1 /* 2 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/symbolTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 #include "gc_interface/collectedHeap.inline.hpp" 30 #include "memory/sharedHeap.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/fprofiler.hpp" 33 #include "runtime/java.hpp" 34 #include "services/management.hpp" 35 #include "utilities/copy.hpp" 36 #include "utilities/workgroup.hpp" 37 38 SharedHeap* SharedHeap::_sh; 39 40 // The set of potentially parallel tasks in strong root scanning. 41 enum SH_process_strong_roots_tasks { 42 SH_PS_Universe_oops_do, 43 SH_PS_JNIHandles_oops_do, 44 SH_PS_ObjectSynchronizer_oops_do, 45 SH_PS_FlatProfiler_oops_do, 46 SH_PS_Management_oops_do, 47 SH_PS_SystemDictionary_oops_do, 48 SH_PS_jvmti_oops_do, 49 SH_PS_StringTable_oops_do, 50 SH_PS_CodeCache_oops_do, 51 // Leave this one last. 52 SH_PS_NumElements 53 }; 54 55 SharedHeap::SharedHeap(CollectorPolicy* policy_) : 56 CollectedHeap(), 57 _collector_policy(policy_), 58 _perm_gen(NULL), _rem_set(NULL), 59 _strong_roots_parity(0), 60 _process_strong_tasks(new SubTasksDone(SH_PS_NumElements)), 61 _n_par_threads(0), 62 _workers(NULL) 63 { 64 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 65 vm_exit_during_initialization("Failed necessary allocation."); 66 } 67 _sh = this; // ch is static, should be set only once. 68 if ((UseParNewGC || 69 (UseConcMarkSweepGC && CMSParallelRemarkEnabled) || 70 UseG1GC) && 71 ParallelGCThreads > 0) { 72 _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads, 73 /* are_GC_task_threads */true, 74 /* are_ConcurrentGC_threads */false); 75 if (_workers == NULL) { 76 vm_exit_during_initialization("Failed necessary allocation."); 77 } else { 78 _workers->initialize_workers(); 79 } 80 } 81 } 82 83 bool SharedHeap::heap_lock_held_for_gc() { 84 Thread* t = Thread::current(); 85 return Heap_lock->owned_by_self() 86 || ( (t->is_GC_task_thread() || t->is_VM_thread()) 87 && _thread_holds_heap_lock_for_gc); 88 } 89 90 void SharedHeap::set_par_threads(int t) { 91 assert(t == 0 || !UseSerialGC, "Cannot have parallel threads"); 92 _n_par_threads = t; 93 _process_strong_tasks->set_n_threads(t); 94 } 95 96 class AssertIsPermClosure: public OopClosure { 97 public: 98 virtual void do_oop(oop* p) { 99 assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm."); 100 } 101 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 102 }; 103 static AssertIsPermClosure assert_is_perm_closure; 104 105 #ifdef ASSERT 106 class AssertNonScavengableClosure: public OopClosure { 107 public: 108 virtual void do_oop(oop* p) { 109 assert(!Universe::heap()->is_in_partial_collection(*p), 110 "Referent should not be scavengable."); } 111 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 112 }; 113 static AssertNonScavengableClosure assert_is_non_scavengable_closure; 114 #endif 115 116 void SharedHeap::change_strong_roots_parity() { 117 // Also set the new collection parity. 118 assert(_strong_roots_parity >= 0 && _strong_roots_parity <= 2, 119 "Not in range."); 120 _strong_roots_parity++; 121 if (_strong_roots_parity == 3) _strong_roots_parity = 1; 122 assert(_strong_roots_parity >= 1 && _strong_roots_parity <= 2, 123 "Not in range."); 124 } 125 126 SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* outer, bool activate) 127 : MarkScope(activate) 128 { 129 if (_active) { 130 outer->change_strong_roots_parity(); 131 } 132 } 133 134 SharedHeap::StrongRootsScope::~StrongRootsScope() { 135 // nothing particular 136 } 137 138 void SharedHeap::process_strong_roots(bool activate_scope, 139 bool collecting_perm_gen, 140 ScanningOption so, 141 OopClosure* roots, 142 CodeBlobClosure* code_roots, 143 OopsInGenClosure* perm_blk) { 144 StrongRootsScope srs(this, activate_scope); 145 // General strong roots. 146 assert(_strong_roots_parity != 0, "must have called prologue code"); 147 if (!_process_strong_tasks->is_task_claimed(SH_PS_Universe_oops_do)) { 148 Universe::oops_do(roots); 149 ReferenceProcessor::oops_do(roots); 150 // Consider perm-gen discovered lists to be strong. 151 perm_gen()->ref_processor()->weak_oops_do(roots); 152 } 153 // Global (strong) JNI handles 154 if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do)) 155 JNIHandles::oops_do(roots); 156 // All threads execute this; the individual threads are task groups. 157 if (ParallelGCThreads > 0) { 158 Threads::possibly_parallel_oops_do(roots, code_roots); 159 } else { 160 Threads::oops_do(roots, code_roots); 161 } 162 if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do)) 163 ObjectSynchronizer::oops_do(roots); 164 if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do)) 165 FlatProfiler::oops_do(roots); 166 if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do)) 167 Management::oops_do(roots); 168 if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do)) 169 JvmtiExport::oops_do(roots); 170 171 if (!_process_strong_tasks->is_task_claimed(SH_PS_SystemDictionary_oops_do)) { 172 if (so & SO_AllClasses) { 173 SystemDictionary::oops_do(roots); 174 } else if (so & SO_SystemClasses) { 175 SystemDictionary::always_strong_oops_do(roots); 176 } 177 } 178 179 if (!_process_strong_tasks->is_task_claimed(SH_PS_StringTable_oops_do)) { 180 if (so & SO_Strings || (!collecting_perm_gen && !JavaObjectsInPerm)) { 181 StringTable::oops_do(roots); 182 } 183 if (JavaObjectsInPerm) { 184 // Verify the string table contents are in the perm gen 185 NOT_PRODUCT(StringTable::oops_do(&assert_is_perm_closure)); 186 } 187 } 188 189 if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) { 190 if (so & SO_CodeCache) { 191 // (Currently, CMSCollector uses this to do intermediate-strength collections.) 192 assert(collecting_perm_gen, "scanning all of code cache"); 193 assert(code_roots != NULL, "must supply closure for code cache"); 194 if (code_roots != NULL) { 195 CodeCache::blobs_do(code_roots); 196 } 197 } else if (so & (SO_SystemClasses|SO_AllClasses)) { 198 if (!collecting_perm_gen) { 199 // If we are collecting from class statics, but we are not going to 200 // visit all of the CodeCache, collect from the non-perm roots if any. 201 // This makes the code cache function temporarily as a source of strong 202 // roots for oops, until the next major collection. 203 // 204 // If collecting_perm_gen is true, we require that this phase will call 205 // CodeCache::do_unloading. This will kill off nmethods with expired 206 // weak references, such as stale invokedynamic targets. 207 CodeCache::scavenge_root_nmethods_do(code_roots); 208 } 209 } 210 // Verify that the code cache contents are not subject to 211 // movement by a scavenging collection. 212 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, /*do_marking=*/ false)); 213 DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable)); 214 } 215 216 if (!collecting_perm_gen) { 217 // All threads perform this; coordination is handled internally. 218 219 rem_set()->younger_refs_iterate(perm_gen(), perm_blk); 220 } 221 _process_strong_tasks->all_tasks_completed(); 222 } 223 224 class AlwaysTrueClosure: public BoolObjectClosure { 225 public: 226 void do_object(oop p) { ShouldNotReachHere(); } 227 bool do_object_b(oop p) { return true; } 228 }; 229 static AlwaysTrueClosure always_true; 230 231 class SkipAdjustingSharedStrings: public OopClosure { 232 OopClosure* _clo; 233 public: 234 SkipAdjustingSharedStrings(OopClosure* clo) : _clo(clo) {} 235 236 virtual void do_oop(oop* p) { 237 oop o = (*p); 238 if (!o->is_shared_readwrite()) { 239 _clo->do_oop(p); 240 } 241 } 242 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 243 }; 244 245 // Unmarked shared Strings in the StringTable (which got there due to 246 // being in the constant pools of as-yet unloaded shared classes) were 247 // not marked and therefore did not have their mark words preserved. 248 // These entries are also deliberately not purged from the string 249 // table during unloading of unmarked strings. If an identity hash 250 // code was computed for any of these objects, it will not have been 251 // cleared to zero during the forwarding process or by the 252 // RecursiveAdjustSharedObjectClosure, and will be confused by the 253 // adjusting process as a forwarding pointer. We need to skip 254 // forwarding StringTable entries which contain unmarked shared 255 // Strings. Actually, since shared strings won't be moving, we can 256 // just skip adjusting any shared entries in the string table. 257 258 void SharedHeap::process_weak_roots(OopClosure* root_closure, 259 CodeBlobClosure* code_roots, 260 OopClosure* non_root_closure) { 261 // Global (weak) JNI handles 262 JNIHandles::weak_oops_do(&always_true, root_closure); 263 264 CodeCache::blobs_do(code_roots); 265 if (UseSharedSpaces && !DumpSharedSpaces) { 266 SkipAdjustingSharedStrings skip_closure(root_closure); 267 StringTable::oops_do(&skip_closure); 268 } else { 269 StringTable::oops_do(root_closure); 270 } 271 } 272 273 void SharedHeap::set_barrier_set(BarrierSet* bs) { 274 _barrier_set = bs; 275 // Cached barrier set for fast access in oops 276 oopDesc::set_bs(bs); 277 } 278 279 void SharedHeap::post_initialize() { 280 ref_processing_init(); 281 } 282 283 void SharedHeap::ref_processing_init() { 284 perm_gen()->ref_processor_init(); 285 } 286 287 // Some utilities. 288 void SharedHeap::print_size_transition(outputStream* out, 289 size_t bytes_before, 290 size_t bytes_after, 291 size_t capacity) { 292 out->print(" %d%s->%d%s(%d%s)", 293 byte_size_in_proper_unit(bytes_before), 294 proper_unit_for_byte_size(bytes_before), 295 byte_size_in_proper_unit(bytes_after), 296 proper_unit_for_byte_size(bytes_after), 297 byte_size_in_proper_unit(capacity), 298 proper_unit_for_byte_size(capacity)); 299 }