1 /*
2 * Copyright (c) 2001, 2024, 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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24
25 #ifndef SHARE_GC_SERIAL_DEFNEWGENERATION_HPP
26 #define SHARE_GC_SERIAL_DEFNEWGENERATION_HPP
27
28 #include "gc/serial/cSpaceCounters.hpp"
29 #include "gc/serial/generation.hpp"
30 #include "gc/serial/tenuredGeneration.hpp"
31 #include "gc/shared/ageTable.hpp"
32 #include "gc/shared/copyFailedInfo.hpp"
33 #include "gc/shared/gc_globals.hpp"
34 #include "gc/shared/generationCounters.hpp"
35 #include "gc/shared/stringdedup/stringDedup.hpp"
36 #include "gc/shared/tlab_globals.hpp"
37 #include "utilities/align.hpp"
38 #include "utilities/stack.hpp"
39
40 class ContiguousSpace;
41 class CSpaceCounters;
42 class OldGenScanClosure;
43 class YoungGenScanClosure;
44 class DefNewTracer;
45 class ScanWeakRefClosure;
46 class SerialHeap;
47 class STWGCTimer;
48
49 // DefNewGeneration is a young generation containing eden, from- and
50 // to-space.
51
52 class DefNewGeneration: public Generation {
53 friend class VMStructs;
54
55 TenuredGeneration* _old_gen;
56
57 uint _tenuring_threshold; // Tenuring threshold for next collection.
58 AgeTable _age_table;
59 // Size of object to pretenure in words; command line provides bytes
60 size_t _pretenure_size_threshold_words;
61
62 // ("Weak") Reference processing support
63 SpanSubjectToDiscoveryClosure _span_based_discoverer;
64 ReferenceProcessor* _ref_processor;
65
66 AgeTable* age_table() { return &_age_table; }
67
68 // Initialize state to optimistically assume no promotion failure will
69 // happen.
70 void init_assuming_no_promotion_failure();
71 // True iff a promotion has failed in the current collection.
72 bool _promotion_failed;
73 bool promotion_failed() { return _promotion_failed; }
74 PromotionFailedInfo _promotion_failed_info;
75
76 // Handling promotion failure. A young generation collection
77 // can fail if a live object cannot be copied out of its
78 // location in eden or from-space during the collection. If
79 // a collection fails, the young generation is left in a
80 // consistent state such that it can be collected by a
81 // full collection.
82 // Before the collection
83 // Objects are in eden or from-space
84 // All roots into the young generation point into eden or from-space.
85 //
86 // After a failed collection
87 // Objects may be in eden, from-space, or to-space
88 // An object A in eden or from-space may have a copy B
89 // in to-space. If B exists, all roots that once pointed
90 // to A must now point to B.
91 // All objects in the young generation are unmarked.
92 // Eden, from-space, and to-space will all be collected by
93 // the full collection.
94 void handle_promotion_failure(oop);
95
96 // In the absence of promotion failure, we wouldn't look at "from-space"
97 // objects after a young-gen collection. When promotion fails, however,
98 // the subsequent full collection will look at from-space objects:
99 // therefore we must remove their forwarding pointers.
100 void remove_forwarding_pointers();
101
102 Stack<oop, mtGC> _promo_failure_scan_stack;
103 void drain_promo_failure_scan_stack(void);
104 bool _promo_failure_drain_in_progress;
105
106 // Performance Counters
107 GenerationCounters* _gen_counters;
108 CSpaceCounters* _eden_counters;
109 CSpaceCounters* _from_counters;
110 CSpaceCounters* _to_counters;
111
112 // sizing information
113 size_t _max_eden_size;
114 size_t _max_survivor_size;
115
116 // Allocation support
117 bool _should_allocate_from_space;
118 bool should_allocate_from_space() const {
119 return _should_allocate_from_space;
120 }
121 void clear_should_allocate_from_space() {
122 _should_allocate_from_space = false;
123 }
124 void set_should_allocate_from_space() {
125 _should_allocate_from_space = true;
126 }
127
128 // Tenuring
129 void adjust_desired_tenuring_threshold();
130
131 // Spaces
132 ContiguousSpace* _eden_space;
133 ContiguousSpace* _from_space;
134 ContiguousSpace* _to_space;
135
136 // Saved mark word, for to-space
137 HeapWord* _saved_mark_word;
138
139 STWGCTimer* _gc_timer;
140
141 DefNewTracer* _gc_tracer;
142
143 StringDedup::Requests _string_dedup_requests;
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_down(n, alignment) : alignment;
150 }
151
152 public:
153 DefNewGeneration(ReservedSpace rs,
154 size_t initial_byte_size,
155 size_t min_byte_size,
156 size_t max_byte_size,
157 const char* policy="Serial young collection pauses");
158
159 // allocate and initialize ("weak") refs processing support
160 void ref_processor_init();
161 ReferenceProcessor* ref_processor() { return _ref_processor; }
162
163 // Accessing spaces
164 ContiguousSpace* eden() const { return _eden_space; }
165 ContiguousSpace* from() const { return _from_space; }
166 ContiguousSpace* to() const { return _to_space; }
167
168 HeapWord* saved_mark_word() const { return _saved_mark_word; }
169 void set_saved_mark_word() { _saved_mark_word = to()->top(); }
170 bool saved_mark_at_top() { return _saved_mark_word == _to_space->top(); }
171
172 // Space enquiries
173 size_t capacity() const;
174 size_t used() const;
175 size_t free() const;
176 size_t max_capacity() const;
177 size_t capacity_before_gc() const;
178
179 // Returns "TRUE" iff "p" points into the used areas in each space of young-gen.
180 bool is_in(const void* p) const;
181
182 // Return an estimate of the maximum allocation that could be performed
183 // in the generation without triggering any collection or expansion
184 // activity. It is "unsafe" because no locks are taken; the result
185 // should be treated as an approximation, not a guarantee, for use in
186 // heuristic resizing decisions.
187 size_t unsafe_max_alloc_nogc() const;
188
189 size_t contiguous_available() const;
190
191 size_t max_eden_size() const { return _max_eden_size; }
192 size_t max_survivor_size() const { return _max_survivor_size; }
193
194 // Thread-local allocation buffers
195 bool supports_tlab_allocation() const { return true; }
196 size_t tlab_capacity() const;
197 size_t tlab_used() const;
198 size_t unsafe_max_tlab_alloc() const;
199
200 // Grow the generation by the specified number of bytes.
201 // The size of bytes is assumed to be properly aligned.
202 // Return true if the expansion was successful.
203 bool expand(size_t bytes);
204
205
206 // Iteration
207 void object_iterate(ObjectClosure* blk);
208
209 HeapWord* block_start(const void* p) const;
210
211 // Allocation support
212 virtual bool should_allocate(size_t word_size, bool is_tlab) {
213 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
214
215 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
216
217 const bool non_zero = word_size > 0;
218 const bool overflows = word_size >= overflow_limit;
219 const bool check_too_big = _pretenure_size_threshold_words > 0;
220 const bool not_too_big = word_size < _pretenure_size_threshold_words;
221 const bool size_ok = is_tlab || !check_too_big || not_too_big;
222
223 bool result = !overflows &&
224 non_zero &&
225 size_ok;
226
227 return result;
228 }
229
230 HeapWord* allocate(size_t word_size, bool is_tlab);
231 HeapWord* allocate_from_space(size_t word_size);
232
233 HeapWord* par_allocate(size_t word_size, bool is_tlab);
234
235 void gc_epilogue(bool full);
236
237 // Save the tops for eden, from, and to
238 void record_spaces_top();
239
240 // Accessing marks
241 void save_marks();
242
243 bool no_allocs_since_save_marks();
244
245 // Need to declare the full complement of closures, whether we'll
246 // override them or not, or get message from the compiler:
247 // oop_since_save_marks_iterate_nv hides virtual function...
248 template <typename OopClosureType>
249 void oop_since_save_marks_iterate(OopClosureType* cl);
250
251 // For Old collection (part of running Full GC), the DefNewGeneration can
252 // contribute the free part of "to-space" as the scratch space.
253 void contribute_scratch(void*& scratch, size_t& num_words);
254
255 // Reset for contribution of "to-space".
256 void reset_scratch();
257
258 // GC support
259 void compute_new_size();
260
261 // Returns true if the collection is likely to be safely
262 // completed. Even if this method returns true, a collection
263 // may not be guaranteed to succeed, and the system should be
264 // able to safely unwind and recover from that failure, albeit
265 // at some additional cost.
266 bool collection_attempt_is_safe();
267
268 virtual void collect(bool full,
269 bool clear_all_soft_refs,
270 size_t size,
271 bool is_tlab);
272
273 HeapWord* expand_and_allocate(size_t size, bool is_tlab);
274
275 oop copy_to_survivor_space(oop old);
276 uint tenuring_threshold() { return _tenuring_threshold; }
277
278 // Performance Counter support
279 void update_counters();
280
281 // Printing
282 virtual const char* name() const;
283 virtual const char* short_name() const { return "DefNew"; }
284
285 void print_on(outputStream* st) const;
286
287 void verify();
288
289 bool promo_failure_scan_is_complete() const {
290 return _promo_failure_scan_stack.is_empty();
291 }
292
293 DefNewTracer* gc_tracer() const { return _gc_tracer; }
294
295 protected:
296 // If clear_space is true, clear the survivor spaces. Eden is
297 // cleared if the minimum size of eden is 0. If mangle_space
298 // is true, also mangle the space in debug mode.
299 void compute_space_boundaries(uintx minimum_eden_size,
300 bool clear_space,
301 bool mangle_space);
302
303 // Return adjusted new size for NewSizeThreadIncrease.
304 // If any overflow happens, revert to previous new size.
305 size_t adjust_for_thread_increase(size_t new_size_candidate,
306 size_t new_size_before,
307 size_t alignment,
308 size_t thread_increase_size) const;
309
310 size_t calculate_thread_increase_size(int threads_count) const;
311
312
313 // Scavenge support
314 void swap_spaces();
315 };
316
317 #endif // SHARE_GC_SERIAL_DEFNEWGENERATION_HPP