1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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).
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23 */
24
25 #ifndef SHARE_VM_MEMORY_DEFNEWGENERATION_HPP
26 #define SHARE_VM_MEMORY_DEFNEWGENERATION_HPP
27
28 #include "gc_implementation/shared/ageTable.hpp"
29 #include "gc_implementation/shared/cSpaceCounters.hpp"
30 #include "gc_implementation/shared/generationCounters.hpp"
31 #include "gc_implementation/shared/copyFailedInfo.hpp"
32 #include "utilities/stack.hpp"
33
34 class ContiguousSpace;
35 class ScanClosure;
36 class STWGCTimer;
37
38 // DefNewGeneration is a young generation containing eden, from- and
39 // to-space.
40
41 class DefNewGeneration: public Generation {
42 friend class VMStructs;
43
44 protected:
45 Generation* _next_gen;
46 uint _tenuring_threshold; // Tenuring threshold for next collection.
47 ageTable _age_table;
48 // Size of object to pretenure in words; command line provides bytes
49 size_t _pretenure_size_threshold_words;
50
51 ageTable* age_table() { return &_age_table; }
52
53 // Initialize state to optimistically assume no promotion failure will
54 // happen.
55 void init_assuming_no_promotion_failure();
56 // True iff a promotion has failed in the current collection.
57 bool _promotion_failed;
58 bool promotion_failed() { return _promotion_failed; }
59 PromotionFailedInfo _promotion_failed_info;
60
61 // Handling promotion failure. A young generation collection
62 // can fail if a live object cannot be copied out of its
63 // location in eden or from-space during the collection. If
64 // a collection fails, the young generation is left in a
65 // consistent state such that it can be collected by a
66 // full collection.
67 // Before the collection
68 // Objects are in eden or from-space
69 // All roots into the young generation point into eden or from-space.
70 //
71 // After a failed collection
72 // Objects may be in eden, from-space, or to-space
73 // An object A in eden or from-space may have a copy B
74 // in to-space. If B exists, all roots that once pointed
75 // to A must now point to B.
76 // All objects in the young generation are unmarked.
77 // Eden, from-space, and to-space will all be collected by
78 // the full collection.
79 void handle_promotion_failure(oop);
80
81 // In the absence of promotion failure, we wouldn't look at "from-space"
82 // objects after a young-gen collection. When promotion fails, however,
83 // the subsequent full collection will look at from-space objects:
84 // therefore we must remove their forwarding pointers.
85 void remove_forwarding_pointers();
86
87 // Preserve the mark of "obj", if necessary, in preparation for its mark
88 // word being overwritten with a self-forwarding-pointer.
89 void preserve_mark_if_necessary(oop obj, markOop m);
90 void preserve_mark(oop obj, markOop m); // work routine used by the above
91
92 // Together, these keep <object with a preserved mark, mark value> pairs.
93 // They should always contain the same number of elements.
94 Stack<oop, mtGC> _objs_with_preserved_marks;
95 Stack<markOop, mtGC> _preserved_marks_of_objs;
96
97 // Promotion failure handling
98 ExtendedOopClosure *_promo_failure_scan_stack_closure;
99 void set_promo_failure_scan_stack_closure(ExtendedOopClosure *scan_stack_closure) {
100 _promo_failure_scan_stack_closure = scan_stack_closure;
101 }
102
103 Stack<oop, mtGC> _promo_failure_scan_stack;
104 void drain_promo_failure_scan_stack(void);
105 bool _promo_failure_drain_in_progress;
106
107 // Performance Counters
108 GenerationCounters* _gen_counters;
109 CSpaceCounters* _eden_counters;
110 CSpaceCounters* _from_counters;
111 CSpaceCounters* _to_counters;
112
113 // sizing information
114 size_t _max_eden_size;
115 size_t _max_survivor_size;
116
117 // Allocation support
118 bool _should_allocate_from_space;
119 bool should_allocate_from_space() const {
120 return _should_allocate_from_space;
121 }
122 void clear_should_allocate_from_space() {
123 _should_allocate_from_space = false;
124 }
125 void set_should_allocate_from_space() {
126 _should_allocate_from_space = true;
127 }
128
129 // Tenuring
130 void adjust_desired_tenuring_threshold();
131
132 // Spaces
133 ContiguousSpace* _eden_space;
134 ContiguousSpace* _from_space;
135 ContiguousSpace* _to_space;
136
137 STWGCTimer* _gc_timer;
138
139 enum SomeProtectedConstants {
140 // Generations are GenGrain-aligned and have size that are multiples of
141 // GenGrain.
142 MinFreeScratchWords = 100
143 };
144
145 // Return the size of a survivor space if this generation were of size
146 // gen_size.
147 size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
148 size_t n = gen_size / (SurvivorRatio + 2);
149 return n > alignment ? align_size_down(n, alignment) : alignment;
150 }
151
152 public: // was "protected" but caused compile error on win32
153 class IsAliveClosure: public BoolObjectClosure {
154 Generation* _g;
155 public:
156 IsAliveClosure(Generation* g);
157 bool do_object_b(oop p);
158 };
159
160 class KeepAliveClosure: public OopClosure {
161 protected:
162 ScanWeakRefClosure* _cl;
163 CardTableRS* _rs;
164 template <class T> void do_oop_work(T* p);
165 public:
166 KeepAliveClosure(ScanWeakRefClosure* cl);
167 virtual void do_oop(oop* p);
168 virtual void do_oop(narrowOop* p);
169 };
170
171 class FastKeepAliveClosure: public KeepAliveClosure {
172 protected:
173 HeapWord* _boundary;
174 template <class T> void do_oop_work(T* p);
175 public:
176 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
177 virtual void do_oop(oop* p);
178 virtual void do_oop(narrowOop* p);
179 };
180
181 class EvacuateFollowersClosure: public VoidClosure {
182 GenCollectedHeap* _gch;
183 int _level;
184 ScanClosure* _scan_cur_or_nonheap;
185 ScanClosure* _scan_older;
186 public:
187 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
188 ScanClosure* cur, ScanClosure* older);
189 void do_void();
190 };
191
192 class FastEvacuateFollowersClosure: public VoidClosure {
193 GenCollectedHeap* _gch;
194 int _level;
195 DefNewGeneration* _gen;
196 FastScanClosure* _scan_cur_or_nonheap;
197 FastScanClosure* _scan_older;
198 public:
199 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
200 DefNewGeneration* gen,
201 FastScanClosure* cur,
202 FastScanClosure* older);
203 void do_void();
204 };
205
206 public:
207 DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
208 const char* policy="Copy");
209
210 virtual void ref_processor_init();
211
212 virtual Generation::Name kind() { return Generation::DefNew; }
213
214 // Accessing spaces
215 ContiguousSpace* eden() const { return _eden_space; }
216 ContiguousSpace* from() const { return _from_space; }
217 ContiguousSpace* to() const { return _to_space; }
218
219 virtual CompactibleSpace* first_compaction_space() const;
220
221 // Space enquiries
222 size_t capacity() const;
223 size_t used() const;
224 size_t free() const;
225 size_t max_capacity() const;
226 size_t capacity_before_gc() const;
227 size_t unsafe_max_alloc_nogc() const;
228 size_t contiguous_available() const;
229
230 size_t max_eden_size() const { return _max_eden_size; }
231 size_t max_survivor_size() const { return _max_survivor_size; }
232
233 bool supports_inline_contig_alloc() const { return true; }
234 HeapWord** top_addr() const;
235 HeapWord** end_addr() const;
236
237 // Thread-local allocation buffers
238 bool supports_tlab_allocation() const { return true; }
239 size_t tlab_capacity() const;
240 size_t tlab_used() const;
241 size_t unsafe_max_tlab_alloc() const;
242
243 // Grow the generation by the specified number of bytes.
244 // The size of bytes is assumed to be properly aligned.
245 // Return true if the expansion was successful.
246 bool expand(size_t bytes);
247
248 // DefNewGeneration cannot currently expand except at
249 // a GC.
250 virtual bool is_maximal_no_gc() const { return true; }
251
252 // Iteration
253 void object_iterate(ObjectClosure* blk);
254
255 void younger_refs_iterate(OopsInGenClosure* cl);
256
257 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
258
259 // Allocation support
260 virtual bool should_allocate(size_t word_size, bool is_tlab) {
261 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
262
263 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
264
265 const bool non_zero = word_size > 0;
266 const bool overflows = word_size >= overflow_limit;
267 const bool check_too_big = _pretenure_size_threshold_words > 0;
268 const bool not_too_big = word_size < _pretenure_size_threshold_words;
269 const bool size_ok = is_tlab || !check_too_big || not_too_big;
270
271 bool result = !overflows &&
272 non_zero &&
273 size_ok;
274
275 return result;
276 }
277
278 HeapWord* allocate(size_t word_size, bool is_tlab);
279 HeapWord* allocate_from_space(size_t word_size);
280
281 HeapWord* par_allocate(size_t word_size, bool is_tlab);
282
283 virtual void gc_epilogue(bool full);
284
285 // Save the tops for eden, from, and to
286 virtual void record_spaces_top();
287
288 // Doesn't require additional work during GC prologue and epilogue
289 virtual bool performs_in_place_marking() const { return false; }
290
291 // Accessing marks
292 void save_marks();
293 void reset_saved_marks();
294 bool no_allocs_since_save_marks();
295
296 // Need to declare the full complement of closures, whether we'll
297 // override them or not, or get message from the compiler:
298 // oop_since_save_marks_iterate_nv hides virtual function...
299 #define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
300 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
301
302 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)
303
304 #undef DefNew_SINCE_SAVE_MARKS_DECL
305
306 // For non-youngest collection, the DefNewGeneration can contribute
307 // "to-space".
308 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
309 size_t max_alloc_words);
310
311 // Reset for contribution of "to-space".
312 virtual void reset_scratch();
313
314 // GC support
315 virtual void compute_new_size();
316
317 // Returns true if the collection is likely to be safely
318 // completed. Even if this method returns true, a collection
319 // may not be guaranteed to succeed, and the system should be
320 // able to safely unwind and recover from that failure, albeit
321 // at some additional cost. Override superclass's implementation.
322 virtual bool collection_attempt_is_safe();
323
324 virtual void collect(bool full,
325 bool clear_all_soft_refs,
326 size_t size,
327 bool is_tlab);
328 HeapWord* expand_and_allocate(size_t size,
329 bool is_tlab,
330 bool parallel = false);
331
332 oop copy_to_survivor_space(oop old);
333 uint tenuring_threshold() { return _tenuring_threshold; }
334
335 // Performance Counter support
336 void update_counters();
337
338 // Printing
339 virtual const char* name() const;
340 virtual const char* short_name() const { return "DefNew"; }
341
342 // PrintHeapAtGC support.
343 void print_on(outputStream* st) const;
344
345 void verify();
346
347 bool promo_failure_scan_is_complete() const {
348 return _promo_failure_scan_stack.is_empty();
349 }
350
351 protected:
352 // If clear_space is true, clear the survivor spaces. Eden is
353 // cleared if the minimum size of eden is 0. If mangle_space
354 // is true, also mangle the space in debug mode.
355 void compute_space_boundaries(uintx minimum_eden_size,
356 bool clear_space,
357 bool mangle_space);
358 // Scavenge support
359 void swap_spaces();
360 };
361
362 #endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP