jdk-24/hotspot/src/share/vm/gc/g1/g1RootProcessor.cpp

/*
 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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#include "precompiled.hpp"

#include "classfile/stringTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "gc/g1/bufferingOopClosure.hpp"
#include "gc/g1/g1CodeBlobClosure.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectorPolicy.hpp"
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1RemSet.inline.hpp"
#include "gc/g1/g1RootProcessor.hpp"
#include "gc/g1/heapRegion.inline.hpp"
#include "memory/allocation.inline.hpp"
#include "runtime/fprofiler.hpp"
#include "runtime/mutex.hpp"
#include "services/management.hpp"

void G1RootProcessor::worker_has_discovered_all_strong_classes() {
  assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");

  uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
  if (new_value == n_workers()) {
    // This thread is last. Notify the others.
    MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
    _lock.notify_all();
  }
}

void G1RootProcessor::wait_until_all_strong_classes_discovered() {
  assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");

  if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
    MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
    while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
      _lock.wait(Mutex::_no_safepoint_check_flag, 0, false);
    }
  }
}

G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :
    _g1h(g1h),
    _process_strong_tasks(G1RP_PS_NumElements),
    _srs(n_workers),
    _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false, Monitor::_safepoint_check_never),
    _n_workers_discovered_strong_classes(0) {}

void G1RootProcessor::evacuate_roots(OopClosure* scan_non_heap_roots,
                                     OopClosure* scan_non_heap_weak_roots,
                                     CLDClosure* scan_strong_clds,
                                     CLDClosure* scan_weak_clds,
                                     bool trace_metadata,
                                     uint worker_i) {
  // First scan the shared roots.
  double ext_roots_start = os::elapsedTime();
  G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();

  BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
  BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);

  OopClosure* const weak_roots = &buf_scan_non_heap_weak_roots;
  OopClosure* const strong_roots = &buf_scan_non_heap_roots;

  // CodeBlobClosures are not interoperable with BufferingOopClosures
  G1CodeBlobClosure root_code_blobs(scan_non_heap_roots);

  process_java_roots(strong_roots,
                     trace_metadata ? scan_strong_clds : NULL,
                     scan_strong_clds,
                     trace_metadata ? NULL : scan_weak_clds,
                     &root_code_blobs,
                     phase_times,
                     worker_i);

  // This is the point where this worker thread will not find more strong CLDs/nmethods.
  // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
  if (trace_metadata) {
    worker_has_discovered_all_strong_classes();
  }

  process_vm_roots(strong_roots, weak_roots, phase_times, worker_i);

  {
    // Now the CM ref_processor roots.
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_refProcessor_oops_do)) {
      // We need to treat the discovered reference lists of the
      // concurrent mark ref processor as roots and keep entries
      // (which are added by the marking threads) on them live
      // until they can be processed at the end of marking.
      _g1h->ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
    }
  }

  if (trace_metadata) {
    {
      G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongCLD, worker_i);
      // Barrier to make sure all workers passed
      // the strong CLD and strong nmethods phases.
      wait_until_all_strong_classes_discovered();
    }

    // Now take the complement of the strong CLDs.
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WeakCLDRoots, worker_i);
    ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
  } else {
    phase_times->record_time_secs(G1GCPhaseTimes::WaitForStrongCLD, worker_i, 0.0);
    phase_times->record_time_secs(G1GCPhaseTimes::WeakCLDRoots, worker_i, 0.0);
  }

  // Finish up any enqueued closure apps (attributed as object copy time).
  buf_scan_non_heap_roots.done();
  buf_scan_non_heap_weak_roots.done();

  double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
      + buf_scan_non_heap_weak_roots.closure_app_seconds();

  phase_times->record_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, obj_copy_time_sec);

  double ext_root_time_sec = os::elapsedTime() - ext_roots_start - obj_copy_time_sec;

  phase_times->record_time_secs(G1GCPhaseTimes::ExtRootScan, worker_i, ext_root_time_sec);

  // During conc marking we have to filter the per-thread SATB buffers
  // to make sure we remove any oops into the CSet (which will show up
  // as implicitly live).
  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SATBFiltering, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_filter_satb_buffers) && _g1h->collector_state()->mark_in_progress()) {
      JavaThread::satb_mark_queue_set().filter_thread_buffers();
    }
  }

  _process_strong_tasks.all_tasks_completed(n_workers());
}

void G1RootProcessor::process_strong_roots(OopClosure* oops,
                                           CLDClosure* clds,
                                           CodeBlobClosure* blobs) {

  process_java_roots(oops, clds, clds, NULL, blobs, NULL, 0);
  process_vm_roots(oops, NULL, NULL, 0);

  _process_strong_tasks.all_tasks_completed(n_workers());
}

void G1RootProcessor::process_all_roots(OopClosure* oops,
                                        CLDClosure* clds,
                                        CodeBlobClosure* blobs) {

  process_java_roots(oops, NULL, clds, clds, NULL, NULL, 0);
  process_vm_roots(oops, oops, NULL, 0);

  if (!_process_strong_tasks.is_task_claimed(G1RP_PS_CodeCache_oops_do)) {
    CodeCache::blobs_do(blobs);
  }

  _process_strong_tasks.all_tasks_completed(n_workers());
}

void G1RootProcessor::process_java_roots(OopClosure* strong_roots,
                                         CLDClosure* thread_stack_clds,
                                         CLDClosure* strong_clds,
                                         CLDClosure* weak_clds,
                                         CodeBlobClosure* strong_code,
                                         G1GCPhaseTimes* phase_times,
                                         uint worker_i) {
  assert(thread_stack_clds == NULL || weak_clds == NULL, "There is overlap between those, only one may be set");
  // Iterating over the CLDG and the Threads are done early to allow us to
  // first process the strong CLDs and nmethods and then, after a barrier,
  // let the thread process the weak CLDs and nmethods.
  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
      ClassLoaderDataGraph::roots_cld_do(strong_clds, weak_clds);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
    bool is_par = n_workers() > 1;
    Threads::possibly_parallel_oops_do(is_par, strong_roots, thread_stack_clds, strong_code);
  }
}

void G1RootProcessor::process_vm_roots(OopClosure* strong_roots,
                                       OopClosure* weak_roots,
                                       G1GCPhaseTimes* phase_times,
                                       uint worker_i) {
  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Universe_oops_do)) {
      Universe::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
      JNIHandles::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
      ObjectSynchronizer::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::FlatProfilerRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
      FlatProfiler::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_Management_oops_do)) {
      Management::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_jvmti_oops_do)) {
      JvmtiExport::oops_do(strong_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_i);
    if (!_process_strong_tasks.is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
      SystemDictionary::roots_oops_do(strong_roots, weak_roots);
    }
  }

  {
    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i);
    // All threads execute the following. A specific chunk of buckets
    // from the StringTable are the individual tasks.
    if (weak_roots != NULL) {
      StringTable::possibly_parallel_oops_do(weak_roots);
    }
  }
}

uint G1RootProcessor::n_workers() const {
  return _srs.n_threads();
}