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.
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/shared/gcTrace.hpp"
29 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
30 #include "gc_implementation/shared/copyFailedInfo.hpp"
31 #include "memory/defNewGeneration.hpp"
32 #include "utilities/taskqueue.hpp"
33
34 class ChunkArray;
35 class ParScanWithoutBarrierClosure;
36 class ParScanWithBarrierClosure;
37 class ParRootScanWithoutBarrierClosure;
38 class ParRootScanWithBarrierTwoGensClosure;
39 class ParEvacuateFollowersClosure;
40
41 // It would be better if these types could be kept local to the .cpp file,
42 // but they must be here to allow ParScanClosure::do_oop_work to be defined
43 // in genOopClosures.inline.hpp.
44
45 typedef Padded<OopTaskQueue> ObjToScanQueue;
46 typedef GenericTaskQueueSet<ObjToScanQueue, mtGC> ObjToScanQueueSet;
47
48 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
49 private:
50 ParScanWeakRefClosure* _par_cl;
51 protected:
52 template <class T> void do_oop_work(T* p);
53 public:
54 ParKeepAliveClosure(ParScanWeakRefClosure* cl);
55 virtual void do_oop(oop* p);
56 virtual void do_oop(narrowOop* p);
57 };
58
59 // The state needed by thread performing parallel young-gen collection.
60 class ParScanThreadState {
61 friend class ParScanThreadStateSet;
62 private:
63 ObjToScanQueue *_work_queue;
64 Stack<oop, mtGC>* const _overflow_stack;
65
66 ParGCAllocBuffer _to_space_alloc_buffer;
67
68 ParScanWithoutBarrierClosure _to_space_closure; // scan_without_gc_barrier
69 ParScanWithBarrierClosure _old_gen_closure; // scan_with_gc_barrier
70 ParRootScanWithoutBarrierClosure _to_space_root_closure; // scan_root_without_gc_barrier
71 // One of these two will be passed to process_strong_roots, which will
72 // set its generation. The first is for two-gen configs where the
73 // old gen collects the perm gen; the second is for arbitrary configs.
74 // The second isn't used right now (it used to be used for the train, an
75 // incremental collector) but the declaration has been left as a reminder.
76 ParRootScanWithBarrierTwoGensClosure _older_gen_closure;
77 // This closure will always be bound to the old gen; it will be used
78 // in evacuate_followers.
79 ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier
80 ParEvacuateFollowersClosure _evacuate_followers;
81 DefNewGeneration::IsAliveClosure _is_alive_closure;
82 ParScanWeakRefClosure _scan_weak_ref_closure;
83 ParKeepAliveClosure _keep_alive_closure;
84
85
86 Space* _to_space;
87 Space* to_space() { return _to_space; }
88
89 ParNewGeneration* _young_gen;
90 ParNewGeneration* young_gen() const { return _young_gen; }
91
92 Generation* _old_gen;
93 Generation* old_gen() { return _old_gen; }
94
95 HeapWord *_young_old_boundary;
96
97 int _hash_seed;
98 int _thread_num;
99 ageTable _ageTable;
100
101 bool _to_space_full;
102
103 #if TASKQUEUE_STATS
104 size_t _term_attempts;
105 size_t _overflow_refills;
106 size_t _overflow_refill_objs;
107 #endif // TASKQUEUE_STATS
108
109 // Stats for promotion failure
110 PromotionFailedInfo _promotion_failed_info;
111
112 // Timing numbers.
113 double _start;
114 double _start_strong_roots;
115 double _strong_roots_time;
116 double _start_term;
117 double _term_time;
118
119 // Helper for trim_queues. Scans subset of an array and makes
120 // remainder available for work stealing.
121 void scan_partial_array_and_push_remainder(oop obj);
122
123 // In support of CMS' parallel rescan of survivor space.
124 ChunkArray* _survivor_chunk_array;
125 ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; }
126
127 void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size);
128
129 ParScanThreadState(Space* to_space_, ParNewGeneration* gen_,
130 Generation* old_gen_, int thread_num_,
131 ObjToScanQueueSet* work_queue_set_,
132 Stack<oop, mtGC>* overflow_stacks_,
133 size_t desired_plab_sz_,
134 ParallelTaskTerminator& term_);
135
136 public:
137 ageTable* age_table() {return &_ageTable;}
138
139 ObjToScanQueue* work_queue() { return _work_queue; }
140
141 ParGCAllocBuffer* to_space_alloc_buffer() {
142 return &_to_space_alloc_buffer;
143 }
144
145 ParEvacuateFollowersClosure& evacuate_followers_closure() { return _evacuate_followers; }
146 DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; }
147 ParScanWeakRefClosure& scan_weak_ref_closure() { return _scan_weak_ref_closure; }
148 ParKeepAliveClosure& keep_alive_closure() { return _keep_alive_closure; }
149 ParScanClosure& older_gen_closure() { return _older_gen_closure; }
150 ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; };
151
152 // Decrease queue size below "max_size".
153 void trim_queues(int max_size);
154
155 // Private overflow stack usage
156 Stack<oop, mtGC>* overflow_stack() { return _overflow_stack; }
157 bool take_from_overflow_stack();
158 void push_on_overflow_stack(oop p);
159
160 // Is new_obj a candidate for scan_partial_array_and_push_remainder method.
161 inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const;
162
163 int* hash_seed() { return &_hash_seed; }
164 int thread_num() { return _thread_num; }
165
166 // Allocate a to-space block of size "sz", or else return NULL.
167 HeapWord* alloc_in_to_space_slow(size_t word_sz);
168
169 HeapWord* alloc_in_to_space(size_t word_sz) {
170 HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz);
171 if (obj != NULL) return obj;
172 else return alloc_in_to_space_slow(word_sz);
173 }
174
175 HeapWord* young_old_boundary() { return _young_old_boundary; }
176
177 void set_young_old_boundary(HeapWord *boundary) {
178 _young_old_boundary = boundary;
179 }
180
181 // Undo the most recent allocation ("obj", of "word_sz").
182 void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz);
183
184 // Promotion failure stats
185 void register_promotion_failure(size_t sz) {
186 _promotion_failed_info.register_copy_failure(sz);
187 }
188 PromotionFailedInfo& promotion_failed_info() {
189 return _promotion_failed_info;
190 }
191 bool promotion_failed() {
192 return _promotion_failed_info.has_failed();
193 }
194 void print_promotion_failure_size();
195
196 #if TASKQUEUE_STATS
197 TaskQueueStats & taskqueue_stats() const { return _work_queue->stats; }
198
199 size_t term_attempts() const { return _term_attempts; }
200 size_t overflow_refills() const { return _overflow_refills; }
201 size_t overflow_refill_objs() const { return _overflow_refill_objs; }
202
203 void note_term_attempt() { ++_term_attempts; }
204 void note_overflow_refill(size_t objs) {
205 ++_overflow_refills; _overflow_refill_objs += objs;
206 }
207
208 void reset_stats();
209 #endif // TASKQUEUE_STATS
210
211 void start_strong_roots() {
212 _start_strong_roots = os::elapsedTime();
213 }
214 void end_strong_roots() {
215 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
216 }
217 double strong_roots_time() const { return _strong_roots_time; }
218 void start_term_time() {
219 TASKQUEUE_STATS_ONLY(note_term_attempt());
220 _start_term = os::elapsedTime();
221 }
222 void end_term_time() {
223 _term_time += (os::elapsedTime() - _start_term);
224 }
225 double term_time() const { return _term_time; }
226
227 double elapsed_time() const {
228 return os::elapsedTime() - _start;
229 }
230 };
231
232 class ParNewGenTask: public AbstractGangTask {
233 private:
234 ParNewGeneration* _gen;
235 Generation* _next_gen;
236 HeapWord* _young_old_boundary;
237 class ParScanThreadStateSet* _state_set;
238
239 public:
240 ParNewGenTask(ParNewGeneration* gen,
241 Generation* next_gen,
242 HeapWord* young_old_boundary,
243 ParScanThreadStateSet* state_set);
244
245 HeapWord* young_old_boundary() { return _young_old_boundary; }
246
247 void work(uint worker_id);
248
249 // Reset the terminator in ParScanThreadStateSet for
250 // "active_workers" threads.
251 virtual void set_for_termination(int active_workers);
252 };
253
254 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
255 protected:
256 template <class T> void do_oop_work(T* p);
257 public:
258 KeepAliveClosure(ScanWeakRefClosure* cl);
259 virtual void do_oop(oop* p);
260 virtual void do_oop(narrowOop* p);
261 };
262
263 class EvacuateFollowersClosureGeneral: public VoidClosure {
264 private:
265 GenCollectedHeap* _gch;
266 int _level;
267 OopsInGenClosure* _scan_cur_or_nonheap;
268 OopsInGenClosure* _scan_older;
269 public:
270 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
271 OopsInGenClosure* cur,
272 OopsInGenClosure* older);
273 virtual void do_void();
274 };
275
276 // Closure for scanning ParNewGeneration.
277 // Same as ScanClosure, except does parallel GC barrier.
278 class ScanClosureWithParBarrier: public ScanClosure {
279 protected:
280 template <class T> void do_oop_work(T* p);
281 public:
282 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier);
283 virtual void do_oop(oop* p);
284 virtual void do_oop(narrowOop* p);
285 };
286
287 // Implements AbstractRefProcTaskExecutor for ParNew.
288 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
289 private:
290 ParNewGeneration& _generation;
291 ParScanThreadStateSet& _state_set;
292 public:
293 ParNewRefProcTaskExecutor(ParNewGeneration& generation,
294 ParScanThreadStateSet& state_set)
295 : _generation(generation), _state_set(state_set)
296 { }
297
298 // Executes a task using worker threads.
299 virtual void execute(ProcessTask& task);
300 virtual void execute(EnqueueTask& task);
301 // Switch to single threaded mode.
302 virtual void set_single_threaded_mode();
303 };
304
305
306 // A Generation that does parallel young-gen collection.
307
308 class ParNewGeneration: public DefNewGeneration {
309 friend class ParNewGenTask;
310 friend class ParNewRefProcTask;
311 friend class ParNewRefProcTaskExecutor;
312 friend class ParScanThreadStateSet;
313 friend class ParEvacuateFollowersClosure;
314
315 private:
316 // The per-worker-thread work queues
317 ObjToScanQueueSet* _task_queues;
318
319 // Per-worker-thread local overflow stacks
320 Stack<oop, mtGC>* _overflow_stacks;
321
322 // Desired size of survivor space plab's
323 PLABStats _plab_stats;
324
325 // A list of from-space images of to-be-scanned objects, threaded through
326 // klass-pointers (klass information already copied to the forwarded
327 // image.) Manipulated with CAS.
328 oop _overflow_list;
329 NOT_PRODUCT(ssize_t _num_par_pushes;)
330
331 // If true, older generation does not support promotion undo, so avoid.
332 static bool _avoid_promotion_undo;
333
334 // This closure is used by the reference processor to filter out
335 // references to live referent.
336 DefNewGeneration::IsAliveClosure _is_alive_closure;
337
338 static oop real_forwardee_slow(oop obj);
339 static void waste_some_time();
340
341 // Preserve the mark of "obj", if necessary, in preparation for its mark
342 // word being overwritten with a self-forwarding-pointer.
343 void preserve_mark_if_necessary(oop obj, markOop m);
344
345 void handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer);
346
347 protected:
348
349 bool _survivor_overflow;
350
351 bool avoid_promotion_undo() { return _avoid_promotion_undo; }
352 void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; }
353
354 bool survivor_overflow() { return _survivor_overflow; }
355 void set_survivor_overflow(bool v) { _survivor_overflow = v; }
356
357 public:
358 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level);
359
360 ~ParNewGeneration() {
361 for (uint i = 0; i < ParallelGCThreads; i++)
362 delete _task_queues->queue(i);
363
364 delete _task_queues;
365 }
366
367 virtual void ref_processor_init();
368 virtual Generation::Name kind() { return Generation::ParNew; }
369 virtual const char* name() const;
370 virtual const char* short_name() const { return "ParNew"; }
371
372 // override
373 virtual bool refs_discovery_is_mt() const {
374 assert(UseParNewGC, "ParNewGeneration only when UseParNewGC");
375 return ParallelGCThreads > 1;
376 }
377
378 // Make the collection virtual.
379 virtual void collect(bool full,
380 bool clear_all_soft_refs,
381 size_t size,
382 bool is_tlab);
383
384 // This needs to be visible to the closure function.
385 // "obj" is the object to be copied, "m" is a recent value of its mark
386 // that must not contain a forwarding pointer (though one might be
387 // inserted in "obj"s mark word by a parallel thread).
388 inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state,
389 oop obj, size_t obj_sz, markOop m) {
390 if (_avoid_promotion_undo) {
391 return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state,
392 obj, obj_sz, m);
393 }
394
395 return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m);
396 }
397
398 oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state,
399 oop obj, size_t obj_sz, markOop m);
400
401 oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state,
402 oop obj, size_t obj_sz, markOop m);
403
404 // in support of testing overflow code
405 NOT_PRODUCT(int _overflow_counter;)
406 NOT_PRODUCT(bool should_simulate_overflow();)
407
408 // Accessor for overflow list
409 oop overflow_list() { return _overflow_list; }
410
411 // Push the given (from-space) object on the global overflow list.
412 void push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state);
413
414 // If the global overflow list is non-empty, move some tasks from it
415 // onto "work_q" (which need not be empty). No more than 1/4 of the
416 // available space on "work_q" is used.
417 bool take_from_overflow_list(ParScanThreadState* par_scan_state);
418 bool take_from_overflow_list_work(ParScanThreadState* par_scan_state);
419
420 // The task queues to be used by parallel GC threads.
421 ObjToScanQueueSet* task_queues() {
422 return _task_queues;
423 }
424
425 PLABStats* plab_stats() {
426 return &_plab_stats;
427 }
428
429 size_t desired_plab_sz() {
430 return _plab_stats.desired_plab_sz();
431 }
432
433 static oop real_forwardee(oop obj);
434
435 DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);)
436 };
437
438 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARNEWGENERATION_HPP