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_implementation/g1/bufferingOopClosure.hpp"
  31 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  32 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  33 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  34 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  35 #include "gc_implementation/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   uint n_workers = _g1h->n_par_threads();
  94   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
  95 
  96   uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
  97   if (new_value == n_workers) {
  98     // This thread is last. Notify the others.
  99     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
 100     _lock.notify_all();
 101   }
 102 }
 103 
 104 void G1RootProcessor::wait_until_all_strong_classes_discovered() {
 105   uint n_workers = _g1h->n_par_threads();
 106   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
 107 
 108   if ((uint)_n_workers_discovered_strong_classes != n_workers) {
 109     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
 110     while ((uint)_n_workers_discovered_strong_classes != n_workers) {
 111       _lock.wait(Mutex::_no_safepoint_check_flag, 0, false);
 112     }
 113   }
 114 }
 115 
 116 G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h) :
 117     _g1h(g1h),
 118     _process_strong_tasks(new SubTasksDone(G1RP_PS_NumElements)),
 119     _srs(),
 120     _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false, Monitor::_safepoint_check_never),
 121     _n_workers_discovered_strong_classes(0) {}
 122 
 123 void G1RootProcessor::evacuate_roots(OopClosure* scan_non_heap_roots,
 124                                      OopClosure* scan_non_heap_weak_roots,
 125                                      CLDClosure* scan_strong_clds,
 126                                      CLDClosure* scan_weak_clds,
 127                                      bool trace_metadata,
 128                                      uint worker_i) {
 129   // First scan the shared roots.
 130   double ext_roots_start = os::elapsedTime();
 131   G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
 132 
 133   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
 134   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
 135 
 136   OopClosure* const weak_roots = &buf_scan_non_heap_weak_roots;
 137   OopClosure* const strong_roots = &buf_scan_non_heap_roots;
 138 
 139   // CodeBlobClosures are not interoperable with BufferingOopClosures
 140   G1CodeBlobClosure root_code_blobs(scan_non_heap_roots);
 141 
 142   process_java_roots(strong_roots,
 143                      trace_metadata ? scan_strong_clds : NULL,
 144                      scan_strong_clds,
 145                      trace_metadata ? NULL : scan_weak_clds,
 146                      &root_code_blobs,
 147                      phase_times,
 148                      worker_i);
 149 
 150   // This is the point where this worker thread will not find more strong CLDs/nmethods.
 151   // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
 152   if (trace_metadata) {
 153     worker_has_discovered_all_strong_classes();
 154   }
 155 
 156   process_vm_roots(strong_roots, weak_roots, phase_times, worker_i);
 157 
 158   {
 159     // Now the CM ref_processor roots.
 160     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_i);
 161     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_refProcessor_oops_do)) {
 162       // We need to treat the discovered reference lists of the
 163       // concurrent mark ref processor as roots and keep entries
 164       // (which are added by the marking threads) on them live
 165       // until they can be processed at the end of marking.
 166       _g1h->ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
 167     }
 168   }
 169 
 170   if (trace_metadata) {
 171     {
 172       G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongCLD, worker_i);
 173       // Barrier to make sure all workers passed
 174       // the strong CLD and strong nmethods phases.
 175       wait_until_all_strong_classes_discovered();
 176     }
 177 
 178     // Now take the complement of the strong CLDs.
 179     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WeakCLDRoots, worker_i);
 180     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
 181   } else {
 182     phase_times->record_time_secs(G1GCPhaseTimes::WaitForStrongCLD, worker_i, 0.0);
 183     phase_times->record_time_secs(G1GCPhaseTimes::WeakCLDRoots, worker_i, 0.0);
 184   }
 185 
 186   // Finish up any enqueued closure apps (attributed as object copy time).
 187   buf_scan_non_heap_roots.done();
 188   buf_scan_non_heap_weak_roots.done();
 189 
 190   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
 191       + buf_scan_non_heap_weak_roots.closure_app_seconds();
 192 
 193   phase_times->record_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, obj_copy_time_sec);
 194 
 195   double ext_root_time_sec = os::elapsedTime() - ext_roots_start - obj_copy_time_sec;
 196 
 197   phase_times->record_time_secs(G1GCPhaseTimes::ExtRootScan, worker_i, ext_root_time_sec);
 198 
 199   // During conc marking we have to filter the per-thread SATB buffers
 200   // to make sure we remove any oops into the CSet (which will show up
 201   // as implicitly live).
 202   {
 203     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SATBFiltering, worker_i);
 204     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_filter_satb_buffers) && _g1h->mark_in_progress()) {
 205       JavaThread::satb_mark_queue_set().filter_thread_buffers();
 206     }
 207   }
 208 
 209   _process_strong_tasks->all_tasks_completed();
 210 }
 211 
 212 void G1RootProcessor::process_strong_roots(OopClosure* oops,
 213                                            CLDClosure* clds,
 214                                            CodeBlobClosure* blobs) {
 215 
 216   process_java_roots(oops, clds, clds, NULL, blobs, NULL, 0);
 217   process_vm_roots(oops, NULL, NULL, 0);
 218 
 219   _process_strong_tasks->all_tasks_completed();
 220 }
 221 
 222 void G1RootProcessor::process_all_roots(OopClosure* oops,
 223                                         CLDClosure* clds,
 224                                         CodeBlobClosure* blobs) {
 225 
 226   process_java_roots(oops, NULL, clds, clds, NULL, NULL, 0);
 227   process_vm_roots(oops, oops, NULL, 0);
 228 
 229   if (!_process_strong_tasks->is_task_claimed(G1RP_PS_CodeCache_oops_do)) {
 230     CodeCache::blobs_do(blobs);
 231   }
 232 
 233   _process_strong_tasks->all_tasks_completed();
 234 }
 235 
 236 void G1RootProcessor::process_java_roots(OopClosure* strong_roots,
 237                                          CLDClosure* thread_stack_clds,
 238                                          CLDClosure* strong_clds,
 239                                          CLDClosure* weak_clds,
 240                                          CodeBlobClosure* strong_code,
 241                                          G1GCPhaseTimes* phase_times,
 242                                          uint worker_i) {
 243   assert(thread_stack_clds == NULL || weak_clds == NULL, "There is overlap between those, only one may be set");
 244   // Iterating over the CLDG and the Threads are done early to allow us to
 245   // first process the strong CLDs and nmethods and then, after a barrier,
 246   // let the thread process the weak CLDs and nmethods.
 247   {
 248     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_i);
 249     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
 250       ClassLoaderDataGraph::roots_cld_do(strong_clds, weak_clds);
 251     }
 252   }
 253 
 254   {
 255     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
 256     bool is_par = _g1h->n_par_threads() > 1;
 257     Threads::possibly_parallel_oops_do(is_par, strong_roots, thread_stack_clds, strong_code);
 258   }
 259 }
 260 
 261 void G1RootProcessor::process_vm_roots(OopClosure* strong_roots,
 262                                        OopClosure* weak_roots,
 263                                        G1GCPhaseTimes* phase_times,
 264                                        uint worker_i) {
 265   {
 266     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_i);
 267     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Universe_oops_do)) {
 268       Universe::oops_do(strong_roots);
 269     }
 270   }
 271 
 272   {
 273     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_i);
 274     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
 275       JNIHandles::oops_do(strong_roots);
 276     }
 277   }
 278 
 279   {
 280     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_i);
 281     if (!_process_strong_tasks-> is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
 282       ObjectSynchronizer::oops_do(strong_roots);
 283     }
 284   }
 285 
 286   {
 287     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::FlatProfilerRoots, worker_i);
 288     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
 289       FlatProfiler::oops_do(strong_roots);
 290     }
 291   }
 292 
 293   {
 294     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_i);
 295     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Management_oops_do)) {
 296       Management::oops_do(strong_roots);
 297     }
 298   }
 299 
 300   {
 301     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_i);
 302     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_jvmti_oops_do)) {
 303       JvmtiExport::oops_do(strong_roots);
 304     }
 305   }
 306 
 307   {
 308     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_i);
 309     if (!_process_strong_tasks->is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
 310       SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 311     }
 312   }
 313 
 314   {
 315     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i);
 316     // All threads execute the following. A specific chunk of buckets
 317     // from the StringTable are the individual tasks.
 318     if (weak_roots != NULL) {
 319       StringTable::possibly_parallel_oops_do(weak_roots);
 320     }
 321   }
 322 }
 323 
 324 void G1RootProcessor::scan_remembered_sets(G1ParPushHeapRSClosure* scan_rs,
 325                                            OopClosure* scan_non_heap_weak_roots,
 326                                            uint worker_i) {
 327   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
 328 
 329   _g1h->g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
 330 }
 331 
 332 void G1RootProcessor::set_num_workers(uint active_workers) {
 333   _process_strong_tasks->set_n_threads(active_workers);
 334 }