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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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/preservedMarks.hpp"
36 #include "gc/shared/stringdedup/stringDedup.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38 #include "utilities/align.hpp"
39 #include "utilities/stack.hpp"
40
41 class ContiguousSpace;
42 class CSpaceCounters;
43 class OldGenScanClosure;
44 class YoungGenScanClosure;
45 class DefNewTracer;
46 class ScanWeakRefClosure;
47 class SerialHeap;
48 class STWGCTimer;
49
50 // DefNewGeneration is a young generation containing eden, from- and
51 // to-space.
52
53 class DefNewGeneration: public Generation {
54 friend class VMStructs;
55
56 TenuredGeneration* _old_gen;
57
58 uint _tenuring_threshold; // Tenuring threshold for next collection.
59 AgeTable _age_table;
60 // Size of object to pretenure in words; command line provides bytes
61 size_t _pretenure_size_threshold_words;
62
63 // ("Weak") Reference processing support
64 SpanSubjectToDiscoveryClosure _span_based_discoverer;
65 ReferenceProcessor* _ref_processor;
66
67 AgeTable* age_table() { return &_age_table; }
68
69 // Initialize state to optimistically assume no promotion failure will
70 // happen.
71 void init_assuming_no_promotion_failure();
72 // True iff a promotion has failed in the current collection.
73 bool _promotion_failed;
74 bool promotion_failed() { return _promotion_failed; }
75 PromotionFailedInfo _promotion_failed_info;
76
77 // Handling promotion failure. A young generation collection
78 // can fail if a live object cannot be copied out of its
79 // location in eden or from-space during the collection. If
80 // a collection fails, the young generation is left in a
81 // consistent state such that it can be collected by a
82 // full collection.
83 // Before the collection
84 // Objects are in eden or from-space
85 // All roots into the young generation point into eden or from-space.
86 //
87 // After a failed collection
88 // Objects may be in eden, from-space, or to-space
89 // An object A in eden or from-space may have a copy B
90 // in to-space. If B exists, all roots that once pointed
91 // to A must now point to B.
92 // All objects in the young generation are unmarked.
93 // Eden, from-space, and to-space will all be collected by
94 // the full collection.
95 void handle_promotion_failure(oop);
96
97 // In the absence of promotion failure, we wouldn't look at "from-space"
98 // objects after a young-gen collection. When promotion fails, however,
99 // the subsequent full collection will look at from-space objects:
100 // therefore we must remove their forwarding pointers.
101 void remove_forwarding_pointers();
102
103 virtual void restore_preserved_marks();
104
105 // Preserved marks
106 PreservedMarksSet _preserved_marks_set;
107
108 Stack<oop, mtGC> _promo_failure_scan_stack;
109 void drain_promo_failure_scan_stack(void);
110 bool _promo_failure_drain_in_progress;
111
112 // Performance Counters
113 GenerationCounters* _gen_counters;
114 CSpaceCounters* _eden_counters;
115 CSpaceCounters* _from_counters;
116 CSpaceCounters* _to_counters;
117
118 // sizing information
119 size_t _max_eden_size;
120 size_t _max_survivor_size;
121
122 // Allocation support
123 bool _should_allocate_from_space;
124 bool should_allocate_from_space() const {
125 return _should_allocate_from_space;
126 }
127 void clear_should_allocate_from_space() {
128 _should_allocate_from_space = false;
129 }
130 void set_should_allocate_from_space() {
131 _should_allocate_from_space = true;
132 }
133
134 // Tenuring
135 void adjust_desired_tenuring_threshold();
136
137 // Spaces
138 ContiguousSpace* _eden_space;
139 ContiguousSpace* _from_space;
140 ContiguousSpace* _to_space;
141
142 // Saved mark word, for to-space
143 HeapWord* _saved_mark_word;
144
145 STWGCTimer* _gc_timer;
146
147 DefNewTracer* _gc_tracer;
148
149 StringDedup::Requests _string_dedup_requests;
150
151 // Return the size of a survivor space if this generation were of size
152 // gen_size.
153 size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
154 size_t n = gen_size / (SurvivorRatio + 2);
155 return n > alignment ? align_down(n, alignment) : alignment;
156 }
157
158 public:
159 DefNewGeneration(ReservedSpace rs,
160 size_t initial_byte_size,
161 size_t min_byte_size,
162 size_t max_byte_size,
163 const char* policy="Serial young collection pauses");
164
165 // allocate and initialize ("weak") refs processing support
166 void ref_processor_init();
167 ReferenceProcessor* ref_processor() { return _ref_processor; }
168
169 // Accessing spaces
170 ContiguousSpace* eden() const { return _eden_space; }
171 ContiguousSpace* from() const { return _from_space; }
172 ContiguousSpace* to() const { return _to_space; }
173
174 HeapWord* saved_mark_word() const { return _saved_mark_word; }
175 void set_saved_mark_word() { _saved_mark_word = to()->top(); }
176 bool saved_mark_at_top() { return _saved_mark_word == _to_space->top(); }
177
178 // Space enquiries
179 size_t capacity() const;
180 size_t used() const;
181 size_t free() const;
182 size_t max_capacity() const;
183 size_t capacity_before_gc() const;
184
185 // Returns "TRUE" iff "p" points into the used areas in each space of young-gen.
186 bool is_in(const void* p) const;
187
188 // Return an estimate of the maximum allocation that could be performed
189 // in the generation without triggering any collection or expansion
190 // activity. It is "unsafe" because no locks are taken; the result
191 // should be treated as an approximation, not a guarantee, for use in
192 // heuristic resizing decisions.
193 size_t unsafe_max_alloc_nogc() const;
194
195 size_t contiguous_available() const;
196
197 size_t max_eden_size() const { return _max_eden_size; }
198 size_t max_survivor_size() const { return _max_survivor_size; }
199
200 // Thread-local allocation buffers
201 bool supports_tlab_allocation() const { return true; }
202 size_t tlab_capacity() const;
203 size_t tlab_used() const;
204 size_t unsafe_max_tlab_alloc() const;
205
206 // Grow the generation by the specified number of bytes.
207 // The size of bytes is assumed to be properly aligned.
208 // Return true if the expansion was successful.
209 bool expand(size_t bytes);
210
211
212 // Iteration
213 void object_iterate(ObjectClosure* blk);
214
215 HeapWord* block_start(const void* p) const;
216
217 // Allocation support
218 virtual bool should_allocate(size_t word_size, bool is_tlab) {
219 assert(UseTLAB || !is_tlab, "Should not allocate tlab");
220
221 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
222
223 const bool non_zero = word_size > 0;
224 const bool overflows = word_size >= overflow_limit;
225 const bool check_too_big = _pretenure_size_threshold_words > 0;
226 const bool not_too_big = word_size < _pretenure_size_threshold_words;
227 const bool size_ok = is_tlab || !check_too_big || not_too_big;
228
229 bool result = !overflows &&
230 non_zero &&
231 size_ok;
232
233 return result;
234 }
235
236 HeapWord* allocate(size_t word_size, bool is_tlab);
237 HeapWord* allocate_from_space(size_t word_size);
238
239 HeapWord* par_allocate(size_t word_size, bool is_tlab);
240
241 void gc_epilogue(bool full);
242
243 // Save the tops for eden, from, and to
244 void record_spaces_top();
245
246 // Accessing marks
247 void save_marks();
248
249 bool no_allocs_since_save_marks();
250
251 // Need to declare the full complement of closures, whether we'll
252 // override them or not, or get message from the compiler:
253 // oop_since_save_marks_iterate_nv hides virtual function...
254 template <typename OopClosureType>
255 void oop_since_save_marks_iterate(OopClosureType* cl);
256
257 // For Old collection (part of running Full GC), the DefNewGeneration can
258 // contribute the free part of "to-space" as the scratch space.
259 void contribute_scratch(void*& scratch, size_t& num_words);
260
261 // Reset for contribution of "to-space".
262 void reset_scratch();
263
264 // GC support
265 void compute_new_size();
266
267 // Returns true if the collection is likely to be safely
268 // completed. Even if this method returns true, a collection
269 // may not be guaranteed to succeed, and the system should be
270 // able to safely unwind and recover from that failure, albeit
271 // at some additional cost.
272 bool collection_attempt_is_safe();
273
274 virtual void collect(bool full,
275 bool clear_all_soft_refs,
276 size_t size,
277 bool is_tlab);
278
279 HeapWord* expand_and_allocate(size_t size, bool is_tlab);
280
281 oop copy_to_survivor_space(oop old);
282 uint tenuring_threshold() { return _tenuring_threshold; }
283
284 // Performance Counter support
285 void update_counters();
286
287 // Printing
288 virtual const char* name() const;
289 virtual const char* short_name() const { return "DefNew"; }
290
291 void print_on(outputStream* st) const;
292
293 void verify();
294
295 bool promo_failure_scan_is_complete() const {
296 return _promo_failure_scan_stack.is_empty();
297 }
298
299 DefNewTracer* gc_tracer() const { return _gc_tracer; }
300
301 protected:
302 // If clear_space is true, clear the survivor spaces. Eden is
303 // cleared if the minimum size of eden is 0. If mangle_space
304 // is true, also mangle the space in debug mode.
305 void compute_space_boundaries(uintx minimum_eden_size,
306 bool clear_space,
307 bool mangle_space);
308
309 // Return adjusted new size for NewSizeThreadIncrease.
310 // If any overflow happens, revert to previous new size.
311 size_t adjust_for_thread_increase(size_t new_size_candidate,
312 size_t new_size_before,
313 size_t alignment,
314 size_t thread_increase_size) const;
315
316 size_t calculate_thread_increase_size(int threads_count) const;
317
318
319 // Scavenge support
320 void swap_spaces();
321 };
322
323 #endif // SHARE_GC_SERIAL_DEFNEWGENERATION_HPP