1 /*
   2  * Copyright (c) 2015, 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 
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "gc/g1/bufferingOopClosure.hpp"
  31 #include "gc/g1/g1CodeBlobClosure.hpp"
  32 #include "gc/g1/g1CollectedHeap.inline.hpp"
  33 #include "gc/g1/g1CollectorState.hpp"
  34 #include "gc/g1/g1GCPhaseTimes.hpp"
  35 #include "gc/g1/g1Policy.hpp"
  36 #include "gc/g1/g1RootClosures.hpp"
  37 #include "gc/g1/g1RootProcessor.hpp"
  38 #include "gc/g1/heapRegion.inline.hpp"
  39 #include "memory/allocation.inline.hpp"
  40 #include "runtime/fprofiler.hpp"
  41 #include "runtime/mutex.hpp"
  42 #include "services/management.hpp"
  43 
  44 void G1RootProcessor::worker_has_discovered_all_strong_classes() {
  45   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
  46 
  47   uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
  48   if (new_value == n_workers()) {
  49     // This thread is last. Notify the others.
  50     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
  51     _lock.notify_all();
  52   }
  53 }
  54 
  55 void G1RootProcessor::wait_until_all_strong_classes_discovered() {
  56   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
  57 
  58   if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
  59     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
  60     while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
  61       _lock.wait(Mutex::_no_safepoint_check_flag, 0, false);
  62     }
  63   }
  64 }
  65 
  66 G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :
  67     _g1h(g1h),
  68     _process_strong_tasks(G1RP_PS_NumElements),
  69     _srs(n_workers),
  70     _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false, Monitor::_safepoint_check_never),
  71     _n_workers_discovered_strong_classes(0) {}
  72 
  73 void G1RootProcessor::evacuate_roots(G1EvacuationRootClosures* closures, uint worker_i) {
  74   double ext_roots_start = os::elapsedTime();
  75   G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
  76 
  77   process_java_roots(closures, phase_times, worker_i);
  78 
  79   // This is the point where this worker thread will not find more strong CLDs/nmethods.
  80   // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
  81   if (closures->trace_metadata()) {
  82     worker_has_discovered_all_strong_classes();
  83   }
  84 
  85   process_vm_roots(closures, phase_times, worker_i);
  86   process_string_table_roots(closures, phase_times, worker_i);
  87 
  88   {
  89     // Now the CM ref_processor roots.
  90     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_i);
  91     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_refProcessor_oops_do)) {
  92       // We need to treat the discovered reference lists of the
  93       // concurrent mark ref processor as roots and keep entries
  94       // (which are added by the marking threads) on them live
  95       // until they can be processed at the end of marking.
  96       _g1h->ref_processor_cm()->weak_oops_do(closures->strong_oops());
  97     }
  98   }
  99 
 100   if (closures->trace_metadata()) {
 101     {
 102       G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongCLD, worker_i);
 103       // Barrier to make sure all workers passed
 104       // the strong CLD and strong nmethods phases.
 105       wait_until_all_strong_classes_discovered();
 106     }
 107 
 108     // Now take the complement of the strong CLDs.
 109     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WeakCLDRoots, worker_i);
 110     assert(closures->second_pass_weak_clds() != NULL, "Should be non-null if we are tracing metadata.");
 111     ClassLoaderDataGraph::roots_cld_do(NULL, closures->second_pass_weak_clds());
 112   } else {
 113     phase_times->record_time_secs(G1GCPhaseTimes::WaitForStrongCLD, worker_i, 0.0);
 114     phase_times->record_time_secs(G1GCPhaseTimes::WeakCLDRoots, worker_i, 0.0);
 115     assert(closures->second_pass_weak_clds() == NULL, "Should be null if not tracing metadata.");
 116   }
 117 
 118   // Finish up any enqueued closure apps (attributed as object copy time).
 119   closures->flush();
 120 
 121   double obj_copy_time_sec = closures->closure_app_seconds();
 122 
 123   phase_times->record_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, obj_copy_time_sec);
 124 
 125   double ext_root_time_sec = os::elapsedTime() - ext_roots_start - obj_copy_time_sec;
 126 
 127   phase_times->record_time_secs(G1GCPhaseTimes::ExtRootScan, worker_i, ext_root_time_sec);
 128 
 129   // During conc marking we have to filter the per-thread SATB buffers
 130   // to make sure we remove any oops into the CSet (which will show up
 131   // as implicitly live).
 132   {
 133     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SATBFiltering, worker_i);
 134     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_filter_satb_buffers) && _g1h->collector_state()->mark_in_progress()) {
 135       JavaThread::satb_mark_queue_set().filter_thread_buffers();
 136     }
 137   }
 138 
 139   _process_strong_tasks.all_tasks_completed(n_workers());
 140 }
 141 
 142 // Adaptor to pass the closures to the strong roots in the VM.
 143 class StrongRootsClosures : public G1RootClosures {
 144   OopClosure* _roots;
 145   CLDClosure* _clds;
 146   CodeBlobClosure* _blobs;
 147 public:
 148   StrongRootsClosures(OopClosure* roots, CLDClosure* clds, CodeBlobClosure* blobs) :
 149       _roots(roots), _clds(clds), _blobs(blobs) {}
 150 
 151   OopClosure* weak_oops()   { return NULL; }
 152   OopClosure* strong_oops() { return _roots; }
 153 
 154   CLDClosure* weak_clds()        { return NULL; }
 155   CLDClosure* strong_clds()      { return _clds; }
 156 
 157   CodeBlobClosure* strong_codeblobs() { return _blobs; }
 158 };
 159 
 160 void G1RootProcessor::process_strong_roots(OopClosure* oops,
 161                                            CLDClosure* clds,
 162                                            CodeBlobClosure* blobs) {
 163   StrongRootsClosures closures(oops, clds, blobs);
 164 
 165   process_java_roots(&closures, NULL, 0);
 166   process_vm_roots(&closures, NULL, 0);
 167 
 168   _process_strong_tasks.all_tasks_completed(n_workers());
 169 }
 170 
 171 // Adaptor to pass the closures to all the roots in the VM.
 172 class AllRootsClosures : public G1RootClosures {
 173   OopClosure* _roots;
 174   CLDClosure* _clds;
 175 public:
 176   AllRootsClosures(OopClosure* roots, CLDClosure* clds) :
 177       _roots(roots), _clds(clds) {}
 178 
 179   OopClosure* weak_oops() { return _roots; }
 180   OopClosure* strong_oops() { return _roots; }
 181 
 182   // By returning the same CLDClosure for both weak and strong CLDs we ensure
 183   // that a single walk of the CLDG will invoke the closure on all CLDs i the
 184   // system.
 185   CLDClosure* weak_clds() { return _clds; }
 186   CLDClosure* strong_clds() { return _clds; }
 187 
 188   // We don't want to visit code blobs more than once, so we return NULL for the
 189   // strong case and walk the entire code cache as a separate step.
 190   CodeBlobClosure* strong_codeblobs() { return NULL; }
 191 };
 192 
 193 void G1RootProcessor::process_all_roots(OopClosure* oops,
 194                                         CLDClosure* clds,
 195                                         CodeBlobClosure* blobs) {
 196   AllRootsClosures closures(oops, clds);
 197 
 198   process_java_roots(&closures, NULL, 0);
 199   process_vm_roots(&closures, NULL, 0);
 200 
 201   process_string_table_roots(&closures, NULL, 0);
 202   process_code_cache_roots(blobs, NULL, 0);
 203 
 204   _process_strong_tasks.all_tasks_completed(n_workers());
 205 }
 206 
 207 void G1RootProcessor::process_all_roots_no_string_table(OopClosure* oops,
 208                                                         CLDClosure* clds,
 209                                                         CodeBlobClosure* blobs) {
 210   assert(!ClassUnloading, "Should only be used when class unloading is disabled");
 211   AllRootsClosures closures(oops, clds);
 212 
 213   process_java_roots(&closures, NULL, 0);
 214   process_vm_roots(&closures, NULL, 0);
 215 
 216   process_code_cache_roots(blobs, NULL, 0);
 217 
 218   _process_strong_tasks.all_tasks_completed(n_workers());
 219 }
 220 
 221 void G1RootProcessor::process_java_roots(G1RootClosures* closures,
 222                                          G1GCPhaseTimes* phase_times,
 223                                          uint worker_i) {
 224   // Iterating over the CLDG and the Threads are done early to allow us to
 225   // first process the strong CLDs and nmethods and then, after a barrier,
 226   // let the thread process the weak CLDs and nmethods.
 227   {
 228     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_i);
 229     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
 230       ClassLoaderDataGraph::roots_cld_do(closures->strong_clds(), closures->weak_clds());
 231     }
 232   }
 233 
 234   {
 235     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
 236     bool is_par = n_workers() > 1;
 237     Threads::possibly_parallel_oops_do(is_par,
 238                                        closures->strong_oops(),
 239                                        closures->strong_codeblobs());
 240   }
 241 }
 242 
 243 void G1RootProcessor::process_vm_roots(G1RootClosures* closures,
 244                                        G1GCPhaseTimes* phase_times,
 245                                        uint worker_i) {
 246   OopClosure* strong_roots = closures->strong_oops();
 247   OopClosure* weak_roots = closures->weak_oops();
 248 
 249   {
 250     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_i);
 251     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Universe_oops_do)) {
 252       Universe::oops_do(strong_roots);
 253     }
 254   }
 255 
 256   {
 257     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_i);
 258     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
 259       JNIHandles::oops_do(strong_roots);
 260     }
 261   }
 262 
 263   {
 264     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_i);
 265     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
 266       ObjectSynchronizer::oops_do(strong_roots);
 267     }
 268   }
 269 
 270   {
 271     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::FlatProfilerRoots, worker_i);
 272     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
 273       FlatProfiler::oops_do(strong_roots);
 274     }
 275   }
 276 
 277   {
 278     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_i);
 279     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Management_oops_do)) {
 280       Management::oops_do(strong_roots);
 281     }
 282   }
 283 
 284   {
 285     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_i);
 286     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_jvmti_oops_do)) {
 287       JvmtiExport::oops_do(strong_roots);
 288     }
 289   }
 290 
 291   {
 292     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_i);
 293     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
 294       SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 295     }
 296   }
 297 }
 298 
 299 void G1RootProcessor::process_string_table_roots(G1RootClosures* closures,
 300                                                  G1GCPhaseTimes* phase_times,
 301                                                  uint worker_i) {
 302   assert(closures->weak_oops() != NULL, "Should only be called when all roots are processed");
 303   G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i);
 304   // All threads execute the following. A specific chunk of buckets
 305   // from the StringTable are the individual tasks.
 306   StringTable::possibly_parallel_oops_do(closures->weak_oops());
 307 }
 308 
 309 void G1RootProcessor::process_code_cache_roots(CodeBlobClosure* code_closure,
 310                                                G1GCPhaseTimes* phase_times,
 311                                                uint worker_i) {
 312   if (!_process_strong_tasks.is_task_claimed(G1RP_PS_CodeCache_oops_do)) {
 313     CodeCache::blobs_do(code_closure);
 314   }
 315 }
 316 
 317 uint G1RootProcessor::n_workers() const {
 318   return _srs.n_threads();
 319 }