Mercurial > hg > truffle
annotate src/share/vm/memory/referenceProcessor.cpp @ 1972:f95d63e2154a
6989984: Use standard include model for Hospot
Summary: Replaced MakeDeps and the includeDB files with more standardized solutions.
Reviewed-by: coleenp, kvn, kamg
| author | stefank |
|---|---|
| date | Tue, 23 Nov 2010 13:22:55 -0800 |
| parents | 8b10f48633dc |
| children | fd1d227ef1b9 |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2001, 2010, 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 oop ReferenceProcessor::_sentinelRef = NULL; |
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39 const int subclasses_of_ref = REF_PHANTOM - REF_OTHER; |
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40 |
| 0 | 41 // List of discovered references. |
| 42 class DiscoveredList { | |
| 43 public: | |
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44 DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { } |
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45 oop head() const { |
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46 return UseCompressedOops ? oopDesc::decode_heap_oop_not_null(_compressed_head) : |
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47 _oop_head; |
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48 } |
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49 HeapWord* adr_head() { |
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50 return UseCompressedOops ? (HeapWord*)&_compressed_head : |
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51 (HeapWord*)&_oop_head; |
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52 } |
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53 void set_head(oop o) { |
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54 if (UseCompressedOops) { |
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55 // Must compress the head ptr. |
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56 _compressed_head = oopDesc::encode_heap_oop_not_null(o); |
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57 } else { |
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58 _oop_head = o; |
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59 } |
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60 } |
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61 bool empty() const { return head() == ReferenceProcessor::sentinel_ref(); } |
| 0 | 62 size_t length() { return _len; } |
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63 void set_length(size_t len) { _len = len; } |
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64 void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); } |
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65 void dec_length(size_t dec) { _len -= dec; } |
| 0 | 66 private: |
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67 // Set value depending on UseCompressedOops. This could be a template class |
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68 // but then we have to fix all the instantiations and declarations that use this class. |
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69 oop _oop_head; |
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70 narrowOop _compressed_head; |
| 0 | 71 size_t _len; |
| 72 }; | |
| 73 | |
| 74 void referenceProcessor_init() { | |
| 75 ReferenceProcessor::init_statics(); | |
| 76 } | |
| 77 | |
| 78 void ReferenceProcessor::init_statics() { | |
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79 assert(_sentinelRef == NULL, "should be initialized precisely once"); |
| 0 | 80 EXCEPTION_MARK; |
| 81 _sentinelRef = instanceKlass::cast( | |
| 1142 | 82 SystemDictionary::Reference_klass())-> |
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83 allocate_permanent_instance(THREAD); |
| 0 | 84 |
| 85 // Initialize the master soft ref clock. | |
| 86 java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); | |
| 87 | |
| 88 if (HAS_PENDING_EXCEPTION) { | |
| 89 Handle ex(THREAD, PENDING_EXCEPTION); | |
| 90 vm_exit_during_initialization(ex); | |
| 91 } | |
| 92 assert(_sentinelRef != NULL && _sentinelRef->is_oop(), | |
| 93 "Just constructed it!"); | |
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94 _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
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95 _default_soft_ref_policy = new COMPILER2_PRESENT(LRUMaxHeapPolicy()) |
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96 NOT_COMPILER2(LRUCurrentHeapPolicy()); |
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97 if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { |
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98 vm_exit_during_initialization("Could not allocate reference policy object"); |
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99 } |
| 0 | 100 guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
| 101 RefDiscoveryPolicy == ReferentBasedDiscovery, | |
| 102 "Unrecongnized RefDiscoveryPolicy"); | |
| 103 } | |
| 104 | |
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105 ReferenceProcessor* |
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106 ReferenceProcessor::create_ref_processor(MemRegion span, |
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107 bool atomic_discovery, |
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108 bool mt_discovery, |
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109 BoolObjectClosure* is_alive_non_header, |
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110 int parallel_gc_threads, |
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111 bool mt_processing, |
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112 bool dl_needs_barrier) { |
| 0 | 113 int mt_degree = 1; |
| 114 if (parallel_gc_threads > 1) { | |
| 115 mt_degree = parallel_gc_threads; | |
| 116 } | |
| 117 ReferenceProcessor* rp = | |
| 118 new ReferenceProcessor(span, atomic_discovery, | |
| 119 mt_discovery, mt_degree, | |
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120 mt_processing && (parallel_gc_threads > 0), |
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121 dl_needs_barrier); |
| 0 | 122 if (rp == NULL) { |
| 123 vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); | |
| 124 } | |
| 125 rp->set_is_alive_non_header(is_alive_non_header); | |
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126 rp->setup_policy(false /* default soft ref policy */); |
| 0 | 127 return rp; |
| 128 } | |
| 129 | |
| 130 ReferenceProcessor::ReferenceProcessor(MemRegion span, | |
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131 bool atomic_discovery, |
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132 bool mt_discovery, |
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133 int mt_degree, |
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134 bool mt_processing, |
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135 bool discovered_list_needs_barrier) : |
| 0 | 136 _discovering_refs(false), |
| 137 _enqueuing_is_done(false), | |
| 138 _is_alive_non_header(NULL), | |
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139 _discovered_list_needs_barrier(discovered_list_needs_barrier), |
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140 _bs(NULL), |
| 0 | 141 _processing_is_mt(mt_processing), |
| 142 _next_id(0) | |
| 143 { | |
| 144 _span = span; | |
| 145 _discovery_is_atomic = atomic_discovery; | |
| 146 _discovery_is_mt = mt_discovery; | |
| 147 _num_q = mt_degree; | |
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148 _max_num_q = mt_degree; |
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149 _discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, _max_num_q * subclasses_of_ref); |
| 0 | 150 if (_discoveredSoftRefs == NULL) { |
| 151 vm_exit_during_initialization("Could not allocated RefProc Array"); | |
| 152 } | |
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153 _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_q]; |
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154 _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_q]; |
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155 _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q]; |
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156 assert(sentinel_ref() != NULL, "_sentinelRef is NULL"); |
| 0 | 157 // Initialized all entries to _sentinelRef |
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158 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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159 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 160 _discoveredSoftRefs[i].set_length(0); |
| 161 } | |
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162 // If we do barreirs, cache a copy of the barrier set. |
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163 if (discovered_list_needs_barrier) { |
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164 _bs = Universe::heap()->barrier_set(); |
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165 } |
| 0 | 166 } |
| 167 | |
| 168 #ifndef PRODUCT | |
| 169 void ReferenceProcessor::verify_no_references_recorded() { | |
| 170 guarantee(!_discovering_refs, "Discovering refs?"); | |
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171 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 172 guarantee(_discoveredSoftRefs[i].empty(), |
| 173 "Found non-empty discovered list"); | |
| 174 } | |
| 175 } | |
| 176 #endif | |
| 177 | |
| 178 void ReferenceProcessor::weak_oops_do(OopClosure* f) { | |
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179 // Should this instead be |
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180 // for (int i = 0; i < subclasses_of_ref; i++_ { |
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181 // for (int j = 0; j < _num_q; j++) { |
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182 // int index = i * _max_num_q + j; |
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183 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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184 if (UseCompressedOops) { |
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185 f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head()); |
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186 } else { |
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187 f->do_oop((oop*)_discoveredSoftRefs[i].adr_head()); |
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188 } |
| 0 | 189 } |
| 190 } | |
| 191 | |
| 192 void ReferenceProcessor::oops_do(OopClosure* f) { | |
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193 f->do_oop(adr_sentinel_ref()); |
| 0 | 194 } |
| 195 | |
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196 void ReferenceProcessor::update_soft_ref_master_clock() { |
| 0 | 197 // Update (advance) the soft ref master clock field. This must be done |
| 198 // after processing the soft ref list. | |
| 199 jlong now = os::javaTimeMillis(); | |
| 200 jlong clock = java_lang_ref_SoftReference::clock(); | |
| 201 NOT_PRODUCT( | |
| 202 if (now < clock) { | |
| 203 warning("time warp: %d to %d", clock, now); | |
| 204 } | |
| 205 ) | |
| 206 // In product mode, protect ourselves from system time being adjusted | |
| 207 // externally and going backward; see note in the implementation of | |
| 208 // GenCollectedHeap::time_since_last_gc() for the right way to fix | |
| 209 // this uniformly throughout the VM; see bug-id 4741166. XXX | |
| 210 if (now > clock) { | |
| 211 java_lang_ref_SoftReference::set_clock(now); | |
| 212 } | |
| 213 // Else leave clock stalled at its old value until time progresses | |
| 214 // past clock value. | |
| 215 } | |
| 216 | |
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217 void ReferenceProcessor::process_discovered_references( |
| 0 | 218 BoolObjectClosure* is_alive, |
| 219 OopClosure* keep_alive, | |
| 220 VoidClosure* complete_gc, | |
| 221 AbstractRefProcTaskExecutor* task_executor) { | |
| 222 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
| 223 | |
| 224 assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); | |
| 225 // Stop treating discovered references specially. | |
| 226 disable_discovery(); | |
| 227 | |
| 228 bool trace_time = PrintGCDetails && PrintReferenceGC; | |
| 229 // Soft references | |
| 230 { | |
| 231 TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); | |
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232 process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, |
| 0 | 233 is_alive, keep_alive, complete_gc, task_executor); |
| 234 } | |
| 235 | |
| 236 update_soft_ref_master_clock(); | |
| 237 | |
| 238 // Weak references | |
| 239 { | |
| 240 TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); | |
| 241 process_discovered_reflist(_discoveredWeakRefs, NULL, true, | |
| 242 is_alive, keep_alive, complete_gc, task_executor); | |
| 243 } | |
| 244 | |
| 245 // Final references | |
| 246 { | |
| 247 TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); | |
| 248 process_discovered_reflist(_discoveredFinalRefs, NULL, false, | |
| 249 is_alive, keep_alive, complete_gc, task_executor); | |
| 250 } | |
| 251 | |
| 252 // Phantom references | |
| 253 { | |
| 254 TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); | |
| 255 process_discovered_reflist(_discoveredPhantomRefs, NULL, false, | |
| 256 is_alive, keep_alive, complete_gc, task_executor); | |
| 257 } | |
| 258 | |
| 259 // Weak global JNI references. It would make more sense (semantically) to | |
| 260 // traverse these simultaneously with the regular weak references above, but | |
| 261 // that is not how the JDK1.2 specification is. See #4126360. Native code can | |
| 262 // thus use JNI weak references to circumvent the phantom references and | |
| 263 // resurrect a "post-mortem" object. | |
| 264 { | |
| 265 TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); | |
| 266 if (task_executor != NULL) { | |
| 267 task_executor->set_single_threaded_mode(); | |
| 268 } | |
| 269 process_phaseJNI(is_alive, keep_alive, complete_gc); | |
| 270 } | |
| 271 } | |
| 272 | |
| 273 #ifndef PRODUCT | |
| 274 // Calculate the number of jni handles. | |
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275 uint ReferenceProcessor::count_jni_refs() { |
| 0 | 276 class AlwaysAliveClosure: public BoolObjectClosure { |
| 277 public: | |
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278 virtual bool do_object_b(oop obj) { return true; } |
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279 virtual void do_object(oop obj) { assert(false, "Don't call"); } |
| 0 | 280 }; |
| 281 | |
| 282 class CountHandleClosure: public OopClosure { | |
| 283 private: | |
| 284 int _count; | |
| 285 public: | |
| 286 CountHandleClosure(): _count(0) {} | |
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287 void do_oop(oop* unused) { _count++; } |
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288 void do_oop(narrowOop* unused) { ShouldNotReachHere(); } |
| 0 | 289 int count() { return _count; } |
| 290 }; | |
| 291 CountHandleClosure global_handle_count; | |
| 292 AlwaysAliveClosure always_alive; | |
| 293 JNIHandles::weak_oops_do(&always_alive, &global_handle_count); | |
| 294 return global_handle_count.count(); | |
| 295 } | |
| 296 #endif | |
| 297 | |
| 298 void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, | |
| 299 OopClosure* keep_alive, | |
| 300 VoidClosure* complete_gc) { | |
| 301 #ifndef PRODUCT | |
| 302 if (PrintGCDetails && PrintReferenceGC) { | |
| 303 unsigned int count = count_jni_refs(); | |
| 304 gclog_or_tty->print(", %u refs", count); | |
| 305 } | |
| 306 #endif | |
| 307 JNIHandles::weak_oops_do(is_alive, keep_alive); | |
| 308 // Finally remember to keep sentinel around | |
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309 keep_alive->do_oop(adr_sentinel_ref()); |
| 0 | 310 complete_gc->do_void(); |
| 311 } | |
| 312 | |
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313 |
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314 template <class T> |
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315 bool enqueue_discovered_ref_helper(ReferenceProcessor* ref, |
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316 AbstractRefProcTaskExecutor* task_executor) { |
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317 |
| 0 | 318 // Remember old value of pending references list |
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319 T* pending_list_addr = (T*)java_lang_ref_Reference::pending_list_addr(); |
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320 T old_pending_list_value = *pending_list_addr; |
| 0 | 321 |
| 322 // Enqueue references that are not made active again, and | |
| 323 // clear the decks for the next collection (cycle). | |
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324 ref->enqueue_discovered_reflists((HeapWord*)pending_list_addr, task_executor); |
| 0 | 325 // Do the oop-check on pending_list_addr missed in |
| 326 // enqueue_discovered_reflist. We should probably | |
| 327 // do a raw oop_check so that future such idempotent | |
| 328 // oop_stores relying on the oop-check side-effect | |
| 329 // may be elided automatically and safely without | |
| 330 // affecting correctness. | |
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331 oop_store(pending_list_addr, oopDesc::load_decode_heap_oop(pending_list_addr)); |
| 0 | 332 |
| 333 // Stop treating discovered references specially. | |
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334 ref->disable_discovery(); |
| 0 | 335 |
| 336 // Return true if new pending references were added | |
| 337 return old_pending_list_value != *pending_list_addr; | |
| 338 } | |
| 339 | |
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340 bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
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341 NOT_PRODUCT(verify_ok_to_handle_reflists()); |
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342 if (UseCompressedOops) { |
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343 return enqueue_discovered_ref_helper<narrowOop>(this, task_executor); |
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344 } else { |
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345 return enqueue_discovered_ref_helper<oop>(this, task_executor); |
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346 } |
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347 } |
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348 |
| 0 | 349 void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
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350 HeapWord* pending_list_addr) { |
| 0 | 351 // Given a list of refs linked through the "discovered" field |
| 352 // (java.lang.ref.Reference.discovered) chain them through the | |
| 353 // "next" field (java.lang.ref.Reference.next) and prepend | |
| 354 // to the pending list. | |
| 355 if (TraceReferenceGC && PrintGCDetails) { | |
| 356 gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " | |
| 357 INTPTR_FORMAT, (address)refs_list.head()); | |
| 358 } | |
| 359 oop obj = refs_list.head(); | |
| 360 // Walk down the list, copying the discovered field into | |
| 361 // the next field and clearing it (except for the last | |
| 362 // non-sentinel object which is treated specially to avoid | |
| 363 // confusion with an active reference). | |
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364 while (obj != sentinel_ref()) { |
| 0 | 365 assert(obj->is_instanceRef(), "should be reference object"); |
| 366 oop next = java_lang_ref_Reference::discovered(obj); | |
| 367 if (TraceReferenceGC && PrintGCDetails) { | |
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368 gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next " INTPTR_FORMAT, |
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369 obj, next); |
| 0 | 370 } |
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371 assert(java_lang_ref_Reference::next(obj) == NULL, |
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372 "The reference should not be enqueued"); |
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373 if (next == sentinel_ref()) { // obj is last |
| 0 | 374 // Swap refs_list into pendling_list_addr and |
| 375 // set obj's next to what we read from pending_list_addr. | |
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376 oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
| 0 | 377 // Need oop_check on pending_list_addr above; |
| 378 // see special oop-check code at the end of | |
| 379 // enqueue_discovered_reflists() further below. | |
| 380 if (old == NULL) { | |
| 381 // obj should be made to point to itself, since | |
| 382 // pending list was empty. | |
| 383 java_lang_ref_Reference::set_next(obj, obj); | |
| 384 } else { | |
| 385 java_lang_ref_Reference::set_next(obj, old); | |
| 386 } | |
| 387 } else { | |
| 388 java_lang_ref_Reference::set_next(obj, next); | |
| 389 } | |
| 390 java_lang_ref_Reference::set_discovered(obj, (oop) NULL); | |
| 391 obj = next; | |
| 392 } | |
| 393 } | |
| 394 | |
| 395 // Parallel enqueue task | |
| 396 class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { | |
| 397 public: | |
| 398 RefProcEnqueueTask(ReferenceProcessor& ref_processor, | |
| 399 DiscoveredList discovered_refs[], | |
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400 HeapWord* pending_list_addr, |
| 0 | 401 oop sentinel_ref, |
| 402 int n_queues) | |
| 403 : EnqueueTask(ref_processor, discovered_refs, | |
| 404 pending_list_addr, sentinel_ref, n_queues) | |
| 405 { } | |
| 406 | |
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407 virtual void work(unsigned int work_id) { |
| 0 | 408 assert(work_id < (unsigned int)_ref_processor.num_q(), "Index out-of-bounds"); |
| 409 // Simplest first cut: static partitioning. | |
| 410 int index = work_id; | |
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411 // The increment on "index" must correspond to the maximum number of queues |
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412 // (n_queues) with which that ReferenceProcessor was created. That |
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413 // is because of the "clever" way the discovered references lists were |
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414 // allocated and are indexed into. That number is ParallelGCThreads |
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415 // currently. Assert that. |
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416 assert(_n_queues == (int) ParallelGCThreads, "Different number not expected"); |
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417 for (int j = 0; |
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418 j < subclasses_of_ref; |
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419 j++, index += _n_queues) { |
| 0 | 420 _ref_processor.enqueue_discovered_reflist( |
| 421 _refs_lists[index], _pending_list_addr); | |
| 422 _refs_lists[index].set_head(_sentinel_ref); | |
| 423 _refs_lists[index].set_length(0); | |
| 424 } | |
| 425 } | |
| 426 }; | |
| 427 | |
| 428 // Enqueue references that are not made active again | |
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429 void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr, |
| 0 | 430 AbstractRefProcTaskExecutor* task_executor) { |
| 431 if (_processing_is_mt && task_executor != NULL) { | |
| 432 // Parallel code | |
| 433 RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, | |
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434 pending_list_addr, sentinel_ref(), _max_num_q); |
| 0 | 435 task_executor->execute(tsk); |
| 436 } else { | |
| 437 // Serial code: call the parent class's implementation | |
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438 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 439 enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
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440 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 441 _discoveredSoftRefs[i].set_length(0); |
| 442 } | |
| 443 } | |
| 444 } | |
| 445 | |
| 446 // Iterator for the list of discovered references. | |
| 447 class DiscoveredListIterator { | |
| 448 public: | |
| 449 inline DiscoveredListIterator(DiscoveredList& refs_list, | |
| 450 OopClosure* keep_alive, | |
| 451 BoolObjectClosure* is_alive); | |
| 452 | |
| 453 // End Of List. | |
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454 inline bool has_next() const { return _next != ReferenceProcessor::sentinel_ref(); } |
| 0 | 455 |
| 456 // Get oop to the Reference object. | |
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457 inline oop obj() const { return _ref; } |
| 0 | 458 |
| 459 // Get oop to the referent object. | |
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460 inline oop referent() const { return _referent; } |
| 0 | 461 |
| 462 // Returns true if referent is alive. | |
| 463 inline bool is_referent_alive() const; | |
| 464 | |
| 465 // Loads data for the current reference. | |
| 466 // The "allow_null_referent" argument tells us to allow for the possibility | |
| 467 // of a NULL referent in the discovered Reference object. This typically | |
| 468 // happens in the case of concurrent collectors that may have done the | |
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469 // discovery concurrently, or interleaved, with mutator execution. |
| 0 | 470 inline void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); |
| 471 | |
| 472 // Move to the next discovered reference. | |
| 473 inline void next(); | |
| 474 | |
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475 // Remove the current reference from the list |
| 0 | 476 inline void remove(); |
| 477 | |
| 478 // Make the Reference object active again. | |
| 479 inline void make_active() { java_lang_ref_Reference::set_next(_ref, NULL); } | |
| 480 | |
| 481 // Make the referent alive. | |
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482 inline void make_referent_alive() { |
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483 if (UseCompressedOops) { |
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484 _keep_alive->do_oop((narrowOop*)_referent_addr); |
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485 } else { |
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486 _keep_alive->do_oop((oop*)_referent_addr); |
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487 } |
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488 } |
| 0 | 489 |
| 490 // Update the discovered field. | |
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491 inline void update_discovered() { |
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492 // First _prev_next ref actually points into DiscoveredList (gross). |
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493 if (UseCompressedOops) { |
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494 _keep_alive->do_oop((narrowOop*)_prev_next); |
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495 } else { |
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496 _keep_alive->do_oop((oop*)_prev_next); |
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497 } |
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498 } |
| 0 | 499 |
| 500 // NULL out referent pointer. | |
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501 inline void clear_referent() { oop_store_raw(_referent_addr, NULL); } |
| 0 | 502 |
| 503 // Statistics | |
| 504 NOT_PRODUCT( | |
| 505 inline size_t processed() const { return _processed; } | |
| 506 inline size_t removed() const { return _removed; } | |
| 507 ) | |
| 508 | |
| 509 inline void move_to_next(); | |
| 510 | |
| 511 private: | |
| 512 DiscoveredList& _refs_list; | |
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513 HeapWord* _prev_next; |
| 0 | 514 oop _ref; |
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515 HeapWord* _discovered_addr; |
| 0 | 516 oop _next; |
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517 HeapWord* _referent_addr; |
| 0 | 518 oop _referent; |
| 519 OopClosure* _keep_alive; | |
| 520 BoolObjectClosure* _is_alive; | |
| 521 DEBUG_ONLY( | |
| 522 oop _first_seen; // cyclic linked list check | |
| 523 ) | |
| 524 NOT_PRODUCT( | |
| 525 size_t _processed; | |
| 526 size_t _removed; | |
| 527 ) | |
| 528 }; | |
| 529 | |
| 530 inline DiscoveredListIterator::DiscoveredListIterator(DiscoveredList& refs_list, | |
| 531 OopClosure* keep_alive, | |
| 532 BoolObjectClosure* is_alive) | |
| 533 : _refs_list(refs_list), | |
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534 _prev_next(refs_list.adr_head()), |
| 0 | 535 _ref(refs_list.head()), |
| 536 #ifdef ASSERT | |
| 537 _first_seen(refs_list.head()), | |
| 538 #endif | |
| 539 #ifndef PRODUCT | |
| 540 _processed(0), | |
| 541 _removed(0), | |
| 542 #endif | |
| 543 _next(refs_list.head()), | |
| 544 _keep_alive(keep_alive), | |
| 545 _is_alive(is_alive) | |
| 546 { } | |
| 547 | |
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548 inline bool DiscoveredListIterator::is_referent_alive() const { |
| 0 | 549 return _is_alive->do_object_b(_referent); |
| 550 } | |
| 551 | |
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552 inline void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
| 0 | 553 _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
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554 oop discovered = java_lang_ref_Reference::discovered(_ref); |
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555 assert(_discovered_addr && discovered->is_oop_or_null(), |
| 0 | 556 "discovered field is bad"); |
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557 _next = discovered; |
| 0 | 558 _referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
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559 _referent = java_lang_ref_Reference::referent(_ref); |
| 0 | 560 assert(Universe::heap()->is_in_reserved_or_null(_referent), |
| 561 "Wrong oop found in java.lang.Reference object"); | |
| 562 assert(allow_null_referent ? | |
| 563 _referent->is_oop_or_null() | |
| 564 : _referent->is_oop(), | |
| 565 "bad referent"); | |
| 566 } | |
| 567 | |
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568 inline void DiscoveredListIterator::next() { |
| 0 | 569 _prev_next = _discovered_addr; |
| 570 move_to_next(); | |
| 571 } | |
| 572 | |
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573 inline void DiscoveredListIterator::remove() { |
| 0 | 574 assert(_ref->is_oop(), "Dropping a bad reference"); |
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575 oop_store_raw(_discovered_addr, NULL); |
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576 // First _prev_next ref actually points into DiscoveredList (gross). |
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577 if (UseCompressedOops) { |
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578 // Remove Reference object from list. |
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579 oopDesc::encode_store_heap_oop_not_null((narrowOop*)_prev_next, _next); |
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580 } else { |
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581 // Remove Reference object from list. |
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582 oopDesc::store_heap_oop((oop*)_prev_next, _next); |
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583 } |
| 0 | 584 NOT_PRODUCT(_removed++); |
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585 _refs_list.dec_length(1); |
| 0 | 586 } |
| 587 | |
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588 inline void DiscoveredListIterator::move_to_next() { |
| 0 | 589 _ref = _next; |
| 590 assert(_ref != _first_seen, "cyclic ref_list found"); | |
| 591 NOT_PRODUCT(_processed++); | |
| 592 } | |
| 593 | |
| 594 // NOTE: process_phase*() are largely similar, and at a high level | |
| 595 // merely iterate over the extant list applying a predicate to | |
| 596 // each of its elements and possibly removing that element from the | |
| 597 // list and applying some further closures to that element. | |
| 598 // We should consider the possibility of replacing these | |
| 599 // process_phase*() methods by abstracting them into | |
| 600 // a single general iterator invocation that receives appropriate | |
| 601 // closures that accomplish this work. | |
| 602 | |
| 603 // (SoftReferences only) Traverse the list and remove any SoftReferences whose | |
| 604 // referents are not alive, but that should be kept alive for policy reasons. | |
| 605 // Keep alive the transitive closure of all such referents. | |
| 606 void | |
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607 ReferenceProcessor::process_phase1(DiscoveredList& refs_list, |
| 0 | 608 ReferencePolicy* policy, |
| 609 BoolObjectClosure* is_alive, | |
| 610 OopClosure* keep_alive, | |
| 611 VoidClosure* complete_gc) { | |
| 612 assert(policy != NULL, "Must have a non-NULL policy"); | |
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613 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 614 // Decide which softly reachable refs should be kept alive. |
| 615 while (iter.has_next()) { | |
| 616 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); | |
| 617 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); | |
| 618 if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { | |
| 619 if (TraceReferenceGC) { | |
| 620 gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", | |
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621 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 622 } |
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623 // Remove Reference object from list |
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624 iter.remove(); |
| 0 | 625 // Make the Reference object active again |
| 626 iter.make_active(); | |
| 627 // keep the referent around | |
| 628 iter.make_referent_alive(); | |
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629 iter.move_to_next(); |
| 0 | 630 } else { |
| 631 iter.next(); | |
| 632 } | |
| 633 } | |
| 634 // Close the reachable set | |
| 635 complete_gc->do_void(); | |
| 636 NOT_PRODUCT( | |
| 637 if (PrintGCDetails && TraceReferenceGC) { | |
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638 gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d " |
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639 "discovered Refs by policy list " INTPTR_FORMAT, |
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640 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 641 } |
| 642 ) | |
| 643 } | |
| 644 | |
| 645 // Traverse the list and remove any Refs that are not active, or | |
| 646 // whose referents are either alive or NULL. | |
| 647 void | |
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648 ReferenceProcessor::pp2_work(DiscoveredList& refs_list, |
| 0 | 649 BoolObjectClosure* is_alive, |
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650 OopClosure* keep_alive) { |
| 0 | 651 assert(discovery_is_atomic(), "Error"); |
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652 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 653 while (iter.has_next()) { |
| 654 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
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655 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) |
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656 assert(next == NULL, "Should not discover inactive Reference"); |
| 0 | 657 if (iter.is_referent_alive()) { |
| 658 if (TraceReferenceGC) { | |
| 659 gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", | |
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660 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 661 } |
| 662 // The referent is reachable after all. | |
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663 // Remove Reference object from list. |
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664 iter.remove(); |
| 0 | 665 // Update the referent pointer as necessary: Note that this |
| 666 // should not entail any recursive marking because the | |
| 667 // referent must already have been traversed. | |
| 668 iter.make_referent_alive(); | |
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669 iter.move_to_next(); |
| 0 | 670 } else { |
| 671 iter.next(); | |
| 672 } | |
| 673 } | |
| 674 NOT_PRODUCT( | |
| 675 if (PrintGCDetails && TraceReferenceGC) { | |
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676 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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677 "Refs in discovered list " INTPTR_FORMAT, |
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678 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 679 } |
| 680 ) | |
| 681 } | |
| 682 | |
| 683 void | |
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684 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, |
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685 BoolObjectClosure* is_alive, |
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686 OopClosure* keep_alive, |
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687 VoidClosure* complete_gc) { |
| 0 | 688 assert(!discovery_is_atomic(), "Error"); |
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689 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 690 while (iter.has_next()) { |
| 691 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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692 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
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693 oop next = java_lang_ref_Reference::next(iter.obj()); |
| 0 | 694 if ((iter.referent() == NULL || iter.is_referent_alive() || |
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695 next != NULL)) { |
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696 assert(next->is_oop_or_null(), "bad next field"); |
| 0 | 697 // Remove Reference object from list |
| 698 iter.remove(); | |
| 699 // Trace the cohorts | |
| 700 iter.make_referent_alive(); | |
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701 if (UseCompressedOops) { |
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702 keep_alive->do_oop((narrowOop*)next_addr); |
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703 } else { |
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704 keep_alive->do_oop((oop*)next_addr); |
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705 } |
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706 iter.move_to_next(); |
| 0 | 707 } else { |
| 708 iter.next(); | |
| 709 } | |
| 710 } | |
| 711 // Now close the newly reachable set | |
| 712 complete_gc->do_void(); | |
| 713 NOT_PRODUCT( | |
| 714 if (PrintGCDetails && TraceReferenceGC) { | |
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715 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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716 "Refs in discovered list " INTPTR_FORMAT, |
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717 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 718 } |
| 719 ) | |
| 720 } | |
| 721 | |
| 722 // Traverse the list and process the referents, by either | |
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723 // clearing them or keeping them (and their reachable |
| 0 | 724 // closure) alive. |
| 725 void | |
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726 ReferenceProcessor::process_phase3(DiscoveredList& refs_list, |
| 0 | 727 bool clear_referent, |
| 728 BoolObjectClosure* is_alive, | |
| 729 OopClosure* keep_alive, | |
| 730 VoidClosure* complete_gc) { | |
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731 ResourceMark rm; |
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732 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 733 while (iter.has_next()) { |
| 734 iter.update_discovered(); | |
| 735 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
| 736 if (clear_referent) { | |
| 737 // NULL out referent pointer | |
| 738 iter.clear_referent(); | |
| 739 } else { | |
| 740 // keep the referent around | |
| 741 iter.make_referent_alive(); | |
| 742 } | |
| 743 if (TraceReferenceGC) { | |
| 744 gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", | |
| 745 clear_referent ? "cleared " : "", | |
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746 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 747 } |
| 748 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); | |
| 749 iter.next(); | |
| 750 } | |
| 751 // Remember to keep sentinel pointer around | |
| 752 iter.update_discovered(); | |
| 753 // Close the reachable set | |
| 754 complete_gc->do_void(); | |
| 755 } | |
| 756 | |
| 757 void | |
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758 ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& refs_list) { |
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759 oop obj = refs_list.head(); |
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760 while (obj != sentinel_ref()) { |
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761 oop discovered = java_lang_ref_Reference::discovered(obj); |
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762 java_lang_ref_Reference::set_discovered_raw(obj, NULL); |
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763 obj = discovered; |
| 0 | 764 } |
|
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765 refs_list.set_head(sentinel_ref()); |
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766 refs_list.set_length(0); |
| 0 | 767 } |
| 768 | |
|
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769 void ReferenceProcessor::abandon_partial_discovery() { |
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770 // loop over the lists |
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771 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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772 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
|
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773 gclog_or_tty->print_cr( |
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774 "\nAbandoning %s discovered list", |
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775 list_name(i)); |
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776 } |
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777 abandon_partial_discovered_list(_discoveredSoftRefs[i]); |
| 0 | 778 } |
| 779 } | |
| 780 | |
| 781 class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 782 public: | |
| 783 RefProcPhase1Task(ReferenceProcessor& ref_processor, | |
| 784 DiscoveredList refs_lists[], | |
| 785 ReferencePolicy* policy, | |
| 786 bool marks_oops_alive) | |
| 787 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
| 788 _policy(policy) | |
| 789 { } | |
| 790 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 791 OopClosure& keep_alive, | |
| 792 VoidClosure& complete_gc) | |
| 793 { | |
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794 Thread* thr = Thread::current(); |
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795 int refs_list_index = ((WorkerThread*)thr)->id(); |
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796 _ref_processor.process_phase1(_refs_lists[refs_list_index], _policy, |
| 0 | 797 &is_alive, &keep_alive, &complete_gc); |
| 798 } | |
| 799 private: | |
| 800 ReferencePolicy* _policy; | |
| 801 }; | |
| 802 | |
| 803 class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 804 public: | |
| 805 RefProcPhase2Task(ReferenceProcessor& ref_processor, | |
| 806 DiscoveredList refs_lists[], | |
| 807 bool marks_oops_alive) | |
| 808 : ProcessTask(ref_processor, refs_lists, marks_oops_alive) | |
| 809 { } | |
| 810 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 811 OopClosure& keep_alive, | |
| 812 VoidClosure& complete_gc) | |
| 813 { | |
| 814 _ref_processor.process_phase2(_refs_lists[i], | |
| 815 &is_alive, &keep_alive, &complete_gc); | |
| 816 } | |
| 817 }; | |
| 818 | |
| 819 class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 820 public: | |
| 821 RefProcPhase3Task(ReferenceProcessor& ref_processor, | |
| 822 DiscoveredList refs_lists[], | |
| 823 bool clear_referent, | |
| 824 bool marks_oops_alive) | |
| 825 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
| 826 _clear_referent(clear_referent) | |
| 827 { } | |
| 828 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 829 OopClosure& keep_alive, | |
| 830 VoidClosure& complete_gc) | |
| 831 { | |
|
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832 // Don't use "refs_list_index" calculated in this way because |
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833 // balance_queues() has moved the Ref's into the first n queues. |
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834 // Thread* thr = Thread::current(); |
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835 // int refs_list_index = ((WorkerThread*)thr)->id(); |
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836 // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent, |
| 0 | 837 _ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
| 838 &is_alive, &keep_alive, &complete_gc); | |
| 839 } | |
| 840 private: | |
| 841 bool _clear_referent; | |
| 842 }; | |
| 843 | |
| 844 // Balances reference queues. | |
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845 // Move entries from all queues[0, 1, ..., _max_num_q-1] to |
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846 // queues[0, 1, ..., _num_q-1] because only the first _num_q |
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847 // corresponding to the active workers will be processed. |
| 0 | 848 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
| 849 { | |
| 850 // calculate total length | |
| 851 size_t total_refs = 0; | |
|
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852 if (TraceReferenceGC && PrintGCDetails) { |
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853 gclog_or_tty->print_cr("\nBalance ref_lists "); |
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854 } |
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855 |
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856 for (int i = 0; i < _max_num_q; ++i) { |
| 0 | 857 total_refs += ref_lists[i].length(); |
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858 if (TraceReferenceGC && PrintGCDetails) { |
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859 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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860 } |
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861 } |
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862 if (TraceReferenceGC && PrintGCDetails) { |
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863 gclog_or_tty->print_cr(" = %d", total_refs); |
| 0 | 864 } |
| 865 size_t avg_refs = total_refs / _num_q + 1; | |
| 866 int to_idx = 0; | |
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867 for (int from_idx = 0; from_idx < _max_num_q; from_idx++) { |
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868 bool move_all = false; |
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869 if (from_idx >= _num_q) { |
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870 move_all = ref_lists[from_idx].length() > 0; |
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871 } |
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872 while ((ref_lists[from_idx].length() > avg_refs) || |
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873 move_all) { |
| 0 | 874 assert(to_idx < _num_q, "Sanity Check!"); |
| 875 if (ref_lists[to_idx].length() < avg_refs) { | |
| 876 // move superfluous refs | |
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877 size_t refs_to_move; |
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878 // Move all the Ref's if the from queue will not be processed. |
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879 if (move_all) { |
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880 refs_to_move = MIN2(ref_lists[from_idx].length(), |
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881 avg_refs - ref_lists[to_idx].length()); |
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882 } else { |
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883 refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, |
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884 avg_refs - ref_lists[to_idx].length()); |
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885 } |
| 0 | 886 oop move_head = ref_lists[from_idx].head(); |
| 887 oop move_tail = move_head; | |
| 888 oop new_head = move_head; | |
| 889 // find an element to split the list on | |
| 890 for (size_t j = 0; j < refs_to_move; ++j) { | |
| 891 move_tail = new_head; | |
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892 new_head = java_lang_ref_Reference::discovered(new_head); |
| 0 | 893 } |
| 894 java_lang_ref_Reference::set_discovered(move_tail, ref_lists[to_idx].head()); | |
| 895 ref_lists[to_idx].set_head(move_head); | |
|
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896 ref_lists[to_idx].inc_length(refs_to_move); |
| 0 | 897 ref_lists[from_idx].set_head(new_head); |
|
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898 ref_lists[from_idx].dec_length(refs_to_move); |
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899 if (ref_lists[from_idx].length() == 0) { |
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900 break; |
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901 } |
| 0 | 902 } else { |
|
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903 to_idx = (to_idx + 1) % _num_q; |
| 0 | 904 } |
| 905 } | |
| 906 } | |
|
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907 #ifdef ASSERT |
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908 size_t balanced_total_refs = 0; |
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909 for (int i = 0; i < _max_num_q; ++i) { |
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910 balanced_total_refs += ref_lists[i].length(); |
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911 if (TraceReferenceGC && PrintGCDetails) { |
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912 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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913 } |
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914 } |
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915 if (TraceReferenceGC && PrintGCDetails) { |
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916 gclog_or_tty->print_cr(" = %d", balanced_total_refs); |
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917 gclog_or_tty->flush(); |
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918 } |
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919 assert(total_refs == balanced_total_refs, "Balancing was incomplete"); |
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920 #endif |
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921 } |
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922 |
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923 void ReferenceProcessor::balance_all_queues() { |
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924 balance_queues(_discoveredSoftRefs); |
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925 balance_queues(_discoveredWeakRefs); |
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926 balance_queues(_discoveredFinalRefs); |
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927 balance_queues(_discoveredPhantomRefs); |
| 0 | 928 } |
| 929 | |
| 930 void | |
| 931 ReferenceProcessor::process_discovered_reflist( | |
| 932 DiscoveredList refs_lists[], | |
| 933 ReferencePolicy* policy, | |
| 934 bool clear_referent, | |
| 935 BoolObjectClosure* is_alive, | |
| 936 OopClosure* keep_alive, | |
| 937 VoidClosure* complete_gc, | |
| 938 AbstractRefProcTaskExecutor* task_executor) | |
| 939 { | |
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940 bool mt_processing = task_executor != NULL && _processing_is_mt; |
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941 // If discovery used MT and a dynamic number of GC threads, then |
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942 // the queues must be balanced for correctness if fewer than the |
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943 // maximum number of queues were used. The number of queue used |
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944 // during discovery may be different than the number to be used |
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945 // for processing so don't depend of _num_q < _max_num_q as part |
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946 // of the test. |
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947 bool must_balance = _discovery_is_mt; |
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948 |
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949 if ((mt_processing && ParallelRefProcBalancingEnabled) || |
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950 must_balance) { |
| 0 | 951 balance_queues(refs_lists); |
| 952 } | |
| 953 if (PrintReferenceGC && PrintGCDetails) { | |
| 954 size_t total = 0; | |
| 955 for (int i = 0; i < _num_q; ++i) { | |
| 956 total += refs_lists[i].length(); | |
| 957 } | |
| 958 gclog_or_tty->print(", %u refs", total); | |
| 959 } | |
| 960 | |
| 961 // Phase 1 (soft refs only): | |
| 962 // . Traverse the list and remove any SoftReferences whose | |
| 963 // referents are not alive, but that should be kept alive for | |
| 964 // policy reasons. Keep alive the transitive closure of all | |
| 965 // such referents. | |
| 966 if (policy != NULL) { | |
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967 if (mt_processing) { |
| 0 | 968 RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
| 969 task_executor->execute(phase1); | |
| 970 } else { | |
| 971 for (int i = 0; i < _num_q; i++) { | |
| 972 process_phase1(refs_lists[i], policy, | |
| 973 is_alive, keep_alive, complete_gc); | |
| 974 } | |
| 975 } | |
| 976 } else { // policy == NULL | |
| 977 assert(refs_lists != _discoveredSoftRefs, | |
| 978 "Policy must be specified for soft references."); | |
| 979 } | |
| 980 | |
| 981 // Phase 2: | |
| 982 // . Traverse the list and remove any refs whose referents are alive. | |
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983 if (mt_processing) { |
| 0 | 984 RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
| 985 task_executor->execute(phase2); | |
| 986 } else { | |
| 987 for (int i = 0; i < _num_q; i++) { | |
| 988 process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); | |
| 989 } | |
| 990 } | |
| 991 | |
| 992 // Phase 3: | |
| 993 // . Traverse the list and process referents as appropriate. | |
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994 if (mt_processing) { |
| 0 | 995 RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
| 996 task_executor->execute(phase3); | |
| 997 } else { | |
| 998 for (int i = 0; i < _num_q; i++) { | |
| 999 process_phase3(refs_lists[i], clear_referent, | |
| 1000 is_alive, keep_alive, complete_gc); | |
| 1001 } | |
| 1002 } | |
| 1003 } | |
| 1004 | |
| 1005 void ReferenceProcessor::clean_up_discovered_references() { | |
| 1006 // loop over the lists | |
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1007 // Should this instead be |
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1008 // for (int i = 0; i < subclasses_of_ref; i++_ { |
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1009 // for (int j = 0; j < _num_q; j++) { |
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1010 // int index = i * _max_num_q + j; |
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1011 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 1012 if (TraceReferenceGC && PrintGCDetails && ((i % _num_q) == 0)) { |
| 1013 gclog_or_tty->print_cr( | |
| 1014 "\nScrubbing %s discovered list of Null referents", | |
| 1015 list_name(i)); | |
| 1016 } | |
| 1017 clean_up_discovered_reflist(_discoveredSoftRefs[i]); | |
| 1018 } | |
| 1019 } | |
| 1020 | |
| 1021 void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { | |
| 1022 assert(!discovery_is_atomic(), "Else why call this method?"); | |
| 1023 DiscoveredListIterator iter(refs_list, NULL, NULL); | |
| 1024 while (iter.has_next()) { | |
| 1025 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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1026 oop next = java_lang_ref_Reference::next(iter.obj()); |
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1027 assert(next->is_oop_or_null(), "bad next field"); |
| 0 | 1028 // If referent has been cleared or Reference is not active, |
| 1029 // drop it. | |
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1030 if (iter.referent() == NULL || next != NULL) { |
| 0 | 1031 debug_only( |
| 1032 if (PrintGCDetails && TraceReferenceGC) { | |
| 1033 gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " | |
| 1034 INTPTR_FORMAT " with next field: " INTPTR_FORMAT | |
| 1035 " and referent: " INTPTR_FORMAT, | |
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1036 iter.obj(), next, iter.referent()); |
| 0 | 1037 } |
| 1038 ) | |
| 1039 // Remove Reference object from list | |
| 1040 iter.remove(); | |
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1041 iter.move_to_next(); |
| 0 | 1042 } else { |
| 1043 iter.next(); | |
| 1044 } | |
| 1045 } | |
| 1046 NOT_PRODUCT( | |
| 1047 if (PrintGCDetails && TraceReferenceGC) { | |
| 1048 gclog_or_tty->print( | |
| 1049 " Removed %d Refs with NULL referents out of %d discovered Refs", | |
| 1050 iter.removed(), iter.processed()); | |
| 1051 } | |
| 1052 ) | |
| 1053 } | |
| 1054 | |
| 1055 inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { | |
| 1056 int id = 0; | |
| 1057 // Determine the queue index to use for this object. | |
| 1058 if (_discovery_is_mt) { | |
| 1059 // During a multi-threaded discovery phase, | |
| 1060 // each thread saves to its "own" list. | |
| 1061 Thread* thr = Thread::current(); | |
| 1062 assert(thr->is_GC_task_thread(), | |
| 1063 "Dubious cast from Thread* to WorkerThread*?"); | |
| 1064 id = ((WorkerThread*)thr)->id(); | |
| 1065 } else { | |
| 1066 // single-threaded discovery, we save in round-robin | |
| 1067 // fashion to each of the lists. | |
| 1068 if (_processing_is_mt) { | |
| 1069 id = next_id(); | |
| 1070 } | |
| 1071 } | |
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1072 assert(0 <= id && id < _max_num_q, "Id is out-of-bounds (call Freud?)"); |
| 0 | 1073 |
| 1074 // Get the discovered queue to which we will add | |
| 1075 DiscoveredList* list = NULL; | |
| 1076 switch (rt) { | |
| 1077 case REF_OTHER: | |
| 1078 // Unknown reference type, no special treatment | |
| 1079 break; | |
| 1080 case REF_SOFT: | |
| 1081 list = &_discoveredSoftRefs[id]; | |
| 1082 break; | |
| 1083 case REF_WEAK: | |
| 1084 list = &_discoveredWeakRefs[id]; | |
| 1085 break; | |
| 1086 case REF_FINAL: | |
| 1087 list = &_discoveredFinalRefs[id]; | |
| 1088 break; | |
| 1089 case REF_PHANTOM: | |
| 1090 list = &_discoveredPhantomRefs[id]; | |
| 1091 break; | |
| 1092 case REF_NONE: | |
| 1093 // we should not reach here if we are an instanceRefKlass | |
| 1094 default: | |
| 1095 ShouldNotReachHere(); | |
| 1096 } | |
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1097 if (TraceReferenceGC && PrintGCDetails) { |
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1098 gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT, |
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1099 id, list); |
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1100 } |
| 0 | 1101 return list; |
| 1102 } | |
| 1103 | |
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1104 inline void |
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1105 ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, |
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1106 oop obj, |
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1107 HeapWord* discovered_addr) { |
| 0 | 1108 assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
| 1109 // First we must make sure this object is only enqueued once. CAS in a non null | |
| 1110 // discovered_addr. | |
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1111 oop current_head = refs_list.head(); |
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1112 |
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1113 // Note: In the case of G1, this specific pre-barrier is strictly |
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1114 // not necessary because the only case we are interested in |
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1115 // here is when *discovered_addr is NULL (see the CAS further below), |
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1116 // so this will expand to nothing. As a result, we have manually |
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1117 // elided this out for G1, but left in the test for some future |
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1118 // collector that might have need for a pre-barrier here. |
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1119 if (_discovered_list_needs_barrier && !UseG1GC) { |
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1120 if (UseCompressedOops) { |
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1121 _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
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1122 } else { |
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1123 _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
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1124 } |
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1125 guarantee(false, "Need to check non-G1 collector"); |
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1126 } |
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1127 oop retest = oopDesc::atomic_compare_exchange_oop(current_head, discovered_addr, |
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1128 NULL); |
| 0 | 1129 if (retest == NULL) { |
| 1130 // This thread just won the right to enqueue the object. | |
| 1131 // We have separate lists for enqueueing so no synchronization | |
| 1132 // is necessary. | |
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1133 refs_list.set_head(obj); |
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1134 refs_list.inc_length(1); |
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1135 if (_discovered_list_needs_barrier) { |
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1136 _bs->write_ref_field((void*)discovered_addr, current_head); |
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1137 } |
| 0 | 1138 } else { |
| 1139 // If retest was non NULL, another thread beat us to it: | |
| 1140 // The reference has already been discovered... | |
| 1141 if (TraceReferenceGC) { | |
| 1142 gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", | |
| 1143 obj, obj->blueprint()->internal_name()); | |
| 1144 } | |
| 1145 } | |
| 1146 } | |
| 1147 | |
| 1148 // We mention two of several possible choices here: | |
| 1149 // #0: if the reference object is not in the "originating generation" | |
| 1150 // (or part of the heap being collected, indicated by our "span" | |
| 1151 // we don't treat it specially (i.e. we scan it as we would | |
| 1152 // a normal oop, treating its references as strong references). | |
| 1153 // This means that references can't be enqueued unless their | |
| 1154 // referent is also in the same span. This is the simplest, | |
| 1155 // most "local" and most conservative approach, albeit one | |
| 1156 // that may cause weak references to be enqueued least promptly. | |
| 1157 // We call this choice the "ReferenceBasedDiscovery" policy. | |
| 1158 // #1: the reference object may be in any generation (span), but if | |
| 1159 // the referent is in the generation (span) being currently collected | |
| 1160 // then we can discover the reference object, provided | |
| 1161 // the object has not already been discovered by | |
| 1162 // a different concurrently running collector (as may be the | |
| 1163 // case, for instance, if the reference object is in CMS and | |
| 1164 // the referent in DefNewGeneration), and provided the processing | |
| 1165 // of this reference object by the current collector will | |
| 1166 // appear atomic to every other collector in the system. | |
| 1167 // (Thus, for instance, a concurrent collector may not | |
| 1168 // discover references in other generations even if the | |
| 1169 // referent is in its own generation). This policy may, | |
| 1170 // in certain cases, enqueue references somewhat sooner than | |
| 1171 // might Policy #0 above, but at marginally increased cost | |
| 1172 // and complexity in processing these references. | |
| 1173 // We call this choice the "RefeferentBasedDiscovery" policy. | |
| 1174 bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { | |
| 1175 // We enqueue references only if we are discovering refs | |
| 1176 // (rather than processing discovered refs). | |
| 1177 if (!_discovering_refs || !RegisterReferences) { | |
| 1178 return false; | |
| 1179 } | |
| 1180 // We only enqueue active references. | |
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1181 oop next = java_lang_ref_Reference::next(obj); |
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1182 if (next != NULL) { |
| 0 | 1183 return false; |
| 1184 } | |
| 1185 | |
| 1186 HeapWord* obj_addr = (HeapWord*)obj; | |
| 1187 if (RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
| 1188 !_span.contains(obj_addr)) { | |
| 1189 // Reference is not in the originating generation; | |
| 1190 // don't treat it specially (i.e. we want to scan it as a normal | |
| 1191 // object with strong references). | |
| 1192 return false; | |
| 1193 } | |
| 1194 | |
| 1195 // We only enqueue references whose referents are not (yet) strongly | |
| 1196 // reachable. | |
| 1197 if (is_alive_non_header() != NULL) { | |
| 1198 oop referent = java_lang_ref_Reference::referent(obj); | |
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1199 // In the case of non-concurrent discovery, the last |
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1200 // disjunct below should hold. It may not hold in the |
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1201 // case of concurrent discovery because mutators may |
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1202 // concurrently clear() a Reference. |
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1203 assert(UseConcMarkSweepGC || UseG1GC || referent != NULL, |
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1204 "Refs with null referents already filtered"); |
| 0 | 1205 if (is_alive_non_header()->do_object_b(referent)) { |
| 1206 return false; // referent is reachable | |
| 1207 } | |
| 1208 } | |
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1209 if (rt == REF_SOFT) { |
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1210 // For soft refs we can decide now if these are not |
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1211 // current candidates for clearing, in which case we |
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1212 // can mark through them now, rather than delaying that |
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1213 // to the reference-processing phase. Since all current |
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1214 // time-stamp policies advance the soft-ref clock only |
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1215 // at a major collection cycle, this is always currently |
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1216 // accurate. |
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1217 if (!_current_soft_ref_policy->should_clear_reference(obj)) { |
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1218 return false; |
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1219 } |
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1220 } |
| 0 | 1221 |
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1222 HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
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1223 const oop discovered = java_lang_ref_Reference::discovered(obj); |
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1224 assert(discovered->is_oop_or_null(), "bad discovered field"); |
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1225 if (discovered != NULL) { |
| 0 | 1226 // The reference has already been discovered... |
| 1227 if (TraceReferenceGC) { | |
| 1228 gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", | |
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1229 obj, obj->blueprint()->internal_name()); |
| 0 | 1230 } |
| 1231 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
| 1232 // assumes that an object is not processed twice; | |
| 1233 // if it's been already discovered it must be on another | |
| 1234 // generation's discovered list; so we won't discover it. | |
| 1235 return false; | |
| 1236 } else { | |
| 1237 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, | |
| 1238 "Unrecognized policy"); | |
| 1239 // Check assumption that an object is not potentially | |
| 1240 // discovered twice except by concurrent collectors that potentially | |
| 1241 // trace the same Reference object twice. | |
| 1242 assert(UseConcMarkSweepGC, | |
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1243 "Only possible with an incremental-update concurrent collector"); |
| 0 | 1244 return true; |
| 1245 } | |
| 1246 } | |
| 1247 | |
| 1248 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
| 1249 oop referent = java_lang_ref_Reference::referent(obj); | |
| 1250 assert(referent->is_oop(), "bad referent"); | |
| 1251 // enqueue if and only if either: | |
| 1252 // reference is in our span or | |
| 1253 // we are an atomic collector and referent is in our span | |
| 1254 if (_span.contains(obj_addr) || | |
| 1255 (discovery_is_atomic() && _span.contains(referent))) { | |
| 1256 // should_enqueue = true; | |
| 1257 } else { | |
| 1258 return false; | |
| 1259 } | |
| 1260 } else { | |
| 1261 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
| 1262 _span.contains(obj_addr), "code inconsistency"); | |
| 1263 } | |
| 1264 | |
| 1265 // Get the right type of discovered queue head. | |
| 1266 DiscoveredList* list = get_discovered_list(rt); | |
| 1267 if (list == NULL) { | |
| 1268 return false; // nothing special needs to be done | |
| 1269 } | |
| 1270 | |
| 1271 if (_discovery_is_mt) { | |
| 1272 add_to_discovered_list_mt(*list, obj, discovered_addr); | |
| 1273 } else { | |
|
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1274 // If "_discovered_list_needs_barrier", we do write barriers when |
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1275 // updating the discovered reference list. Otherwise, we do a raw store |
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1276 // here: the field will be visited later when processing the discovered |
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1277 // references. |
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1278 oop current_head = list->head(); |
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1279 // As in the case further above, since we are over-writing a NULL |
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1280 // pre-value, we can safely elide the pre-barrier here for the case of G1. |
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1281 assert(discovered == NULL, "control point invariant"); |
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1282 if (_discovered_list_needs_barrier && !UseG1GC) { // safe to elide for G1 |
|
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1283 if (UseCompressedOops) { |
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1284 _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
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1285 } else { |
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1286 _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
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1287 } |
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1288 guarantee(false, "Need to check non-G1 collector"); |
|
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1289 } |
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1290 oop_store_raw(discovered_addr, current_head); |
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1291 if (_discovered_list_needs_barrier) { |
|
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1292 _bs->write_ref_field((void*)discovered_addr, current_head); |
|
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1293 } |
| 0 | 1294 list->set_head(obj); |
|
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1295 list->inc_length(1); |
| 0 | 1296 } |
| 1297 | |
| 1298 // In the MT discovery case, it is currently possible to see | |
| 1299 // the following message multiple times if several threads | |
| 1300 // discover a reference about the same time. Only one will | |
| 1301 // however have actually added it to the disocvered queue. | |
| 1302 // One could let add_to_discovered_list_mt() return an | |
| 1303 // indication for success in queueing (by 1 thread) or | |
| 1304 // failure (by all other threads), but I decided the extra | |
| 1305 // code was not worth the effort for something that is | |
| 1306 // only used for debugging support. | |
| 1307 if (TraceReferenceGC) { | |
| 1308 oop referent = java_lang_ref_Reference::referent(obj); | |
| 1309 if (PrintGCDetails) { | |
| 1310 gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)", | |
|
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1311 obj, obj->blueprint()->internal_name()); |
| 0 | 1312 } |
| 1313 assert(referent->is_oop(), "Enqueued a bad referent"); | |
| 1314 } | |
| 1315 assert(obj->is_oop(), "Enqueued a bad reference"); | |
| 1316 return true; | |
| 1317 } | |
| 1318 | |
| 1319 // Preclean the discovered references by removing those | |
| 1320 // whose referents are alive, and by marking from those that | |
| 1321 // are not active. These lists can be handled here | |
| 1322 // in any order and, indeed, concurrently. | |
| 1323 void ReferenceProcessor::preclean_discovered_references( | |
| 1324 BoolObjectClosure* is_alive, | |
| 1325 OopClosure* keep_alive, | |
| 1326 VoidClosure* complete_gc, | |
|
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1327 YieldClosure* yield, |
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1328 bool should_unload_classes) { |
| 0 | 1329 |
| 1330 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
| 1331 | |
| 935 | 1332 #ifdef ASSERT |
| 1333 bool must_remember_klasses = ClassUnloading && !UseConcMarkSweepGC || | |
|
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1334 CMSClassUnloadingEnabled && UseConcMarkSweepGC || |
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1335 ExplicitGCInvokesConcurrentAndUnloadsClasses && |
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1336 UseConcMarkSweepGC && should_unload_classes; |
| 935 | 1337 RememberKlassesChecker mx(must_remember_klasses); |
| 1338 #endif | |
| 0 | 1339 // Soft references |
| 1340 { | |
| 1341 TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, | |
| 1342 false, gclog_or_tty); | |
|
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1343 for (int i = 0; i < _max_num_q; i++) { |
|
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1344 if (yield->should_return()) { |
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1345 return; |
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1346 } |
| 0 | 1347 preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
| 1348 keep_alive, complete_gc, yield); | |
| 1349 } | |
| 1350 } | |
| 1351 | |
| 1352 // Weak references | |
| 1353 { | |
| 1354 TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, | |
| 1355 false, gclog_or_tty); | |
| 1356 for (int i = 0; i < _num_q; i++) { | |
|
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1357 if (yield->should_return()) { |
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1358 return; |
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1359 } |
| 0 | 1360 preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
| 1361 keep_alive, complete_gc, yield); | |
| 1362 } | |
| 1363 } | |
| 1364 | |
| 1365 // Final references | |
| 1366 { | |
| 1367 TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, | |
| 1368 false, gclog_or_tty); | |
| 1369 for (int i = 0; i < _num_q; i++) { | |
|
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1370 if (yield->should_return()) { |
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1371 return; |
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1372 } |
| 0 | 1373 preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
| 1374 keep_alive, complete_gc, yield); | |
| 1375 } | |
| 1376 } | |
| 1377 | |
| 1378 // Phantom references | |
| 1379 { | |
| 1380 TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, | |
| 1381 false, gclog_or_tty); | |
| 1382 for (int i = 0; i < _num_q; i++) { | |
|
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1383 if (yield->should_return()) { |
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1384 return; |
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1385 } |
| 0 | 1386 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
| 1387 keep_alive, complete_gc, yield); | |
| 1388 } | |
| 1389 } | |
| 1390 } | |
| 1391 | |
| 1392 // Walk the given discovered ref list, and remove all reference objects | |
| 1393 // whose referents are still alive, whose referents are NULL or which | |
|
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1394 // are not active (have a non-NULL next field). NOTE: When we are |
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1395 // thus precleaning the ref lists (which happens single-threaded today), |
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1396 // we do not disable refs discovery to honour the correct semantics of |
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1397 // java.lang.Reference. As a result, we need to be careful below |
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1398 // that ref removal steps interleave safely with ref discovery steps |
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1399 // (in this thread). |
|
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1400 void |
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1401 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
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1402 BoolObjectClosure* is_alive, |
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1403 OopClosure* keep_alive, |
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1404 VoidClosure* complete_gc, |
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1405 YieldClosure* yield) { |
| 0 | 1406 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 1407 while (iter.has_next()) { | |
| 1408 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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1409 oop obj = iter.obj(); |
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1410 oop next = java_lang_ref_Reference::next(obj); |
| 0 | 1411 if (iter.referent() == NULL || iter.is_referent_alive() || |
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1412 next != NULL) { |
| 0 | 1413 // The referent has been cleared, or is alive, or the Reference is not |
| 1414 // active; we need to trace and mark its cohort. | |
| 1415 if (TraceReferenceGC) { | |
| 1416 gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", | |
| 1417 iter.obj(), iter.obj()->blueprint()->internal_name()); | |
| 1418 } | |
| 1419 // Remove Reference object from list | |
| 1420 iter.remove(); | |
| 1421 // Keep alive its cohort. | |
| 1422 iter.make_referent_alive(); | |
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1423 if (UseCompressedOops) { |
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1424 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); |
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1425 keep_alive->do_oop(next_addr); |
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1426 } else { |
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1427 oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); |
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1428 keep_alive->do_oop(next_addr); |
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1429 } |
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1430 iter.move_to_next(); |
| 0 | 1431 } else { |
| 1432 iter.next(); | |
| 1433 } | |
| 1434 } | |
| 1435 // Close the reachable set | |
| 1436 complete_gc->do_void(); | |
| 1437 | |
| 1438 NOT_PRODUCT( | |
| 1439 if (PrintGCDetails && PrintReferenceGC) { | |
|
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1440 gclog_or_tty->print_cr(" Dropped %d Refs out of %d " |
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1441 "Refs in discovered list " INTPTR_FORMAT, |
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1442 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 1443 } |
| 1444 ) | |
| 1445 } | |
| 1446 | |
| 1447 const char* ReferenceProcessor::list_name(int i) { | |
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1448 assert(i >= 0 && i <= _max_num_q * subclasses_of_ref, "Out of bounds index"); |
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1449 int j = i / _max_num_q; |
| 0 | 1450 switch (j) { |
| 1451 case 0: return "SoftRef"; | |
| 1452 case 1: return "WeakRef"; | |
| 1453 case 2: return "FinalRef"; | |
| 1454 case 3: return "PhantomRef"; | |
| 1455 } | |
| 1456 ShouldNotReachHere(); | |
| 1457 return NULL; | |
| 1458 } | |
| 1459 | |
| 1460 #ifndef PRODUCT | |
| 1461 void ReferenceProcessor::verify_ok_to_handle_reflists() { | |
| 1462 // empty for now | |
| 1463 } | |
| 1464 #endif | |
| 1465 | |
| 1466 void ReferenceProcessor::verify() { | |
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1467 guarantee(sentinel_ref() != NULL && sentinel_ref()->is_oop(), "Lost _sentinelRef"); |
| 0 | 1468 } |
| 1469 | |
| 1470 #ifndef PRODUCT | |
| 1471 void ReferenceProcessor::clear_discovered_references() { | |
| 1472 guarantee(!_discovering_refs, "Discovering refs?"); | |
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1473 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 1474 oop obj = _discoveredSoftRefs[i].head(); |
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1475 while (obj != sentinel_ref()) { |
| 0 | 1476 oop next = java_lang_ref_Reference::discovered(obj); |
| 1477 java_lang_ref_Reference::set_discovered(obj, (oop) NULL); | |
| 1478 obj = next; | |
| 1479 } | |
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1480 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 1481 _discoveredSoftRefs[i].set_length(0); |
| 1482 } | |
| 1483 } | |
| 1484 #endif // PRODUCT |