1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)parNewGeneration.hpp 1.48 07/05/17 15:52:44 JVM"
3 #endif
4 /*
5 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 class ChunkArray;
29 class ParScanWithoutBarrierClosure;
30 class ParScanWithBarrierClosure;
31 class ParRootScanWithoutBarrierClosure;
32 class ParRootScanWithBarrierTwoGensClosure;
33 class ParEvacuateFollowersClosure;
34
35 // It would be better if these types could be kept local to the .cpp file,
36 // but they must be here to allow ParScanClosure::do_oop_work to be defined
37 // in genOopClosures.inline.hpp.
38
39
40 typedef OopTaskQueue ObjToScanQueue;
41 typedef OopTaskQueueSet ObjToScanQueueSet;
42
43 // Enable this to get push/pop/steal stats.
44 const int PAR_STATS_ENABLED = 0;
45
46 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
47 ParScanWeakRefClosure* _par_cl;
48 public:
49 ParKeepAliveClosure(ParScanWeakRefClosure* cl);
50 void do_oop(oop* p);
51 };
52
53 // The state needed by thread performing parallel young-gen collection.
54 class ParScanThreadState {
55 friend class ParScanThreadStateSet;
56 ObjToScanQueue *_work_queue;
57
58 ParGCAllocBuffer _to_space_alloc_buffer;
59
60 ParScanWithoutBarrierClosure _to_space_closure; // scan_without_gc_barrier
61 ParScanWithBarrierClosure _old_gen_closure; // scan_with_gc_barrier
62 ParRootScanWithoutBarrierClosure _to_space_root_closure; // scan_root_without_gc_barrier
63 // One of these two will be passed to process_strong_roots, which will
64 // set its generation. The first is for two-gen configs where the
65 // old gen collects the perm gen; the second is for arbitrary configs.
66 // The second isn't used right now (it used to be used for the train, an
67 // incremental collector) but the declaration has been left as a reminder.
68 ParRootScanWithBarrierTwoGensClosure _older_gen_closure;
69 // This closure will always be bound to the old gen; it will be used
70 // in evacuate_followers.
71 ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier
72 ParEvacuateFollowersClosure _evacuate_followers;
73 DefNewGeneration::IsAliveClosure _is_alive_closure;
74 ParScanWeakRefClosure _scan_weak_ref_closure;
75 ParKeepAliveClosure _keep_alive_closure;
76
77
78 Space* _to_space;
79 Space* to_space() { return _to_space; }
80
81 Generation* _old_gen;
82 Generation* old_gen() { return _old_gen; }
83
84 HeapWord *_young_old_boundary;
85
86 int _hash_seed;
87 int _thread_num;
88 ageTable _ageTable;
89
90 bool _to_space_full;
91
92 int _pushes, _pops, _steals, _steal_attempts, _term_attempts;
93 int _overflow_pushes, _overflow_refills, _overflow_refill_objs;
94
95 // Timing numbers.
96 double _start;
97 double _start_strong_roots;
98 double _strong_roots_time;
99 double _start_term;
100 double _term_time;
101
102 // Helper for trim_queues. Scans subset of an array and makes
103 // remainder available for work stealing.
104 void scan_partial_array_and_push_remainder(oop obj);
105
106 // In support of CMS' parallel rescan of survivor space.
107 ChunkArray* _survivor_chunk_array;
108 ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; }
109
110 void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size);
111
112 ParScanThreadState(Space* to_space_, ParNewGeneration* gen_,
113 Generation* old_gen_, int thread_num_,
114 ObjToScanQueueSet* work_queue_set_, size_t desired_plab_sz_,
115 ParallelTaskTerminator& term_);
116
117 public:
118 ageTable* age_table() {return &_ageTable;}
119
120 ObjToScanQueue* work_queue() { return _work_queue; }
121
122 ParGCAllocBuffer* to_space_alloc_buffer() {
123 return &_to_space_alloc_buffer;
124 }
125
126 ParEvacuateFollowersClosure& evacuate_followers_closure() { return _evacuate_followers; }
127 DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; }
128 ParScanWeakRefClosure& scan_weak_ref_closure() { return _scan_weak_ref_closure; }
129 ParKeepAliveClosure& keep_alive_closure() { return _keep_alive_closure; }
130 ParScanClosure& older_gen_closure() { return _older_gen_closure; }
131 ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; };
132
133 // Decrease queue size below "max_size".
134 void trim_queues(int max_size);
135
136 // Is new_obj a candidate for scan_partial_array_and_push_remainder method.
137 inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const;
138
139 int* hash_seed() { return &_hash_seed; }
140 int thread_num() { return _thread_num; }
141
142 // Allocate a to-space block of size "sz", or else return NULL.
143 HeapWord* alloc_in_to_space_slow(size_t word_sz);
144
145 HeapWord* alloc_in_to_space(size_t word_sz) {
146 HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz);
147 if (obj != NULL) return obj;
148 else return alloc_in_to_space_slow(word_sz);
149 }
150
151 HeapWord* young_old_boundary() { return _young_old_boundary; }
152
153 void set_young_old_boundary(HeapWord *boundary) {
154 _young_old_boundary = boundary;
155 }
156
157 // Undo the most recent allocation ("obj", of "word_sz").
158 void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz);
159
160 int pushes() { return _pushes; }
161 int pops() { return _pops; }
162 int steals() { return _steals; }
163 int steal_attempts() { return _steal_attempts; }
164 int term_attempts() { return _term_attempts; }
165 int overflow_pushes() { return _overflow_pushes; }
166 int overflow_refills() { return _overflow_refills; }
167 int overflow_refill_objs() { return _overflow_refill_objs; }
168
169 void note_push() { if (PAR_STATS_ENABLED) _pushes++; }
170 void note_pop() { if (PAR_STATS_ENABLED) _pops++; }
171 void note_steal() { if (PAR_STATS_ENABLED) _steals++; }
172 void note_steal_attempt() { if (PAR_STATS_ENABLED) _steal_attempts++; }
173 void note_term_attempt() { if (PAR_STATS_ENABLED) _term_attempts++; }
174 void note_overflow_push() { if (PAR_STATS_ENABLED) _overflow_pushes++; }
175 void note_overflow_refill(int objs) {
176 if (PAR_STATS_ENABLED) {
177 _overflow_refills++;
178 _overflow_refill_objs += objs;
179 }
180 }
181
182 void start_strong_roots() {
183 _start_strong_roots = os::elapsedTime();
184 }
185 void end_strong_roots() {
186 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
187 }
188 double strong_roots_time() { return _strong_roots_time; }
189 void start_term_time() {
190 note_term_attempt();
191 _start_term = os::elapsedTime();
192 }
193 void end_term_time() {
194 _term_time += (os::elapsedTime() - _start_term);
195 }
196 double term_time() { return _term_time; }
197
198 double elapsed() {
199 return os::elapsedTime() - _start;
200 }
201
202 };
203
204 class ParNewGenTask: public AbstractGangTask {
205 ParNewGeneration* _gen;
206 Generation* _next_gen;
207 HeapWord* _young_old_boundary;
208 class ParScanThreadStateSet* _state_set;
209
210 public:
211 ParNewGenTask(ParNewGeneration* gen,
212 Generation* next_gen,
213 HeapWord* young_old_boundary,
214 ParScanThreadStateSet* state_set);
215
216 HeapWord* young_old_boundary() { return _young_old_boundary; }
217
218 void work(int i);
219 };
220
221 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
222 public:
223 KeepAliveClosure(ScanWeakRefClosure* cl);
224 void do_oop(oop* p);
225 };
226
227 class EvacuateFollowersClosureGeneral: public VoidClosure {
228 GenCollectedHeap* _gch;
229 int _level;
230 OopsInGenClosure* _scan_cur_or_nonheap;
231 OopsInGenClosure* _scan_older;
232 public:
233 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
234 OopsInGenClosure* cur,
235 OopsInGenClosure* older);
236 void do_void();
237 };
238
239 // Closure for scanning ParNewGeneration.
240 // Same as ScanClosure, except does parallel GC barrier.
241 class ScanClosureWithParBarrier: public ScanClosure {
242 public:
243 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier);
244 void do_oop(oop* p);
245 };
246
247 // Implements AbstractRefProcTaskExecutor for ParNew.
248 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
249 public:
250
251 ParNewRefProcTaskExecutor(ParNewGeneration& generation,
252 ParScanThreadStateSet& state_set)
253 : _generation(generation), _state_set(state_set)
254 { }
255
256 // Executes a task using worker threads.
257 virtual void execute(ProcessTask& task);
258 virtual void execute(EnqueueTask& task);
259 // Switch to single threaded mode.
260 virtual void set_single_threaded_mode();
261 private:
262 ParNewGeneration& _generation;
263 ParScanThreadStateSet& _state_set;
264 };
265
266
267 // A Generation that does parallel young-gen collection.
268
269 class ParNewGeneration: public DefNewGeneration {
270 friend class ParNewGenTask;
271 friend class ParNewRefProcTask;
272 friend class ParNewRefProcTaskExecutor;
273 friend class ParScanThreadStateSet;
274
275 // XXX use a global constant instead of 64!
276 struct ObjToScanQueuePadded {
277 ObjToScanQueue work_queue;
278 char pad[64 - sizeof(ObjToScanQueue)]; // prevent false sharing
279 };
280
281 // The per-thread work queues, available here for stealing.
282 ObjToScanQueueSet* _task_queues;
283
284 // Desired size of survivor space plab's
285 PLABStats _plab_stats;
286
287 // A list of from-space images of to-be-scanned objects, threaded through
288 // klass-pointers (klass information already copied to the forwarded
289 // image.) Manipulated with CAS.
290 oop _overflow_list;
291
292 // If true, older generation does not support promotion undo, so avoid.
293 static bool _avoid_promotion_undo;
294
295 // This closure is used by the reference processor to filter out
296 // references to live referent.
297 DefNewGeneration::IsAliveClosure _is_alive_closure;
298
299 static oop real_forwardee_slow(oop obj);
300 static void waste_some_time();
301
302 // Preserve the mark of "obj", if necessary, in preparation for its mark
303 // word being overwritten with a self-forwarding-pointer.
304 void preserve_mark_if_necessary(oop obj, markOop m);
305
306 protected:
307
308 bool _survivor_overflow;
309
310 bool avoid_promotion_undo() { return _avoid_promotion_undo; }
311 void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; }
312
313 bool survivor_overflow() { return _survivor_overflow; }
314 void set_survivor_overflow(bool v) { _survivor_overflow = v; }
315
316 // Adjust the tenuring threshold. See the implementation for
317 // the details of the policy.
318 virtual void adjust_desired_tenuring_threshold();
319
320 public:
321 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level);
322
323 ~ParNewGeneration() {
324 for (uint i = 0; i < ParallelGCThreads; i++)
325 delete _task_queues->queue(i);
326
327 delete _task_queues;
328 }
329
330 virtual void ref_processor_init();
331 virtual Generation::Name kind() { return Generation::ParNew; }
332 virtual const char* name() const;
333 virtual const char* short_name() const { return "ParNew"; }
334
335 // override
336 virtual bool refs_discovery_is_mt() const {
337 assert(UseParNewGC, "ParNewGeneration only when UseParNewGC");
338 return ParallelGCThreads > 1;
339 }
340
341 // Make the collection virtual.
342 virtual void collect(bool full,
343 bool clear_all_soft_refs,
344 size_t size,
345 bool is_tlab);
346
347 // This needs to be visible to the closure function.
348 // "obj" is the object to be copied, "m" is a recent value of its mark
349 // that must not contain a forwarding pointer (though one might be
350 // inserted in "obj"s mark word by a parallel thread).
351 inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state,
352 oop obj, size_t obj_sz, markOop m) {
353 if (_avoid_promotion_undo) {
354 return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state,
355 obj, obj_sz, m);
356 }
357
358 return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m);
359 }
360
361 oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state,
362 oop obj, size_t obj_sz, markOop m);
363
364 oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state,
365 oop obj, size_t obj_sz, markOop m);
366
367 // Push the given (from-space) object on the global overflow list.
368 void push_on_overflow_list(oop from_space_obj);
369
370 // If the global overflow list is non-empty, move some tasks from it
371 // onto "work_q" (which must be empty). No more than 1/4 of the
372 // max_elems of "work_q" are moved.
373 bool take_from_overflow_list(ParScanThreadState* par_scan_state);
374
375 // The task queues to be used by parallel GC threads.
376 ObjToScanQueueSet* task_queues() {
377 return _task_queues;
378 }
379
380 PLABStats* plab_stats() {
381 return &_plab_stats;
382 }
383
384 size_t desired_plab_sz() {
385 return _plab_stats.desired_plab_sz();
386 }
387
388 static oop real_forwardee(oop obj);
389
390 DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);)
391 };