1 /*
2 * Copyright (c) 2000, 2018, 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_GC_SHARED_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
27
28 #include "gc/shared/collectedHeap.hpp"
29 #include "gc/shared/collectorPolicy.hpp"
30 #include "gc/shared/generation.hpp"
31 #include "gc/shared/softRefGenPolicy.hpp"
32
33 class AdaptiveSizePolicy;
34 class GCPolicyCounters;
35 class GenerationSpec;
36 class StrongRootsScope;
37 class SubTasksDone;
38 class WorkGang;
39
40 // A "GenCollectedHeap" is a CollectedHeap that uses generational
41 // collection. It has two generations, young and old.
42 class GenCollectedHeap : public CollectedHeap {
43 friend class GenCollectorPolicy;
44 friend class Generation;
45 friend class DefNewGeneration;
46 friend class TenuredGeneration;
47 friend class ConcurrentMarkSweepGeneration;
48 friend class CMSCollector;
49 friend class GenMarkSweep;
50 friend class VM_GenCollectForAllocation;
51 friend class VM_GenCollectFull;
52 friend class VM_GenCollectFullConcurrent;
53 friend class VM_GC_HeapInspection;
54 friend class VM_HeapDumper;
55 friend class HeapInspection;
56 friend class GCCauseSetter;
57 friend class VMStructs;
58 public:
59 friend class VM_PopulateDumpSharedSpace;
60
61 enum GenerationType {
62 YoungGen,
63 OldGen
64 };
65
66 private:
67 Generation* _young_gen;
68 Generation* _old_gen;
69
70 GenerationSpec* _young_gen_spec;
71 GenerationSpec* _old_gen_spec;
72
73 // The singleton CardTable Remembered Set.
74 CardTableRS* _rem_set;
75
76 // The generational collector policy.
77 GenCollectorPolicy* _gen_policy;
78
79 SoftRefGenPolicy _soft_ref_gen_policy;
80
81 // The sizing of the heap is controlled by a sizing policy.
82 AdaptiveSizePolicy* _size_policy;
83
84 GCPolicyCounters* _gc_policy_counters;
85
86 // Indicates that the most recent previous incremental collection failed.
87 // The flag is cleared when an action is taken that might clear the
88 // condition that caused that incremental collection to fail.
89 bool _incremental_collection_failed;
90
91 // In support of ExplicitGCInvokesConcurrent functionality
92 unsigned int _full_collections_completed;
93
94 // Collects the given generation.
95 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
96 bool run_verification, bool clear_soft_refs,
97 bool restore_marks_for_biased_locking);
98
99 // Reserve aligned space for the heap as needed by the contained generations.
100 char* allocate(size_t alignment, ReservedSpace* heap_rs);
101
102 // Initialize ("weak") refs processing support
103 void ref_processing_init();
104
105 protected:
106
107 // The set of potentially parallel tasks in root scanning.
108 enum GCH_strong_roots_tasks {
109 GCH_PS_Universe_oops_do,
110 GCH_PS_JNIHandles_oops_do,
111 GCH_PS_ObjectSynchronizer_oops_do,
112 GCH_PS_FlatProfiler_oops_do,
113 GCH_PS_Management_oops_do,
114 GCH_PS_SystemDictionary_oops_do,
115 GCH_PS_ClassLoaderDataGraph_oops_do,
116 GCH_PS_jvmti_oops_do,
117 GCH_PS_CodeCache_oops_do,
118 GCH_PS_aot_oops_do,
119 GCH_PS_younger_gens,
120 // Leave this one last.
121 GCH_PS_NumElements
122 };
123
124 // Data structure for claiming the (potentially) parallel tasks in
125 // (gen-specific) roots processing.
126 SubTasksDone* _process_strong_tasks;
127
128 GCMemoryManager* _young_manager;
129 GCMemoryManager* _old_manager;
130
131 // Helper functions for allocation
132 HeapWord* attempt_allocation(size_t size,
133 bool is_tlab,
134 bool first_only);
135
136 // Helper function for two callbacks below.
137 // Considers collection of the first max_level+1 generations.
138 void do_collection(bool full,
139 bool clear_all_soft_refs,
140 size_t size,
141 bool is_tlab,
142 GenerationType max_generation);
143
144 // Callback from VM_GenCollectForAllocation operation.
