1 /*
2 * Copyright (c) 2001, 2008, 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 class EdenSpace;
26 class ContiguousSpace;
27 class ScanClosure;
28
29 // DefNewGeneration is a young generation containing eden, from- and
30 // to-space.
31
32 class DefNewGeneration: public Generation {
33 friend class VMStructs;
34
35 protected:
36 Generation* _next_gen;
37 int _tenuring_threshold; // Tenuring threshold for next collection.
38 ageTable _age_table;
39 // Size of object to pretenure in words; command line provides bytes
40 size_t _pretenure_size_threshold_words;
41
42 ageTable* age_table() { return &_age_table; }
43 // Initialize state to optimistically assume no promotion failure will
44 // happen.
45 void init_assuming_no_promotion_failure();
46 // True iff a promotion has failed in the current collection.
47 bool _promotion_failed;
48 bool promotion_failed() { return _promotion_failed; }
49
50 // Handling promotion failure. A young generation collection
51 // can fail if a live object cannot be copied out of its
52 // location in eden or from-space during the collection. If
53 // a collection fails, the young generation is left in a
54 // consistent state such that it can be collected by a
55 // full collection.
56 // Before the collection
57 // Objects are in eden or from-space
58 // All roots into the young generation point into eden or from-space.
59 //
60 // After a failed collection
61 // Objects may be in eden, from-space, or to-space
62 // An object A in eden or from-space may have a copy B
63 // in to-space. If B exists, all roots that once pointed
64 // to A must now point to B.
65 // All objects in the young generation are unmarked.
66 // Eden, from-space, and to-space will all be collected by
67 // the full collection.
68 void handle_promotion_failure(oop);
69
70 // In the absence of promotion failure, we wouldn't look at "from-space"
71 // objects after a young-gen collection. When promotion fails, however,
72 // the subsequent full collection will look at from-space objects:
73 // therefore we must remove their forwarding pointers.
74 void remove_forwarding_pointers();
75
76 // Preserve the mark of "obj", if necessary, in preparation for its mark
77 // word being overwritten with a self-forwarding-pointer.
78 void preserve_mark_if_necessary(oop obj, markOop m);
79
80 // Together, these keep <object with a preserved mark, mark value> pairs.
81 // They should always contain the same number of elements.
82 Stack<oop> _objs_with_preserved_marks;
83 Stack<markOop> _preserved_marks_of_objs;
84
85 // Returns true if the collection can be safely attempted.
86 // If this method returns false, a collection is not
87 // guaranteed to fail but the system may not be able
88 // to recover from the failure.
89 bool collection_attempt_is_safe();
90
91 // Promotion failure handling
92 OopClosure *_promo_failure_scan_stack_closure;
93 void set_promo_failure_scan_stack_closure(OopClosure *scan_stack_closure) {
94 _promo_failure_scan_stack_closure = scan_stack_closure;
95 }
96
97 Stack<oop> _promo_failure_scan_stack;
98 void drain_promo_failure_scan_stack(void);
99 bool _promo_failure_drain_in_progress;
100
101 // Performance Counters
102 GenerationCounters* _gen_counters;
103 CSpaceCounters* _eden_counters;
104 CSpaceCounters* _from_counters;
105 CSpaceCounters* _to_counters;
106
107 // sizing information
108 size_t _max_eden_size;
109 size_t _max_survivor_size;
110
111 // Allocation support
112 bool _should_allocate_from_space;
113 bool should_allocate_from_space() const {
114 return _should_allocate_from_space;
115 }
116 void clear_should_allocate_from_space() {
117 _should_allocate_from_space = false;
118 }
119 void set_should_allocate_from_space() {
120 _should_allocate_from_space = true;
121 }
122
123 protected:
124 // Spaces
125 EdenSpace* _eden_space;
126 ContiguousSpace* _from_space;
127 ContiguousSpace* _to_space;
128
129 enum SomeProtectedConstants {
130 // Generations are GenGrain-aligned and have size that are multiples of
131 // GenGrain.
132 MinFreeScratchWords = 100
133 };
134
135 // Return the size of a survivor space if this generation were of size
136 // gen_size.
137 size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
138 size_t n = gen_size / (SurvivorRatio + 2);
139 return n > alignment ? align_size_down(n, alignment) : alignment;
140 }
141
142 public: // was "protected" but caused compile error on win32
143 class IsAliveClosure: public BoolObjectClosure {
144 Generation* _g;
145 public:
146 IsAliveClosure(Generation* g);
147 void do_object(oop p);
148 bool do_object_b(oop p);
149 };
150
151 class KeepAliveClosure: public OopClosure {
152 protected:
153 ScanWeakRefClosure* _cl;
154 CardTableRS* _rs;
155 template <class T> void do_oop_work(T* p);
156 public:
157 KeepAliveClosure(ScanWeakRefClosure* cl);
158 virtual void do_oop(oop* p);
159 virtual void do_oop(narrowOop* p);
160 };
161
162 class FastKeepAliveClosure: public KeepAliveClosure {
163 protected:
164 HeapWord* _boundary;
165 template <class T> void do_oop_work(T* p);
166 public:
167 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
168 virtual void do_oop(oop* p);
169 virtual void do_oop(narrowOop* p);
170 };
171
172 class EvacuateFollowersClosure: public VoidClosure {
173 GenCollectedHeap* _gch;
174 int _level;
175 ScanClosure* _scan_cur_or_nonheap;
176 ScanClosure* _scan_older;
177 public:
178 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
179 ScanClosure* cur, ScanClosure* older);
180 void do_void();
181 };
182
183 class FastEvacuateFollowersClosure: public VoidClosure {
184 GenCollectedHeap* _gch;
185 int _level;
186 DefNewGeneration* _gen;
187 FastScanClosure* _scan_cur_or_nonheap;
188 FastScanClosure* _scan_older;
189 public:
190 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
191 DefNewGeneration* gen,
192 FastScanClosure* cur,
193 FastScanClosure* older);
194 void do_void();
195 };
196
197 public:
198 DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
199 const char* policy="Copy");
200
201 virtual Generation::Name kind() { return Generation::DefNew; }
202
203 // Accessing spaces
204 EdenSpace* eden() const { return _eden_space; }
205 ContiguousSpace* from() const { return _from_space; }
206 ContiguousSpace* to() const { return _to_space; }
207
208 virtual CompactibleSpace* first_compaction_space() const;
209
210 // Space enquiries
211 size_t capacity() const;
212 size_t used() const;
213 size_t free() const;
214 size_t max_capacity() const;
215 size_t capacity_before_gc() const;
216 size_t unsafe_max_alloc_nogc() const;
217 size_t contiguous_available() const;
218
219 size_t max_eden_size() const { return _max_eden_size; }
220 size_t max_survivor_size() const { return _max_survivor_size; }
221
222 bool supports_inline_contig_alloc() const { return true; }
223 HeapWord** top_addr() const;
224 HeapWord** end_addr() const;
225
226 // Thread-local allocation buffers
227 bool supports_tlab_allocation() const { return true; }
228 size_t tlab_capacity() const;
229 size_t unsafe_max_tlab_alloc() const;
230
231 // Grow the generation by the specified number of bytes.
232 // The size of bytes is assumed to be properly aligned.
233 // Return true if the expansion was successful.
234 bool expand(size_t bytes);
235
236 // DefNewGeneration cannot currently expand except at
237 // a GC.
238 virtual bool is_maximal_no_gc() const { return true; }
239
240 // Iteration
241 void object_iterate(ObjectClosure* blk);
242 void object_iterate_since_last_GC(ObjectClosure* cl);
243
244 void younger_refs_iterate(OopsInGenClosure* cl);
245
246 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
247
248 // Allocation support
249 virtual bool should_allocate(size_t word_size, bool is_tlab) {
250 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
251
252 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
253
254 const bool non_zero = word_size > 0;
255 const bool overflows = word_size >= overflow_limit;
256 const bool check_too_big = _pretenure_size_threshold_words > 0;
257 const bool not_too_big = word_size < _pretenure_size_threshold_words;
258 const bool size_ok = is_tlab || !check_too_big || not_too_big;
259
260 bool result = !overflows &&
261 non_zero &&
262 size_ok;
263
264 return result;
265 }
266
267 HeapWord* allocate(size_t word_size, bool is_tlab);
268 HeapWord* allocate_from_space(size_t word_size);
269
270 HeapWord* par_allocate(size_t word_size, bool is_tlab);
271
272 // Prologue & Epilogue
273 virtual void gc_prologue(bool full);
274 virtual void gc_epilogue(bool full);
275
276 // Save the tops for eden, from, and to
277 virtual void record_spaces_top();
278
279 // Doesn't require additional work during GC prologue and epilogue
280 virtual bool performs_in_place_marking() const { return false; }
281
282 // Accessing marks
283 void save_marks();
284 void reset_saved_marks();
285 bool no_allocs_since_save_marks();
286
287 // Need to declare the full complement of closures, whether we'll
288 // override them or not, or get message from the compiler:
289 // oop_since_save_marks_iterate_nv hides virtual function...
290 #define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
291 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
292
293 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)
294
295 #undef DefNew_SINCE_SAVE_MARKS_DECL
296
297 // For non-youngest collection, the DefNewGeneration can contribute
298 // "to-space".
299 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
300 size_t max_alloc_words);
301
302 // Reset for contribution of "to-space".
303 virtual void reset_scratch();
304
305 // GC support
306 virtual void compute_new_size();
307 virtual void collect(bool full,
308 bool clear_all_soft_refs,
309 size_t size,
310 bool is_tlab);
311 HeapWord* expand_and_allocate(size_t size,
312 bool is_tlab,
313 bool parallel = false);
314
315 oop copy_to_survivor_space(oop old);
316 int tenuring_threshold() { return _tenuring_threshold; }
317
318 // Performance Counter support
319 void update_counters();
320
321 // Printing
322 virtual const char* name() const;
323 virtual const char* short_name() const { return "DefNew"; }
324
325 bool must_be_youngest() const { return true; }
326 bool must_be_oldest() const { return false; }
327
328 // PrintHeapAtGC support.
329 void print_on(outputStream* st) const;
330
331 void verify(bool allow_dirty);
332
333 bool promo_failure_scan_is_complete() const {
334 return _promo_failure_scan_stack.is_empty();
335 }
336
337 protected:
338 // If clear_space is true, clear the survivor spaces. Eden is
339 // cleared if the minimum size of eden is 0. If mangle_space
340 // is true, also mangle the space in debug mode.
341 void compute_space_boundaries(uintx minimum_eden_size,
342 bool clear_space,
343 bool mangle_space);
344 // Scavenge support
345 void swap_spaces();
346 };