1 /*
   2  * Copyright (c) 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 
  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/g1CollectedHeap.inline.hpp"
  32 #include "gc/g1/g1CollectorPolicy.hpp"
  33 #include "gc/g1/g1GCPhaseTimes.hpp"
  34 #include "gc/g1/g1RemSet.inline.hpp"
  35 #include "gc/g1/g1RootProcessor.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "runtime/fprofiler.hpp"
  38 #include "runtime/mutex.hpp"
  39 #include "services/management.hpp"
  40 
  41 class G1CodeBlobClosure : public CodeBlobClosure {
  42   class HeapRegionGatheringOopClosure : public OopClosure {
  43     G1CollectedHeap* _g1h;
  44     OopClosure* _work;
  45     nmethod* _nm;
  46 
  47     template <typename T>
  48     void do_oop_work(T* p) {
  49       _work->do_oop(p);
  50       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
  51       if (!oopDesc::is_null(oop_or_narrowoop)) {
  52         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
  53         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
  54         assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
  55         hr->add_strong_code_root(_nm);
  56       }
  57     }
  58 
  59   public:
  60     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
  61 
  62     void do_oop(oop* o) {
  63       do_oop_work(o);
  64     }
  65 
  66     void do_oop(narrowOop* o) {
  67       do_oop_work(o);
  68     }
  69 
  70     void set_nm(nmethod* nm) {
  71       _nm = nm;
  72     }
  73   };
  74 
  75   HeapRegionGatheringOopClosure _oc;
  76 public:
  77   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
  78 
  79   void do_code_blob(CodeBlob* cb) {
  80     nmethod* nm = cb->as_nmethod_or_null();
  81     if (nm != NULL) {
  82       if (!nm->test_set_oops_do_mark()) {
  83         _oc.set_nm(nm);
  84         nm->oops_do(&_oc);
  85         nm->fix_oop_relocations();
  86       }
  87     }
  88   }
  89 };
  90 
  91 
  92 void G1RootProcessor::worker_has_discovered_all_strong_classes() {
  93   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
  94 
  95   uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
  96   if (new_value == n_workers()) {
  97     // This thread is last. Notify the others.
  98     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
  99     _lock.notify_all();
 100   }
 101 }
 102 
 103 void G1RootProcessor::wait_until_all_strong_classes_discovered() {
 104   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
 105 
 106   if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
 107     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
 108     while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
 109       _lock.wait(Mutex::_no_safepoint_check_flag, 0, false);
 110     }
 111   }
 112 }
 113 
 114 G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :
 115     _g1h(g1h),
 116     _process_strong_tasks(new SubTasksDone(G1RP_PS_NumElements)),
 117     _srs(n_workers),
 118     _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false, Monitor::_safepoint_check_never),
 119     _n_workers_discovered_strong_classes(0) {}
 120 
 121 void G1RootProcessor::evacuate_roots(OopClosure* scan_non_heap_roots,
 122                                      OopClosure* scan_non_heap_weak_roots,
 123                                      CLDClosure* scan_strong_clds,
 124                                      CLDClosure* scan_weak_clds,
 125                                      bool trace_metadata,
 126                                      uint worker_i) {
 127   // First scan the shared roots.
 128   double ext_roots_start = os::elapsedTime();
 129   G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
 130 
 131   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
 132   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
 133 
 134   OopClosure* const weak_roots = &buf_scan_non_heap_weak_roots;
 135   OopClosure* const strong_roots = &buf_scan_non_heap_roots;
 136 
 137   // CodeBlobClosures are not interoperable with BufferingOopClosures
 138   G1CodeBlobClosure root_code_blobs(scan_non_heap_roots);
 139 
 140   process_java_roots(strong_roots,
 141                      trace_metadata ? scan_strong_clds : NULL,
 142                      scan_strong_clds,
 143                      trace_metadata ? NULL : scan_weak_clds,
 144                      &root_code_blobs,
 145                      phase_times,
 146                      worker_i);
 147 
 148   // This is the point where this worker thread will not find more strong CLDs/nmethods.
 149   // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
 150   if (trace_metadata) {
 151     worker_has_discovered_all_strong_classes();
 152   }
 153 
 154   process_vm_roots(strong_roots, weak_roots, phase_times, worker_i);
 155 
 156   {
 157     // Now the CM ref_processor roots.
 158     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_i);
 159     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_refProcessor_oops_do)) {
 160       // We need to treat the discovered reference lists of the
 161       // concurrent mark ref processor as roots and keep entries
 162       // (which are added by the marking threads) on them live
 163       // until they can be processed at the end of marking.
 164       _g1h->ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
 165     }
 166   }
 167 
 168   if (trace_metadata) {
 169     {
 170       G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongCLD, worker_i);
 171       // Barrier to make sure all workers passed
 172       // the strong CLD and strong nmethods phases.
 173       wait_until_all_strong_classes_discovered();
 174     }
 175 
 176     // Now take the complement of the strong CLDs.
 177     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WeakCLDRoots, worker_i);
 178     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
 179   } else {
 180     phase_times->record_time_secs(G1GCPhaseTimes::WaitForStrongCLD, worker_i, 0.0);
 181     phase_times->record_time_secs(G1GCPhaseTimes::WeakCLDRoots, worker_i, 0.0);
 182   }
 183 
 184   // Finish up any enqueued closure apps (attributed as object copy time).
 185   buf_scan_non_heap_roots.done();
 186   buf_scan_non_heap_weak_roots.done();
 187 
 188   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
 189       + buf_scan_non_heap_weak_roots.closure_app_seconds();
 190 
 191   phase_times->record_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, obj_copy_time_sec);
 192 
 193   double ext_root_time_sec = os::elapsedTime() - ext_roots_start - obj_copy_time_sec;
 194 
 195   phase_times->record_time_secs(G1GCPhaseTimes::ExtRootScan, worker_i, ext_root_time_sec);
 196 
 197   // During conc marking we have to filter the per-thread SATB buffers
 198   // to make sure we remove any oops into the CSet (which will show up
 199   // as implicitly live).
 200   {
 201     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SATBFiltering, worker_i);
 202     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_filter_satb_buffers) && _g1h->mark_in_progress()) {
 203       JavaThread::satb_mark_queue_set().filter_thread_buffers();
 204     }
 205   }
 206 
 207   _process_strong_tasks->all_tasks_completed(n_workers());
 208 }
 209 
 210 void G1RootProcessor::process_strong_roots(OopClosure* oops,
 211                                            CLDClosure* clds,
 212                                            CodeBlobClosure* blobs) {
 213 
 214   process_java_roots(oops, clds, clds, NULL, blobs, NULL, 0);
 215   process_vm_roots(oops, NULL, NULL, 0);
 216 
 217   _process_strong_tasks->all_tasks_completed(n_workers());
 218 }
 219 
 220 void G1RootProcessor::process_all_roots(OopClosure* oops,
 221                                         CLDClosure* clds,
 222                                         CodeBlobClosure* blobs) {
 223 
 224   process_java_roots(oops, NULL, clds, clds, NULL, NULL, 0);
 225   process_vm_roots(oops, oops, NULL, 0);
 226 
 227   if (!_process_strong_tasks->is_task_claimed(G1RP_PS_CodeCache_oops_do)) {
 228     CodeCache::blobs_do(blobs);
 229   }
 230 
 231   _process_strong_tasks->all_tasks_completed(n_workers());
 232 }
 233 
 234 void G1RootProcessor::process_java_roots(OopClosure* strong_roots,
 235                                          CLDClosure* thread_stack_clds,
 236                                          CLDClosure* strong_clds,
 237                                          CLDClosure* weak_clds,
 238                                          CodeBlobClosure* strong_code,
 239                                          G1GCPhaseTimes* phase_times,
 240                                          uint worker_i) {
 241   assert(thread_stack_clds == NULL || weak_clds == NULL, "There is overlap between those, only one may be set");
 242   // Iterating over the CLDG and the Threads are done early to allow us to
 243   // first process the strong CLDs and nmethods and then, after a barrier,
 244   // let the thread process the weak CLDs and nmethods.
 245   {
 246     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_i);
 247     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
 248       ClassLoaderDataGraph::roots_cld_do(strong_clds, weak_clds);
 249     }
 250   }
 251 
 252   {
 253     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
 254     bool is_par = n_workers() > 1;
 255     Threads::possibly_parallel_oops_do(is_par, strong_roots, thread_stack_clds, strong_code);
 256   }
 257 }
 258 
 259 void G1RootProcessor::process_vm_roots(OopClosure* strong_roots,
 260                                        OopClosure* weak_roots,
 261                                        G1GCPhaseTimes* phase_times,
 262                                        uint worker_i) {
 263   {
 264     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_i);
 265     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Universe_oops_do)) {
 266       Universe::oops_do(strong_roots);
 267     }
 268   }
 269 
 270   {
 271     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_i);
 272     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
 273       JNIHandles::oops_do(strong_roots);
 274     }
 275   }
 276 
 277   {
 278     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_i);
 279     if (!_process_strong_tasks-> is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
 280       ObjectSynchronizer::oops_do(strong_roots);
 281     }
 282   }
 283 
 284   {
 285     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::FlatProfilerRoots, worker_i);
 286     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
 287       FlatProfiler::oops_do(strong_roots);
 288     }
 289   }
 290 
 291   {
 292     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_i);
 293     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Management_oops_do)) {
 294       Management::oops_do(strong_roots);
 295     }
 296   }
 297 
 298   {
 299     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_i);
 300     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_jvmti_oops_do)) {
 301       JvmtiExport::oops_do(strong_roots);
 302     }
 303   }
 304 
 305   {
 306     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_i);
 307     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
 308       SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 309     }
 310   }
 311 
 312   {
 313     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i);
 314     // All threads execute the following. A specific chunk of buckets
 315     // from the StringTable are the individual tasks.
 316     if (weak_roots != NULL) {
 317       StringTable::possibly_parallel_oops_do(weak_roots);
 318     }
 319   }
 320 }
 321 
 322 void G1RootProcessor::scan_remembered_sets(G1ParPushHeapRSClosure* scan_rs,
 323                                            OopClosure* scan_non_heap_weak_roots,
 324                                            uint worker_i) {
 325   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
 326 
 327   _g1h->g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
 328 }
 329 
 330 uint G1RootProcessor::n_workers() const {
 331   return _srs.n_threads();
 332 }