145 // This function does everything necessary/possible to satisfy an
146 // allocation request that failed in the youngest generation that should
147 // have handled it (including collection, expansion, etc.)
148 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
149
150 // Callback from VM_GenCollectFull operation.
151 // Perform a full collection of the first max_level+1 generations.
152 virtual void do_full_collection(bool clear_all_soft_refs);
153 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
154
155 // Does the "cause" of GC indicate that
156 // we absolutely __must__ clear soft refs?
157 bool must_clear_all_soft_refs();
158
159 GenCollectedHeap(GenCollectorPolicy *policy,
160 Generation::Name young,
161 Generation::Name old,
162 const char* policy_counters_name);
163
164 virtual void check_gen_kinds() = 0;
165
166 public:
167
168 // Returns JNI_OK on success
169 virtual jint initialize();
170 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
171
172 void initialize_size_policy(size_t init_eden_size,
173 size_t init_promo_size,
174 size_t init_survivor_size);
175
176 // Does operations required after initialization has been done.
177 void post_initialize();
178
179 Generation* young_gen() const { return _young_gen; }
180 Generation* old_gen() const { return _old_gen; }
181
182 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
183 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
184
185 GenerationSpec* young_gen_spec() const;
186 GenerationSpec* old_gen_spec() const;
187
188 // The generational collector policy.
189 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
190
191 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
192
193 virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
194
195 // Adaptive size policy
196 virtual AdaptiveSizePolicy* size_policy() {
197 return _size_policy;
198 }
199
200 // Performance Counter support
201 GCPolicyCounters* counters() { return _gc_policy_counters; }
202
203 // Return the (conservative) maximum heap alignment
204 static size_t conservative_max_heap_alignment() {
205 return Generation::GenGrain;
206 }
207
208 size_t capacity() const;
209 size_t used() const;
210
211 // Save the "used_region" for both generations.
212 void save_used_regions();
213
214 size_t max_capacity() const;
215
216 HeapWord* mem_allocate(size_t size, Klass* klass, Thread* thread,
217 bool* gc_overhead_limit_was_exceeded);
218
219 // We may support a shared contiguous allocation area, if the youngest
220 // generation does.
221 bool supports_inline_contig_alloc() const;
222 HeapWord* volatile* top_addr() const;
223 HeapWord** end_addr() const;
224
225 // Perform a full collection of the heap; intended for use in implementing
226 // "System.gc". This implies as full a collection as the CollectedHeap
227 // supports. Caller does not hold the Heap_lock on entry.
228 virtual void collect(GCCause::Cause cause);
229
230 // The same as above but assume that the caller holds the Heap_lock.
231 void collect_locked(GCCause::Cause cause);
232
233 // Perform a full collection of generations up to and including max_generation.
234 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
235 void collect(GCCause::Cause cause, GenerationType max_generation);
236
237 // Returns "TRUE" iff "p" points into the committed areas of the heap.
238 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
239 // be expensive to compute in general, so, to prevent
240 // their inadvertent use in product jvm's, we restrict their use to
241 // assertion checking or verification only.
242 bool is_in(const void* p) const;
243
244 // Returns true if the reference is to an object in the reserved space
245 // for the young generation.
246 // Assumes the the young gen address range is less than that of the old gen.
247 bool is_in_young(oop p);
248
249 #ifdef ASSERT
250 bool is_in_partial_collection(const void* p);
251 #endif
252
253 virtual bool is_scavengable(oop obj) {
254 return is_in_young(obj);
255 }
256
257 // Optimized nmethod scanning support routines
258 virtual void register_nmethod(nmethod* nm);
259 virtual void verify_nmethod(nmethod* nmethod);
260
261 // Iteration functions.
262 void oop_iterate_no_header(OopClosure* cl);
263 void oop_iterate(ExtendedOopClosure* cl);
264 void object_iterate(ObjectClosure* cl);
265 void safe_object_iterate(ObjectClosure* cl);
266 Space* space_containing(const void* addr) const;
267
268 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
269 // each address in the (reserved) heap is a member of exactly
270 // one block. The defining characteristic of a block is that it is
271 // possible to find its size, and thus to progress forward to the next
272 // block. (Blocks may be of different sizes.) Thus, blocks may
273 // represent Java objects, or they might be free blocks in a
274 // free-list-based heap (or subheap), as long as the two kinds are
275 // distinguishable and the size of each is determinable.
276
277 // Returns the address of the start of the "block" that contains the
278 // address "addr". We say "blocks" instead of "object" since some heaps
279 // may not pack objects densely; a chunk may either be an object or a
280 // non-object.
281 virtual HeapWord* block_start(const void* addr) const;
282
283 // Requires "addr" to be the start of a chunk, and returns its size.
284 // "addr + size" is required to be the start of a new chunk, or the end
285 // of the active area of the heap. Assumes (and verifies in non-product
286 // builds) that addr is in the allocated part of the heap and is
287 // the start of a chunk.
288 virtual size_t block_size(const HeapWord* addr) const;
289
290 // Requires "addr" to be the start of a block, and returns "TRUE" iff
291 // the block is an object. Assumes (and verifies in non-product
292 // builds) that addr is in the allocated part of the heap and is
293 // the start of a chunk.
294 virtual bool block_is_obj(const HeapWord* addr) const;
295
296 // Section on TLAB's.
297 virtual bool supports_tlab_allocation() const;
298 virtual size_t tlab_capacity(Thread* thr) const;
299 virtual size_t tlab_used(Thread* thr) const;
300 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
301 virtual HeapWord* allocate_new_tlab(size_t size);
302
303 // The "requestor" generation is performing some garbage collection
304 // action for which it would be useful to have scratch space. The
305 // requestor promises to allocate no more than "max_alloc_words" in any
306 // older generation (via promotion say.) Any blocks of space that can
307 // be provided are returned as a list of ScratchBlocks, sorted by
308 // decreasing size.
309 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
310 // Allow each generation to reset any scratch space that it has
311 // contributed as it needs.
312 void release_scratch();
313
314 // Ensure parsability: override
315 virtual void ensure_parsability(bool retire_tlabs);
316
317 // Time in ms since the longest time a collector ran in
318 // in any generation.
319 virtual jlong millis_since_last_gc();
320
321 // Total number of full collections completed.
322 unsigned int total_full_collections_completed() {
323 assert(_full_collections_completed <= _total_full_collections,
324 "Can't complete more collections than were started");
325 return _full_collections_completed;
326 }
327
328 // Update above counter, as appropriate, at the end of a stop-world GC cycle
329 unsigned int update_full_collections_completed();
330 // Update above counter, as appropriate, at the end of a concurrent GC cycle
331 unsigned int update_full_collections_completed(unsigned int count);
332
333 // Update "time of last gc" for all generations to "now".
334 void update_time_of_last_gc(jlong now) {
335 _young_gen->update_time_of_last_gc(now);
336 _old_gen->update_time_of_last_gc(now);
337 }
338
339 // Update the gc statistics for each generation.
340 void update_gc_stats(Generation* current_generation, bool full) {
341 _old_gen->update_gc_stats(current_generation, full);
342 }
343
344 bool no_gc_in_progress() { return !is_gc_active(); }
345
346 // Override.
347 void prepare_for_verify();
348
349 // Override.
350 void verify(VerifyOption option);
351
352 // Override.
353 virtual void print_on(outputStream* st) const;
354 virtual void print_gc_threads_on(outputStream* st) const;
355 virtual void gc_threads_do(ThreadClosure* tc) const;
356 virtual void print_tracing_info() const;
357
358 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
359
360 // The functions below are helper functions that a subclass of
361 // "CollectedHeap" can use in the implementation of its virtual
362 // functions.
363
364 class GenClosure : public StackObj {
365 public:
366 virtual void do_generation(Generation* gen) = 0;
367 };
368
369 // Apply "cl.do_generation" to all generations in the heap
370 // If "old_to_young" determines the order.
371 void generation_iterate(GenClosure* cl, bool old_to_young);
372
373 // Return "true" if all generations have reached the
374 // maximal committed limit that they can reach, without a garbage
375 // collection.
376 virtual bool is_maximal_no_gc() const;
377
378 // This function returns the CardTableRS object that allows us to scan
379 // generations in a fully generational heap.
380 CardTableRS* rem_set() { return _rem_set; }
381
382 // Convenience function to be used in situations where the heap type can be
383 // asserted to be this type.
384 static GenCollectedHeap* heap();
385
386 // The ScanningOption determines which of the roots
387 // the closure is applied to:
388 // "SO_None" does none;
389 enum ScanningOption {
390 SO_None = 0x0,
391 SO_AllCodeCache = 0x8,
392 SO_ScavengeCodeCache = 0x10
393 };
394
395 protected:
396 void process_roots(StrongRootsScope* scope,
397 ScanningOption so,
398 OopClosure* strong_roots,
399 OopClosure* weak_roots,
400 CLDClosure* strong_cld_closure,
401 CLDClosure* weak_cld_closure,
402 CodeBlobToOopClosure* code_roots);
403
404 void process_string_table_roots(StrongRootsScope* scope,
405 OopClosure* root_closure);
406
407 // Accessor for memory state verification support
408 NOT_PRODUCT(
409 virtual size_t skip_header_HeapWords() { return 0; }
410 )
411
412 virtual void gc_prologue(bool full);
413 virtual void gc_epilogue(bool full);
414
415 public:
416 void young_process_roots(StrongRootsScope* scope,
417 OopsInGenClosure* root_closure,
418 OopsInGenClosure* old_gen_closure,
419 CLDClosure* cld_closure);
420
421 void full_process_roots(StrongRootsScope* scope,
422 bool is_adjust_phase,
423 ScanningOption so,
424 bool only_strong_roots,
425 OopsInGenClosure* root_closure,
426 CLDClosure* cld_closure);
427
428 // Apply "root_closure" to all the weak roots of the system.
429 // These include JNI weak roots, string table,
430 // and referents of reachable weak refs.
431 void gen_process_weak_roots(OopClosure* root_closure);
432
433 // Set the saved marks of generations, if that makes sense.
434 // In particular, if any generation might iterate over the oops
435 // in other generations, it should call this method.
436 void save_marks();
437
438 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
439 // allocated since the last call to save_marks in generations at or above
440 // "level". The "cur" closure is
441 // applied to references in the generation at "level", and the "older"
442 // closure to older generations.
443 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
444 void oop_since_save_marks_iterate(GenerationType start_gen, \
445 OopClosureType* cur, \
446 OopClosureType* older);
447
448 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
449
450 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
451
452 // Returns "true" iff no allocations have occurred since the last
453 // call to "save_marks".
454 bool no_allocs_since_save_marks();
455
456 // Returns true if an incremental collection is likely to fail.
457 // We optionally consult the young gen, if asked to do so;
458 // otherwise we base our answer on whether the previous incremental
459 // collection attempt failed with no corrective action as of yet.
460 bool incremental_collection_will_fail(bool consult_young) {
461 // The first disjunct remembers if an incremental collection failed, even
462 // when we thought (second disjunct) that it would not.
463 return incremental_collection_failed() ||
464 (consult_young && !_young_gen->collection_attempt_is_safe());
465 }
466
467 // If a generation bails out of an incremental collection,
468 // it sets this flag.
469 bool incremental_collection_failed() const {
470 return _incremental_collection_failed;
471 }
472 void set_incremental_collection_failed() {
473 _incremental_collection_failed = true;
474 }
475 void clear_incremental_collection_failed() {
476 _incremental_collection_failed = false;
477 }
478
479 // Promotion of obj into gen failed. Try to promote obj to higher
480 // gens in ascending order; return the new location of obj if successful.
481 // Otherwise, try expand-and-allocate for obj in both the young and old
482 // generation; return the new location of obj if successful. Otherwise, return NULL.
483 oop handle_failed_promotion(Generation* old_gen,
484 oop obj,
485 size_t obj_size);
486
487
488 private:
489 // Return true if an allocation should be attempted in the older generation
490 // if it fails in the younger generation. Return false, otherwise.
491 bool should_try_older_generation_allocation(size_t word_size) const;
492
493 // Try to allocate space by expanding the heap.
494 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
495
496 HeapWord* mem_allocate_work(size_t size,
497 bool is_tlab,
498 bool* gc_overhead_limit_was_exceeded);
499
500 // Override
501 void check_for_non_bad_heap_word_value(HeapWord* addr,
502 size_t size) PRODUCT_RETURN;
503
504 // For use by mark-sweep. As implemented, mark-sweep-compact is global
505 // in an essential way: compaction is performed across generations, by
506 // iterating over spaces.
507 void prepare_for_compaction();
508
509 // Perform a full collection of the generations up to and including max_generation.
510 // This is the low level interface used by the public versions of
511 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
512 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
513
514 // Save the tops of the spaces in all generations
515 void record_gen_tops_before_GC() PRODUCT_RETURN;
516 };
517
518 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP