1 /*
2 * Copyright (c) 2001, 2010, 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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7 * published by the Free Software Foundation.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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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 "memory/generation.inline.hpp"
32 #include "utilities/stack.hpp"
33
34 class EdenSpace;
35 class ContiguousSpace;
36 class ScanClosure;
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 int _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 // Initialize state to optimistically assume no promotion failure will
53 // happen.
54 void init_assuming_no_promotion_failure();
55 // True iff a promotion has failed in the current collection.
56 bool _promotion_failed;
57 bool promotion_failed() { return _promotion_failed; }
58
59 // Handling promotion failure. A young generation collection
60 // can fail if a live object cannot be copied out of its
61 // location in eden or from-space during the collection. If
62 // a collection fails, the young generation is left in a
63 // consistent state such that it can be collected by a
64 // full collection.
65 // Before the collection
66 // Objects are in eden or from-space
67 // All roots into the young generation point into eden or from-space.
68 //
69 // After a failed collection
70 // Objects may be in eden, from-space, or to-space
71 // An object A in eden or from-space may have a copy B
72 // in to-space. If B exists, all roots that once pointed
73 // to A must now point to B.
74 // All objects in the young generation are unmarked.
75 // Eden, from-space, and to-space will all be collected by
76 // the full collection.
77 void handle_promotion_failure(oop);
78
79 // In the absence of promotion failure, we wouldn't look at "from-space"
80 // objects after a young-gen collection. When promotion fails, however,
81 // the subsequent full collection will look at from-space objects:
82 // therefore we must remove their forwarding pointers.
83 void remove_forwarding_pointers();
84
85 // Preserve the mark of "obj", if necessary, in preparation for its mark
86 // word being overwritten with a self-forwarding-pointer.
87 void preserve_mark_if_necessary(oop obj, markOop m);
88
89 // Together, these keep <object with a preserved mark, mark value> pairs.
90 // They should always contain the same number of elements.
91 Stack<oop> _objs_with_preserved_marks;
92 Stack<markOop> _preserved_marks_of_objs;
93
94 // Returns true if the collection can be safely attempted.
95 // If this method returns false, a collection is not
96 // guaranteed to fail but the system may not be able
97 // to recover from the failure.
98 bool collection_attempt_is_safe();
99
100 // Promotion failure handling
101 OopClosure *_promo_failure_scan_stack_closure;
102 void set_promo_failure_scan_stack_closure(OopClosure *scan_stack_closure) {
103 _promo_failure_scan_stack_closure = scan_stack_closure;
104 }
105
106 Stack<oop> _promo_failure_scan_stack;
107 void drain_promo_failure_scan_stack(void);
108 bool _promo_failure_drain_in_progress;
109
110 // Performance Counters
111 GenerationCounters* _gen_counters;
112 CSpaceCounters* _eden_counters;
113 CSpaceCounters* _from_counters;
114 CSpaceCounters* _to_counters;
115
116 // sizing information
117 size_t _max_eden_size;
118 size_t _max_survivor_size;
119
120 // Allocation support
121 bool _should_allocate_from_space;
122 bool should_allocate_from_space() const {
123 return _should_allocate_from_space;
124 }
125 void clear_should_allocate_from_space() {
126 _should_allocate_from_space = false;
127 }
128 void set_should_allocate_from_space() {
129 _should_allocate_from_space = true;
130 }
131
132 protected:
133 // Spaces
134 EdenSpace* _eden_space;
135 ContiguousSpace* _from_space;
136 ContiguousSpace* _to_space;
137
138 enum SomeProtectedConstants {
139 // Generations are GenGrain-aligned and have size that are multiples of
140 // GenGrain.
141 MinFreeScratchWords = 100
142 };
143
144 // Return the size of a survivor space if this generation were of size
145 // gen_size.
146 size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
147 size_t n = gen_size / (SurvivorRatio + 2);
148 return n > alignment ? align_size_down(n, alignment) : alignment;
149 }
150
151 public: // was "protected" but caused compile error on win32
152 class IsAliveClosure: public BoolObjectClosure {
153 Generation* _g;
154 public:
155 IsAliveClosure(Generation* g);
156 void do_object(oop p);
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 Generation::Name kind() { return Generation::DefNew; }
211
212 // Accessing spaces
213 EdenSpace* eden() const { return _eden_space; }
214 ContiguousSpace* from() const { return _from_space; }
215 ContiguousSpace* to() const { return _to_space; }
216
217 virtual CompactibleSpace* first_compaction_space() const;
218
219 // Space enquiries
220 size_t capacity() const;
221 size_t used() const;
222 size_t free() const;
223 size_t max_capacity() const;
224 size_t capacity_before_gc() const;
225 size_t unsafe_max_alloc_nogc() const;
226 size_t contiguous_available() const;
227
228 size_t max_eden_size() const { return _max_eden_size; }
229 size_t max_survivor_size() const { return _max_survivor_size; }
230
231 bool supports_inline_contig_alloc() const { return true; }
232 HeapWord** top_addr() const;
233 HeapWord** end_addr() const;
234
235 // Thread-local allocation buffers
236 bool supports_tlab_allocation() const { return true; }
237 size_t tlab_capacity() const;
238 size_t unsafe_max_tlab_alloc() const;
239
240 // Grow the generation by the specified number of bytes.
241 // The size of bytes is assumed to be properly aligned.
242 // Return true if the expansion was successful.
243 bool expand(size_t bytes);
244
245 // DefNewGeneration cannot currently expand except at
246 // a GC.
247 virtual bool is_maximal_no_gc() const { return true; }
248
249 // Iteration
250 void object_iterate(ObjectClosure* blk);
251 void object_iterate_since_last_GC(ObjectClosure* cl);
252
253 void younger_refs_iterate(OopsInGenClosure* cl);
254
255 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
256
257 // Allocation support
258 virtual bool should_allocate(size_t word_size, bool is_tlab) {
259 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
260
261 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
262
263 const bool non_zero = word_size > 0;
264 const bool overflows = word_size >= overflow_limit;
265 const bool check_too_big = _pretenure_size_threshold_words > 0;
266 const bool not_too_big = word_size < _pretenure_size_threshold_words;
267 const bool size_ok = is_tlab || !check_too_big || not_too_big;
268
269 bool result = !overflows &&
270 non_zero &&
271 size_ok;
272
273 return result;
274 }
275
276 HeapWord* allocate(size_t word_size, bool is_tlab);
277 HeapWord* allocate_from_space(size_t word_size);
278
279 HeapWord* par_allocate(size_t word_size, bool is_tlab);
280
281 // Prologue & Epilogue
282 virtual void gc_prologue(bool full);
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 virtual void collect(bool full,
317 bool clear_all_soft_refs,
318 size_t size,
319 bool is_tlab);
320 HeapWord* expand_and_allocate(size_t size,
321 bool is_tlab,
322 bool parallel = false);
323
324 oop copy_to_survivor_space(oop old);
325 int tenuring_threshold() { return _tenuring_threshold; }
326
327 // Performance Counter support
328 void update_counters();
329
330 // Printing
331 virtual const char* name() const;
332 virtual const char* short_name() const { return "DefNew"; }
333
334 bool must_be_youngest() const { return true; }
335 bool must_be_oldest() const { return false; }
336
337 // PrintHeapAtGC support.
338 void print_on(outputStream* st) const;
339
340 void verify(bool allow_dirty);
341
342 bool promo_failure_scan_is_complete() const {
343 return _promo_failure_scan_stack.is_empty();
344 }
345
346 protected:
347 // If clear_space is true, clear the survivor spaces. Eden is
348 // cleared if the minimum size of eden is 0. If mangle_space
349 // is true, also mangle the space in debug mode.
350 void compute_space_boundaries(uintx minimum_eden_size,
351 bool clear_space,
352 bool mangle_space);
353 // Scavenge support
354 void swap_spaces();
355 };
356
357 #endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP