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