1 /*
2 * Copyright (c) 2000, 2013, 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 */
24
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
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;
46 friend class VM_GenCollectFull;
47 friend class VM_GenCollectFullConcurrent;
48 friend class VM_GC_HeapInspection;
49 friend class VM_HeapDumper;
50 friend class HeapInspection;
51 friend class GCCauseSetter;
52 friend class VMStructs;
53 public:
54 enum SomeConstants {
55 max_gens = 10
56 };
57
58 friend class VM_PopulateDumpSharedSpace;
59
60 protected:
61 // Fields:
62 static GenCollectedHeap* _gch;
63
64 private:
65 int _n_gens;
66 Generation* _gens[max_gens];
67 GenerationSpec** _gen_specs;
68
69 // The generational collector policy.
70 GenCollectorPolicy* _gen_policy;
71
72 // Indicates that the most recent previous incremental collection failed.
73 // The flag is cleared when an action is taken that might clear the
74 // condition that caused that incremental collection to fail.
75 bool _incremental_collection_failed;
76
77 // In support of ExplicitGCInvokesConcurrent functionality
78 unsigned int _full_collections_completed;
79
80 // Data structure for claiming the (potentially) parallel tasks in
81 // (gen-specific) roots processing.
82 SubTasksDone* _process_strong_tasks;
83
84 // In block contents verification, the number of header words to skip
85 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
86
87 protected:
88 // Helper functions for allocation
89 HeapWord* attempt_allocation(size_t size,
90 bool is_tlab,
91 bool first_only);
92
93 // Helper function for two callbacks below.
94 // Considers collection of the first max_level+1 generations.
95 void do_collection(bool full,
96 bool clear_all_soft_refs,
97 size_t size,
98 bool is_tlab,
99 int max_level);
100
101 // Callback from VM_GenCollectForAllocation operation.
102 // This function does everything necessary/possible to satisfy an
103 // allocation request that failed in the youngest generation that should
104 // have handled it (including collection, expansion, etc.)
105 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
106
107 // Callback from VM_GenCollectFull operation.
108 // Perform a full collection of the first max_level+1 generations.
109 virtual void do_full_collection(bool clear_all_soft_refs);
110 void do_full_collection(bool clear_all_soft_refs, int max_level);
111
112 // Does the "cause" of GC indicate that
113 // we absolutely __must__ clear soft refs?
114 bool must_clear_all_soft_refs();
115
116 public:
117 GenCollectedHeap(GenCollectorPolicy *policy);
118
119 GCStats* gc_stats(int level) const;
120
121 // Returns JNI_OK on success
122 virtual jint initialize();
123 char* allocate(size_t alignment,
124 size_t* _total_reserved, int* _n_covered_regions,
125 ReservedSpace* heap_rs);
126
127 // Does operations required after initialization has been done.
128 void post_initialize();
129
130 // Initialize ("weak") refs processing support
131 virtual void ref_processing_init();
132
133 virtual CollectedHeap::Name kind() const {
134 return CollectedHeap::GenCollectedHeap;
135 }
136
137 // The generational collector policy.
138 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
139 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
140
141 // Adaptive size policy
142 virtual AdaptiveSizePolicy* size_policy() {
143 return gen_policy()->size_policy();
144 }
145
146 // Return the (conservative) maximum heap alignment
147 static size_t conservative_max_heap_alignment() {
148 return Generation::GenGrain;
149 }
150
151 size_t capacity() const;
152 size_t used() const;
153
154 // Save the "used_region" for generations level and lower.
155 void save_used_regions(int level);
156
157 size_t max_capacity() const;
158
159 HeapWord* mem_allocate(size_t size,
160 bool* gc_overhead_limit_was_exceeded);
161
162 // We may support a shared contiguous allocation area, if the youngest
163 // generation does.
164 bool supports_inline_contig_alloc() const;
165 HeapWord** top_addr() const;
166 HeapWord** end_addr() const;
167
168 // Does this heap support heap inspection? (+PrintClassHistogram)
169 virtual bool supports_heap_inspection() const { return true; }
170
171 // Perform a full collection of the heap; intended for use in implementing
172 // "System.gc". This implies as full a collection as the CollectedHeap
173 // supports. Caller does not hold the Heap_lock on entry.
174 void collect(GCCause::Cause cause);
175
176 // The same as above but assume that the caller holds the Heap_lock.
177 void collect_locked(GCCause::Cause cause);
178
179 // Perform a full collection of the first max_level+1 generations.
180 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
181 void collect(GCCause::Cause cause, int max_level);
182
183 // Returns "TRUE" iff "p" points into the committed areas of the heap.
184 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
185 // be expensive to compute in general, so, to prevent
186 // their inadvertent use in product jvm's, we restrict their use to
187 // assertion checking or verification only.
188 bool is_in(const void* p) const;
189
190 // override
191 bool is_in_closed_subset(const void* p) const {
192 if (UseConcMarkSweepGC) {
193 return is_in_reserved(p);
194 } else {
195 return is_in(p);
196 }
197 }
198
199 // Returns true if the reference is to an object in the reserved space
200 // for the young generation.
201 // Assumes the the young gen address range is less than that of the old gen.
202 bool is_in_young(oop p);
203
204 #ifdef ASSERT
205 virtual bool is_in_partial_collection(const void* p);
206 #endif
207
208 virtual bool is_scavengable(const void* addr) {
209 return is_in_young((oop)addr);
210 }
211
212 // Iteration functions.
213 void oop_iterate(ExtendedOopClosure* cl);
214 void object_iterate(ObjectClosure* cl);
215 void safe_object_iterate(ObjectClosure* cl);
216 Space* space_containing(const void* addr) const;
217
218 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
219 // each address in the (reserved) heap is a member of exactly
220 // one block. The defining characteristic of a block is that it is
221 // possible to find its size, and thus to progress forward to the next
222 // block. (Blocks may be of different sizes.) Thus, blocks may
223 // represent Java objects, or they might be free blocks in a
224 // free-list-based heap (or subheap), as long as the two kinds are
225 // distinguishable and the size of each is determinable.
226
227 // Returns the address of the start of the "block" that contains the
228 // address "addr". We say "blocks" instead of "object" since some heaps
229 // may not pack objects densely; a chunk may either be an object or a
230 // non-object.
231 virtual HeapWord* block_start(const void* addr) const;
232
233 // Requires "addr" to be the start of a chunk, and returns its size.
234 // "addr + size" is required to be the start of a new chunk, or the end
235 // of the active area of the heap. Assumes (and verifies in non-product
236 // builds) that addr is in the allocated part of the heap and is
237 // the start of a chunk.
238 virtual size_t block_size(const HeapWord* addr) const;
239
240 // Requires "addr" to be the start of a block, and returns "TRUE" iff
241 // the block is an object. Assumes (and verifies in non-product
242 // builds) that addr is in the allocated part of the heap and is
243 // the start of a chunk.
244 virtual bool block_is_obj(const HeapWord* addr) const;
245
246 // Section on TLAB's.
247 virtual bool supports_tlab_allocation() const;
248 virtual size_t tlab_capacity(Thread* thr) const;
249 virtual size_t tlab_used(Thread* thr) const;
250 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
251 virtual HeapWord* allocate_new_tlab(size_t size);
252
253 // Can a compiler initialize a new object without store barriers?
254 // This permission only extends from the creation of a new object
255 // via a TLAB up to the first subsequent safepoint.
256 virtual bool can_elide_tlab_store_barriers() const {
257 return true;
258 }
259
260 virtual bool card_mark_must_follow_store() const {
261 return UseConcMarkSweepGC;
262 }
263
264 // We don't need barriers for stores to objects in the
265 // young gen and, a fortiori, for initializing stores to
266 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
267 // only and may need to be re-examined in case other
268 // kinds of collectors are implemented in the future.
269 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
270 // We wanted to assert that:-
271 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
272 // "Check can_elide_initializing_store_barrier() for this collector");
273 // but unfortunately the flag UseSerialGC need not necessarily always
274 // be set when DefNew+Tenured are being used.
275 return is_in_young(new_obj);
276 }
277
278 // The "requestor" generation is performing some garbage collection
279 // action for which it would be useful to have scratch space. The
280 // requestor promises to allocate no more than "max_alloc_words" in any
281 // older generation (via promotion say.) Any blocks of space that can
282 // be provided are returned as a list of ScratchBlocks, sorted by
283 // decreasing size.
284 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
285 // Allow each generation to reset any scratch space that it has
286 // contributed as it needs.
287 void release_scratch();
288
289 // Ensure parsability: override
290 virtual void ensure_parsability(bool retire_tlabs);
291
292 // Time in ms since the longest time a collector ran in
293 // in any generation.
