Mercurial > hg > truffle
annotate src/share/vm/memory/referenceProcessor.cpp @ 3980:8229bd737950
7075646: G1: fix inconsistencies in the monitoring data
Summary: Fixed a few inconsistencies in the monitoring data, in particular when reported from jstat.
Reviewed-by: jmasa, brutisso, johnc
author | tonyp |
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date | Fri, 23 Sep 2011 16:07:49 -0400 |
parents | 4dfb2df418f2 |
children | d1bdeef3e3e2 |
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 #include "precompiled.hpp" |
26 #include "classfile/javaClasses.hpp" | |
27 #include "classfile/systemDictionary.hpp" | |
28 #include "gc_interface/collectedHeap.hpp" | |
29 #include "gc_interface/collectedHeap.inline.hpp" | |
30 #include "memory/referencePolicy.hpp" | |
31 #include "memory/referenceProcessor.hpp" | |
32 #include "oops/oop.inline.hpp" | |
33 #include "runtime/java.hpp" | |
34 #include "runtime/jniHandles.hpp" | |
0 | 35 |
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36 ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = NULL; |
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37 ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = NULL; |
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38 bool ReferenceProcessor::_pending_list_uses_discovered_field = false; |
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39 |
0 | 40 void referenceProcessor_init() { |
41 ReferenceProcessor::init_statics(); | |
42 } | |
43 | |
44 void ReferenceProcessor::init_statics() { | |
45 // Initialize the master soft ref clock. | |
46 java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); | |
47 | |
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48 _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
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49 _default_soft_ref_policy = new COMPILER2_PRESENT(LRUMaxHeapPolicy()) |
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50 NOT_COMPILER2(LRUCurrentHeapPolicy()); |
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51 if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { |
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52 vm_exit_during_initialization("Could not allocate reference policy object"); |
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53 } |
0 | 54 guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
55 RefDiscoveryPolicy == ReferentBasedDiscovery, | |
56 "Unrecongnized RefDiscoveryPolicy"); | |
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57 _pending_list_uses_discovered_field = JDK_Version::current().pending_list_uses_discovered_field(); |
0 | 58 } |
59 | |
60 ReferenceProcessor::ReferenceProcessor(MemRegion span, | |
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61 bool mt_processing, |
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62 int mt_processing_degree, |
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63 bool mt_discovery, |
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64 int mt_discovery_degree, |
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65 bool atomic_discovery, |
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66 BoolObjectClosure* is_alive_non_header, |
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67 bool discovered_list_needs_barrier) : |
0 | 68 _discovering_refs(false), |
69 _enqueuing_is_done(false), | |
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70 _is_alive_non_header(is_alive_non_header), |
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71 _discovered_list_needs_barrier(discovered_list_needs_barrier), |
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72 _bs(NULL), |
0 | 73 _processing_is_mt(mt_processing), |
74 _next_id(0) | |
75 { | |
76 _span = span; | |
77 _discovery_is_atomic = atomic_discovery; | |
78 _discovery_is_mt = mt_discovery; | |
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79 _num_q = MAX2(1, mt_processing_degree); |
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80 _max_num_q = MAX2(_num_q, mt_discovery_degree); |
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81 _discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, |
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82 _max_num_q * number_of_subclasses_of_ref()); |
0 | 83 if (_discoveredSoftRefs == NULL) { |
84 vm_exit_during_initialization("Could not allocated RefProc Array"); | |
85 } | |
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86 _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_q]; |
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87 _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_q]; |
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88 _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q]; |
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89 // Initialized all entries to NULL |
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90 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
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91 _discoveredSoftRefs[i].set_head(NULL); |
0 | 92 _discoveredSoftRefs[i].set_length(0); |
93 } | |
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94 // If we do barriers, cache a copy of the barrier set. |
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95 if (discovered_list_needs_barrier) { |
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96 _bs = Universe::heap()->barrier_set(); |
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97 } |
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98 setup_policy(false /* default soft ref policy */); |
0 | 99 } |
100 | |
101 #ifndef PRODUCT | |
102 void ReferenceProcessor::verify_no_references_recorded() { | |
103 guarantee(!_discovering_refs, "Discovering refs?"); | |
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104 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
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105 guarantee(_discoveredSoftRefs[i].is_empty(), |
0 | 106 "Found non-empty discovered list"); |
107 } | |
108 } | |
109 #endif | |
110 | |
111 void ReferenceProcessor::weak_oops_do(OopClosure* f) { | |
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112 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
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113 if (UseCompressedOops) { |
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114 f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head()); |
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115 } else { |
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116 f->do_oop((oop*)_discoveredSoftRefs[i].adr_head()); |
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117 } |
0 | 118 } |
119 } | |
120 | |
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121 void ReferenceProcessor::update_soft_ref_master_clock() { |
0 | 122 // Update (advance) the soft ref master clock field. This must be done |
123 // after processing the soft ref list. | |
124 jlong now = os::javaTimeMillis(); | |
125 jlong clock = java_lang_ref_SoftReference::clock(); | |
126 NOT_PRODUCT( | |
127 if (now < clock) { | |
128 warning("time warp: %d to %d", clock, now); | |
129 } | |
130 ) | |
131 // In product mode, protect ourselves from system time being adjusted | |
132 // externally and going backward; see note in the implementation of | |
133 // GenCollectedHeap::time_since_last_gc() for the right way to fix | |
134 // this uniformly throughout the VM; see bug-id 4741166. XXX | |
135 if (now > clock) { | |
136 java_lang_ref_SoftReference::set_clock(now); | |
137 } | |
138 // Else leave clock stalled at its old value until time progresses | |
139 // past clock value. | |
140 } | |
141 | |
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142 void ReferenceProcessor::process_discovered_references( |
0 | 143 BoolObjectClosure* is_alive, |
144 OopClosure* keep_alive, | |
145 VoidClosure* complete_gc, | |
146 AbstractRefProcTaskExecutor* task_executor) { | |
147 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
148 | |
149 assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); | |
150 // Stop treating discovered references specially. | |
151 disable_discovery(); | |
152 | |
153 bool trace_time = PrintGCDetails && PrintReferenceGC; | |
154 // Soft references | |
155 { | |
156 TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); | |
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157 process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, |
0 | 158 is_alive, keep_alive, complete_gc, task_executor); |
159 } | |
160 | |
161 update_soft_ref_master_clock(); | |
162 | |
163 // Weak references | |
164 { | |
165 TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); | |
166 process_discovered_reflist(_discoveredWeakRefs, NULL, true, | |
167 is_alive, keep_alive, complete_gc, task_executor); | |
168 } | |
169 | |
170 // Final references | |
171 { | |
172 TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); | |
173 process_discovered_reflist(_discoveredFinalRefs, NULL, false, | |
174 is_alive, keep_alive, complete_gc, task_executor); | |
175 } | |
176 | |
177 // Phantom references | |
178 { | |
179 TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); | |
180 process_discovered_reflist(_discoveredPhantomRefs, NULL, false, | |
181 is_alive, keep_alive, complete_gc, task_executor); | |
182 } | |
183 | |
184 // Weak global JNI references. It would make more sense (semantically) to | |
185 // traverse these simultaneously with the regular weak references above, but | |
186 // that is not how the JDK1.2 specification is. See #4126360. Native code can | |
187 // thus use JNI weak references to circumvent the phantom references and | |
188 // resurrect a "post-mortem" object. | |
189 { | |
190 TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); | |
191 if (task_executor != NULL) { | |
192 task_executor->set_single_threaded_mode(); | |
193 } | |
194 process_phaseJNI(is_alive, keep_alive, complete_gc); | |
195 } | |
196 } | |
197 | |
198 #ifndef PRODUCT | |
199 // Calculate the number of jni handles. | |
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200 uint ReferenceProcessor::count_jni_refs() { |
0 | 201 class AlwaysAliveClosure: public BoolObjectClosure { |
202 public: | |
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203 virtual bool do_object_b(oop obj) { return true; } |
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204 virtual void do_object(oop obj) { assert(false, "Don't call"); } |
0 | 205 }; |
206 | |
207 class CountHandleClosure: public OopClosure { | |
208 private: | |
209 int _count; | |
210 public: | |
211 CountHandleClosure(): _count(0) {} | |
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212 void do_oop(oop* unused) { _count++; } |
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213 void do_oop(narrowOop* unused) { ShouldNotReachHere(); } |
0 | 214 int count() { return _count; } |
215 }; | |
216 CountHandleClosure global_handle_count; | |
217 AlwaysAliveClosure always_alive; | |
218 JNIHandles::weak_oops_do(&always_alive, &global_handle_count); | |
219 return global_handle_count.count(); | |
220 } | |
221 #endif | |
222 | |
223 void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, | |
224 OopClosure* keep_alive, | |
225 VoidClosure* complete_gc) { | |
226 #ifndef PRODUCT | |
227 if (PrintGCDetails && PrintReferenceGC) { | |
228 unsigned int count = count_jni_refs(); | |
229 gclog_or_tty->print(", %u refs", count); | |
230 } | |
231 #endif | |
232 JNIHandles::weak_oops_do(is_alive, keep_alive); | |
233 complete_gc->do_void(); | |
234 } | |
235 | |
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236 |
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237 template <class T> |
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238 bool enqueue_discovered_ref_helper(ReferenceProcessor* ref, |
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239 AbstractRefProcTaskExecutor* task_executor) { |
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240 |
0 | 241 // Remember old value of pending references list |
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242 T* pending_list_addr = (T*)java_lang_ref_Reference::pending_list_addr(); |
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243 T old_pending_list_value = *pending_list_addr; |
0 | 244 |
245 // Enqueue references that are not made active again, and | |
246 // clear the decks for the next collection (cycle). | |
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247 ref->enqueue_discovered_reflists((HeapWord*)pending_list_addr, task_executor); |
0 | 248 // Do the oop-check on pending_list_addr missed in |
249 // enqueue_discovered_reflist. We should probably | |
250 // do a raw oop_check so that future such idempotent | |
251 // oop_stores relying on the oop-check side-effect | |
252 // may be elided automatically and safely without | |
253 // affecting correctness. | |
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254 oop_store(pending_list_addr, oopDesc::load_decode_heap_oop(pending_list_addr)); |
0 | 255 |
256 // Stop treating discovered references specially. | |
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257 ref->disable_discovery(); |
0 | 258 |
259 // Return true if new pending references were added | |
260 return old_pending_list_value != *pending_list_addr; | |
261 } | |
262 | |
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263 bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
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264 NOT_PRODUCT(verify_ok_to_handle_reflists()); |
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265 if (UseCompressedOops) { |
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266 return enqueue_discovered_ref_helper<narrowOop>(this, task_executor); |
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267 } else { |
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268 return enqueue_discovered_ref_helper<oop>(this, task_executor); |
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269 } |
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270 } |
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271 |
0 | 272 void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
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273 HeapWord* pending_list_addr) { |
0 | 274 // Given a list of refs linked through the "discovered" field |
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275 // (java.lang.ref.Reference.discovered), self-loop their "next" field |
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276 // thus distinguishing them from active References, then |
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277 // prepend them to the pending list. |
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278 // BKWRD COMPATIBILITY NOTE: For older JDKs (prior to the fix for 4956777), |
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279 // the "next" field is used to chain the pending list, not the discovered |
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280 // field. |
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281 |
0 | 282 if (TraceReferenceGC && PrintGCDetails) { |
283 gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " | |
284 INTPTR_FORMAT, (address)refs_list.head()); | |
285 } | |
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286 |
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287 oop obj = NULL; |
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288 oop next_d = refs_list.head(); |
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289 if (pending_list_uses_discovered_field()) { // New behaviour |
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290 // Walk down the list, self-looping the next field |
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291 // so that the References are not considered active. |
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292 while (obj != next_d) { |
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293 obj = next_d; |
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294 assert(obj->is_instanceRef(), "should be reference object"); |
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295 next_d = java_lang_ref_Reference::discovered(obj); |
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296 if (TraceReferenceGC && PrintGCDetails) { |
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297 gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next_d " INTPTR_FORMAT, |
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298 obj, next_d); |
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299 } |
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300 assert(java_lang_ref_Reference::next(obj) == NULL, |
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301 "Reference not active; should not be discovered"); |
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302 // Self-loop next, so as to make Ref not active. |
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303 java_lang_ref_Reference::set_next(obj, obj); |
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304 if (next_d == obj) { // obj is last |
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305 // Swap refs_list into pendling_list_addr and |
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306 // set obj's discovered to what we read from pending_list_addr. |
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307 oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
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308 // Need oop_check on pending_list_addr above; |
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309 // see special oop-check code at the end of |
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310 // enqueue_discovered_reflists() further below. |
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311 java_lang_ref_Reference::set_discovered(obj, old); // old may be NULL |
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312 } |
0 | 313 } |
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314 } else { // Old behaviour |
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315 // Walk down the list, copying the discovered field into |
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316 // the next field and clearing the discovered field. |
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317 while (obj != next_d) { |
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318 obj = next_d; |
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319 assert(obj->is_instanceRef(), "should be reference object"); |
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320 next_d = java_lang_ref_Reference::discovered(obj); |
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321 if (TraceReferenceGC && PrintGCDetails) { |
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322 gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next_d " INTPTR_FORMAT, |
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323 obj, next_d); |
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324 } |
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325 assert(java_lang_ref_Reference::next(obj) == NULL, |
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326 "The reference should not be enqueued"); |
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327 if (next_d == obj) { // obj is last |
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328 // Swap refs_list into pendling_list_addr and |
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329 // set obj's next to what we read from pending_list_addr. |
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330 oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
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331 // Need oop_check on pending_list_addr above; |
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332 // see special oop-check code at the end of |
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333 // enqueue_discovered_reflists() further below. |
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334 if (old == NULL) { |
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335 // obj should be made to point to itself, since |
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336 // pending list was empty. |
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337 java_lang_ref_Reference::set_next(obj, obj); |
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338 } else { |
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339 java_lang_ref_Reference::set_next(obj, old); |
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340 } |
0 | 341 } else { |
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342 java_lang_ref_Reference::set_next(obj, next_d); |
0 | 343 } |
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344 java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
0 | 345 } |
346 } | |
347 } | |
348 | |
349 // Parallel enqueue task | |
350 class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { | |
351 public: | |
352 RefProcEnqueueTask(ReferenceProcessor& ref_processor, | |
353 DiscoveredList discovered_refs[], | |
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354 HeapWord* pending_list_addr, |
0 | 355 int n_queues) |
356 : EnqueueTask(ref_processor, discovered_refs, | |
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357 pending_list_addr, n_queues) |
0 | 358 { } |
359 | |
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360 virtual void work(unsigned int work_id) { |
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361 assert(work_id < (unsigned int)_ref_processor.max_num_q(), "Index out-of-bounds"); |
0 | 362 // Simplest first cut: static partitioning. |
363 int index = work_id; | |
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364 // The increment on "index" must correspond to the maximum number of queues |
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365 // (n_queues) with which that ReferenceProcessor was created. That |
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366 // is because of the "clever" way the discovered references lists were |
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367 // allocated and are indexed into. |
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368 assert(_n_queues == (int) _ref_processor.max_num_q(), "Different number not expected"); |
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369 for (int j = 0; |
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370 j < ReferenceProcessor::number_of_subclasses_of_ref(); |
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371 j++, index += _n_queues) { |
0 | 372 _ref_processor.enqueue_discovered_reflist( |
373 _refs_lists[index], _pending_list_addr); | |
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374 _refs_lists[index].set_head(NULL); |
0 | 375 _refs_lists[index].set_length(0); |
376 } | |
377 } | |
378 }; | |
379 | |
380 // Enqueue references that are not made active again | |
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381 void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr, |
0 | 382 AbstractRefProcTaskExecutor* task_executor) { |
383 if (_processing_is_mt && task_executor != NULL) { | |
384 // Parallel code | |
385 RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, | |
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386 pending_list_addr, _max_num_q); |
0 | 387 task_executor->execute(tsk); |
388 } else { | |
389 // Serial code: call the parent class's implementation | |
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390 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
0 | 391 enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
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392 _discoveredSoftRefs[i].set_head(NULL); |
0 | 393 _discoveredSoftRefs[i].set_length(0); |
394 } | |
395 } | |
396 } | |
397 | |
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398 void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
0 | 399 _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
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400 oop discovered = java_lang_ref_Reference::discovered(_ref); |
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401 assert(_discovered_addr && discovered->is_oop_or_null(), |
0 | 402 "discovered field is bad"); |
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403 _next = discovered; |
0 | 404 _referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
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405 _referent = java_lang_ref_Reference::referent(_ref); |
0 | 406 assert(Universe::heap()->is_in_reserved_or_null(_referent), |
407 "Wrong oop found in java.lang.Reference object"); | |
408 assert(allow_null_referent ? | |
409 _referent->is_oop_or_null() | |
410 : _referent->is_oop(), | |
411 "bad referent"); | |
412 } | |
413 | |
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414 void DiscoveredListIterator::remove() { |
0 | 415 assert(_ref->is_oop(), "Dropping a bad reference"); |
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416 oop_store_raw(_discovered_addr, NULL); |
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417 |
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418 // First _prev_next ref actually points into DiscoveredList (gross). |
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419 oop new_next; |
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420 if (_next == _ref) { |
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421 // At the end of the list, we should make _prev point to itself. |
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422 // If _ref is the first ref, then _prev_next will be in the DiscoveredList, |
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423 // and _prev will be NULL. |
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424 new_next = _prev; |
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425 } else { |
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426 new_next = _next; |
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427 } |
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428 |
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429 if (UseCompressedOops) { |
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430 // Remove Reference object from list. |
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431 oopDesc::encode_store_heap_oop((narrowOop*)_prev_next, new_next); |
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432 } else { |
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433 // Remove Reference object from list. |
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434 oopDesc::store_heap_oop((oop*)_prev_next, new_next); |
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435 } |
0 | 436 NOT_PRODUCT(_removed++); |
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437 _refs_list.dec_length(1); |
0 | 438 } |
439 | |
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440 // Make the Reference object active again. |
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441 void DiscoveredListIterator::make_active() { |
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442 // For G1 we don't want to use set_next - it |
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443 // will dirty the card for the next field of |
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444 // the reference object and will fail |
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445 // CT verification. |
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446 if (UseG1GC) { |
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447 BarrierSet* bs = oopDesc::bs(); |
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448 HeapWord* next_addr = java_lang_ref_Reference::next_addr(_ref); |
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449 |
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450 if (UseCompressedOops) { |
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451 bs->write_ref_field_pre((narrowOop*)next_addr, NULL); |
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452 } else { |
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453 bs->write_ref_field_pre((oop*)next_addr, NULL); |
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454 } |
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455 java_lang_ref_Reference::set_next_raw(_ref, NULL); |
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456 } else { |
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457 java_lang_ref_Reference::set_next(_ref, NULL); |
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458 } |
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459 } |
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460 |
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461 void DiscoveredListIterator::clear_referent() { |
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462 oop_store_raw(_referent_addr, NULL); |
0 | 463 } |
464 | |
465 // NOTE: process_phase*() are largely similar, and at a high level | |
466 // merely iterate over the extant list applying a predicate to | |
467 // each of its elements and possibly removing that element from the | |
468 // list and applying some further closures to that element. | |
469 // We should consider the possibility of replacing these | |
470 // process_phase*() methods by abstracting them into | |
471 // a single general iterator invocation that receives appropriate | |
472 // closures that accomplish this work. | |
473 | |
474 // (SoftReferences only) Traverse the list and remove any SoftReferences whose | |
475 // referents are not alive, but that should be kept alive for policy reasons. | |
476 // Keep alive the transitive closure of all such referents. | |
477 void | |
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478 ReferenceProcessor::process_phase1(DiscoveredList& refs_list, |
0 | 479 ReferencePolicy* policy, |
480 BoolObjectClosure* is_alive, | |
481 OopClosure* keep_alive, | |
482 VoidClosure* complete_gc) { | |
483 assert(policy != NULL, "Must have a non-NULL policy"); | |
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484 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
0 | 485 // Decide which softly reachable refs should be kept alive. |
486 while (iter.has_next()) { | |
487 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); | |
488 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); | |
489 if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { | |
490 if (TraceReferenceGC) { | |
491 gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", | |
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492 iter.obj(), iter.obj()->blueprint()->internal_name()); |
0 | 493 } |
452
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494 // Remove Reference object from list |
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495 iter.remove(); |
0 | 496 // Make the Reference object active again |
497 iter.make_active(); | |
498 // keep the referent around | |
499 iter.make_referent_alive(); | |
452
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500 iter.move_to_next(); |
0 | 501 } else { |
502 iter.next(); | |
503 } | |
504 } | |
505 // Close the reachable set | |
506 complete_gc->do_void(); | |
507 NOT_PRODUCT( | |
508 if (PrintGCDetails && TraceReferenceGC) { | |
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509 gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d " |
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510 "discovered Refs by policy, from list " INTPTR_FORMAT, |
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511 iter.removed(), iter.processed(), (address)refs_list.head()); |
0 | 512 } |
513 ) | |
514 } | |
515 | |
516 // Traverse the list and remove any Refs that are not active, or | |
517 // whose referents are either alive or NULL. | |
518 void | |
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519 ReferenceProcessor::pp2_work(DiscoveredList& refs_list, |
0 | 520 BoolObjectClosure* is_alive, |
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521 OopClosure* keep_alive) { |
0 | 522 assert(discovery_is_atomic(), "Error"); |
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523 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
0 | 524 while (iter.has_next()) { |
525 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
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526 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) |
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527 assert(next == NULL, "Should not discover inactive Reference"); |
0 | 528 if (iter.is_referent_alive()) { |
529 if (TraceReferenceGC) { | |
530 gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", | |
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531 iter.obj(), iter.obj()->blueprint()->internal_name()); |
0 | 532 } |
533 // The referent is reachable after all. | |
452
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534 // Remove Reference object from list. |
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535 iter.remove(); |
0 | 536 // Update the referent pointer as necessary: Note that this |
537 // should not entail any recursive marking because the | |
538 // referent must already have been traversed. | |
539 iter.make_referent_alive(); | |
452
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540 iter.move_to_next(); |
0 | 541 } else { |
542 iter.next(); | |
543 } | |
544 } | |
545 NOT_PRODUCT( | |
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546 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) { |
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547 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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548 "Refs in discovered list " INTPTR_FORMAT, |
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549 iter.removed(), iter.processed(), (address)refs_list.head()); |
0 | 550 } |
551 ) | |
552 } | |
553 | |
554 void | |
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555 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, |
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556 BoolObjectClosure* is_alive, |
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557 OopClosure* keep_alive, |
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558 VoidClosure* complete_gc) { |
0 | 559 assert(!discovery_is_atomic(), "Error"); |
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560 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
0 | 561 while (iter.has_next()) { |
562 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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563 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
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564 oop next = java_lang_ref_Reference::next(iter.obj()); |
0 | 565 if ((iter.referent() == NULL || iter.is_referent_alive() || |
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566 next != NULL)) { |
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567 assert(next->is_oop_or_null(), "bad next field"); |
0 | 568 // Remove Reference object from list |
569 iter.remove(); | |
570 // Trace the cohorts | |
571 iter.make_referent_alive(); | |
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572 if (UseCompressedOops) { |
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573 keep_alive->do_oop((narrowOop*)next_addr); |
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574 } else { |
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575 keep_alive->do_oop((oop*)next_addr); |
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576 } |
452
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577 iter.move_to_next(); |
0 | 578 } else { |
579 iter.next(); | |
580 } | |
581 } | |
582 // Now close the newly reachable set | |
583 complete_gc->do_void(); | |
584 NOT_PRODUCT( | |
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585 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) { |
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586 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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587 "Refs in discovered list " INTPTR_FORMAT, |
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588 iter.removed(), iter.processed(), (address)refs_list.head()); |
0 | 589 } |
590 ) | |
591 } | |
592 | |
593 // Traverse the list and process the referents, by either | |
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594 // clearing them or keeping them (and their reachable |
0 | 595 // closure) alive. |
596 void | |
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597 ReferenceProcessor::process_phase3(DiscoveredList& refs_list, |
0 | 598 bool clear_referent, |
599 BoolObjectClosure* is_alive, | |
600 OopClosure* keep_alive, | |
601 VoidClosure* complete_gc) { | |
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602 ResourceMark rm; |
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603 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
0 | 604 while (iter.has_next()) { |
605 iter.update_discovered(); | |
606 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
607 if (clear_referent) { | |
608 // NULL out referent pointer | |
609 iter.clear_referent(); | |
610 } else { | |
611 // keep the referent around | |
612 iter.make_referent_alive(); | |
613 } | |
614 if (TraceReferenceGC) { | |
615 gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", | |
616 clear_referent ? "cleared " : "", | |
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617 iter.obj(), iter.obj()->blueprint()->internal_name()); |
0 | 618 } |
619 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); | |
620 iter.next(); | |
621 } | |
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622 // Remember to update the next pointer of the last ref. |
0 | 623 iter.update_discovered(); |
624 // Close the reachable set | |
625 complete_gc->do_void(); | |
626 } | |
627 | |
628 void | |
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629 ReferenceProcessor::clear_discovered_references(DiscoveredList& refs_list) { |
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630 oop obj = NULL; |
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631 oop next = refs_list.head(); |
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632 while (next != obj) { |
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633 obj = next; |
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634 next = java_lang_ref_Reference::discovered(obj); |
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635 java_lang_ref_Reference::set_discovered_raw(obj, NULL); |
0 | 636 } |
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637 refs_list.set_head(NULL); |
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638 refs_list.set_length(0); |
0 | 639 } |
640 | |
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641 void |
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642 ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& refs_list) { |
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643 clear_discovered_references(refs_list); |
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644 } |
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645 |
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646 void ReferenceProcessor::abandon_partial_discovery() { |
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647 // loop over the lists |
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648 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
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649 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
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650 gclog_or_tty->print_cr("\nAbandoning %s discovered list", list_name(i)); |
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651 } |
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652 abandon_partial_discovered_list(_discoveredSoftRefs[i]); |
0 | 653 } |
654 } | |
655 | |
656 class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
657 public: | |
658 RefProcPhase1Task(ReferenceProcessor& ref_processor, | |
659 DiscoveredList refs_lists[], | |
660 ReferencePolicy* policy, | |
661 bool marks_oops_alive) | |
662 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
663 _policy(policy) | |
664 { } | |
665 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
666 OopClosure& keep_alive, | |
667 VoidClosure& complete_gc) | |
668 { | |
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669 Thread* thr = Thread::current(); |
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670 int refs_list_index = ((WorkerThread*)thr)->id(); |
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671 _ref_processor.process_phase1(_refs_lists[refs_list_index], _policy, |
0 | 672 &is_alive, &keep_alive, &complete_gc); |
673 } | |
674 private: | |
675 ReferencePolicy* _policy; | |
676 }; | |
677 | |
678 class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
679 public: | |
680 RefProcPhase2Task(ReferenceProcessor& ref_processor, | |
681 DiscoveredList refs_lists[], | |
682 bool marks_oops_alive) | |
683 : ProcessTask(ref_processor, refs_lists, marks_oops_alive) | |
684 { } | |
685 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
686 OopClosure& keep_alive, | |
687 VoidClosure& complete_gc) | |
688 { | |
689 _ref_processor.process_phase2(_refs_lists[i], | |
690 &is_alive, &keep_alive, &complete_gc); | |
691 } | |
692 }; | |
693 | |
694 class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
695 public: | |
696 RefProcPhase3Task(ReferenceProcessor& ref_processor, | |
697 DiscoveredList refs_lists[], | |
698 bool clear_referent, | |
699 bool marks_oops_alive) | |
700 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
701 _clear_referent(clear_referent) | |
702 { } | |
703 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
704 OopClosure& keep_alive, | |
705 VoidClosure& complete_gc) | |
706 { | |
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707 // Don't use "refs_list_index" calculated in this way because |
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708 // balance_queues() has moved the Ref's into the first n queues. |
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709 // Thread* thr = Thread::current(); |
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710 // int refs_list_index = ((WorkerThread*)thr)->id(); |
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711 // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent, |
0 | 712 _ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
713 &is_alive, &keep_alive, &complete_gc); | |
714 } | |
715 private: | |
716 bool _clear_referent; | |
717 }; | |
718 | |
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719 void ReferenceProcessor::set_discovered(oop ref, oop value) { |
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720 if (_discovered_list_needs_barrier) { |
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721 java_lang_ref_Reference::set_discovered(ref, value); |
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722 } else { |
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723 java_lang_ref_Reference::set_discovered_raw(ref, value); |
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724 } |
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725 } |
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726 |
0 | 727 // Balances reference queues. |
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728 // Move entries from all queues[0, 1, ..., _max_num_q-1] to |
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729 // queues[0, 1, ..., _num_q-1] because only the first _num_q |
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730 // corresponding to the active workers will be processed. |
0 | 731 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
732 { | |
733 // calculate total length | |
734 size_t total_refs = 0; | |
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735 if (TraceReferenceGC && PrintGCDetails) { |
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736 gclog_or_tty->print_cr("\nBalance ref_lists "); |
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737 } |
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738 |
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739 for (int i = 0; i < _max_num_q; ++i) { |
0 | 740 total_refs += ref_lists[i].length(); |
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741 if (TraceReferenceGC && PrintGCDetails) { |
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742 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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743 } |
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744 } |
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745 if (TraceReferenceGC && PrintGCDetails) { |
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746 gclog_or_tty->print_cr(" = %d", total_refs); |
0 | 747 } |
748 size_t avg_refs = total_refs / _num_q + 1; | |
749 int to_idx = 0; | |
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750 for (int from_idx = 0; from_idx < _max_num_q; from_idx++) { |
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751 bool move_all = false; |
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752 if (from_idx >= _num_q) { |
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753 move_all = ref_lists[from_idx].length() > 0; |
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754 } |
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755 while ((ref_lists[from_idx].length() > avg_refs) || |
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756 move_all) { |
0 | 757 assert(to_idx < _num_q, "Sanity Check!"); |
758 if (ref_lists[to_idx].length() < avg_refs) { | |
759 // move superfluous refs | |
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760 size_t refs_to_move; |
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761 // Move all the Ref's if the from queue will not be processed. |
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762 if (move_all) { |
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763 refs_to_move = MIN2(ref_lists[from_idx].length(), |
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764 avg_refs - ref_lists[to_idx].length()); |
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765 } else { |
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766 refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, |
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767 avg_refs - ref_lists[to_idx].length()); |
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768 } |
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769 |
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770 assert(refs_to_move > 0, "otherwise the code below will fail"); |
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771 |
0 | 772 oop move_head = ref_lists[from_idx].head(); |
773 oop move_tail = move_head; | |
774 oop new_head = move_head; | |
775 // find an element to split the list on | |
776 for (size_t j = 0; j < refs_to_move; ++j) { | |
777 move_tail = new_head; | |
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778 new_head = java_lang_ref_Reference::discovered(new_head); |
0 | 779 } |
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780 |
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781 // Add the chain to the to list. |
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782 if (ref_lists[to_idx].head() == NULL) { |
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783 // to list is empty. Make a loop at the end. |
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784 set_discovered(move_tail, move_tail); |
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785 } else { |
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786 set_discovered(move_tail, ref_lists[to_idx].head()); |
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787 } |
0 | 788 ref_lists[to_idx].set_head(move_head); |
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789 ref_lists[to_idx].inc_length(refs_to_move); |
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790 |
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791 // Remove the chain from the from list. |
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792 if (move_tail == new_head) { |
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793 // We found the end of the from list. |
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794 ref_lists[from_idx].set_head(NULL); |
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795 } else { |
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796 ref_lists[from_idx].set_head(new_head); |
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797 } |
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798 ref_lists[from_idx].dec_length(refs_to_move); |
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799 if (ref_lists[from_idx].length() == 0) { |
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800 break; |
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801 } |
0 | 802 } else { |
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803 to_idx = (to_idx + 1) % _num_q; |
0 | 804 } |
805 } | |
806 } | |
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807 #ifdef ASSERT |
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808 size_t balanced_total_refs = 0; |
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809 for (int i = 0; i < _max_num_q; ++i) { |
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810 balanced_total_refs += ref_lists[i].length(); |
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811 if (TraceReferenceGC && PrintGCDetails) { |
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812 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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813 } |
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814 } |
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815 if (TraceReferenceGC && PrintGCDetails) { |
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816 gclog_or_tty->print_cr(" = %d", balanced_total_refs); |
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817 gclog_or_tty->flush(); |
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818 } |
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819 assert(total_refs == balanced_total_refs, "Balancing was incomplete"); |
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820 #endif |
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821 } |
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822 |
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823 void ReferenceProcessor::balance_all_queues() { |
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824 balance_queues(_discoveredSoftRefs); |
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825 balance_queues(_discoveredWeakRefs); |
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826 balance_queues(_discoveredFinalRefs); |
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827 balance_queues(_discoveredPhantomRefs); |
0 | 828 } |
829 | |
830 void | |
831 ReferenceProcessor::process_discovered_reflist( | |
832 DiscoveredList refs_lists[], | |
833 ReferencePolicy* policy, | |
834 bool clear_referent, | |
835 BoolObjectClosure* is_alive, | |
836 OopClosure* keep_alive, | |
837 VoidClosure* complete_gc, | |
838 AbstractRefProcTaskExecutor* task_executor) | |
839 { | |
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840 bool mt_processing = task_executor != NULL && _processing_is_mt; |
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841 // If discovery used MT and a dynamic number of GC threads, then |
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842 // the queues must be balanced for correctness if fewer than the |
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843 // maximum number of queues were used. The number of queue used |
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844 // during discovery may be different than the number to be used |
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845 // for processing so don't depend of _num_q < _max_num_q as part |
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846 // of the test. |
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847 bool must_balance = _discovery_is_mt; |
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848 |
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849 if ((mt_processing && ParallelRefProcBalancingEnabled) || |
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850 must_balance) { |
0 | 851 balance_queues(refs_lists); |
852 } | |
853 if (PrintReferenceGC && PrintGCDetails) { | |
854 size_t total = 0; | |
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855 for (int i = 0; i < _max_num_q; ++i) { |
0 | 856 total += refs_lists[i].length(); |
857 } | |
858 gclog_or_tty->print(", %u refs", total); | |
859 } | |
860 | |
861 // Phase 1 (soft refs only): | |
862 // . Traverse the list and remove any SoftReferences whose | |
863 // referents are not alive, but that should be kept alive for | |
864 // policy reasons. Keep alive the transitive closure of all | |
865 // such referents. | |
866 if (policy != NULL) { | |
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867 if (mt_processing) { |
0 | 868 RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
869 task_executor->execute(phase1); | |
870 } else { | |
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871 for (int i = 0; i < _max_num_q; i++) { |
0 | 872 process_phase1(refs_lists[i], policy, |
873 is_alive, keep_alive, complete_gc); | |
874 } | |
875 } | |
876 } else { // policy == NULL | |
877 assert(refs_lists != _discoveredSoftRefs, | |
878 "Policy must be specified for soft references."); | |
879 } | |
880 | |
881 // Phase 2: | |
882 // . Traverse the list and remove any refs whose referents are alive. | |
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883 if (mt_processing) { |
0 | 884 RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
885 task_executor->execute(phase2); | |
886 } else { | |
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887 for (int i = 0; i < _max_num_q; i++) { |
0 | 888 process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); |
889 } | |
890 } | |
891 | |
892 // Phase 3: | |
893 // . Traverse the list and process referents as appropriate. | |
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894 if (mt_processing) { |
0 | 895 RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
896 task_executor->execute(phase3); | |
897 } else { | |
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898 for (int i = 0; i < _max_num_q; i++) { |
0 | 899 process_phase3(refs_lists[i], clear_referent, |
900 is_alive, keep_alive, complete_gc); | |
901 } | |
902 } | |
903 } | |
904 | |
905 void ReferenceProcessor::clean_up_discovered_references() { | |
906 // loop over the lists | |
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907 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
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908 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
0 | 909 gclog_or_tty->print_cr( |
910 "\nScrubbing %s discovered list of Null referents", | |
911 list_name(i)); | |
912 } | |
913 clean_up_discovered_reflist(_discoveredSoftRefs[i]); | |
914 } | |
915 } | |
916 | |
917 void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { | |
918 assert(!discovery_is_atomic(), "Else why call this method?"); | |
919 DiscoveredListIterator iter(refs_list, NULL, NULL); | |
920 while (iter.has_next()) { | |
921 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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922 oop next = java_lang_ref_Reference::next(iter.obj()); |
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923 assert(next->is_oop_or_null(), "bad next field"); |
0 | 924 // If referent has been cleared or Reference is not active, |
925 // drop it. | |
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926 if (iter.referent() == NULL || next != NULL) { |
0 | 927 debug_only( |
928 if (PrintGCDetails && TraceReferenceGC) { | |
929 gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " | |
930 INTPTR_FORMAT " with next field: " INTPTR_FORMAT | |
931 " and referent: " INTPTR_FORMAT, | |
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932 iter.obj(), next, iter.referent()); |
0 | 933 } |
934 ) | |
935 // Remove Reference object from list | |
936 iter.remove(); | |
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937 iter.move_to_next(); |
0 | 938 } else { |
939 iter.next(); | |
940 } | |
941 } | |
942 NOT_PRODUCT( | |
943 if (PrintGCDetails && TraceReferenceGC) { | |
944 gclog_or_tty->print( | |
945 " Removed %d Refs with NULL referents out of %d discovered Refs", | |
946 iter.removed(), iter.processed()); | |
947 } | |
948 ) | |
949 } | |
950 | |
951 inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { | |
952 int id = 0; | |
953 // Determine the queue index to use for this object. | |
954 if (_discovery_is_mt) { | |
955 // During a multi-threaded discovery phase, | |
956 // each thread saves to its "own" list. | |
957 Thread* thr = Thread::current(); | |
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958 id = thr->as_Worker_thread()->id(); |
0 | 959 } else { |
960 // single-threaded discovery, we save in round-robin | |
961 // fashion to each of the lists. | |
962 if (_processing_is_mt) { | |
963 id = next_id(); | |
964 } | |
965 } | |
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966 assert(0 <= id && id < _max_num_q, "Id is out-of-bounds (call Freud?)"); |
0 | 967 |
968 // Get the discovered queue to which we will add | |
969 DiscoveredList* list = NULL; | |
970 switch (rt) { | |
971 case REF_OTHER: | |
972 // Unknown reference type, no special treatment | |
973 break; | |
974 case REF_SOFT: | |
975 list = &_discoveredSoftRefs[id]; | |
976 break; | |
977 case REF_WEAK: | |
978 list = &_discoveredWeakRefs[id]; | |
979 break; | |
980 case REF_FINAL: | |
981 list = &_discoveredFinalRefs[id]; | |
982 break; | |
983 case REF_PHANTOM: | |
984 list = &_discoveredPhantomRefs[id]; | |
985 break; | |
986 case REF_NONE: | |
987 // we should not reach here if we are an instanceRefKlass | |
988 default: | |
989 ShouldNotReachHere(); | |
990 } | |
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991 if (TraceReferenceGC && PrintGCDetails) { |
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992 gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT, id, list); |
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993 } |
0 | 994 return list; |
995 } | |
996 | |
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997 inline void |
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998 ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, |
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999 oop obj, |
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1000 HeapWord* discovered_addr) { |
0 | 1001 assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
1002 // First we must make sure this object is only enqueued once. CAS in a non null | |
1003 // discovered_addr. | |
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1004 oop current_head = refs_list.head(); |
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1005 // The last ref must have its discovered field pointing to itself. |
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1006 oop next_discovered = (current_head != NULL) ? current_head : obj; |
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1007 |
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1008 // Note: In the case of G1, this specific pre-barrier is strictly |
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1009 // not necessary because the only case we are interested in |
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1010 // here is when *discovered_addr is NULL (see the CAS further below), |
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1011 // so this will expand to nothing. As a result, we have manually |
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1012 // elided this out for G1, but left in the test for some future |
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1013 // collector that might have need for a pre-barrier here, e.g.:- |
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1014 // _bs->write_ref_field_pre((oop* or narrowOop*)discovered_addr, next_discovered); |
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1015 assert(!_discovered_list_needs_barrier || UseG1GC, |
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1016 "Need to check non-G1 collector: " |
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1017 "may need a pre-write-barrier for CAS from NULL below"); |
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1018 oop retest = oopDesc::atomic_compare_exchange_oop(next_discovered, discovered_addr, |
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1019 NULL); |
0 | 1020 if (retest == NULL) { |
1021 // This thread just won the right to enqueue the object. | |
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1022 // We have separate lists for enqueueing, so no synchronization |
0 | 1023 // is necessary. |
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1024 refs_list.set_head(obj); |
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1025 refs_list.inc_length(1); |
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1026 if (_discovered_list_needs_barrier) { |
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1027 _bs->write_ref_field((void*)discovered_addr, next_discovered); |
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1028 } |
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1029 |
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1030 if (TraceReferenceGC) { |
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1031 gclog_or_tty->print_cr("Discovered reference (mt) (" INTPTR_FORMAT ": %s)", |
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1032 obj, obj->blueprint()->internal_name()); |
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1033 } |
0 | 1034 } else { |
1035 // If retest was non NULL, another thread beat us to it: | |
1036 // The reference has already been discovered... | |
1037 if (TraceReferenceGC) { | |
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1038 gclog_or_tty->print_cr("Already discovered reference (" INTPTR_FORMAT ": %s)", |
0 | 1039 obj, obj->blueprint()->internal_name()); |
1040 } | |
1041 } | |
1042 } | |
1043 | |
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1044 #ifndef PRODUCT |
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1045 // Non-atomic (i.e. concurrent) discovery might allow us |
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1046 // to observe j.l.References with NULL referents, being those |
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1047 // cleared concurrently by mutators during (or after) discovery. |
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1048 void ReferenceProcessor::verify_referent(oop obj) { |
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1049 bool da = discovery_is_atomic(); |
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1050 oop referent = java_lang_ref_Reference::referent(obj); |
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1051 assert(da ? referent->is_oop() : referent->is_oop_or_null(), |
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1052 err_msg("Bad referent " INTPTR_FORMAT " found in Reference " |
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1053 INTPTR_FORMAT " during %satomic discovery ", |
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1054 (intptr_t)referent, (intptr_t)obj, da ? "" : "non-")); |
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1055 } |
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1056 #endif |
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1057 |
0 | 1058 // We mention two of several possible choices here: |
1059 // #0: if the reference object is not in the "originating generation" | |
1060 // (or part of the heap being collected, indicated by our "span" | |
1061 // we don't treat it specially (i.e. we scan it as we would | |
1062 // a normal oop, treating its references as strong references). | |
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1063 // This means that references can't be discovered unless their |
0 | 1064 // referent is also in the same span. This is the simplest, |
1065 // most "local" and most conservative approach, albeit one | |
1066 // that may cause weak references to be enqueued least promptly. | |
1067 // We call this choice the "ReferenceBasedDiscovery" policy. | |
1068 // #1: the reference object may be in any generation (span), but if | |
1069 // the referent is in the generation (span) being currently collected | |
1070 // then we can discover the reference object, provided | |
1071 // the object has not already been discovered by | |
1072 // a different concurrently running collector (as may be the | |
1073 // case, for instance, if the reference object is in CMS and | |
1074 // the referent in DefNewGeneration), and provided the processing | |
1075 // of this reference object by the current collector will | |
1076 // appear atomic to every other collector in the system. | |
1077 // (Thus, for instance, a concurrent collector may not | |
1078 // discover references in other generations even if the | |
1079 // referent is in its own generation). This policy may, | |
1080 // in certain cases, enqueue references somewhat sooner than | |
1081 // might Policy #0 above, but at marginally increased cost | |
1082 // and complexity in processing these references. | |
1083 // We call this choice the "RefeferentBasedDiscovery" policy. | |
1084 bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { | |
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1085 // Make sure we are discovering refs (rather than processing discovered refs). |
0 | 1086 if (!_discovering_refs || !RegisterReferences) { |
1087 return false; | |
1088 } | |
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1089 // We only discover active references. |
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1090 oop next = java_lang_ref_Reference::next(obj); |
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1091 if (next != NULL) { // Ref is no longer active |
0 | 1092 return false; |
1093 } | |
1094 | |
1095 HeapWord* obj_addr = (HeapWord*)obj; | |
1096 if (RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
1097 !_span.contains(obj_addr)) { | |
1098 // Reference is not in the originating generation; | |
1099 // don't treat it specially (i.e. we want to scan it as a normal | |
1100 // object with strong references). | |
1101 return false; | |
1102 } | |
1103 | |
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1104 // We only discover references whose referents are not (yet) |
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1105 // known to be strongly reachable. |
0 | 1106 if (is_alive_non_header() != NULL) { |
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1107 verify_referent(obj); |
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1108 if (is_alive_non_header()->do_object_b(java_lang_ref_Reference::referent(obj))) { |
0 | 1109 return false; // referent is reachable |
1110 } | |
1111 } | |
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1112 if (rt == REF_SOFT) { |
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1113 // For soft refs we can decide now if these are not |
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1114 // current candidates for clearing, in which case we |
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1115 // can mark through them now, rather than delaying that |
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1116 // to the reference-processing phase. Since all current |
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1117 // time-stamp policies advance the soft-ref clock only |
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1118 // at a major collection cycle, this is always currently |
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1119 // accurate. |
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1120 if (!_current_soft_ref_policy->should_clear_reference(obj)) { |
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1121 return false; |
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1122 } |
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1123 } |
0 | 1124 |
3979
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1125 ResourceMark rm; // Needed for tracing. |
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1126 |
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1127 HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
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1128 const oop discovered = java_lang_ref_Reference::discovered(obj); |
113
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1129 assert(discovered->is_oop_or_null(), "bad discovered field"); |
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1130 if (discovered != NULL) { |
0 | 1131 // The reference has already been discovered... |
1132 if (TraceReferenceGC) { | |
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1133 gclog_or_tty->print_cr("Already discovered reference (" INTPTR_FORMAT ": %s)", |
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1134 obj, obj->blueprint()->internal_name()); |
0 | 1135 } |
1136 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
1137 // assumes that an object is not processed twice; | |
1138 // if it's been already discovered it must be on another | |
1139 // generation's discovered list; so we won't discover it. | |
1140 return false; | |
1141 } else { | |
1142 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, | |
1143 "Unrecognized policy"); | |
1144 // Check assumption that an object is not potentially | |
1145 // discovered twice except by concurrent collectors that potentially | |
1146 // trace the same Reference object twice. | |
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1147 assert(UseConcMarkSweepGC || UseG1GC, |
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1148 "Only possible with a concurrent marking collector"); |
0 | 1149 return true; |
1150 } | |
1151 } | |
1152 | |
1153 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
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1154 verify_referent(obj); |
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1155 // Discover if and only if EITHER: |
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1156 // .. reference is in our span, OR |
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1157 // .. we are an atomic collector and referent is in our span |
0 | 1158 if (_span.contains(obj_addr) || |
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1159 (discovery_is_atomic() && |
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1160 _span.contains(java_lang_ref_Reference::referent(obj)))) { |
0 | 1161 // should_enqueue = true; |
1162 } else { | |
1163 return false; | |
1164 } | |
1165 } else { | |
1166 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
1167 _span.contains(obj_addr), "code inconsistency"); | |
1168 } | |
1169 | |
1170 // Get the right type of discovered queue head. | |
1171 DiscoveredList* list = get_discovered_list(rt); | |
1172 if (list == NULL) { | |
1173 return false; // nothing special needs to be done | |
1174 } | |
1175 | |
1176 if (_discovery_is_mt) { | |
1177 add_to_discovered_list_mt(*list, obj, discovered_addr); | |
1178 } else { | |
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1179 // If "_discovered_list_needs_barrier", we do write barriers when |
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1180 // updating the discovered reference list. Otherwise, we do a raw store |
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1181 // here: the field will be visited later when processing the discovered |
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1182 // references. |
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1183 oop current_head = list->head(); |
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1184 // The last ref must have its discovered field pointing to itself. |
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1185 oop next_discovered = (current_head != NULL) ? current_head : obj; |
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1186 |
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1187 // As in the case further above, since we are over-writing a NULL |
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1188 // pre-value, we can safely elide the pre-barrier here for the case of G1. |
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1189 // e.g.:- _bs->write_ref_field_pre((oop* or narrowOop*)discovered_addr, next_discovered); |
342
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1190 assert(discovered == NULL, "control point invariant"); |
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1191 assert(!_discovered_list_needs_barrier || UseG1GC, |
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1192 "For non-G1 collector, may need a pre-write-barrier for CAS from NULL below"); |
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1193 oop_store_raw(discovered_addr, next_discovered); |
342
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1194 if (_discovered_list_needs_barrier) { |
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1195 _bs->write_ref_field((void*)discovered_addr, next_discovered); |
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1196 } |
0 | 1197 list->set_head(obj); |
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1198 list->inc_length(1); |
0 | 1199 |
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1200 if (TraceReferenceGC) { |
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1201 gclog_or_tty->print_cr("Discovered reference (" INTPTR_FORMAT ": %s)", |
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1202 obj, obj->blueprint()->internal_name()); |
0 | 1203 } |
1204 } | |
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1205 assert(obj->is_oop(), "Discovered a bad reference"); |
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1206 verify_referent(obj); |
0 | 1207 return true; |
1208 } | |
1209 | |
1210 // Preclean the discovered references by removing those | |
1211 // whose referents are alive, and by marking from those that | |
1212 // are not active. These lists can be handled here | |
1213 // in any order and, indeed, concurrently. | |
1214 void ReferenceProcessor::preclean_discovered_references( | |
1215 BoolObjectClosure* is_alive, | |
1216 OopClosure* keep_alive, | |
1217 VoidClosure* complete_gc, | |
1190
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1218 YieldClosure* yield, |
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1219 bool should_unload_classes) { |
0 | 1220 |
1221 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
1222 | |
935 | 1223 #ifdef ASSERT |
1224 bool must_remember_klasses = ClassUnloading && !UseConcMarkSweepGC || | |
1190
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1225 CMSClassUnloadingEnabled && UseConcMarkSweepGC || |
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1226 ExplicitGCInvokesConcurrentAndUnloadsClasses && |
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1227 UseConcMarkSweepGC && should_unload_classes; |
935 | 1228 RememberKlassesChecker mx(must_remember_klasses); |
1229 #endif | |
0 | 1230 // Soft references |
1231 { | |
1232 TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, | |
1233 false, gclog_or_tty); | |
1833
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1234 for (int i = 0; i < _max_num_q; i++) { |
452
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1235 if (yield->should_return()) { |
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1236 return; |
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|
1237 } |
0 | 1238 preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
1239 keep_alive, complete_gc, yield); | |
1240 } | |
1241 } | |
1242 | |
1243 // Weak references | |
1244 { | |
1245 TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, | |
1246 false, gclog_or_tty); | |
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1247 for (int i = 0; i < _max_num_q; i++) { |
452
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1248 if (yield->should_return()) { |
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1249 return; |
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|
1250 } |
0 | 1251 preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
1252 keep_alive, complete_gc, yield); | |
1253 } | |
1254 } | |
1255 | |
1256 // Final references | |
1257 { | |
1258 TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, | |
1259 false, gclog_or_tty); | |
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1260 for (int i = 0; i < _max_num_q; i++) { |
452
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|
1261 if (yield->should_return()) { |
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|
1262 return; |
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|
1263 } |
0 | 1264 preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
1265 keep_alive, complete_gc, yield); | |
1266 } | |
1267 } | |
1268 | |
1269 // Phantom references | |
1270 { | |
1271 TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, | |
1272 false, gclog_or_tty); | |
2369
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1273 for (int i = 0; i < _max_num_q; i++) { |
452
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|
1274 if (yield->should_return()) { |
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|
1275 return; |
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|
1276 } |
0 | 1277 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
1278 keep_alive, complete_gc, yield); | |
1279 } | |
1280 } | |
1281 } | |
1282 | |
1283 // Walk the given discovered ref list, and remove all reference objects | |
1284 // whose referents are still alive, whose referents are NULL or which | |
452
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1285 // are not active (have a non-NULL next field). NOTE: When we are |
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1286 // thus precleaning the ref lists (which happens single-threaded today), |
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1287 // we do not disable refs discovery to honour the correct semantics of |
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1288 // java.lang.Reference. As a result, we need to be careful below |
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1289 // that ref removal steps interleave safely with ref discovery steps |
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1290 // (in this thread). |
113
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1291 void |
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1292 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
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1293 BoolObjectClosure* is_alive, |
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1294 OopClosure* keep_alive, |
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1295 VoidClosure* complete_gc, |
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1296 YieldClosure* yield) { |
0 | 1297 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
1298 while (iter.has_next()) { | |
1299 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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1300 oop obj = iter.obj(); |
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1301 oop next = java_lang_ref_Reference::next(obj); |
0 | 1302 if (iter.referent() == NULL || iter.is_referent_alive() || |
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1303 next != NULL) { |
0 | 1304 // The referent has been cleared, or is alive, or the Reference is not |
1305 // active; we need to trace and mark its cohort. | |
1306 if (TraceReferenceGC) { | |
1307 gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", | |
1308 iter.obj(), iter.obj()->blueprint()->internal_name()); | |
1309 } | |
1310 // Remove Reference object from list | |
1311 iter.remove(); | |
1312 // Keep alive its cohort. | |
1313 iter.make_referent_alive(); | |
113
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1314 if (UseCompressedOops) { |
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1315 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); |
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1316 keep_alive->do_oop(next_addr); |
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1317 } else { |
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1318 oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); |
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1319 keep_alive->do_oop(next_addr); |
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1320 } |
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1321 iter.move_to_next(); |
0 | 1322 } else { |
1323 iter.next(); | |
1324 } | |
1325 } | |
1326 // Close the reachable set | |
1327 complete_gc->do_void(); | |
1328 | |
1329 NOT_PRODUCT( | |
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|
1330 if (PrintGCDetails && PrintReferenceGC && (iter.processed() > 0)) { |
1833
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1331 gclog_or_tty->print_cr(" Dropped %d Refs out of %d " |
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1332 "Refs in discovered list " INTPTR_FORMAT, |
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1333 iter.removed(), iter.processed(), (address)refs_list.head()); |
0 | 1334 } |
1335 ) | |
1336 } | |
1337 | |
1338 const char* ReferenceProcessor::list_name(int i) { | |
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|
1339 assert(i >= 0 && i <= _max_num_q * number_of_subclasses_of_ref(), |
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|
1340 "Out of bounds index"); |
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|
1341 |
1833
8b10f48633dc
6984287: Regularize how GC parallel workers are specified.
jmasa
parents:
1552
diff
changeset
|
1342 int j = i / _max_num_q; |
0 | 1343 switch (j) { |
1344 case 0: return "SoftRef"; | |
1345 case 1: return "WeakRef"; | |
1346 case 2: return "FinalRef"; | |
1347 case 3: return "PhantomRef"; | |
1348 } | |
1349 ShouldNotReachHere(); | |
1350 return NULL; | |
1351 } | |
1352 | |
1353 #ifndef PRODUCT | |
1354 void ReferenceProcessor::verify_ok_to_handle_reflists() { | |
1355 // empty for now | |
1356 } | |
1357 #endif | |
1358 | |
1359 #ifndef PRODUCT | |
1360 void ReferenceProcessor::clear_discovered_references() { | |
1361 guarantee(!_discovering_refs, "Discovering refs?"); | |
3979
4dfb2df418f2
6484982: G1: process references during evacuation pauses
johnc
parents:
3917
diff
changeset
|
1362 for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { |
3915
c2bf0120ee5d
7085906: Replace the permgen allocated sentinelRef with a self-looped end
stefank
parents:
2369
diff
changeset
|
1363 clear_discovered_references(_discoveredSoftRefs[i]); |
0 | 1364 } |
1365 } | |
3915
c2bf0120ee5d
7085906: Replace the permgen allocated sentinelRef with a self-looped end
stefank
parents:
2369
diff
changeset
|
1366 |
0 | 1367 #endif // PRODUCT |