constituent generations | |
330 // to "now". | |
331 void update_time_of_last_gc(jlong now) { | |
332 for (int i = 0; i < _n_gens; i++) { | |
333 _gens[i]->update_time_of_last_gc(now); | |
334 } | |
335 perm_gen()->update_time_of_last_gc(now); | |
336 } | |
337 | |
338 // Update the gc statistics for each generation. | |
339 // "level" is the level of the lastest collection | |
340 void update_gc_stats(int current_level, bool full) { | |
341 for (int i = 0; i < _n_gens; i++) { | |
342 _gens[i]->update_gc_stats(current_level, full); | |
343 } | |
344 perm_gen()->update_gc_stats(current_level, full); | |
345 } | |
346 | |
347 // Override. | |
348 bool no_gc_in_progress() { return !is_gc_active(); } | |
349 | |
350 // Override. | |
351 void prepare_for_verify(); | |
352 | |
353 // Override. | |
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354 void verify(bool allow_dirty, bool silent, bool /* option */); |
0 | 355 |
356 // Override. | |
357 void print() const; | |
358 void print_on(outputStream* st) const; | |
359 virtual void print_gc_threads_on(outputStream* st) const; | |
360 virtual void gc_threads_do(ThreadClosure* tc) const; | |
361 virtual void print_tracing_info() const; | |
362 | |
363 // PrintGC, PrintGCDetails support | |
364 void print_heap_change(size_t prev_used) const; | |
365 void print_perm_heap_change(size_t perm_prev_used) const; | |
366 | |
367 // The functions below are helper functions that a subclass of | |
368 // "CollectedHeap" can use in the implementation of its virtual | |
369 // functions. | |
370 | |
371 class GenClosure : public StackObj { | |
372 public: | |
373 virtual void do_generation(Generation* gen) = 0; | |
374 }; | |
375 | |
376 // Apply "cl.do_generation" to all generations in the heap (not including | |
377 // the permanent generation). If "old_to_young" determines the order. | |
378 void generation_iterate(GenClosure* cl, bool old_to_young); | |
379 | |
380 void space_iterate(SpaceClosure* cl); | |
381 | |
382 // Return "true" if all generations (but perm) have reached the | |
383 // maximal committed limit that they can reach, without a garbage | |
384 // collection. | |
385 virtual bool is_maximal_no_gc() const; | |
386 | |
387 // Return the generation before "gen", or else NULL. | |
388 Generation* prev_gen(Generation* gen) const { | |
389 int l = gen->level(); | |
390 if (l == 0) return NULL; | |
391 else return _gens[l-1]; | |
392 } | |
393 | |
394 // Return the generation after "gen", or else NULL. | |
395 Generation* next_gen(Generation* gen) const { | |
396 int l = gen->level() + 1; | |
397 if (l == _n_gens) return NULL; | |
398 else return _gens[l]; | |
399 } | |
400 | |
401 Generation* get_gen(int i) const { | |
402 if (i >= 0 && i < _n_gens) | |
403 return _gens[i]; | |
404 else | |
405 return NULL; | |
406 } | |
407 | |
408 int n_gens() const { | |
409 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity"); | |
410 return _n_gens; | |
411 } | |
412 | |
413 // Convenience function to be used in situations where the heap type can be | |
414 // asserted to be this type. | |
415 static GenCollectedHeap* heap(); | |
416 | |
417 void set_par_threads(int t); | |
418 | |
419 | |
420 // Invoke the "do_oop" method of one of the closures "not_older_gens" | |
421 // or "older_gens" on root locations for the generation at | |
422 // "level". (The "older_gens" closure is used for scanning references | |
423 // from older generations; "not_older_gens" is used everywhere else.) | |
424 // If "younger_gens_as_roots" is false, younger generations are | |
425 // not scanned as roots; in this case, the caller must be arranging to | |
426 // scan the younger generations itself. (For example, a generation might | |
427 // explicitly mark reachable objects in younger generations, to avoid | |
428 // excess storage retention.) If "collecting_perm_gen" is false, then | |
429 // roots that may only contain references to permGen objects are not | |
430 // scanned. The "so" argument determines which of the roots | |
431 // the closure is applied to: | |
432 // "SO_None" does none; | |
433 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary; | |
434 // "SO_SystemClasses" to all the "system" classes and loaders; | |
435 // "SO_Symbols_and_Strings" applies the closure to all entries in | |
436 // SymbolsTable and StringTable. | |
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437 void gen_process_strong_roots(int level, |
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438 bool younger_gens_as_roots, |
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439 // The remaining arguments are in an order |
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440 // consistent with SharedHeap::process_strong_roots: |
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441 bool activate_scope, |
0 | 442 bool collecting_perm_gen, |
443 SharedHeap::ScanningOption so, | |
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444 OopsInGenClosure* not_older_gens, |
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445 bool do_code_roots, |
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446 OopsInGenClosure* older_gens); |
0 | 447 |
448 // Apply "blk" to all the weak roots of the system. These include | |
449 // JNI weak roots, the code cache, system dictionary, symbol table, | |
450 // string table, and referents of reachable weak refs. | |
451 void gen_process_weak_roots(OopClosure* root_closure, | |
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452 CodeBlobClosure* code_roots, |
0 | 453 OopClosure* non_root_closure); |
454 | |
455 // Set the saved marks of generations, if that makes sense. | |
456 // In particular, if any generation might iterate over the oops | |
457 // in other generations, it should call this method. | |
458 void save_marks(); | |
459 | |
460 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects | |
461 // allocated since the last call to save_marks in generations at or above | |
462 // "level" (including the permanent generation.) The "cur" closure is | |
463 // applied to references in the generation at "level", and the "older" | |
464 // closure to older (and permanent) generations. | |
465 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \ | |
466 void oop_since_save_marks_iterate(int level, \ | |
467 OopClosureType* cur, \ | |
468 OopClosureType* older); | |
469 | |
470 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL) | |
471 | |
472 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL | |
473 | |
474 // Returns "true" iff no allocations have occurred in any generation at | |
475 // "level" or above (including the permanent generation) since the last | |
476 // call to "save_marks". | |
477 bool no_allocs_since_save_marks(int level); | |
478 | |
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479 // Returns true if an incremental collection is likely to fail. |
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480 // We optionally consult the young gen, if asked to do so; |
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481 // otherwise we base our answer on whether the previous incremental |
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482 // collection attempt failed with no corrective action as of yet. |
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483 bool incremental_collection_will_fail(bool consult_young) { |
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484 // Assumes a 2-generation system; the first disjunct remembers if an |
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485 // incremental collection failed, even when we thought (second disjunct) |
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486 // that it would not. |
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487 assert(heap()->collector_policy()->is_two_generation_policy(), |
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488 "the following definition may not be suitable for an n(>2)-generation system"); |
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489 return incremental_collection_failed() || |
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490 (consult_young && !get_gen(0)->collection_attempt_is_safe()); |
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491 } |
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492 |
0 | 493 // If a generation bails out of an incremental collection, |
494 // it sets this flag. | |
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495 bool incremental_collection_failed() const { |
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496 return _incremental_collection_failed; |
0 | 497 } |
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498 void set_incremental_collection_failed() { |
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499 _incremental_collection_failed = true; |
0 | 500 } |
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501 void clear_incremental_collection_failed() { |
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502 _incremental_collection_failed = false; |
0 | 503 } |
504 | |
505 // Promotion of obj into gen failed. Try to promote obj to higher non-perm | |
506 // gens in ascending order; return the new location of obj if successful. | |
507 // Otherwise, try expand-and-allocate for obj in each generation starting at | |
508 // gen; return the new location of obj if successful. Otherwise, return NULL. | |
509 oop handle_failed_promotion(Generation* gen, | |
510 oop obj, | |
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511 size_t obj_size); |
0 | 512 |
513 private: | |
514 // Accessor for memory state verification support | |
515 NOT_PRODUCT( | |
516 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; } | |
517 ) | |
518 | |
519 // Override | |
520 void check_for_non_bad_heap_word_value(HeapWord* addr, | |
521 size_t size) PRODUCT_RETURN; | |
522 | |
523 // For use by mark-sweep. As implemented, mark-sweep-compact is global | |
524 // in an essential way: compaction is performed across generations, by | |
525 // iterating over spaces. | |
526 void prepare_for_compaction(); | |
527 | |
528 // Perform a full collection of the first max_level+1 generations. | |
529 // This is the low level interface used by the public versions of | |
530 // collect() and collect_locked(). Caller holds the Heap_lock on entry. | |
531 void collect_locked(GCCause::Cause cause, int max_level); | |
532 | |
533 // Returns success or failure. | |
534 bool create_cms_collector(); | |
535 | |
536 // In support of ExplicitGCInvokesConcurrent functionality | |
537 bool should_do_concurrent_full_gc(GCCause::Cause cause); | |
538 void collect_mostly_concurrent(GCCause::Cause cause); | |
539 | |
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540 // Save the tops of the spaces in all generations |
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541 void record_gen_tops_before_GC() PRODUCT_RETURN; |
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542 |
0 | 543 protected: |
544 virtual void gc_prologue(bool full); | |
545 virtual void gc_epilogue(bool full); | |
546 | |
547 public: | |
548 virtual void preload_and_dump(TRAPS) KERNEL_RETURN; | |
549 }; | |
1972 | 550 |
551 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP |