1 /*
2 * Copyright (c) 2001, 2012, 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.
8 *
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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).
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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/promotionFailedInfo.hpp"
32 #include "memory/generation.inline.hpp"
33 #include "utilities/stack.hpp"
34
35 class EdenSpace;
36 class ContiguousSpace;
37 class ScanClosure;
38 class STWGCTimer;
39
40 // DefNewGeneration is a young generation containing eden, from- and
41 // to-space.
42
43 class DefNewGeneration: public Generation {
44 friend class VMStructs;
45
46 protected:
47 Generation* _next_gen;
48 int _tenuring_threshold; // Tenuring threshold for next collection.
49 ageTable _age_table;
50 // Size of object to pretenure in words; command line provides bytes
51 size_t _pretenure_size_threshold_words;
52
53 ageTable* age_table() { return &_age_table; }
54
55 // Initialize state to optimistically assume no promotion failure will
56 // happen.
57 void init_assuming_no_promotion_failure();
58 // True iff a promotion has failed in the current collection.
59 bool _promotion_failed;
60 bool promotion_failed() { return _promotion_failed; }
61 PromotionFailedInfo _promotion_failed_info;
62
63 // Handling promotion failure. A young generation collection
64 // can fail if a live object cannot be copied out of its
65 // location in eden or from-space during the collection. If
66 // a collection fails, the young generation is left in a
67 // consistent state such that it can be collected by a
68 // full collection.
69 // Before the collection
70 // Objects are in eden or from-space
71 // All roots into the young generation point into eden or from-space.
72 //
73 // After a failed collection
74 // Objects may be in eden, from-space, or to-space
75 // An object A in eden or from-space may have a copy B
76 // in to-space. If B exists, all roots that once pointed
77 // to A must now point to B.
78 // All objects in the young generation are unmarked.
79 // Eden, from-space, and to-space will all be collected by
80 // the full collection.
81 void handle_promotion_failure(oop);
82
83 // In the absence of promotion failure, we wouldn't look at "from-space"
84 // objects after a young-gen collection. When promotion fails, however,
85 // the subsequent full collection will look at from-space objects:
86 // therefore we must remove their forwarding pointers.
87 void remove_forwarding_pointers();
88
89 // Preserve the mark of "obj", if necessary, in preparation for its mark
90 // word being overwritten with a self-forwarding-pointer.
91 void preserve_mark_if_necessary(oop obj, markOop m);
92 void preserve_mark(oop obj, markOop m); // work routine used by the above
93
94 // Together, these keep <object with a preserved mark, mark value> pairs.
95 // They should always contain the same number of elements.
96 Stack<oop, mtGC> _objs_with_preserved_marks;
97 Stack<markOop, mtGC> _preserved_marks_of_objs;
98
99 // Promotion failure handling
100 OopClosure *_promo_failure_scan_stack_closure;
101 void set_promo_failure_scan_stack_closure(OopClosure *scan_stack_closure) {
102 _promo_failure_scan_stack_closure = scan_stack_closure;
103 }
104
105 Stack<oop, mtGC> _promo_failure_scan_stack;
106 void drain_promo_failure_scan_stack(void);
107 bool _promo_failure_drain_in_progress;
108
109 // Performance Counters
110 GenerationCounters* _gen_counters;
111 CSpaceCounters* _eden_counters;
112 CSpaceCounters* _from_counters;
113 CSpaceCounters* _to_counters;
114
115 // sizing information
116 size_t _max_eden_size;
117 size_t _max_survivor_size;
118
119 // Allocation support
120 bool _should_allocate_from_space;
121 bool should_allocate_from_space() const {
122 return _should_allocate_from_space;
123 }
124 void clear_should_allocate_from_space() {
125 _should_allocate_from_space = false;
126 }
127 void set_should_allocate_from_space() {
128 _should_allocate_from_space = true;
129 }
130
131 protected:
132 // Spaces
133 EdenSpace* _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 void do_object(oop p);
158 bool do_object_b(oop p);
159 };
160
161 class KeepAliveClosure: public OopClosure {
162 protected:
163 ScanWeakRefClosure* _cl;
164 CardTableRS* _rs;
165 template <class T> void do_oop_work(T* p);
166 public:
167 KeepAliveClosure(ScanWeakRefClosure* cl);
168 virtual void do_oop(oop* p);
169 virtual void do_oop(narrowOop* p);
170 };
171
172 class FastKeepAliveClosure: public KeepAliveClosure {
173 protected:
174 HeapWord* _boundary;
175 template <class T> void do_oop_work(T* p);
176 public:
177 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
178 virtual void do_oop(oop* p);
179 virtual void do_oop(narrowOop* p);
180 };
181
182 class EvacuateFollowersClosure: public VoidClosure {
183 GenCollectedHeap* _gch;
184 int _level;
185 ScanClosure* _scan_cur_or_nonheap;
186 ScanClosure* _scan_older;
187 public:
188 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
189 ScanClosure* cur, ScanClosure* older);
190 void do_void();
191 };
192
193 class FastEvacuateFollowersClosure: public VoidClosure {
194 GenCollectedHeap* _gch;
195 int _level;
196 DefNewGeneration* _gen;
197 FastScanClosure* _scan_cur_or_nonheap;
198 FastScanClosure* _scan_older;
199 public:
200 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
201 DefNewGeneration* gen,
202 FastScanClosure* cur,
203 FastScanClosure* older);
204 void do_void();
205 };
206
207 public:
208 DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
209 const char* policy="Copy");
210
211 virtual void ref_processor_init();
212
213 virtual Generation::Name kind() { return Generation::DefNew; }
214
215 // Accessing spaces
216 EdenSpace* eden() const { return _eden_space; }
217 ContiguousSpace* from() const { return _from_space; }
218 ContiguousSpace* to() const { return _to_space; }
219
220 virtual CompactibleSpace* first_compaction_space() const;
221
222 // Space enquiries
223 size_t capacity() const;
224 size_t used() const;
225 size_t free() const;
226 size_t max_capacity() const;
227 size_t capacity_before_gc() const;
228 size_t unsafe_max_alloc_nogc() const;
229 size_t contiguous_available() const;
230
231 size_t max_eden_size() const { return _max_eden_size; }
232 size_t max_survivor_size() const { return _max_survivor_size; }
233
234 bool supports_inline_contig_alloc() const { return true; }
235 HeapWord** top_addr() const;
236 HeapWord** end_addr() const;
237
238 // Thread-local allocation buffers
239 bool supports_tlab_allocation() const { return true; }
240 size_t tlab_capacity() 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 void object_iterate_since_last_GC(ObjectClosure* cl);
255
256 void younger_refs_iterate(OopsInGenClosure* cl);
257
258 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
259
260 // Allocation support
261 virtual bool should_allocate(size_t word_size, bool is_tlab) {
262 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
263
264 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
265
266 const bool non_zero = word_size > 0;
267 const bool overflows = word_size >= overflow_limit;
268 const bool check_too_big = _pretenure_size_threshold_words > 0;
269 const bool not_too_big = word_size < _pretenure_size_threshold_words;
270 const bool size_ok = is_tlab || !check_too_big || not_too_big;
271
272 bool result = !overflows &&
273 non_zero &&
274 size_ok;
275
276 return result;
277 }
278
279 HeapWord* allocate(size_t word_size, bool is_tlab);
280 HeapWord* allocate_from_space(size_t word_size);
281
282 HeapWord* par_allocate(size_t word_size, bool is_tlab);
283
284 // Prologue & Epilogue
285 virtual void gc_prologue(bool full);
286 virtual void gc_epilogue(bool full);
287
288 // Save the tops for eden, from, and to
289 virtual void record_spaces_top();
290
291 // Doesn't require additional work during GC prologue and epilogue
292 virtual bool performs_in_place_marking() const { return false; }
293
294 // Accessing marks
295 void save_marks();
296 void reset_saved_marks();
297 bool no_allocs_since_save_marks();
298
299 // Need to declare the full complement of closures, whether we'll
300 // override them or not, or get message from the compiler:
301 // oop_since_save_marks_iterate_nv hides virtual function...
302 #define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
303 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
304
305 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)
306
307 #undef DefNew_SINCE_SAVE_MARKS_DECL
308
309 // For non-youngest collection, the DefNewGeneration can contribute
310 // "to-space".
311 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
312 size_t max_alloc_words);
313
314 // Reset for contribution of "to-space".
315 virtual void reset_scratch();
316
317 // GC support
318 virtual void compute_new_size();
319
320 // Returns true if the collection is likely to be safely
321 // completed. Even if this method returns true, a collection
322 // may not be guaranteed to succeed, and the system should be
323 // able to safely unwind and recover from that failure, albeit
324 // at some additional cost. Override superclass's implementation.
325 virtual bool collection_attempt_is_safe();
326
327 virtual void collect(bool full,
328 bool clear_all_soft_refs,
329 size_t size,
330 bool is_tlab);
331 HeapWord* expand_and_allocate(size_t size,
332 bool is_tlab,
333 bool parallel = false);
334
335 oop copy_to_survivor_space(oop old);
336 int tenuring_threshold() { return _tenuring_threshold; }
337
338 // Performance Counter support
339 void update_counters();
340
341 // Printing
342 virtual const char* name() const;
343 virtual const char* short_name() const { return "DefNew"; }
344
345 bool must_be_youngest() const { return true; }
346 bool must_be_oldest() const { return false; }
347
348 // PrintHeapAtGC support.
349 void print_on(outputStream* st) const;
350
351 void verify();
352
353 bool promo_failure_scan_is_complete() const {
354 return _promo_failure_scan_stack.is_empty();
355 }
356
357 protected:
358 // If clear_space is true, clear the survivor spaces. Eden is
359 // cleared if the minimum size of eden is 0. If mangle_space
360 // is true, also mangle the space in debug mode.
361 void compute_space_boundaries(uintx minimum_eden_size,
362 bool clear_space,
363 bool mangle_space);
364 // Scavenge support
365 void swap_spaces();
366 };
367
368 #endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP