1 /* 2 * Copyright (c) 2005, 2015, 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.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 // The caller may block while communicating 42 // with the SLT thread in order to acquire/release the PLL. 43 SurrogateLockerThread* slt = ConcurrentMarkSweepThread::slt(); 44 if (slt != NULL) { 45 slt->manipulatePLL(SurrogateLockerThread::acquirePLL); 46 } else { 47 SurrogateLockerThread::report_missing_slt(); 48 } 49 } 50 51 void VM_CMS_Operation::release_and_notify_pending_list_lock() { 52 // The caller may block while communicating 53 // with the SLT thread in order to acquire/release the PLL. 54 ConcurrentMarkSweepThread::slt()-> 55 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL); 56 } 57 58 void VM_CMS_Operation::verify_before_gc() { 59 if (VerifyBeforeGC && 60 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 61 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id()); 62 HandleMark hm; 63 FreelistLocker x(_collector); 64 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 65 GenCollectedHeap::heap()->prepare_for_verify(); 66 Universe::verify(); 67 } 68 } 69 70 void VM_CMS_Operation::verify_after_gc() { 71 if (VerifyAfterGC && 72 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 73 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id()); 74 HandleMark hm; 75 FreelistLocker x(_collector); 76 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 77 Universe::verify(); 78 } 79 } 80 81 bool VM_CMS_Operation::lost_race() const { 82 if (CMSCollector::abstract_state() == CMSCollector::Idling) { 83 // We lost a race to a foreground collection 84 // -- there's nothing to do 85 return true; 86 } 87 assert(CMSCollector::abstract_state() == legal_state(), 88 "Inconsistent collector state?"); 89 return false; 90 } 91 92 bool VM_CMS_Operation::doit_prologue() { 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 (needs_pll()) { 99 acquire_pending_list_lock(); 100 } 101 // Get the Heap_lock after the pending_list_lock. 102 Heap_lock->lock(); 103 if (lost_race()) { 104 assert(_prologue_succeeded == false, "Initialized in c'tor"); 105 Heap_lock->unlock(); 106 if (needs_pll()) { 107 release_and_notify_pending_list_lock(); 108 } 109 } else { 110 _prologue_succeeded = true; 111 } 112 return _prologue_succeeded; 113 } 114 115 void VM_CMS_Operation::doit_epilogue() { 116 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 117 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 118 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 119 "Possible deadlock"); 120 121 // Release the Heap_lock first. 122 Heap_lock->unlock(); 123 if (needs_pll()) { 124 release_and_notify_pending_list_lock(); 125 } 126 } 127 128 ////////////////////////////////////////////////////////// 129 // Methods in class VM_CMS_Initial_Mark 130 ////////////////////////////////////////////////////////// 131 void VM_CMS_Initial_Mark::doit() { 132 if (lost_race()) { 133 // Nothing to do. 134 return; 135 } 136 HS_PRIVATE_CMS_INITMARK_BEGIN(); 137 138 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark"); 139 140 GenCollectedHeap* gch = GenCollectedHeap::heap(); 141 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark); 142 143 VM_CMS_Operation::verify_before_gc(); 144 145 IsGCActiveMark x; // stop-world GC active 146 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause()); 147 148 VM_CMS_Operation::verify_after_gc(); 149 150 _collector->_gc_timer_cm->register_gc_pause_end(); 151 152 HS_PRIVATE_CMS_INITMARK_END(); 153 } 154 155 ////////////////////////////////////////////////////////// 156 // Methods in class VM_CMS_Final_Remark_Operation 157 ////////////////////////////////////////////////////////// 158 void VM_CMS_Final_Remark::doit() { 159 if (lost_race()) { 160 // Nothing to do. 161 return; 162 } 163 HS_PRIVATE_CMS_REMARK_BEGIN(); 164 165 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark"); 166 167 GenCollectedHeap* gch = GenCollectedHeap::heap(); 168 GCCauseSetter gccs(gch, GCCause::_cms_final_remark); 169 170 VM_CMS_Operation::verify_before_gc(); 171 172 IsGCActiveMark x; // stop-world GC active 173 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause()); 174 175 VM_CMS_Operation::verify_after_gc(); 176 177 _collector->save_heap_summary(); 178 _collector->_gc_timer_cm->register_gc_pause_end(); 179 180 HS_PRIVATE_CMS_REMARK_END(); 181 } 182 183 // VM operation to invoke a concurrent collection of a 184 // GenCollectedHeap heap. 185 void VM_GenCollectFullConcurrent::doit() { 186 assert(Thread::current()->is_VM_thread(), "Should be VM thread"); 187 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected"); 188 189 GenCollectedHeap* gch = GenCollectedHeap::heap(); 190 if (_gc_count_before == gch->total_collections()) { 191 // The "full" of do_full_collection call below "forces" 192 // a collection; the second arg, 0, below ensures that 193 // only the young gen is collected. XXX In the future, 194 // we'll probably need to have something in this interface 195 // to say do this only if we are sure we will not bail 196 // out to a full collection in this attempt, but that's 197 // for the future. 198 assert(SafepointSynchronize::is_at_safepoint(), 199 "We can only be executing this arm of if at a safepoint"); 200 GCCauseSetter gccs(gch, _gc_cause); 201 gch->do_full_collection(gch->must_clear_all_soft_refs(), 202 0 /* collect only youngest gen */); 203 } // Else no need for a foreground young gc 204 assert((_gc_count_before < gch->total_collections()) || 205 (GC_locker::is_active() /* gc may have been skipped */ 206 && (_gc_count_before == gch->total_collections())), 207 "total_collections() should be monotonically increasing"); 208 209 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 210 assert(_full_gc_count_before <= gch->total_full_collections(), "Error"); 211 if (gch->total_full_collections() == _full_gc_count_before) { 212 // Nudge the CMS thread to start a concurrent collection. 213 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause); 214 } else { 215 assert(_full_gc_count_before < gch->total_full_collections(), "Error"); 216 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done 217 } 218 } 219 220 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const { 221 Thread* thr = Thread::current(); 222 assert(thr != NULL, "Unexpected tid"); 223 if (!thr->is_Java_thread()) { 224 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread"); 225 GenCollectedHeap* gch = GenCollectedHeap::heap(); 226 if (_gc_count_before != gch->total_collections()) { 227 // No need to do a young gc, we'll just nudge the CMS thread 228 // in the doit() method above, to be executed soon. 229 assert(_gc_count_before < gch->total_collections(), 230 "total_collections() should be monotonically increasing"); 231 return false; // no need for foreground young gc 232 } 233 } 234 return true; // may still need foreground young gc 235 } 236 237 238 void VM_GenCollectFullConcurrent::doit_epilogue() { 239 Thread* thr = Thread::current(); 240 assert(thr->is_Java_thread(), "just checking"); 241 JavaThread* jt = (JavaThread*)thr; 242 // Release the Heap_lock first. 243 Heap_lock->unlock(); 244 release_and_notify_pending_list_lock(); 245 246 // It is fine to test whether completed collections has 247 // exceeded our request count without locking because 248 // the completion count is monotonically increasing; 249 // this will break for very long-running apps when the 250 // count overflows and wraps around. XXX fix me !!! 251 // e.g. at the rate of 1 full gc per ms, this could 252 // overflow in about 1000 years. 253 GenCollectedHeap* gch = GenCollectedHeap::heap(); 254 if (_gc_cause != GCCause::_gc_locker && 255 gch->total_full_collections_completed() <= _full_gc_count_before) { 256 // maybe we should change the condition to test _gc_cause == 257 // GCCause::_java_lang_system_gc, instead of 258 // _gc_cause != GCCause::_gc_locker 259 assert(_gc_cause == GCCause::_java_lang_system_gc, 260 "the only way to get here if this was a System.gc()-induced GC"); 261 assert(ExplicitGCInvokesConcurrent, "Error"); 262 // Now, wait for witnessing concurrent gc cycle to complete, 263 // but do so in native mode, because we want to lock the 264 // FullGCEvent_lock, which may be needed by the VM thread 265 // or by the CMS thread, so we do not want to be suspended 266 // while holding that lock. 267 ThreadToNativeFromVM native(jt); 268 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 269 // Either a concurrent or a stop-world full gc is sufficient 270 // witness to our request. 271 while (gch->total_full_collections_completed() <= _full_gc_count_before) { 272 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 273 } 274 } 275 }