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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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 "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 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 // 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 void preserve_mark(oop obj, markOop m); // work routine used by the above
89
90 // Together, these keep <object with a preserved mark, mark value> pairs.
91 // They should always contain the same number of elements.
92 Stack<oop, mtGC> _objs_with_preserved_marks;
93 Stack<markOop, mtGC> _preserved_marks_of_objs;
94
95 // Promotion failure handling
96 ExtendedOopClosure *_promo_failure_scan_stack_closure;
97 void set_promo_failure_scan_stack_closure(ExtendedOopClosure *scan_stack_closure) {
98 _promo_failure_scan_stack_closure = scan_stack_closure;
99 }
100
101 Stack<oop, mtGC> _promo_failure_scan_stack;
102 void drain_promo_failure_scan_stack(void);
103 bool _promo_failure_drain_in_progress;
104
105 // Performance Counters
106 GenerationCounters* _gen_counters;
107 CSpaceCounters* _eden_counters;
108 CSpaceCounters* _from_counters;
109 CSpaceCounters* _to_counters;
110
111 // sizing information
112 size_t _max_eden_size;
113 size_t _max_survivor_size;
114
115 // Allocation support
116 bool _should_allocate_from_space;
117 bool should_allocate_from_space() const {
118 return _should_allocate_from_space;
119 }
120 void clear_should_allocate_from_space() {
121 _should_allocate_from_space = false;
122 }
123 void set_should_allocate_from_space() {
124 _should_allocate_from_space = true;
125 }
126
127 protected:
128 // Spaces
129 EdenSpace* _eden_space;
130 ContiguousSpace* _from_space;
131 ContiguousSpace* _to_space;
132
133 enum SomeProtectedConstants {
134 // Generations are GenGrain-aligned and have size that are multiples of
135 // GenGrain.
136 MinFreeScratchWords = 100
137 };
138
139 // Return the size of a survivor space if this generation were of size
140 // gen_size.
141 size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
142 size_t n = gen_size / (SurvivorRatio + 2);
143 return n > alignment ? align_size_down(n, alignment) : alignment;
144 }
145
146 public: // was "protected" but caused compile error on win32
147 class IsAliveClosure: public BoolObjectClosure {
148 Generation* _g;
149 public:
150 IsAliveClosure(Generation* g);
151 void do_object(oop p);
152 bool do_object_b(oop p);
153 };
154
155 class KeepAliveClosure: public OopClosure {
156 protected:
157 ScanWeakRefClosure* _cl;
158 CardTableRS* _rs;
159 template <class T> void do_oop_work(T* p);
160 public:
161 KeepAliveClosure(ScanWeakRefClosure* cl);
162 virtual void do_oop(oop* p);
163 virtual void do_oop(narrowOop* p);
164 };
165
166 class FastKeepAliveClosure: public KeepAliveClosure {
167 protected:
168 HeapWord* _boundary;
169 template <class T> void do_oop_work(T* p);
170 public:
171 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
172 virtual void do_oop(oop* p);
173 virtual void do_oop(narrowOop* p);
174 };
175
176 class EvacuateFollowersClosure: public VoidClosure {
177 GenCollectedHeap* _gch;
178 int _level;
179 ScanClosure* _scan_cur_or_nonheap;
180 ScanClosure* _scan_older;
181 public:
182 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
183 ScanClosure* cur, ScanClosure* older);
184 void do_void();
185 };
186
187 class FastEvacuateFollowersClosure: public VoidClosure {
188 GenCollectedHeap* _gch;
189 int _level;
190 DefNewGeneration* _gen;
191 FastScanClosure* _scan_cur_or_nonheap;
192 FastScanClosure* _scan_older;
193 public:
194 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
195 DefNewGeneration* gen,
196 FastScanClosure* cur,
197 FastScanClosure* older);
198 void do_void();
199 };
200
201 public:
202 DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
203 const char* policy="Copy");
204
205 virtual Generation::Name kind() { return Generation::DefNew; }
206
207 // Accessing spaces
208 EdenSpace* eden() const { return _eden_space; }
209 ContiguousSpace* from() const { return _from_space; }
210 ContiguousSpace* to() const { return _to_space; }
211
212 virtual CompactibleSpace* first_compaction_space() const;
213
214 // Space enquiries
215 size_t capacity() const;
216 size_t used() const;
217 size_t free() const;
218 size_t max_capacity() const;
219 size_t capacity_before_gc() const;
220 size_t unsafe_max_alloc_nogc() const;
221 size_t contiguous_available() const;
222
223 size_t max_eden_size() const { return _max_eden_size; }
224 size_t max_survivor_size() const { return _max_survivor_size; }
225
226 bool supports_inline_contig_alloc() const { return true; }
227 HeapWord** top_addr() const;
228 HeapWord** end_addr() const;
229
230 // Thread-local allocation buffers
231 bool supports_tlab_allocation() const { return true; }
232 size_t tlab_capacity() const;
233 size_t unsafe_max_tlab_alloc() const;
234
235 // Grow the generation by the specified number of bytes.
236 // The size of bytes is assumed to be properly aligned.
237 // Return true if the expansion was successful.
238 bool expand(size_t bytes);
239
240 // DefNewGeneration cannot currently expand except at
241 // a GC.
242 virtual bool is_maximal_no_gc() const { return true; }
243
244 // Iteration
245 void object_iterate(ObjectClosure* blk);
246 void object_iterate_since_last_GC(ObjectClosure* cl);
247
248 void younger_refs_iterate(OopsInGenClosure* cl);
249
250 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
251
252 // Allocation support
253 virtual bool should_allocate(size_t word_size, bool is_tlab) {
254 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
255
256 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
257
258 const bool non_zero = word_size > 0;
259 const bool overflows = word_size >= overflow_limit;
260 const bool check_too_big = _pretenure_size_threshold_words > 0;
261 const bool not_too_big = word_size < _pretenure_size_threshold_words;
262 const bool size_ok = is_tlab || !check_too_big || not_too_big;
263
264 bool result = !overflows &&
265 non_zero &&
266 size_ok;
267
268 return result;
269 }
270
271 HeapWord* allocate(size_t word_size, bool is_tlab);
272 HeapWord* allocate_from_space(size_t word_size);
273
274 HeapWord* par_allocate(size_t word_size, bool is_tlab);
275
276 // Prologue & Epilogue
277 virtual void gc_prologue(bool full);
278 virtual void gc_epilogue(bool full);
279
280 // Save the tops for eden, from, and to
281 virtual void record_spaces_top();
282
283 // Doesn't require additional work during GC prologue and epilogue
284 virtual bool performs_in_place_marking() const { return false; }
285
286 // Accessing marks
287 void save_marks();
288 void reset_saved_marks();
289 bool no_allocs_since_save_marks();
290
291 // Need to declare the full complement of closures, whether we'll
292 // override them or not, or get message from the compiler:
293 // oop_since_save_marks_iterate_nv hides virtual function...
294 #define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
295 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
296
297 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)
298
299 #undef DefNew_SINCE_SAVE_MARKS_DECL
300
301 // For non-youngest collection, the DefNewGeneration can contribute
302 // "to-space".
303 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
304 size_t max_alloc_words);
305
306 // Reset for contribution of "to-space".
307 virtual void reset_scratch();
308
309 // GC support
310 virtual void compute_new_size();
311
312 // Returns true if the collection is likely to be safely
313 // completed. Even if this method returns true, a collection
314 // may not be guaranteed to succeed, and the system should be
315 // able to safely unwind and recover from that failure, albeit
316 // at some additional cost. Override superclass's implementation.
317 virtual bool collection_attempt_is_safe();
318
319 virtual void collect(bool full,
320 bool clear_all_soft_refs,
321 size_t size,
322 bool is_tlab);
323 HeapWord* expand_and_allocate(size_t size,
324 bool is_tlab,
325 bool parallel = false);
326
327 oop copy_to_survivor_space(oop old);
328 uint tenuring_threshold() { return _tenuring_threshold; }
329
330 // Performance Counter support
331 void update_counters();
332
333 // Printing
334 virtual const char* name() const;
335 virtual const char* short_name() const { return "DefNew"; }
336
337 bool must_be_youngest() const { return true; }
338 bool must_be_oldest() const { return false; }
339
340 // PrintHeapAtGC support.
341 void print_on(outputStream* st) const;
342
343 void verify();
344
345 bool promo_failure_scan_is_complete() const {
346 return _promo_failure_scan_stack.is_empty();
347 }
348
349 protected:
350 // If clear_space is true, clear the survivor spaces. Eden is
351 // cleared if the minimum size of eden is 0. If mangle_space
352 // is true, also mangle the space in debug mode.
353 void compute_space_boundaries(uintx minimum_eden_size,
354 bool clear_space,
355 bool mangle_space);
356 // Scavenge support
357 void swap_spaces();
358 };
359
360 #endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP