Mercurial > hg > truffle
annotate src/share/vm/memory/referenceProcessor.hpp @ 3915:c2bf0120ee5d
7085906: Replace the permgen allocated sentinelRef with a self-looped end
Summary: Remove the sentinelRef and let the last Reference in a discovered chain point back to itself.
Reviewed-by: ysr, jmasa
author | stefank |
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date | Thu, 01 Sep 2011 16:18:17 +0200 |
parents | 92da084fefc9 |
children | eca1193ca245 |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP |
26 #define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP | |
27 | |
28 #include "memory/referencePolicy.hpp" | |
29 #include "oops/instanceRefKlass.hpp" | |
30 | |
0 | 31 // ReferenceProcessor class encapsulates the per-"collector" processing |
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32 // of java.lang.Reference objects for GC. The interface is useful for supporting |
0 | 33 // a generational abstraction, in particular when there are multiple |
34 // generations that are being independently collected -- possibly | |
35 // concurrently and/or incrementally. Note, however, that the | |
36 // ReferenceProcessor class abstracts away from a generational setting | |
37 // by using only a heap interval (called "span" below), thus allowing | |
38 // its use in a straightforward manner in a general, non-generational | |
39 // setting. | |
40 // | |
41 // The basic idea is that each ReferenceProcessor object concerns | |
42 // itself with ("weak") reference processing in a specific "span" | |
43 // of the heap of interest to a specific collector. Currently, | |
44 // the span is a convex interval of the heap, but, efficiency | |
45 // apart, there seems to be no reason it couldn't be extended | |
46 // (with appropriate modifications) to any "non-convex interval". | |
47 | |
48 // forward references | |
49 class ReferencePolicy; | |
50 class AbstractRefProcTaskExecutor; | |
51 class DiscoveredList; | |
52 | |
53 class ReferenceProcessor : public CHeapObj { | |
54 protected: | |
55 MemRegion _span; // (right-open) interval of heap | |
56 // subject to wkref discovery | |
57 bool _discovering_refs; // true when discovery enabled | |
58 bool _discovery_is_atomic; // if discovery is atomic wrt | |
59 // other collectors in configuration | |
60 bool _discovery_is_mt; // true if reference discovery is MT. | |
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61 // If true, setting "next" field of a discovered refs list requires |
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62 // write barrier(s). (Must be true if used in a collector in which |
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63 // elements of a discovered list may be moved during discovery: for |
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64 // example, a collector like Garbage-First that moves objects during a |
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65 // long-term concurrent marking phase that does weak reference |
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66 // discovery.) |
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67 bool _discovered_list_needs_barrier; |
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68 BarrierSet* _bs; // Cached copy of BarrierSet. |
0 | 69 bool _enqueuing_is_done; // true if all weak references enqueued |
70 bool _processing_is_mt; // true during phases when | |
71 // reference processing is MT. | |
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72 int _next_id; // round-robin mod _num_q counter in |
0 | 73 // support of work distribution |
74 | |
75 // For collectors that do not keep GC marking information | |
76 // in the object header, this field holds a closure that | |
77 // helps the reference processor determine the reachability | |
78 // of an oop (the field is currently initialized to NULL for | |
79 // all collectors but the CMS collector). | |
80 BoolObjectClosure* _is_alive_non_header; | |
81 | |
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82 // Soft ref clearing policies |
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83 // . the default policy |
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84 static ReferencePolicy* _default_soft_ref_policy; |
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85 // . the "clear all" policy |
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86 static ReferencePolicy* _always_clear_soft_ref_policy; |
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87 // . the current policy below is either one of the above |
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88 ReferencePolicy* _current_soft_ref_policy; |
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89 |
0 | 90 // The discovered ref lists themselves |
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91 |
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92 // The active MT'ness degree of the queues below |
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93 int _num_q; |
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94 // The maximum MT'ness degree of the queues below |
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95 int _max_num_q; |
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96 // Arrays of lists of oops, one per thread |
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97 DiscoveredList* _discoveredSoftRefs; |
0 | 98 DiscoveredList* _discoveredWeakRefs; |
99 DiscoveredList* _discoveredFinalRefs; | |
100 DiscoveredList* _discoveredPhantomRefs; | |
101 | |
102 public: | |
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103 int num_q() { return _num_q; } |
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104 int max_num_q() { return _max_num_q; } |
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105 void set_active_mt_degree(int v) { _num_q = v; } |
0 | 106 DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; } |
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107 ReferencePolicy* setup_policy(bool always_clear) { |
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108 _current_soft_ref_policy = always_clear ? |
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109 _always_clear_soft_ref_policy : _default_soft_ref_policy; |
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110 _current_soft_ref_policy->setup(); // snapshot the policy threshold |
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111 return _current_soft_ref_policy; |
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112 } |
0 | 113 |
114 public: | |
115 // Process references with a certain reachability level. | |
116 void process_discovered_reflist(DiscoveredList refs_lists[], | |
117 ReferencePolicy* policy, | |
118 bool clear_referent, | |
119 BoolObjectClosure* is_alive, | |
120 OopClosure* keep_alive, | |
121 VoidClosure* complete_gc, | |
122 AbstractRefProcTaskExecutor* task_executor); | |
123 | |
124 void process_phaseJNI(BoolObjectClosure* is_alive, | |
125 OopClosure* keep_alive, | |
126 VoidClosure* complete_gc); | |
127 | |
128 // Work methods used by the method process_discovered_reflist | |
129 // Phase1: keep alive all those referents that are otherwise | |
130 // dead but which must be kept alive by policy (and their closure). | |
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131 void process_phase1(DiscoveredList& refs_list, |
0 | 132 ReferencePolicy* policy, |
133 BoolObjectClosure* is_alive, | |
134 OopClosure* keep_alive, | |
135 VoidClosure* complete_gc); | |
136 // Phase2: remove all those references whose referents are | |
137 // reachable. | |
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138 inline void process_phase2(DiscoveredList& refs_list, |
0 | 139 BoolObjectClosure* is_alive, |
140 OopClosure* keep_alive, | |
141 VoidClosure* complete_gc) { | |
142 if (discovery_is_atomic()) { | |
143 // complete_gc is ignored in this case for this phase | |
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144 pp2_work(refs_list, is_alive, keep_alive); |
0 | 145 } else { |
146 assert(complete_gc != NULL, "Error"); | |
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147 pp2_work_concurrent_discovery(refs_list, is_alive, |
0 | 148 keep_alive, complete_gc); |
149 } | |
150 } | |
151 // Work methods in support of process_phase2 | |
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152 void pp2_work(DiscoveredList& refs_list, |
0 | 153 BoolObjectClosure* is_alive, |
154 OopClosure* keep_alive); | |
155 void pp2_work_concurrent_discovery( | |
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156 DiscoveredList& refs_list, |
0 | 157 BoolObjectClosure* is_alive, |
158 OopClosure* keep_alive, | |
159 VoidClosure* complete_gc); | |
160 // Phase3: process the referents by either clearing them | |
161 // or keeping them alive (and their closure) | |
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162 void process_phase3(DiscoveredList& refs_list, |
0 | 163 bool clear_referent, |
164 BoolObjectClosure* is_alive, | |
165 OopClosure* keep_alive, | |
166 VoidClosure* complete_gc); | |
167 | |
168 // Enqueue references with a certain reachability level | |
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169 void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr); |
0 | 170 |
171 // "Preclean" all the discovered reference lists | |
172 // by removing references with strongly reachable referents. | |
173 // The first argument is a predicate on an oop that indicates | |
174 // its (strong) reachability and the second is a closure that | |
175 // may be used to incrementalize or abort the precleaning process. | |
176 // The caller is responsible for taking care of potential | |
177 // interference with concurrent operations on these lists | |
178 // (or predicates involved) by other threads. Currently | |
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179 // only used by the CMS collector. should_unload_classes is |
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180 // used to aid assertion checking when classes are collected. |
0 | 181 void preclean_discovered_references(BoolObjectClosure* is_alive, |
182 OopClosure* keep_alive, | |
183 VoidClosure* complete_gc, | |
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184 YieldClosure* yield, |
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185 bool should_unload_classes); |
0 | 186 |
187 // Delete entries in the discovered lists that have | |
188 // either a null referent or are not active. Such | |
189 // Reference objects can result from the clearing | |
190 // or enqueueing of Reference objects concurrent | |
191 // with their discovery by a (concurrent) collector. | |
192 // For a definition of "active" see java.lang.ref.Reference; | |
193 // Refs are born active, become inactive when enqueued, | |
194 // and never become active again. The state of being | |
195 // active is encoded as follows: A Ref is active | |
196 // if and only if its "next" field is NULL. | |
197 void clean_up_discovered_references(); | |
198 void clean_up_discovered_reflist(DiscoveredList& refs_list); | |
199 | |
200 // Returns the name of the discovered reference list | |
201 // occupying the i / _num_q slot. | |
202 const char* list_name(int i); | |
203 | |
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204 void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor); |
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205 |
0 | 206 protected: |
207 // "Preclean" the given discovered reference list | |
208 // by removing references with strongly reachable referents. | |
209 // Currently used in support of CMS only. | |
210 void preclean_discovered_reflist(DiscoveredList& refs_list, | |
211 BoolObjectClosure* is_alive, | |
212 OopClosure* keep_alive, | |
213 VoidClosure* complete_gc, | |
214 YieldClosure* yield); | |
215 | |
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216 // round-robin mod _num_q (not: _not_ mode _max_num_q) |
0 | 217 int next_id() { |
218 int id = _next_id; | |
219 if (++_next_id == _num_q) { | |
220 _next_id = 0; | |
221 } | |
222 return id; | |
223 } | |
224 DiscoveredList* get_discovered_list(ReferenceType rt); | |
225 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj, | |
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226 HeapWord* discovered_addr); |
0 | 227 void verify_ok_to_handle_reflists() PRODUCT_RETURN; |
228 | |
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229 void clear_discovered_references(DiscoveredList& refs_list); |
0 | 230 void abandon_partial_discovered_list(DiscoveredList& refs_list); |
231 | |
232 // Calculate the number of jni handles. | |
233 unsigned int count_jni_refs(); | |
234 | |
235 // Balances reference queues. | |
236 void balance_queues(DiscoveredList ref_lists[]); | |
237 | |
238 // Update (advance) the soft ref master clock field. | |
239 void update_soft_ref_master_clock(); | |
240 | |
241 public: | |
242 // constructor | |
243 ReferenceProcessor(): | |
244 _span((HeapWord*)NULL, (HeapWord*)NULL), | |
245 _discoveredSoftRefs(NULL), _discoveredWeakRefs(NULL), | |
246 _discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL), | |
247 _discovering_refs(false), | |
248 _discovery_is_atomic(true), | |
249 _enqueuing_is_done(false), | |
250 _discovery_is_mt(false), | |
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251 _discovered_list_needs_barrier(false), |
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252 _bs(NULL), |
0 | 253 _is_alive_non_header(NULL), |
254 _num_q(0), | |
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255 _max_num_q(0), |
0 | 256 _processing_is_mt(false), |
257 _next_id(0) | |
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258 { } |
0 | 259 |
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260 // Default parameters give you a vanilla reference processor. |
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261 ReferenceProcessor(MemRegion span, |
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262 bool mt_processing = false, int mt_processing_degree = 1, |
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263 bool mt_discovery = false, int mt_discovery_degree = 1, |
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264 bool atomic_discovery = true, |
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265 BoolObjectClosure* is_alive_non_header = NULL, |
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266 bool discovered_list_needs_barrier = false); |
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267 |
0 | 268 // RefDiscoveryPolicy values |
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269 enum DiscoveryPolicy { |
0 | 270 ReferenceBasedDiscovery = 0, |
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271 ReferentBasedDiscovery = 1, |
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272 DiscoveryPolicyMin = ReferenceBasedDiscovery, |
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273 DiscoveryPolicyMax = ReferentBasedDiscovery |
0 | 274 }; |
275 | |
276 static void init_statics(); | |
277 | |
278 public: | |
279 // get and set "is_alive_non_header" field | |
280 BoolObjectClosure* is_alive_non_header() { | |
281 return _is_alive_non_header; | |
282 } | |
283 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) { | |
284 _is_alive_non_header = is_alive_non_header; | |
285 } | |
286 | |
287 // get and set span | |
288 MemRegion span() { return _span; } | |
289 void set_span(MemRegion span) { _span = span; } | |
290 | |
291 // start and stop weak ref discovery | |
292 void enable_discovery() { _discovering_refs = true; } | |
293 void disable_discovery() { _discovering_refs = false; } | |
294 bool discovery_enabled() { return _discovering_refs; } | |
295 | |
296 // whether discovery is atomic wrt other collectors | |
297 bool discovery_is_atomic() const { return _discovery_is_atomic; } | |
298 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; } | |
299 | |
300 // whether discovery is done by multiple threads same-old-timeously | |
301 bool discovery_is_mt() const { return _discovery_is_mt; } | |
302 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; } | |
303 | |
304 // Whether we are in a phase when _processing_ is MT. | |
305 bool processing_is_mt() const { return _processing_is_mt; } | |
306 void set_mt_processing(bool mt) { _processing_is_mt = mt; } | |
307 | |
308 // whether all enqueuing of weak references is complete | |
309 bool enqueuing_is_done() { return _enqueuing_is_done; } | |
310 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; } | |
311 | |
312 // iterate over oops | |
313 void weak_oops_do(OopClosure* f); // weak roots | |
314 | |
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315 // Balance each of the discovered lists. |
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316 void balance_all_queues(); |
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317 |
0 | 318 // Discover a Reference object, using appropriate discovery criteria |
319 bool discover_reference(oop obj, ReferenceType rt); | |
320 | |
321 // Process references found during GC (called by the garbage collector) | |
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322 void process_discovered_references(BoolObjectClosure* is_alive, |
0 | 323 OopClosure* keep_alive, |
324 VoidClosure* complete_gc, | |
325 AbstractRefProcTaskExecutor* task_executor); | |
326 | |
327 public: | |
328 // Enqueue references at end of GC (called by the garbage collector) | |
329 bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL); | |
330 | |
342
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331 // If a discovery is in process that is being superceded, abandon it: all |
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332 // the discovered lists will be empty, and all the objects on them will |
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333 // have NULL discovered fields. Must be called only at a safepoint. |
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334 void abandon_partial_discovery(); |
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335 |
0 | 336 // debugging |
337 void verify_no_references_recorded() PRODUCT_RETURN; | |
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338 void verify_referent(oop obj) PRODUCT_RETURN; |
0 | 339 |
340 // clear the discovered lists (unlinking each entry). | |
341 void clear_discovered_references() PRODUCT_RETURN; | |
342 }; | |
343 | |
344 // A utility class to disable reference discovery in | |
345 // the scope which contains it, for given ReferenceProcessor. | |
346 class NoRefDiscovery: StackObj { | |
347 private: | |
348 ReferenceProcessor* _rp; | |
349 bool _was_discovering_refs; | |
350 public: | |
351 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) { | |
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352 _was_discovering_refs = _rp->discovery_enabled(); |
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353 if (_was_discovering_refs) { |
0 | 354 _rp->disable_discovery(); |
355 } | |
356 } | |
357 | |
358 ~NoRefDiscovery() { | |
359 if (_was_discovering_refs) { | |
360 _rp->enable_discovery(); | |
361 } | |
362 } | |
363 }; | |
364 | |
365 | |
366 // A utility class to temporarily mutate the span of the | |
367 // given ReferenceProcessor in the scope that contains it. | |
368 class ReferenceProcessorSpanMutator: StackObj { | |
369 private: | |
370 ReferenceProcessor* _rp; | |
371 MemRegion _saved_span; | |
372 | |
373 public: | |
374 ReferenceProcessorSpanMutator(ReferenceProcessor* rp, | |
375 MemRegion span): | |
376 _rp(rp) { | |
377 _saved_span = _rp->span(); | |
378 _rp->set_span(span); | |
379 } | |
380 | |
381 ~ReferenceProcessorSpanMutator() { | |
382 _rp->set_span(_saved_span); | |
383 } | |
384 }; | |
385 | |
386 // A utility class to temporarily change the MT'ness of | |
387 // reference discovery for the given ReferenceProcessor | |
388 // in the scope that contains it. | |
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389 class ReferenceProcessorMTDiscoveryMutator: StackObj { |
0 | 390 private: |
391 ReferenceProcessor* _rp; | |
392 bool _saved_mt; | |
393 | |
394 public: | |
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395 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp, |
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396 bool mt): |
0 | 397 _rp(rp) { |
398 _saved_mt = _rp->discovery_is_mt(); | |
399 _rp->set_mt_discovery(mt); | |
400 } | |
401 | |
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402 ~ReferenceProcessorMTDiscoveryMutator() { |
0 | 403 _rp->set_mt_discovery(_saved_mt); |
404 } | |
405 }; | |
406 | |
407 | |
408 // A utility class to temporarily change the disposition | |
409 // of the "is_alive_non_header" closure field of the | |
410 // given ReferenceProcessor in the scope that contains it. | |
411 class ReferenceProcessorIsAliveMutator: StackObj { | |
412 private: | |
413 ReferenceProcessor* _rp; | |
414 BoolObjectClosure* _saved_cl; | |
415 | |
416 public: | |
417 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp, | |
418 BoolObjectClosure* cl): | |
419 _rp(rp) { | |
420 _saved_cl = _rp->is_alive_non_header(); | |
421 _rp->set_is_alive_non_header(cl); | |
422 } | |
423 | |
424 ~ReferenceProcessorIsAliveMutator() { | |
425 _rp->set_is_alive_non_header(_saved_cl); | |
426 } | |
427 }; | |
428 | |
429 // A utility class to temporarily change the disposition | |
430 // of the "discovery_is_atomic" field of the | |
431 // given ReferenceProcessor in the scope that contains it. | |
432 class ReferenceProcessorAtomicMutator: StackObj { | |
433 private: | |
434 ReferenceProcessor* _rp; | |
435 bool _saved_atomic_discovery; | |
436 | |
437 public: | |
438 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp, | |
439 bool atomic): | |
440 _rp(rp) { | |
441 _saved_atomic_discovery = _rp->discovery_is_atomic(); | |
442 _rp->set_atomic_discovery(atomic); | |
443 } | |
444 | |
445 ~ReferenceProcessorAtomicMutator() { | |
446 _rp->set_atomic_discovery(_saved_atomic_discovery); | |
447 } | |
448 }; | |
449 | |
450 | |
451 // A utility class to temporarily change the MT processing | |
452 // disposition of the given ReferenceProcessor instance | |
453 // in the scope that contains it. | |
454 class ReferenceProcessorMTProcMutator: StackObj { | |
455 private: | |
456 ReferenceProcessor* _rp; | |
457 bool _saved_mt; | |
458 | |
459 public: | |
460 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp, | |
461 bool mt): | |
462 _rp(rp) { | |
463 _saved_mt = _rp->processing_is_mt(); | |
464 _rp->set_mt_processing(mt); | |
465 } | |
466 | |
467 ~ReferenceProcessorMTProcMutator() { | |
468 _rp->set_mt_processing(_saved_mt); | |
469 } | |
470 }; | |
471 | |
472 | |
473 // This class is an interface used to implement task execution for the | |
474 // reference processing. | |
475 class AbstractRefProcTaskExecutor { | |
476 public: | |
477 | |
478 // Abstract tasks to execute. | |
479 class ProcessTask; | |
480 class EnqueueTask; | |
481 | |
482 // Executes a task using worker threads. | |
483 virtual void execute(ProcessTask& task) = 0; | |
484 virtual void execute(EnqueueTask& task) = 0; | |
485 | |
486 // Switch to single threaded mode. | |
487 virtual void set_single_threaded_mode() { }; | |
488 }; | |
489 | |
490 // Abstract reference processing task to execute. | |
491 class AbstractRefProcTaskExecutor::ProcessTask { | |
492 protected: | |
493 ProcessTask(ReferenceProcessor& ref_processor, | |
494 DiscoveredList refs_lists[], | |
495 bool marks_oops_alive) | |
496 : _ref_processor(ref_processor), | |
497 _refs_lists(refs_lists), | |
498 _marks_oops_alive(marks_oops_alive) | |
499 { } | |
500 | |
501 public: | |
502 virtual void work(unsigned int work_id, BoolObjectClosure& is_alive, | |
503 OopClosure& keep_alive, | |
504 VoidClosure& complete_gc) = 0; | |
505 | |
506 // Returns true if a task marks some oops as alive. | |
507 bool marks_oops_alive() const | |
508 { return _marks_oops_alive; } | |
509 | |
510 protected: | |
511 ReferenceProcessor& _ref_processor; | |
512 DiscoveredList* _refs_lists; | |
513 const bool _marks_oops_alive; | |
514 }; | |
515 | |
516 // Abstract reference processing task to execute. | |
517 class AbstractRefProcTaskExecutor::EnqueueTask { | |
518 protected: | |
519 EnqueueTask(ReferenceProcessor& ref_processor, | |
520 DiscoveredList refs_lists[], | |
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521 HeapWord* pending_list_addr, |
0 | 522 int n_queues) |
523 : _ref_processor(ref_processor), | |
524 _refs_lists(refs_lists), | |
525 _pending_list_addr(pending_list_addr), | |
526 _n_queues(n_queues) | |
527 { } | |
528 | |
529 public: | |
530 virtual void work(unsigned int work_id) = 0; | |
531 | |
532 protected: | |
533 ReferenceProcessor& _ref_processor; | |
534 DiscoveredList* _refs_lists; | |
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535 HeapWord* _pending_list_addr; |
0 | 536 int _n_queues; |
537 }; | |
1972 | 538 |
539 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP |