1 /*
2 * Copyright (c) 2001, 2010, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARNEWGENERATION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARNEWGENERATION_HPP
27
28 #include "gc_implementation/parNew/parGCAllocBuffer.hpp"
29 #include "memory/defNewGeneration.hpp"
30 #include "utilities/taskqueue.hpp"
31
32 class ChunkArray;
33 class ParScanWithoutBarrierClosure;
34 class ParScanWithBarrierClosure;
35 class ParRootScanWithoutBarrierClosure;
36 class ParRootScanWithBarrierTwoGensClosure;
37 class ParEvacuateFollowersClosure;
38
39 // It would be better if these types could be kept local to the .cpp file,
40 // but they must be here to allow ParScanClosure::do_oop_work to be defined
41 // in genOopClosures.inline.hpp.
42
43 typedef Padded<OopTaskQueue> ObjToScanQueue;
44 typedef GenericTaskQueueSet<ObjToScanQueue> ObjToScanQueueSet;
45
46 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
47 private:
48 ParScanWeakRefClosure* _par_cl;
49 protected:
50 template <class T> void do_oop_work(T* p);
51 public:
52 ParKeepAliveClosure(ParScanWeakRefClosure* cl);
53 virtual void do_oop(oop* p);
54 virtual void do_oop(narrowOop* p);
55 };
56
57 // The state needed by thread performing parallel young-gen collection.
58 class ParScanThreadState {
59 friend class ParScanThreadStateSet;
60 private:
61 ObjToScanQueue *_work_queue;
62 Stack<oop>* const _overflow_stack;
63
64 ParGCAllocBuffer _to_space_alloc_buffer;
65
66 ParScanWithoutBarrierClosure _to_space_closure; // scan_without_gc_barrier
67 ParScanWithBarrierClosure _old_gen_closure; // scan_with_gc_barrier
68 ParRootScanWithoutBarrierClosure _to_space_root_closure; // scan_root_without_gc_barrier
69 // One of these two will be passed to process_strong_roots, which will
70 // set its generation. The first is for two-gen configs where the
71 // old gen collects the perm gen; the second is for arbitrary configs.
72 // The second isn't used right now (it used to be used for the train, an
73 // incremental collector) but the declaration has been left as a reminder.
74 ParRootScanWithBarrierTwoGensClosure _older_gen_closure;
75 // This closure will always be bound to the old gen; it will be used
76 // in evacuate_followers.
77 ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier
78 ParEvacuateFollowersClosure _evacuate_followers;
79 DefNewGeneration::IsAliveClosure _is_alive_closure;
80 ParScanWeakRefClosure _scan_weak_ref_closure;
81 ParKeepAliveClosure _keep_alive_closure;
82
83
84 Space* _to_space;
85 Space* to_space() { return _to_space; }
86
87 ParNewGeneration* _young_gen;
88 ParNewGeneration* young_gen() const { return _young_gen; }
89
90 Generation* _old_gen;
91 Generation* old_gen() { return _old_gen; }
92
93 HeapWord *_young_old_boundary;
94
95 int _hash_seed;
96 int _thread_num;
97 ageTable _ageTable;
98
99 bool _to_space_full;
100
101 #if TASKQUEUE_STATS
102 size_t _term_attempts;
103 size_t _overflow_refills;
104 size_t _overflow_refill_objs;
105 #endif // TASKQUEUE_STATS
106
107 // Stats for promotion failure
108 size_t _promotion_failure_size;
109
110 // Timing numbers.
111 double _start;
112 double _start_strong_roots;
113 double _strong_roots_time;
114 double _start_term;
115 double _term_time;
116
117 // Helper for trim_queues. Scans subset of an array and makes
118 // remainder available for work stealing.
119 void scan_partial_array_and_push_remainder(oop obj);
120
121 // In support of CMS' parallel rescan of survivor space.
122 ChunkArray* _survivor_chunk_array;
123 ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; }
124
125 void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size);
126
127 ParScanThreadState(Space* to_space_, ParNewGeneration* gen_,
128 Generation* old_gen_, int thread_num_,
129 ObjToScanQueueSet* work_queue_set_,
130 Stack<oop>* overflow_stacks_,
131 size_t desired_plab_sz_,
132 ParallelTaskTerminator& term_);
133
134 public:
135 ageTable* age_table() {return &_ageTable;}
136
137 ObjToScanQueue* work_queue() { return _work_queue; }
138
139 ParGCAllocBuffer* to_space_alloc_buffer() {
140 return &_to_space_alloc_buffer;
141 }
142
143 ParEvacuateFollowersClosure& evacuate_followers_closure() { return _evacuate_followers; }
144 DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; }
145 ParScanWeakRefClosure& scan_weak_ref_closure() { return _scan_weak_ref_closure; }
146 ParKeepAliveClosure& keep_alive_closure() { return _keep_alive_closure; }
147 ParScanClosure& older_gen_closure() { return _older_gen_closure; }
148 ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; };
149
150 // Decrease queue size below "max_size".
151 void trim_queues(int max_size);
152
153 // Private overflow stack usage
154 Stack<oop>* overflow_stack() { return _overflow_stack; }
155 bool take_from_overflow_stack();
156 void push_on_overflow_stack(oop p);
157
158 // Is new_obj a candidate for scan_partial_array_and_push_remainder method.
159 inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const;
160
161 int* hash_seed() { return &_hash_seed; }
162 int thread_num() { return _thread_num; }
163
164 // Allocate a to-space block of size "sz", or else return NULL.
165 HeapWord* alloc_in_to_space_slow(size_t word_sz);
166
167 HeapWord* alloc_in_to_space(size_t word_sz) {
168 HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz);
169 if (obj != NULL) return obj;
170 else return alloc_in_to_space_slow(word_sz);
171 }
172
173 HeapWord* young_old_boundary() { return _young_old_boundary; }
174
175 void set_young_old_boundary(HeapWord *boundary) {
176 _young_old_boundary = boundary;
177 }
178
179 // Undo the most recent allocation ("obj", of "word_sz").
180 void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz);
181
182 // Promotion failure stats
183 size_t promotion_failure_size() { return promotion_failure_size(); }
184 void log_promotion_failure(size_t sz) {
185 if (_promotion_failure_size == 0) {
186 _promotion_failure_size = sz;
187 }
188 }
189 void print_and_clear_promotion_failure_size();
190
191 #if TASKQUEUE_STATS
192 TaskQueueStats & taskqueue_stats() const { return _work_queue->stats; }
193
194 size_t term_attempts() const { return _term_attempts; }
195 size_t overflow_refills() const { return _overflow_refills; }
196 size_t overflow_refill_objs() const { return _overflow_refill_objs; }
197
198 void note_term_attempt() { ++_term_attempts; }
199 void note_overflow_refill(size_t objs) {
200 ++_overflow_refills; _overflow_refill_objs += objs;
201 }
202
203 void reset_stats();
204 #endif // TASKQUEUE_STATS
205
206 void start_strong_roots() {
207 _start_strong_roots = os::elapsedTime();
208 }
209 void end_strong_roots() {
210 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
211 }
212 double strong_roots_time() const { return _strong_roots_time; }
213 void start_term_time() {
214 TASKQUEUE_STATS_ONLY(note_term_attempt());
215 _start_term = os::elapsedTime();
216 }
217 void end_term_time() {
218 _term_time += (os::elapsedTime() - _start_term);
219 }
220 double term_time() const { return _term_time; }
221
222 double elapsed_time() const {
223 return os::elapsedTime() - _start;
224 }
225 };
226
227 class ParNewGenTask: public AbstractGangTask {
228 private:
229 ParNewGeneration* _gen;
230 Generation* _next_gen;
231 HeapWord* _young_old_boundary;
232 class ParScanThreadStateSet* _state_set;
233
234 public:
235 ParNewGenTask(ParNewGeneration* gen,
236 Generation* next_gen,
237 HeapWord* young_old_boundary,
238 ParScanThreadStateSet* state_set);
239
240 HeapWord* young_old_boundary() { return _young_old_boundary; }
241
242 void work(int i);
243 };
244
245 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
246 protected:
247 template <class T> void do_oop_work(T* p);
248 public:
249 KeepAliveClosure(ScanWeakRefClosure* cl);
250 virtual void do_oop(oop* p);
251 virtual void do_oop(narrowOop* p);
252 };
253
254 class EvacuateFollowersClosureGeneral: public VoidClosure {
255 private:
256 GenCollectedHeap* _gch;
257 int _level;
258 OopsInGenClosure* _scan_cur_or_nonheap;
259 OopsInGenClosure* _scan_older;
260 public:
261 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
262 OopsInGenClosure* cur,
263 OopsInGenClosure* older);
264 virtual void do_void();
265 };
266
267 // Closure for scanning ParNewGeneration.
268 // Same as ScanClosure, except does parallel GC barrier.
269 class ScanClosureWithParBarrier: public ScanClosure {
270 protected:
271 template <class T> void do_oop_work(T* p);
272 public:
273 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier);
274 virtual void do_oop(oop* p);
275 virtual void do_oop(narrowOop* p);
276 };
277
278 // Implements AbstractRefProcTaskExecutor for ParNew.
279 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
280 private:
281 ParNewGeneration& _generation;
282 ParScanThreadStateSet& _state_set;
283 public:
284 ParNewRefProcTaskExecutor(ParNewGeneration& generation,
285 ParScanThreadStateSet& state_set)
286 : _generation(generation), _state_set(state_set)
287 { }
288
289 // Executes a task using worker threads.
290 virtual void execute(ProcessTask& task);
291 virtual void execute(EnqueueTask& task);
292 // Switch to single threaded mode.
293 virtual void set_single_threaded_mode();
294 };
295
296
297 // A Generation that does parallel young-gen collection.
298
299 class ParNewGeneration: public DefNewGeneration {
300 friend class ParNewGenTask;
301 friend class ParNewRefProcTask;
302 friend class ParNewRefProcTaskExecutor;
303 friend class ParScanThreadStateSet;
304 friend class ParEvacuateFollowersClosure;
305
306 private:
307 // The per-worker-thread work queues
308 ObjToScanQueueSet* _task_queues;
309
310 // Per-worker-thread local overflow stacks
311 Stack<oop>* _overflow_stacks;
312
313 // Desired size of survivor space plab's
314 PLABStats _plab_stats;
315
316 // A list of from-space images of to-be-scanned objects, threaded through
317 // klass-pointers (klass information already copied to the forwarded
318 // image.) Manipulated with CAS.
319 oop _overflow_list;
320 NOT_PRODUCT(ssize_t _num_par_pushes;)
321
322 // If true, older generation does not support promotion undo, so avoid.
323 static bool _avoid_promotion_undo;
324
325 // This closure is used by the reference processor to filter out
326 // references to live referent.
327 DefNewGeneration::IsAliveClosure _is_alive_closure;
328
329 static oop real_forwardee_slow(oop obj);
330 static void waste_some_time();
331
332 // Preserve the mark of "obj", if necessary, in preparation for its mark
333 // word being overwritten with a self-forwarding-pointer.
334 void preserve_mark_if_necessary(oop obj, markOop m);
335
336 protected:
337
338 bool _survivor_overflow;
339
340 bool avoid_promotion_undo() { return _avoid_promotion_undo; }
341 void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; }
342
343 bool survivor_overflow() { return _survivor_overflow; }
344 void set_survivor_overflow(bool v) { _survivor_overflow = v; }
345
346 // Adjust the tenuring threshold. See the implementation for
347 // the details of the policy.
348 virtual void adjust_desired_tenuring_threshold();
349
350 public:
351 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level);
352
353 ~ParNewGeneration() {
354 for (uint i = 0; i < ParallelGCThreads; i++)
355 delete _task_queues->queue(i);
356
357 delete _task_queues;
358 }
359
360 static bool in_use();
361
362 virtual void ref_processor_init();
363 virtual Generation::Name kind() { return Generation::ParNew; }
364 virtual const char* name() const;
365 virtual const char* short_name() const { return "ParNew"; }
366
367 // override
368 virtual bool refs_discovery_is_mt() const {
369 assert(UseParNewGC, "ParNewGeneration only when UseParNewGC");
370 return ParallelGCThreads > 1;
371 }
372
373 // Make the collection virtual.
374 virtual void collect(bool full,
375 bool clear_all_soft_refs,
376 size_t size,
377 bool is_tlab);
378
379 // This needs to be visible to the closure function.
380 // "obj" is the object to be copied, "m" is a recent value of its mark
381 // that must not contain a forwarding pointer (though one might be
382 // inserted in "obj"s mark word by a parallel thread).
383 inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state,
384 oop obj, size_t obj_sz, markOop m) {
385 if (_avoid_promotion_undo) {
386 return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state,
387 obj, obj_sz, m);
388 }
389
390 return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m);
391 }
392
393 oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state,
394 oop obj, size_t obj_sz, markOop m);
395
396 oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state,
397 oop obj, size_t obj_sz, markOop m);
398
399 // in support of testing overflow code
400 NOT_PRODUCT(int _overflow_counter;)
401 NOT_PRODUCT(bool should_simulate_overflow();)
402
403 // Accessor for overflow list
404 oop overflow_list() { return _overflow_list; }
405
406 // Push the given (from-space) object on the global overflow list.
407 void push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state);
408
409 // If the global overflow list is non-empty, move some tasks from it
410 // onto "work_q" (which need not be empty). No more than 1/4 of the
411 // available space on "work_q" is used.
412 bool take_from_overflow_list(ParScanThreadState* par_scan_state);
413 bool take_from_overflow_list_work(ParScanThreadState* par_scan_state);
414
415 // The task queues to be used by parallel GC threads.
416 ObjToScanQueueSet* task_queues() {
417 return _task_queues;
418 }
419
420 PLABStats* plab_stats() {
421 return &_plab_stats;
422 }
423
424 size_t desired_plab_sz() {
425 return _plab_stats.desired_plab_sz();
426 }
427
428 static oop real_forwardee(oop obj);
429
430 DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);)
431 };
432
433 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARNEWGENERATION_HPP