1 /* 2 * Copyright (c) 2005, 2014, 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_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp" 27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 28 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" 29 #include "gc_implementation/shared/gcTimer.hpp" 30 #include "gc_implementation/shared/gcTraceTime.hpp" 31 #include "gc_implementation/shared/isGCActiveMark.hpp" 32 #include "memory/gcLocker.inline.hpp" 33 #include "runtime/interfaceSupport.hpp" 34 #include "runtime/os.hpp" 35 #include "utilities/dtrace.hpp" 36 37 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 38 39 ////////////////////////////////////////////////////////// 40 // Methods in abstract class VM_CMS_Operation 41 ////////////////////////////////////////////////////////// 42 void VM_CMS_Operation::acquire_pending_list_lock() { 43 // The caller may block while communicating 44 // with the SLT thread in order to acquire/release the PLL. 45 ConcurrentMarkSweepThread::slt()-> 46 manipulatePLL(SurrogateLockerThread::acquirePLL); 47 } 48 49 void VM_CMS_Operation::release_and_notify_pending_list_lock() { 50 // The caller may block while communicating 51 // with the SLT thread in order to acquire/release the PLL. 52 ConcurrentMarkSweepThread::slt()-> 53 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL); 54 } 55 56 void VM_CMS_Operation::verify_before_gc() { 57 if (VerifyBeforeGC && 58 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 59 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id()); 60 HandleMark hm; 61 FreelistLocker x(_collector); 62 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 63 Universe::heap()->prepare_for_verify(); 64 Universe::verify(); 65 } 66 } 67 68 void VM_CMS_Operation::verify_after_gc() { 69 if (VerifyAfterGC && 70 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) { 71 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id()); 72 HandleMark hm; 73 FreelistLocker x(_collector); 74 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag); 75 Universe::verify(); 76 } 77 } 78 79 bool VM_CMS_Operation::lost_race() const { 80 if (CMSCollector::abstract_state() == CMSCollector::Idling) { 81 // We lost a race to a foreground collection 82 // -- there's nothing to do 83 return true; 84 } 85 assert(CMSCollector::abstract_state() == legal_state(), 86 "Inconsistent collector state?"); 87 return false; 88 } 89 90 bool VM_CMS_Operation::doit_prologue() { 91 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 92 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 93 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 94 "Possible deadlock"); 95 96 if (needs_pll()) { 97 acquire_pending_list_lock(); 98 } 99 // Get the Heap_lock after the pending_list_lock. 100 Heap_lock->lock(); 101 if (lost_race()) { 102 assert(_prologue_succeeded == false, "Initialized in c'tor"); 103 Heap_lock->unlock(); 104 if (needs_pll()) { 105 release_and_notify_pending_list_lock(); 106 } 107 } else { 108 _prologue_succeeded = true; 109 } 110 return _prologue_succeeded; 111 } 112 113 void VM_CMS_Operation::doit_epilogue() { 114 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking"); 115 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock"); 116 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(), 117 "Possible deadlock"); 118 119 // Release the Heap_lock first. 120 Heap_lock->unlock(); 121 if (needs_pll()) { 122 release_and_notify_pending_list_lock(); 123 } 124 } 125 126 ////////////////////////////////////////////////////////// 127 // Methods in class VM_CMS_Initial_Mark 128 ////////////////////////////////////////////////////////// 129 void VM_CMS_Initial_Mark::doit() { 130 if (lost_race()) { 131 // Nothing to do. 132 return; 133 } 134 HS_PRIVATE_CMS_INITMARK_BEGIN(); 135 136 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark"); 137 138 GenCollectedHeap* gch = GenCollectedHeap::heap(); 139 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark); 140 141 VM_CMS_Operation::verify_before_gc(); 142 143 IsGCActiveMark x; // stop-world GC active 144 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause()); 145 146 VM_CMS_Operation::verify_after_gc(); 147 148 _collector->_gc_timer_cm->register_gc_pause_end(); 149 150 HS_PRIVATE_CMS_INITMARK_END(); 151 } 152 153 ////////////////////////////////////////////////////////// 154 // Methods in class VM_CMS_Final_Remark_Operation 155 ////////////////////////////////////////////////////////// 156 void VM_CMS_Final_Remark::doit() { 157 if (lost_race()) { 158 // Nothing to do. 159 return; 160 } 161 HS_PRIVATE_CMS_REMARK_BEGIN(); 162 163 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark"); 164 165 GenCollectedHeap* gch = GenCollectedHeap::heap(); 166 GCCauseSetter gccs(gch, GCCause::_cms_final_remark); 167 168 VM_CMS_Operation::verify_before_gc(); 169 170 IsGCActiveMark x; // stop-world GC active 171 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause()); 172 173 VM_CMS_Operation::verify_after_gc(); 174 175 _collector->save_heap_summary(); 176 _collector->_gc_timer_cm->register_gc_pause_end(); 177 178 HS_PRIVATE_CMS_REMARK_END(); 179 } 180 181 // VM operation to invoke a concurrent collection of a 182 // GenCollectedHeap heap. 183 void VM_GenCollectFullConcurrent::doit() { 184 assert(Thread::current()->is_VM_thread(), "Should be VM thread"); 185 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected"); 186 187 GenCollectedHeap* gch = GenCollectedHeap::heap(); 188 if (_gc_count_before == gch->total_collections()) { 189 // The "full" of do_full_collection call below "forces" 190 // a collection; the second arg, 0, below ensures that 191 // only the young gen is collected. XXX In the future, 192 // we'll probably need to have something in this interface 193 // to say do this only if we are sure we will not bail 194 // out to a full collection in this attempt, but that's 195 // for the future. 196 assert(SafepointSynchronize::is_at_safepoint(), 197 "We can only be executing this arm of if at a safepoint"); 198 GCCauseSetter gccs(gch, _gc_cause); 199 gch->do_full_collection(gch->must_clear_all_soft_refs(), 200 0 /* collect only youngest gen */); 201 } // Else no need for a foreground young gc 202 assert((_gc_count_before < gch->total_collections()) || 203 (GC_locker::is_active() /* gc may have been skipped */ 204 && (_gc_count_before == gch->total_collections())), 205 "total_collections() should be monotonically increasing"); 206 207 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 208 assert(_full_gc_count_before <= gch->total_full_collections(), "Error"); 209 if (gch->total_full_collections() == _full_gc_count_before) { 210 // Disable iCMS until the full collection is done, and 211 // remember that we did so. 212 CMSCollector::disable_icms(); 213 _disabled_icms = true; 214 // In case CMS thread was in icms_wait(), wake it up. 215 CMSCollector::start_icms(); 216 // Nudge the CMS thread to start a concurrent collection. 217 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause); 218 } else { 219 assert(_full_gc_count_before < gch->total_full_collections(), "Error"); 220 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done 221 } 222 } 223 224 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const { 225 Thread* thr = Thread::current(); 226 assert(thr != NULL, "Unexpected tid"); 227 if (!thr->is_Java_thread()) { 228 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread"); 229 GenCollectedHeap* gch = GenCollectedHeap::heap(); 230 if (_gc_count_before != gch->total_collections()) { 231 // No need to do a young gc, we'll just nudge the CMS thread 232 // in the doit() method above, to be executed soon. 233 assert(_gc_count_before < gch->total_collections(), 234 "total_collections() should be monotonically increasing"); 235 return false; // no need for foreground young gc 236 } 237 } 238 return true; // may still need foreground young gc 239 } 240 241 242 void VM_GenCollectFullConcurrent::doit_epilogue() { 243 Thread* thr = Thread::current(); 244 assert(thr->is_Java_thread(), "just checking"); 245 JavaThread* jt = (JavaThread*)thr; 246 // Release the Heap_lock first. 247 Heap_lock->unlock(); 248 release_and_notify_pending_list_lock(); 249 250 // It is fine to test whether completed collections has 251 // exceeded our request count without locking because 252 // the completion count is monotonically increasing; 253 // this will break for very long-running apps when the 254 // count overflows and wraps around. XXX fix me !!! 255 // e.g. at the rate of 1 full gc per ms, this could 256 // overflow in about 1000 years. 257 GenCollectedHeap* gch = GenCollectedHeap::heap(); 258 if (_gc_cause != GCCause::_gc_locker && 259 gch->total_full_collections_completed() <= _full_gc_count_before) { 260 // maybe we should change the condition to test _gc_cause == 261 // GCCause::_java_lang_system_gc, instead of 262 // _gc_cause != GCCause::_gc_locker 263 assert(_gc_cause == GCCause::_java_lang_system_gc, 264 "the only way to get here if this was a System.gc()-induced GC"); 265 assert(ExplicitGCInvokesConcurrent, "Error"); 266 // Now, wait for witnessing concurrent gc cycle to complete, 267 // but do so in native mode, because we want to lock the 268 // FullGCEvent_lock, which may be needed by the VM thread 269 // or by the CMS thread, so we do not want to be suspended 270 // while holding that lock. 271 ThreadToNativeFromVM native(jt); 272 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 273 // Either a concurrent or a stop-world full gc is sufficient 274 // witness to our request. 275 while (gch->total_full_collections_completed() <= _full_gc_count_before) { 276 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 277 } 278 } 279 // Enable iCMS back if we disabled it earlier. 280 if (_disabled_icms) { 281 CMSCollector::enable_icms(); 282 } 283 }