1 /* 2 * Copyright (c) 2005, 2016, 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/concurrentMarkSweepGeneration.inline.hpp" 27 #include "gc/cms/concurrentMarkSweepThread.hpp" 28 #include "gc/cms/vmCMSOperations.hpp" 29 #include "gc/shared/gcLocker.inline.hpp" 30 #include "gc/shared/gcTimer.hpp" 31 #include "gc/shared/gcTraceTime.inline.hpp" 32 #include "gc/shared/isGCActiveMark.hpp" 33 #include "runtime/interfaceSupport.hpp" 34 #include "runtime/os.hpp" 35 #include "utilities/dtrace.hpp" 36 37 ////////////////////////////////////////////////////////// 38 // Methods in abstract class VM_CMS_Operation 39 ////////////////////////////////////////////////////////// 40 void VM_CMS_Operation::acquire_pending_list_lock() { 41 _pending_list_locker.lock(); 42 } 43 44 void VM_CMS_Operation::release_and_notify_pending_list_lock() { 45 _pending_list_locker.unlock(); 46 } 47 48 void VM_CMS_Operation::verify_before_gc() { 49 if (VerifyBeforeGC && 50 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 51 GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm); 52 HandleMark hm; 53 FreelistLocker x(_collector); 54 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 55 GenCollectedHeap::heap()->prepare_for_verify(); 56 Universe::verify(); 57 } 58 } 59 60 void VM_CMS_Operation::verify_after_gc() { 61 if (VerifyAfterGC && 62 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 63 GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm); 64 HandleMark hm; 65 FreelistLocker x(_collector); 66 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 67 Universe::verify(); 68 } 69 } 70 71 bool VM_CMS_Operation::lost_race() const { 72 if (CMSCollector::abstract_state() == CMSCollector::Idling) { 73 // We lost a race to a foreground collection 74 // -- there's nothing to do 75 return true; 76 } 77 assert(CMSCollector::abstract_state() == legal_state(), 78 "Inconsistent collector state?"); 79 return false; 80 } 81 82 bool VM_CMS_Operation::doit_prologue() { 83 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 84 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 85 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 86 "Possible deadlock"); 87 88 if (needs_pending_list_lock()) { 89 acquire_pending_list_lock(); 90 } 91 // Get the Heap_lock after the pending_list_lock. 92 Heap_lock->lock(); 93 if (lost_race()) { 94 assert(_prologue_succeeded == false, "Initialized in c'tor"); 95 Heap_lock->unlock(); 96 if (needs_pending_list_lock()) { 97 release_and_notify_pending_list_lock(); 98 } 99 } else { 100 _prologue_succeeded = true; 101 } 102 return _prologue_succeeded; 103 } 104 105 void VM_CMS_Operation::doit_epilogue() { 106 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 107 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 108 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 109 "Possible deadlock"); 110 111 // Release the Heap_lock first. 112 Heap_lock->unlock(); 113 if (needs_pending_list_lock()) { 114 release_and_notify_pending_list_lock(); 115 } 116 } 117 118 ////////////////////////////////////////////////////////// 119 // Methods in class VM_CMS_Initial_Mark 120 ////////////////////////////////////////////////////////// 121 void VM_CMS_Initial_Mark::doit() { 122 if (lost_race()) { 123 // Nothing to do. 124 return; 125 } 126 HS_PRIVATE_CMS_INITMARK_BEGIN(); 127 GCIdMark gc_id_mark(_gc_id); 128 129 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark"); 130 131 GenCollectedHeap* gch = GenCollectedHeap::heap(); 132 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark); 133 134 VM_CMS_Operation::verify_before_gc(); 135 136 IsGCActiveMark x; // stop-world GC active 137 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause()); 138 139 VM_CMS_Operation::verify_after_gc(); 140 141 _collector->_gc_timer_cm->register_gc_pause_end(); 142 143 HS_PRIVATE_CMS_INITMARK_END(); 144 } 145 146 ////////////////////////////////////////////////////////// 147 // Methods in class VM_CMS_Final_Remark_Operation 148 ////////////////////////////////////////////////////////// 149 void VM_CMS_Final_Remark::doit() { 150 if (lost_race()) { 151 // Nothing to do. 152 return; 153 } 154 HS_PRIVATE_CMS_REMARK_BEGIN(); 155 GCIdMark gc_id_mark(_gc_id); 156 157 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark"); 158 159 GenCollectedHeap* gch = GenCollectedHeap::heap(); 160 GCCauseSetter gccs(gch, GCCause::_cms_final_remark); 161 162 VM_CMS_Operation::verify_before_gc(); 163 164 IsGCActiveMark x; // stop-world GC active 165 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause()); 166 167 VM_CMS_Operation::verify_after_gc(); 168 169 _collector->save_heap_summary(); 170 _collector->_gc_timer_cm->register_gc_pause_end(); 171 172 HS_PRIVATE_CMS_REMARK_END(); 173 } 174 175 // VM operation to invoke a concurrent collection of a 176 // GenCollectedHeap heap. 177 void VM_GenCollectFullConcurrent::doit() { 178 assert(Thread::current()->is_VM_thread(), "Should be VM thread"); 179 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected"); 180 181 GenCollectedHeap* gch = GenCollectedHeap::heap(); 182 if (_gc_count_before == gch->total_collections()) { 183 // The "full" of do_full_collection call below "forces" 184 // a collection; the second arg, 0, below ensures that 185 // only the young gen is collected. XXX In the future, 186 // we'll probably need to have something in this interface 187 // to say do this only if we are sure we will not bail 188 // out to a full collection in this attempt, but that's 189 // for the future. 190 assert(SafepointSynchronize::is_at_safepoint(), 191 "We can only be executing this arm of if at a safepoint"); 192 GCCauseSetter gccs(gch, _gc_cause); 193 gch->do_full_collection(gch->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen); 194 } // Else no need for a foreground young gc 195 assert((_gc_count_before < gch->total_collections()) || 196 (GCLocker::is_active() /* gc may have been skipped */ 197 && (_gc_count_before == gch->total_collections())), 198 "total_collections() should be monotonically increasing"); 199 200 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 201 assert(_full_gc_count_before <= gch->total_full_collections(), "Error"); 202 if (gch->total_full_collections() == _full_gc_count_before) { 203 // Nudge the CMS thread to start a concurrent collection. 204 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause); 205 } else { 206 assert(_full_gc_count_before < gch->total_full_collections(), "Error"); 207 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done 208 } 209 } 210 211 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const { 212 Thread* thr = Thread::current(); 213 assert(thr != NULL, "Unexpected tid"); 214 if (!thr->is_Java_thread()) { 215 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread"); 216 GenCollectedHeap* gch = GenCollectedHeap::heap(); 217 if (_gc_count_before != gch->total_collections()) { 218 // No need to do a young gc, we'll just nudge the CMS thread 219 // in the doit() method above, to be executed soon. 220 assert(_gc_count_before < gch->total_collections(), 221 "total_collections() should be monotonically increasing"); 222 return false; // no need for foreground young gc 223 } 224 } 225 return true; // may still need foreground young gc 226 } 227 228 229 void VM_GenCollectFullConcurrent::doit_epilogue() { 230 Thread* thr = Thread::current(); 231 assert(thr->is_Java_thread(), "just checking"); 232 JavaThread* jt = (JavaThread*)thr; 233 // Release the Heap_lock first. 234 Heap_lock->unlock(); 235 release_and_notify_pending_list_lock(); 236 237 // It is fine to test whether completed collections has 238 // exceeded our request count without locking because 239 // the completion count is monotonically increasing; 240 // this will break for very long-running apps when the 241 // count overflows and wraps around. XXX fix me !!! 242 // e.g. at the rate of 1 full gc per ms, this could 243 // overflow in about 1000 years. 244 GenCollectedHeap* gch = GenCollectedHeap::heap(); 245 if (_gc_cause != GCCause::_gc_locker && 246 gch->total_full_collections_completed() <= _full_gc_count_before) { 247 // maybe we should change the condition to test _gc_cause == 248 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run, 249 // instead of _gc_cause != GCCause::_gc_locker 250 assert(GCCause::is_user_requested_gc(_gc_cause), 251 "the only way to get here if this was a System.gc()-induced GC"); 252 assert(ExplicitGCInvokesConcurrent, "Error"); 253 // Now, wait for witnessing concurrent gc cycle to complete, 254 // but do so in native mode, because we want to lock the 255 // FullGCEvent_lock, which may be needed by the VM thread 256 // or by the CMS thread, so we do not want to be suspended 257 // while holding that lock. 258 ThreadToNativeFromVM native(jt); 259 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 260 // Either a concurrent or a stop-world full gc is sufficient 261 // witness to our request. 262 while (gch->total_full_collections_completed() <= _full_gc_count_before) { 263 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 264 } 265 } 266 }