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.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 // 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(Info, gc, verify) tm("Verify Before", _collector->_gc_timer_cm); 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(Info, gc, verify) tm("Verify After", _collector->_gc_timer_cm); 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 GCIdMark gc_id_mark(_gc_id); 138 139 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark"); 140 141 GenCollectedHeap* gch = GenCollectedHeap::heap(); 142 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark); 143 144 VM_CMS_Operation::verify_before_gc(); 145 146 IsGCActiveMark x; // stop-world GC active 147 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause()); 148 149 VM_CMS_Operation::verify_after_gc(); 150 151 _collector->_gc_timer_cm->register_gc_pause_end(); 152 153 HS_PRIVATE_CMS_INITMARK_END(); 154 } 155 156 ////////////////////////////////////////////////////////// 157 // Methods in class VM_CMS_Final_Remark_Operation 158 ////////////////////////////////////////////////////////// 159 void VM_CMS_Final_Remark::doit() { 160 if (lost_race()) { 161 // Nothing to do. 162 return; 163 } 164 HS_PRIVATE_CMS_REMARK_BEGIN(); 165 GCIdMark gc_id_mark(_gc_id); 166 167 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark"); 168 169 GenCollectedHeap* gch = GenCollectedHeap::heap(); 170 GCCauseSetter gccs(gch, GCCause::_cms_final_remark); 171 172 VM_CMS_Operation::verify_before_gc(); 173 174 IsGCActiveMark x; // stop-world GC active 175 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause()); 176 177 VM_CMS_Operation::verify_after_gc(); 178 179 _collector->save_heap_summary(); 180 _collector->_gc_timer_cm->register_gc_pause_end(); 181 182 HS_PRIVATE_CMS_REMARK_END(); 183 } 184 185 // VM operation to invoke a concurrent collection of a 186 // GenCollectedHeap heap. 187 void VM_GenCollectFullConcurrent::doit() { 188 assert(Thread::current()->is_VM_thread(), "Should be VM thread"); 189 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected"); 190 191 GenCollectedHeap* gch = GenCollectedHeap::heap(); 192 if (_gc_count_before == gch->total_collections()) { 193 // The "full" of do_full_collection call below "forces" 194 // a collection; the second arg, 0, below ensures that 195 // only the young gen is collected. XXX In the future, 196 // we'll probably need to have something in this interface 197 // to say do this only if we are sure we will not bail 198 // out to a full collection in this attempt, but that's 199 // for the future. 200 assert(SafepointSynchronize::is_at_safepoint(), 201 "We can only be executing this arm of if at a safepoint"); 202 GCCauseSetter gccs(gch, _gc_cause); 203 gch->do_full_collection(gch->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen); 204 } // Else no need for a foreground young gc 205 assert((_gc_count_before < gch->total_collections()) || 206 (GC_locker::is_active() /* gc may have been skipped */ 207 && (_gc_count_before == gch->total_collections())), 208 "total_collections() should be monotonically increasing"); 209 210 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 211 assert(_full_gc_count_before <= gch->total_full_collections(), "Error"); 212 if (gch->total_full_collections() == _full_gc_count_before) { 213 // Nudge the CMS thread to start a concurrent collection. 214 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause); 215 } else { 216 assert(_full_gc_count_before < gch->total_full_collections(), "Error"); 217 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done 218 } 219 } 220 221 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const { 222 Thread* thr = Thread::current(); 223 assert(thr != NULL, "Unexpected tid"); 224 if (!thr->is_Java_thread()) { 225 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread"); 226 GenCollectedHeap* gch = GenCollectedHeap::heap(); 227 if (_gc_count_before != gch->total_collections()) { 228 // No need to do a young gc, we'll just nudge the CMS thread 229 // in the doit() method above, to be executed soon. 230 assert(_gc_count_before < gch->total_collections(), 231 "total_collections() should be monotonically increasing"); 232 return false; // no need for foreground young gc 233 } 234 } 235 return true; // may still need foreground young gc 236 } 237 238 239 void VM_GenCollectFullConcurrent::doit_epilogue() { 240 Thread* thr = Thread::current(); 241 assert(thr->is_Java_thread(), "just checking"); 242 JavaThread* jt = (JavaThread*)thr; 243 // Release the Heap_lock first. 244 Heap_lock->unlock(); 245 release_and_notify_pending_list_lock(); 246 247 // It is fine to test whether completed collections has 248 // exceeded our request count without locking because 249 // the completion count is monotonically increasing; 250 // this will break for very long-running apps when the 251 // count overflows and wraps around. XXX fix me !!! 252 // e.g. at the rate of 1 full gc per ms, this could 253 // overflow in about 1000 years. 254 GenCollectedHeap* gch = GenCollectedHeap::heap(); 255 if (_gc_cause != GCCause::_gc_locker && 256 gch->total_full_collections_completed() <= _full_gc_count_before) { 257 // maybe we should change the condition to test _gc_cause == 258 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run, 259 // instead of _gc_cause != GCCause::_gc_locker 260 assert(GCCause::is_user_requested_gc(_gc_cause), 261 "the only way to get here if this was a System.gc()-induced GC"); 262 assert(ExplicitGCInvokesConcurrent, "Error"); 263 // Now, wait for witnessing concurrent gc cycle to complete, 264 // but do so in native mode, because we want to lock the 265 // FullGCEvent_lock, which may be needed by the VM thread 266 // or by the CMS thread, so we do not want to be suspended 267 // while holding that lock. 268 ThreadToNativeFromVM native(jt); 269 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 270 // Either a concurrent or a stop-world full gc is sufficient 271 // witness to our request. 272 while (gch->total_full_collections_completed() <= _full_gc_count_before) { 273 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 274 } 275 } 276 }