294 virtual jlong millis_since_last_gc();
295
296 // Total number of full collections completed.
297 unsigned int total_full_collections_completed() {
298 assert(_full_collections_completed <= _total_full_collections,
299 "Can't complete more collections than were started");
300 return _full_collections_completed;
301 }
302
303 // Update above counter, as appropriate, at the end of a stop-world GC cycle
304 unsigned int update_full_collections_completed();
305 // Update above counter, as appropriate, at the end of a concurrent GC cycle
306 unsigned int update_full_collections_completed(unsigned int count);
307
308 // Update "time of last gc" for all constituent generations
309 // to "now".
310 void update_time_of_last_gc(jlong now) {
311 for (int i = 0; i < _n_gens; i++) {
312 _gens[i]->update_time_of_last_gc(now);
313 }
314 }
315
316 // Update the gc statistics for each generation.
317 // "level" is the level of the lastest collection
318 void update_gc_stats(int current_level, bool full) {
319 for (int i = 0; i < _n_gens; i++) {
320 _gens[i]->update_gc_stats(current_level, full);
321 }
322 }
323
324 // Override.
325 bool no_gc_in_progress() { return !is_gc_active(); }
326
327 // Override.
328 void prepare_for_verify();
329
330 // Override.
331 void verify(bool silent, VerifyOption option);
332
333 // Override.
334 virtual void print_on(outputStream* st) const;
335 virtual void print_gc_threads_on(outputStream* st) const;
336 virtual void gc_threads_do(ThreadClosure* tc) const;
337 virtual void print_tracing_info() const;
338 virtual void print_on_error(outputStream* st) const;
339
340 // PrintGC, PrintGCDetails support
341 void print_heap_change(size_t prev_used) const;
342
343 // The functions below are helper functions that a subclass of
344 // "CollectedHeap" can use in the implementation of its virtual
345 // functions.
346
347 class GenClosure : public StackObj {
348 public:
349 virtual void do_generation(Generation* gen) = 0;
350 };
351
352 // Apply "cl.do_generation" to all generations in the heap
353 // If "old_to_young" determines the order.
354 void generation_iterate(GenClosure* cl, bool old_to_young);
355
356 void space_iterate(SpaceClosure* cl);
357
358 // Return "true" if all generations have reached the
359 // maximal committed limit that they can reach, without a garbage
360 // collection.
361 virtual bool is_maximal_no_gc() const;
362
363 // Return the generation before "gen".
364 Generation* prev_gen(Generation* gen) const {
365 int l = gen->level();
366 guarantee(l > 0, "Out of bounds");
367 return _gens[l-1];
368 }
369
370 // Return the generation after "gen".
371 Generation* next_gen(Generation* gen) const {
372 int l = gen->level() + 1;
373 guarantee(l < _n_gens, "Out of bounds");
374 return _gens[l];
375 }
376
377 Generation* get_gen(int i) const {
378 guarantee(i >= 0 && i < _n_gens, "Out of bounds");
379 return _gens[i];
380 }
381
382 int n_gens() const {
383 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
384 return _n_gens;
385 }
386
387 // Convenience function to be used in situations where the heap type can be
388 // asserted to be this type.
389 static GenCollectedHeap* heap();
390
391 void set_par_threads(uint t);
392 void set_n_termination(uint t);
393
394 // Invoke the "do_oop" method of one of the closures "not_older_gens"
395 // or "older_gens" on root locations for the generation at
396 // "level". (The "older_gens" closure is used for scanning references
397 // from older generations; "not_older_gens" is used everywhere else.)
398 // If "younger_gens_as_roots" is false, younger generations are
399 // not scanned as roots; in this case, the caller must be arranging to
400 // scan the younger generations itself. (For example, a generation might
401 // explicitly mark reachable objects in younger generations, to avoid
402 // excess storage retention.)
403 // The "so" argument determines which of the roots
404 // the closure is applied to:
405 // "SO_None" does none;
406 enum ScanningOption {
407 SO_None = 0x0,
408 SO_AllCodeCache = 0x8,
409 SO_ScavengeCodeCache = 0x10
410 };
411
412 private:
413 void process_roots(bool activate_scope,
414 ScanningOption so,
415 OopClosure* strong_roots,
416 OopClosure* weak_roots,
417 CLDClosure* strong_cld_closure,
418 CLDClosure* weak_cld_closure,
419 CodeBlobClosure* code_roots);
420
421 void gen_process_roots(int level,
422 bool younger_gens_as_roots,
423 bool activate_scope,
424 ScanningOption so,
425 OopsInGenClosure* not_older_gens,
426 OopsInGenClosure* weak_roots,
427 OopsInGenClosure* older_gens,
428 CLDClosure* cld_closure,
429 CLDClosure* weak_cld_closure,
430 CodeBlobClosure* code_closure);
431
432 public:
433 static const bool StrongAndWeakRoots = false;
434 static const bool StrongRootsOnly = true;
435
436 void gen_process_roots(int level,
437 bool younger_gens_as_roots,
438 bool activate_scope,
439 ScanningOption so,
440 bool only_strong_roots,
441 OopsInGenClosure* not_older_gens,
442 OopsInGenClosure* older_gens,
443 CLDClosure* cld_closure);
444
445 // Apply "root_closure" to all the weak roots of the system.
446 // These include JNI weak roots, string table,
447 // and referents of reachable weak refs.
448 void gen_process_weak_roots(OopClosure* root_closure);
449
450 // Set the saved marks of generations, if that makes sense.
451 // In particular, if any generation might iterate over the oops
452 // in other generations, it should call this method.
453 void save_marks();
454
455 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
456 // allocated since the last call to save_marks in generations at or above
457 // "level". The "cur" closure is
458 // applied to references in the generation at "level", and the "older"
459 // closure to older generations.
460 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
461 void oop_since_save_marks_iterate(int level, \
462 OopClosureType* cur, \
463 OopClosureType* older);
464
465 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
466
467 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
468
469 // Returns "true" iff no allocations have occurred in any generation at
470 // "level" or above since the last
471 // call to "save_marks".
472 bool no_allocs_since_save_marks(int level);
473
474 // Returns true if an incremental collection is likely to fail.
475 // We optionally consult the young gen, if asked to do so;
476 // otherwise we base our answer on whether the previous incremental
477 // collection attempt failed with no corrective action as of yet.
478 bool incremental_collection_will_fail(bool consult_young) {
479 // Assumes a 2-generation system; the first disjunct remembers if an
480 // incremental collection failed, even when we thought (second disjunct)
481 // that it would not.
482 assert(heap()->collector_policy()->is_two_generation_policy(),
483 "the following definition may not be suitable for an n(>2)-generation system");
484 return incremental_collection_failed() ||
485 (consult_young && !get_gen(0)->collection_attempt_is_safe());
486 }
487
488 // If a generation bails out of an incremental collection,
489 // it sets this flag.
490 bool incremental_collection_failed() const {
491 return _incremental_collection_failed;
492 }
493 void set_incremental_collection_failed() {
494 _incremental_collection_failed = true;
495 }
496 void clear_incremental_collection_failed() {
497 _incremental_collection_failed = false;
498 }
499
500 // Promotion of obj into gen failed. Try to promote obj to higher
501 // gens in ascending order; return the new location of obj if successful.
502 // Otherwise, try expand-and-allocate for obj in both the young and old
503 // generation; return the new location of obj if successful. Otherwise, return NULL.
504 oop handle_failed_promotion(Generation* old_gen,
505 oop obj,
506 size_t obj_size);
507
508 private:
509 // Accessor for memory state verification support
510 NOT_PRODUCT(
511 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
512 )
513
514 // Override
515 void check_for_non_bad_heap_word_value(HeapWord* addr,
516 size_t size) PRODUCT_RETURN;
517
518 // For use by mark-sweep. As implemented, mark-sweep-compact is global
519 // in an essential way: compaction is performed across generations, by
520 // iterating over spaces.
521 void prepare_for_compaction();
522
523 // Perform a full collection of the first max_level+1 generations.
524 // This is the low level interface used by the public versions of
525 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
526 void collect_locked(GCCause::Cause cause, int max_level);
527
528 // Returns success or failure.
529 bool create_cms_collector();
530
531 // In support of ExplicitGCInvokesConcurrent functionality
532 bool should_do_concurrent_full_gc(GCCause::Cause cause);
533 void collect_mostly_concurrent(GCCause::Cause cause);
534
535 // Save the tops of the spaces in all generations
536 void record_gen_tops_before_GC() PRODUCT_RETURN;
537
538 protected:
539 virtual void gc_prologue(bool full);
540 virtual void gc_epilogue(bool full);
541 };
542
543 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP