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 
  87   {
  88     // Now the CM ref_processor roots.
  89     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_i);
  90     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_refProcessor_oops_do)) {
  91       // We need to treat the discovered reference lists of the
  92       // concurrent mark ref processor as roots and keep entries
  93       // (which are added by the marking threads) on them live
  94       // until they can be processed at the end of marking.
  95       _g1h->ref_processor_cm()->weak_oops_do(closures->strong_oops());
  96     }
  97   }
  98 
  99   if (closures->trace_metadata()) {
 100     {
 101       G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongCLD, worker_i);
 102       // Barrier to make sure all workers passed
 103       // the strong CLD and strong nmethods phases.
 104       wait_until_all_strong_classes_discovered();
 105     }
 106 
 107     // Now take the complement of the strong CLDs.
 108     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WeakCLDRoots, worker_i);
 109     assert(closures->second_pass_weak_clds() != NULL, "Should be non-null if we are tracing metadata.");
 110     ClassLoaderDataGraph::roots_cld_do(NULL, closures->second_pass_weak_clds());
 111   } else {
 112     phase_times->record_time_secs(G1GCPhaseTimes::WaitForStrongCLD, worker_i, 0.0);
 113     phase_times->record_time_secs(G1GCPhaseTimes::WeakCLDRoots, worker_i, 0.0);
 114     assert(closures->second_pass_weak_clds() == NULL, "Should be null if not tracing metadata.");
 115   }
 116 
 117   // Finish up any enqueued closure apps (attributed as object copy time).
 118   closures->flush();
 119 
 120   double obj_copy_time_sec = closures->closure_app_seconds();
 121 
 122   phase_times->record_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, obj_copy_time_sec);
 123 
 124   double ext_root_time_sec = os::elapsedTime() - ext_roots_start - obj_copy_time_sec;
 125 
 126   phase_times->record_time_secs(G1GCPhaseTimes::ExtRootScan, worker_i, ext_root_time_sec);
 127 
 128   // During conc marking we have to filter the per-thread SATB buffers
 129   // to make sure we remove any oops into the CSet (which will show up
 130   // as implicitly live).
 131   {
 132     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SATBFiltering, worker_i);
 133     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_filter_satb_buffers) && _g1h->collector_state()->mark_in_progress()) {
 134       JavaThread::satb_mark_queue_set().filter_thread_buffers();
 135     }
 136   }
 137 
 138   _process_strong_tasks.all_tasks_completed(n_workers());
 139 }
 140 
 141 // Adaptor to pass the closures to the strong roots in the VM.
 142 class StrongRootsClosures : public G1RootClosures {
 143   OopClosure* _roots;
 144   CLDClosure* _clds;
 145   CodeBlobClosure* _blobs;
 146 public:
 147   StrongRootsClosures(OopClosure* roots, CLDClosure* clds, CodeBlobClosure* blobs) :
 148       _roots(roots), _clds(clds), _blobs(blobs) {}
 149 
 150   OopClosure* weak_oops()   { return NULL; }
 151   OopClosure* strong_oops() { return _roots; }
 152 
 153   CLDClosure* weak_clds()        { return NULL; }
 154   CLDClosure* strong_clds()      { return _clds; }
 155 
 156   CodeBlobClosure* strong_codeblobs() { return _blobs; }
 157 };
 158 
 159 void G1RootProcessor::process_strong_roots(OopClosure* oops,
 160                                            CLDClosure* clds,
 161                                            CodeBlobClosure* blobs) {
 162   StrongRootsClosures closures(oops, clds, blobs);
 163 
 164   process_java_roots(&closures, NULL, 0);
 165   process_vm_roots(&closures, NULL, 0);
 166 
 167   _process_strong_tasks.all_tasks_completed(n_workers());
 168 }
 169 
 170 // Adaptor to pass the closures to all the roots in the VM.
 171 class AllRootsClosures : public G1RootClosures {
 172   OopClosure* _roots;
 173   CLDClosure* _clds;
 174 public:
 175   AllRootsClosures(OopClosure* roots, CLDClosure* clds) :
 176       _roots(roots), _clds(clds) {}
 177 
 178   OopClosure* weak_oops() { return _roots; }
 179   OopClosure* strong_oops() { return _roots; }
 180 
 181   // By returning the same CLDClosure for both weak and strong CLDs we ensure
 182   // that a single walk of the CLDG will invoke the closure on all CLDs i the
 183   // system.
 184   CLDClosure* weak_clds() { return _clds; }
 185   CLDClosure* strong_clds() { return _clds; }
 186 
 187   // We don't want to visit code blobs more than once, so we return NULL for the
 188   // strong case and walk the entire code cache as a separate step.
 189   CodeBlobClosure* strong_codeblobs() { return NULL; }
 190 };
 191 
 192 void G1RootProcessor::process_all_roots(OopClosure* oops,
 193                                         CLDClosure* clds,
 194                                         CodeBlobClosure* blobs) {
 195   AllRootsClosures closures(oops, clds);
 196 
 197   process_java_roots(&closures, NULL, 0);
 198   process_vm_roots(&closures, NULL, 0);
 199 
 200   if (!_process_strong_tasks.is_task_claimed(G1RP_PS_CodeCache_oops_do)) {
 201     CodeCache::blobs_do(blobs);
 202   }
 203 
 204   _process_strong_tasks.all_tasks_completed(n_workers());
 205 }
 206 
 207 void G1RootProcessor::process_java_roots(G1RootClosures* closures,
 208                                          G1GCPhaseTimes* phase_times,
 209                                          uint worker_i) {
 210   // Iterating over the CLDG and the Threads are done early to allow us to
 211   // first process the strong CLDs and nmethods and then, after a barrier,
 212   // let the thread process the weak CLDs and nmethods.
 213   {
 214     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_i);
 215     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
 216       ClassLoaderDataGraph::roots_cld_do(closures->strong_clds(), closures->weak_clds());
 217     }
 218   }
 219 
 220   {
 221     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
 222     bool is_par = n_workers() > 1;
 223     Threads::possibly_parallel_oops_do(is_par,
 224                                        closures->strong_oops(),
 225                                        closures->strong_codeblobs());
 226   }
 227 }
 228 
 229 void G1RootProcessor::process_vm_roots(G1RootClosures* closures,
 230                                        G1GCPhaseTimes* phase_times,
 231                                        uint worker_i) {
 232   OopClosure* strong_roots = closures->strong_oops();
 233   OopClosure* weak_roots = closures->weak_oops();
 234 
 235   {
 236     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_i);
 237     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Universe_oops_do)) {
 238       Universe::oops_do(strong_roots);
 239     }
 240   }
 241 
 242   {
 243     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_i);
 244     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
 245       JNIHandles::oops_do(strong_roots);
 246     }
 247   }
 248 
 249   {
 250     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_i);
 251     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
 252       ObjectSynchronizer::oops_do(strong_roots);
 253     }
 254   }
 255 
 256   {
 257     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::FlatProfilerRoots, worker_i);
 258     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
 259       FlatProfiler::oops_do(strong_roots);
 260     }
 261   }
 262 
 263   {
 264     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_i);
 265     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Management_oops_do)) {
 266       Management::oops_do(strong_roots);
 267     }
 268   }
 269 
 270   {
 271     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_i);
 272     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_jvmti_oops_do)) {
 273       JvmtiExport::oops_do(strong_roots);
 274     }
 275   }
 276 
 277   {
 278     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_i);
 279     if (!_process_strong_tasks.is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
 280       SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 281     }
 282   }
 283 
 284   {
 285     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i);
 286     // All threads execute the following. A specific chunk of buckets
 287     // from the StringTable are the individual tasks.
 288     if (weak_roots != NULL) {
 289       StringTable::possibly_parallel_oops_do(weak_roots);
 290     }
 291   }
 292 }
 293 
 294 uint G1RootProcessor::n_workers() const {
 295   return _srs.n_threads();
 296 }