1 /* 2 * Copyright (c) 2001, 2013, 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/g1/concurrentMarkThread.inline.hpp" 27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 28 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 29 #include "gc_implementation/g1/g1Log.hpp" 30 #include "gc_implementation/g1/g1MMUTracker.hpp" 31 #include "gc_implementation/g1/vm_operations_g1.hpp" 32 #include "memory/resourceArea.hpp" 33 #include "runtime/vmThread.hpp" 34 35 // ======= Concurrent Mark Thread ======== 36 37 // The CM thread is created when the G1 garbage collector is used 38 39 SurrogateLockerThread* 40 ConcurrentMarkThread::_slt = NULL; 41 42 ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) : 43 ConcurrentGCThread(), 44 _cm(cm), 45 _started(false), 46 _in_progress(false), 47 _vtime_accum(0.0), 48 _vtime_mark_accum(0.0) { 49 create_and_start(); 50 } 51 52 class CMCheckpointRootsFinalClosure: public VoidClosure { 53 54 ConcurrentMark* _cm; 55 public: 56 57 CMCheckpointRootsFinalClosure(ConcurrentMark* cm) : 58 _cm(cm) {} 59 60 void do_void(){ 61 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs 62 } 63 }; 64 65 class CMCleanUp: public VoidClosure { 66 ConcurrentMark* _cm; 67 public: 68 69 CMCleanUp(ConcurrentMark* cm) : 70 _cm(cm) {} 71 72 void do_void(){ 73 _cm->cleanup(); 74 } 75 }; 76 77 78 79 void ConcurrentMarkThread::run() { 80 initialize_in_thread(); 81 _vtime_start = os::elapsedVTime(); 82 wait_for_universe_init(); 83 84 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 85 G1CollectorPolicy* g1_policy = g1h->g1_policy(); 86 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); 87 Thread *current_thread = Thread::current(); 88 89 while (!_should_terminate) { 90 // wait until started is set. 91 sleepBeforeNextCycle(); 92 { 93 ResourceMark rm; 94 HandleMark hm; 95 double cycle_start = os::elapsedVTime(); 96 char verbose_str[128]; 97 98 // We have to ensure that we finish scanning the root regions 99 // before the next GC takes place. To ensure this we have to 100 // make sure that we do not join the STS until the root regions 101 // have been scanned. If we did then it's possible that a 102 // subsequent GC could block us from joining the STS and proceed 103 // without the root regions have been scanned which would be a 104 // correctness issue. 105 106 double scan_start = os::elapsedTime(); 107 if (!cm()->has_aborted()) { 108 if (G1Log::fine()) { 109 gclog_or_tty->date_stamp(PrintGCDateStamps); 110 gclog_or_tty->stamp(PrintGCTimeStamps); 111 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]"); 112 } 113 114 _cm->scanRootRegions(); 115 116 double scan_end = os::elapsedTime(); 117 if (G1Log::fine()) { 118 gclog_or_tty->date_stamp(PrintGCDateStamps); 119 gclog_or_tty->stamp(PrintGCTimeStamps); 120 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf]", 121 scan_end - scan_start); 122 } 123 } 124 125 double mark_start_sec = os::elapsedTime(); 126 if (G1Log::fine()) { 127 gclog_or_tty->date_stamp(PrintGCDateStamps); 128 gclog_or_tty->stamp(PrintGCTimeStamps); 129 gclog_or_tty->print_cr("[GC concurrent-mark-start]"); 130 } 131 132 int iter = 0; 133 do { 134 iter++; 135 if (!cm()->has_aborted()) { 136 _cm->markFromRoots(); 137 } 138 139 double mark_end_time = os::elapsedVTime(); 140 double mark_end_sec = os::elapsedTime(); 141 _vtime_mark_accum += (mark_end_time - cycle_start); 142 if (!cm()->has_aborted()) { 143 if (g1_policy->adaptive_young_list_length()) { 144 double now = os::elapsedTime(); 145 double remark_prediction_ms = g1_policy->predict_remark_time_ms(); 146 jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms); 147 os::sleep(current_thread, sleep_time_ms, false); 148 } 149 150 if (G1Log::fine()) { 151 gclog_or_tty->date_stamp(PrintGCDateStamps); 152 gclog_or_tty->stamp(PrintGCTimeStamps); 153 gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf sec]", 154 mark_end_sec - mark_start_sec); 155 } 156 157 CMCheckpointRootsFinalClosure final_cl(_cm); 158 sprintf(verbose_str, "GC remark"); 159 VM_CGC_Operation op(&final_cl, verbose_str, true /* needs_pll */); 160 VMThread::execute(&op); 161 } 162 if (cm()->restart_for_overflow()) { 163 if (G1TraceMarkStackOverflow) { 164 gclog_or_tty->print_cr("Restarting conc marking because of MS overflow " 165 "in remark (restart #%d).", iter); 166 } 167 if (G1Log::fine()) { 168 gclog_or_tty->date_stamp(PrintGCDateStamps); 169 gclog_or_tty->stamp(PrintGCTimeStamps); 170 gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]"); 171 } 172 } 173 } while (cm()->restart_for_overflow()); 174 175 double end_time = os::elapsedVTime(); 176 // Update the total virtual time before doing this, since it will try 177 // to measure it to get the vtime for this marking. We purposely 178 // neglect the presumably-short "completeCleanup" phase here. 179 _vtime_accum = (end_time - _vtime_start); 180 181 if (!cm()->has_aborted()) { 182 if (g1_policy->adaptive_young_list_length()) { 183 double now = os::elapsedTime(); 184 double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms(); 185 jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms); 186 os::sleep(current_thread, sleep_time_ms, false); 187 } 188 189 CMCleanUp cl_cl(_cm); 190 sprintf(verbose_str, "GC cleanup"); 191 VM_CGC_Operation op(&cl_cl, verbose_str, false /* needs_pll */); 192 VMThread::execute(&op); 193 } else { 194 // We don't want to update the marking status if a GC pause 195 // is already underway. 196 _sts.join(); 197 g1h->set_marking_complete(); 198 _sts.leave(); 199 } 200 201 // Check if cleanup set the free_regions_coming flag. If it 202 // hasn't, we can just skip the next step. 203 if (g1h->free_regions_coming()) { 204 // The following will finish freeing up any regions that we 205 // found to be empty during cleanup. We'll do this part 206 // without joining the suspendible set. If an evacuation pause 207 // takes place, then we would carry on freeing regions in 208 // case they are needed by the pause. If a Full GC takes 209 // place, it would wait for us to process the regions 210 // reclaimed by cleanup. 211 212 double cleanup_start_sec = os::elapsedTime(); 213 if (G1Log::fine()) { 214 gclog_or_tty->date_stamp(PrintGCDateStamps); 215 gclog_or_tty->stamp(PrintGCTimeStamps); 216 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]"); 217 } 218 219 // Now do the concurrent cleanup operation. 220 _cm->completeCleanup(); 221 222 // Notify anyone who's waiting that there are no more free 223 // regions coming. We have to do this before we join the STS 224 // (in fact, we should not attempt to join the STS in the 225 // interval between finishing the cleanup pause and clearing 226 // the free_regions_coming flag) otherwise we might deadlock: 227 // a GC worker could be blocked waiting for the notification 228 // whereas this thread will be blocked for the pause to finish 229 // while it's trying to join the STS, which is conditional on 230 // the GC workers finishing. 231 g1h->reset_free_regions_coming(); 232 233 double cleanup_end_sec = os::elapsedTime(); 234 if (G1Log::fine()) { 235 gclog_or_tty->date_stamp(PrintGCDateStamps); 236 gclog_or_tty->stamp(PrintGCTimeStamps); 237 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf]", 238 cleanup_end_sec - cleanup_start_sec); 239 } 240 } 241 guarantee(cm()->cleanup_list_is_empty(), 242 "at this point there should be no regions on the cleanup list"); 243 244 // There is a tricky race before recording that the concurrent 245 // cleanup has completed and a potential Full GC starting around 246 // the same time. We want to make sure that the Full GC calls 247 // abort() on concurrent mark after 248 // record_concurrent_mark_cleanup_completed(), since abort() is 249 // the method that will reset the concurrent mark state. If we 250 // end up calling record_concurrent_mark_cleanup_completed() 251 // after abort() then we might incorrectly undo some of the work 252 // abort() did. Checking the has_aborted() flag after joining 253 // the STS allows the correct ordering of the two methods. There 254 // are two scenarios: 255 // 256 // a) If we reach here before the Full GC, the fact that we have 257 // joined the STS means that the Full GC cannot start until we 258 // leave the STS, so record_concurrent_mark_cleanup_completed() 259 // will complete before abort() is called. 260 // 261 // b) If we reach here during the Full GC, we'll be held up from 262 // joining the STS until the Full GC is done, which means that 263 // abort() will have completed and has_aborted() will return 264 // true to prevent us from calling 265 // record_concurrent_mark_cleanup_completed() (and, in fact, it's 266 // not needed any more as the concurrent mark state has been 267 // already reset). 268 _sts.join(); 269 if (!cm()->has_aborted()) { 270 g1_policy->record_concurrent_mark_cleanup_completed(); 271 } 272 _sts.leave(); 273 274 if (cm()->has_aborted()) { 275 if (G1Log::fine()) { 276 gclog_or_tty->date_stamp(PrintGCDateStamps); 277 gclog_or_tty->stamp(PrintGCTimeStamps); 278 gclog_or_tty->print_cr("[GC concurrent-mark-abort]"); 279 } 280 } 281 282 // We now want to allow clearing of the marking bitmap to be 283 // suspended by a collection pause. 284 _sts.join(); 285 _cm->clearNextBitmap(); 286 _sts.leave(); 287 } 288 289 // Update the number of full collections that have been 290 // completed. This will also notify the FullGCCount_lock in case a 291 // Java thread is waiting for a full GC to happen (e.g., it 292 // called System.gc() with +ExplicitGCInvokesConcurrent). 293 _sts.join(); 294 g1h->increment_old_marking_cycles_completed(true /* concurrent */); 295 _sts.leave(); 296 } 297 assert(_should_terminate, "just checking"); 298 299 terminate(); 300 } 301 302 303 void ConcurrentMarkThread::yield() { 304 _sts.yield("Concurrent Mark"); 305 } 306 307 void ConcurrentMarkThread::stop() { 308 // it is ok to take late safepoints here, if needed 309 MutexLockerEx mu(Terminator_lock); 310 _should_terminate = true; 311 while (!_has_terminated) { 312 Terminator_lock->wait(); 313 } 314 } 315 316 void ConcurrentMarkThread::print() const { 317 print_on(tty); 318 } 319 320 void ConcurrentMarkThread::print_on(outputStream* st) const { 321 st->print("\"G1 Main Concurrent Mark GC Thread\" "); 322 Thread::print_on(st); 323 st->cr(); 324 } 325 326 void ConcurrentMarkThread::sleepBeforeNextCycle() { 327 // We join here because we don't want to do the "shouldConcurrentMark()" 328 // below while the world is otherwise stopped. 329 assert(!in_progress(), "should have been cleared"); 330 331 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 332 while (!started()) { 333 CGC_lock->wait(Mutex::_no_safepoint_check_flag); 334 } 335 set_in_progress(); 336 clear_started(); 337 } 338 339 // Note: As is the case with CMS - this method, although exported 340 // by the ConcurrentMarkThread, which is a non-JavaThread, can only 341 // be called by a JavaThread. Currently this is done at vm creation 342 // time (post-vm-init) by the main/Primordial (Java)Thread. 343 // XXX Consider changing this in the future to allow the CM thread 344 // itself to create this thread? 345 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) { 346 assert(UseG1GC, "SLT thread needed only for concurrent GC"); 347 assert(THREAD->is_Java_thread(), "must be a Java thread"); 348 assert(_slt == NULL, "SLT already created"); 349 _slt = SurrogateLockerThread::make(THREAD); 350 }