1 /* 2 * Copyright (c) 2000, 2013, 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_CodeCache_oops_do, 50 // Leave this one last. 51 SH_PS_NumElements 52 }; 53 54 SharedHeap::SharedHeap(CollectorPolicy* policy_) : 55 CollectedHeap(), 56 _collector_policy(policy_), 57 _perm_gen(NULL), _rem_set(NULL), 58 _strong_roots_parity(0), 59 _process_strong_tasks(new SubTasksDone(SH_PS_NumElements)), 60 _workers(NULL) 61 { 62 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 63 vm_exit_during_initialization("Failed necessary allocation."); 64 } 65 _sh = this; // ch is static, should be set only once. 66 if ((UseParNewGC || 67 (UseConcMarkSweepGC && (CMSParallelInitialMarkEnabled || 68 CMSParallelRemarkEnabled)) || 69 UseG1GC) && 70 ParallelGCThreads > 0) { 71 _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads, 72 /* are_GC_task_threads */true, 73 /* are_ConcurrentGC_threads */false); 74 if (_workers == NULL) { 75 vm_exit_during_initialization("Failed necessary allocation."); 76 } else { 77 _workers->initialize_workers(); 78 } 79 } 80 } 81 82 int SharedHeap::n_termination() { 83 return _process_strong_tasks->n_threads(); 84 } 85 86 void SharedHeap::set_n_termination(int t) { 87 _process_strong_tasks->set_n_threads(t); 88 } 89 90 bool SharedHeap::heap_lock_held_for_gc() { 91 Thread* t = Thread::current(); 92 return Heap_lock->owned_by_self() 93 || ( (t->is_GC_task_thread() || t->is_VM_thread()) 94 && _thread_holds_heap_lock_for_gc); 95 } 96 97 void SharedHeap::set_par_threads(uint t) { 98 assert(t == 0 || !UseSerialGC, "Cannot have parallel threads"); 99 _n_par_threads = t; 100 _process_strong_tasks->set_n_threads(t); 101 } 102 103 class AssertIsPermClosure: public OopClosure { 104 public: 105 virtual void do_oop(oop* p) { 106 assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm."); 107 } 108 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 109 }; 110 static AssertIsPermClosure assert_is_perm_closure; 111 112 #ifdef ASSERT 113 class AssertNonScavengableClosure: public OopClosure { 114 public: 115 virtual void do_oop(oop* p) { 116 assert(!Universe::heap()->is_in_partial_collection(*p), 117 "Referent should not be scavengable."); } 118 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 119 }; 120 static AssertNonScavengableClosure assert_is_non_scavengable_closure; 121 #endif 122 123 void SharedHeap::change_strong_roots_parity() { 124 // Also set the new collection parity. 125 assert(_strong_roots_parity >= 0 && _strong_roots_parity <= 2, 126 "Not in range."); 127 _strong_roots_parity++; 128 if (_strong_roots_parity == 3) _strong_roots_parity = 1; 129 assert(_strong_roots_parity >= 1 && _strong_roots_parity <= 2, 130 "Not in range."); 131 } 132 133 SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* outer, bool activate) 134 : MarkScope(activate) 135 { 136 if (_active) { 137 outer->change_strong_roots_parity(); 138 // Zero the claimed high water mark in the StringTable 139 StringTable::clear_parallel_claimed_index(); 140 } 141 } 142 143 SharedHeap::StrongRootsScope::~StrongRootsScope() { 144 // nothing particular 145 } 146 147 void SharedHeap::process_strong_roots(bool activate_scope, 148 bool collecting_perm_gen, 149 ScanningOption so, 150 OopClosure* roots, 151 CodeBlobClosure* code_roots, 152 OopsInGenClosure* perm_blk) { 153 StrongRootsScope srs(this, activate_scope); 154 // General strong roots. 155 assert(_strong_roots_parity != 0, "must have called prologue code"); 156 // _n_termination for _process_strong_tasks should be set up stream 157 // in a method not running in a GC worker. Otherwise the GC worker 158 // could be trying to change the termination condition while the task 159 // is executing in another GC worker. 160 if (!_process_strong_tasks->is_task_claimed(SH_PS_Universe_oops_do)) { 161 Universe::oops_do(roots); 162 // Consider perm-gen discovered lists to be strong. 163 perm_gen()->ref_processor()->weak_oops_do(roots); 164 } 165 // Global (strong) JNI handles 166 if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do)) 167 JNIHandles::oops_do(roots); 168 169 // All threads execute this; the individual threads are task groups. 170 if (CollectedHeap::use_parallel_gc_threads()) { 171 Threads::possibly_parallel_oops_do(roots, code_roots); 172 } else { 173 Threads::oops_do(roots, code_roots); 174 } 175 176 if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do)) 177 ObjectSynchronizer::oops_do(roots); 178 if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do)) 179 FlatProfiler::oops_do(roots); 180 if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do)) 181 Management::oops_do(roots); 182 if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do)) 183 JvmtiExport::oops_do(roots); 184 185 if (!_process_strong_tasks->is_task_claimed(SH_PS_SystemDictionary_oops_do)) { 186 if (so & SO_AllClasses) { 187 SystemDictionary::oops_do(roots); 188 } else if (so & SO_SystemClasses) { 189 SystemDictionary::always_strong_oops_do(roots); 190 } 191 } 192 193 // All threads execute the following. A specific chunk of buckets 194 // from the StringTable are the individual tasks. 195 if (so & SO_Strings || (!collecting_perm_gen && !JavaObjectsInPerm)) { 196 if (CollectedHeap::use_parallel_gc_threads()) { 197 StringTable::possibly_parallel_oops_do(roots); 198 } else { 199 StringTable::oops_do(roots); 200 } 201 } 202 if (JavaObjectsInPerm) { 203 // Verify the string table contents are in the perm gen 204 if (CollectedHeap::use_parallel_gc_threads()) { 205 NOT_PRODUCT(StringTable::possibly_parallel_oops_do(&assert_is_perm_closure)); 206 } else { 207 NOT_PRODUCT(StringTable::oops_do(&assert_is_perm_closure)); 208 } 209 } 210 211 if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) { 212 if (so & SO_CodeCache) { 213 // (Currently, CMSCollector uses this to do intermediate-strength collections.) 214 assert(collecting_perm_gen, "scanning all of code cache"); 215 assert(code_roots != NULL, "must supply closure for code cache"); 216 if (code_roots != NULL) { 217 CodeCache::blobs_do(code_roots); 218 } 219 } else if (so & (SO_SystemClasses|SO_AllClasses)) { 220 if (!collecting_perm_gen) { 221 // If we are collecting from class statics, but we are not going to 222 // visit all of the CodeCache, collect from the non-perm roots if any. 223 // This makes the code cache function temporarily as a source of strong 224 // roots for oops, until the next major collection. 225 // 226 // If collecting_perm_gen is true, we require that this phase will call 227 // CodeCache::do_unloading. This will kill off nmethods with expired 228 // weak references, such as stale invokedynamic targets. 229 CodeCache::scavenge_root_nmethods_do(code_roots); 230 } 231 } 232 // Verify that the code cache contents are not subject to 233 // movement by a scavenging collection. 234 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, /*do_marking=*/ false)); 235 DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable)); 236 } 237 238 if (!collecting_perm_gen) { 239 // All threads perform this; coordination is handled internally. 240 241 rem_set()->younger_refs_iterate(perm_gen(), perm_blk); 242 } 243 _process_strong_tasks->all_tasks_completed(); 244 } 245 246 class AlwaysTrueClosure: public BoolObjectClosure { 247 public: 248 void do_object(oop p) { ShouldNotReachHere(); } 249 bool do_object_b(oop p) { return true; } 250 }; 251 static AlwaysTrueClosure always_true; 252 253 class SkipAdjustingSharedStrings: public OopClosure { 254 OopClosure* _clo; 255 public: 256 SkipAdjustingSharedStrings(OopClosure* clo) : _clo(clo) {} 257 258 virtual void do_oop(oop* p) { 259 oop o = (*p); 260 if (!o->is_shared_readwrite()) { 261 _clo->do_oop(p); 262 } 263 } 264 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); } 265 }; 266 267 // Unmarked shared Strings in the StringTable (which got there due to 268 // being in the constant pools of as-yet unloaded shared classes) were 269 // not marked and therefore did not have their mark words preserved. 270 // These entries are also deliberately not purged from the string 271 // table during unloading of unmarked strings. If an identity hash 272 // code was computed for any of these objects, it will not have been 273 // cleared to zero during the forwarding process or by the 274 // RecursiveAdjustSharedObjectClosure, and will be confused by the 275 // adjusting process as a forwarding pointer. We need to skip 276 // forwarding StringTable entries which contain unmarked shared 277 // Strings. Actually, since shared strings won't be moving, we can 278 // just skip adjusting any shared entries in the string table. 279 280 void SharedHeap::process_weak_roots(OopClosure* root_closure, 281 CodeBlobClosure* code_roots, 282 OopClosure* non_root_closure) { 283 // Global (weak) JNI handles 284 JNIHandles::weak_oops_do(&always_true, root_closure); 285 286 CodeCache::blobs_do(code_roots); 287 if (UseSharedSpaces && !DumpSharedSpaces) { 288 SkipAdjustingSharedStrings skip_closure(root_closure); 289 StringTable::oops_do(&skip_closure); 290 } else { 291 StringTable::oops_do(root_closure); 292 } 293 } 294 295 void SharedHeap::set_barrier_set(BarrierSet* bs) { 296 _barrier_set = bs; 297 // Cached barrier set for fast access in oops 298 oopDesc::set_bs(bs); 299 } 300 301 void SharedHeap::post_initialize() { 302 ref_processing_init(); 303 } 304 305 void SharedHeap::ref_processing_init() { 306 perm_gen()->ref_processor_init(); 307 } 308 309 // Some utilities. 310 void SharedHeap::print_size_transition(outputStream* out, 311 size_t bytes_before, 312 size_t bytes_after, 313 size_t capacity) { 314 out->print(" %d%s->%d%s(%d%s)", 315 byte_size_in_proper_unit(bytes_before), 316 proper_unit_for_byte_size(bytes_before), 317 byte_size_in_proper_unit(bytes_after), 318 proper_unit_for_byte_size(bytes_after), 319 byte_size_in_proper_unit(capacity), 320 proper_unit_for_byte_size(capacity)); 321 }