1 /* 2 * Copyright (c) 2005, 2017, 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 "gc/cms/cmsHeap.hpp" 27 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp" 28 #include "gc/cms/concurrentMarkSweepThread.hpp" 29 #include "gc/cms/vmCMSOperations.hpp" 30 #include "gc/shared/gcLocker.inline.hpp" 31 #include "gc/shared/gcTimer.hpp" 32 #include "gc/shared/gcTraceTime.inline.hpp" 33 #include "gc/shared/isGCActiveMark.hpp" 34 #include "runtime/handles.inline.hpp" 35 #include "runtime/interfaceSupport.inline.hpp" 36 #include "runtime/os.hpp" 37 #include "utilities/dtrace.hpp" 38 39 ////////////////////////////////////////////////////////// 40 // Methods in abstract class VM_CMS_Operation 41 ////////////////////////////////////////////////////////// 42 void VM_CMS_Operation::verify_before_gc() { 43 if (VerifyBeforeGC && 44 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) { 45 GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm); 46 HandleMark hm; 47 FreelistLocker x(_collector); 48 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 49 CMSHeap::heap()->prepare_for_verify(); 50 Universe::verify(); 51 } 52 } 53 54 void VM_CMS_Operation::verify_after_gc() { 55 if (VerifyAfterGC && 56 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) { 57 GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm); 58 HandleMark hm; 59 FreelistLocker x(_collector); 60 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 61 Universe::verify(); 62 } 63 } 64 65 bool VM_CMS_Operation::lost_race() const { 66 if (CMSCollector::abstract_state() == CMSCollector::Idling) { 67 // We lost a race to a foreground collection 68 // -- there's nothing to do 69 return true; 70 } 71 assert(CMSCollector::abstract_state() == legal_state(), 72 "Inconsistent collector state?"); 73 return false; 74 } 75 76 bool VM_CMS_Operation::doit_prologue() { 77 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 78 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 79 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 80 "Possible deadlock"); 81 82 Heap_lock->lock(); 83 if (lost_race()) { 84 assert(_prologue_succeeded == false, "Initialized in c'tor"); 85 Heap_lock->unlock(); 86 } else { 87 _prologue_succeeded = true; 88 } 89 return _prologue_succeeded; 90 } 91 92 void VM_CMS_Operation::doit_epilogue() { 93 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 94 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 95 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 96 "Possible deadlock"); 97 98 if (Universe::has_reference_pending_list()) { 99 Heap_lock->notify_all(); 100 } 101 Heap_lock->unlock(); 102 } 103 104 ////////////////////////////////////////////////////////// 105 // Methods in class VM_CMS_Initial_Mark 106 ////////////////////////////////////////////////////////// 107 void VM_CMS_Initial_Mark::doit() { 108 if (lost_race()) { 109 // Nothing to do. 110 return; 111 } 112 HS_PRIVATE_CMS_INITMARK_BEGIN(); 113 GCIdMark gc_id_mark(_gc_id); 114 115 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark"); 116 117 CMSHeap* heap = CMSHeap::heap(); 118 GCCauseSetter gccs(heap, GCCause::_cms_initial_mark); 119 120 VM_CMS_Operation::verify_before_gc(); 121 122 IsGCActiveMark x; // stop-world GC active 123 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, heap->gc_cause()); 124 125 VM_CMS_Operation::verify_after_gc(); 126 127 _collector->_gc_timer_cm->register_gc_pause_end(); 128 129 HS_PRIVATE_CMS_INITMARK_END(); 130 } 131 132 ////////////////////////////////////////////////////////// 133 // Methods in class VM_CMS_Final_Remark_Operation 134 ////////////////////////////////////////////////////////// 135 void VM_CMS_Final_Remark::doit() { 136 if (lost_race()) { 137 // Nothing to do. 138 return; 139 } 140 HS_PRIVATE_CMS_REMARK_BEGIN(); 141 GCIdMark gc_id_mark(_gc_id); 142 143 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark"); 144 145 CMSHeap* heap = CMSHeap::heap(); 146 GCCauseSetter gccs(heap, GCCause::_cms_final_remark); 147 148 VM_CMS_Operation::verify_before_gc(); 149 150 IsGCActiveMark x; // stop-world GC active 151 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, heap->gc_cause()); 152 153 VM_CMS_Operation::verify_after_gc(); 154 155 _collector->save_heap_summary(); 156 _collector->_gc_timer_cm->register_gc_pause_end(); 157 158 HS_PRIVATE_CMS_REMARK_END(); 159 } 160 161 // VM operation to invoke a concurrent collection of a 162 // GenCollectedHeap heap. 163 void VM_GenCollectFullConcurrent::doit() { 164 assert(Thread::current()->is_VM_thread(), "Should be VM thread"); 165 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected"); 166 167 CMSHeap* heap = CMSHeap::heap(); 168 if (_gc_count_before == heap->total_collections()) { 169 // The "full" of do_full_collection call below "forces" 170 // a collection; the second arg, 0, below ensures that 171 // only the young gen is collected. XXX In the future, 172 // we'll probably need to have something in this interface 173 // to say do this only if we are sure we will not bail 174 // out to a full collection in this attempt, but that's 175 // for the future. 176 assert(SafepointSynchronize::is_at_safepoint(), 177 "We can only be executing this arm of if at a safepoint"); 178 GCCauseSetter gccs(heap, _gc_cause); 179 heap->do_full_collection(heap->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen); 180 } // Else no need for a foreground young gc 181 assert((_gc_count_before < heap->total_collections()) || 182 (GCLocker::is_active() /* gc may have been skipped */ 183 && (_gc_count_before == heap->total_collections())), 184 "total_collections() should be monotonically increasing"); 185 186 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 187 assert(_full_gc_count_before <= heap->total_full_collections(), "Error"); 188 if (heap->total_full_collections() == _full_gc_count_before) { 189 // Nudge the CMS thread to start a concurrent collection. 190 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause); 191 } else { 192 assert(_full_gc_count_before < heap->total_full_collections(), "Error"); 193 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done 194 } 195 } 196 197 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const { 198 Thread* thr = Thread::current(); 199 assert(thr != NULL, "Unexpected tid"); 200 if (!thr->is_Java_thread()) { 201 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread"); 202 CMSHeap* heap = CMSHeap::heap(); 203 if (_gc_count_before != heap->total_collections()) { 204 // No need to do a young gc, we'll just nudge the CMS thread 205 // in the doit() method above, to be executed soon. 206 assert(_gc_count_before < heap->total_collections(), 207 "total_collections() should be monotonically increasing"); 208 return false; // no need for foreground young gc 209 } 210 } 211 return true; // may still need foreground young gc 212 } 213 214 215 void VM_GenCollectFullConcurrent::doit_epilogue() { 216 Thread* thr = Thread::current(); 217 assert(thr->is_Java_thread(), "just checking"); 218 JavaThread* jt = (JavaThread*)thr; 219 220 if (Universe::has_reference_pending_list()) { 221 Heap_lock->notify_all(); 222 } 223 Heap_lock->unlock(); 224 225 // It is fine to test whether completed collections has 226 // exceeded our request count without locking because 227 // the completion count is monotonically increasing; 228 // this will break for very long-running apps when the 229 // count overflows and wraps around. XXX fix me !!! 230 // e.g. at the rate of 1 full gc per ms, this could 231 // overflow in about 1000 years. 232 CMSHeap* heap = CMSHeap::heap(); 233 if (_gc_cause != GCCause::_gc_locker && 234 heap->total_full_collections_completed() <= _full_gc_count_before) { 235 // maybe we should change the condition to test _gc_cause == 236 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run, 237 // instead of _gc_cause != GCCause::_gc_locker 238 assert(GCCause::is_user_requested_gc(_gc_cause), 239 "the only way to get here if this was a System.gc()-induced GC"); 240 assert(ExplicitGCInvokesConcurrent, "Error"); 241 // Now, wait for witnessing concurrent gc cycle to complete, 242 // but do so in native mode, because we want to lock the 243 // FullGCEvent_lock, which may be needed by the VM thread 244 // or by the CMS thread, so we do not want to be suspended 245 // while holding that lock. 246 ThreadToNativeFromVM native(jt); 247 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 248 // Either a concurrent or a stop-world full gc is sufficient 249 // witness to our request. 250 while (heap->total_full_collections_completed() <= _full_gc_count_before) { 251 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 252 } 253 } 254 }