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/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "gc_implementation/g1/bufferingOopClosure.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/g1GCPhaseTimes.hpp"
#include "gc_implementation/g1/g1RemSet.inline.hpp"
#include "gc_implementation/g1/g1RootProcessor.hpp"
#include "memory/allocation.inline.hpp"
#include "runtime/fprofiler.hpp"
#include "runtime/mutex.hpp"
#include "services/management.hpp"

class G1CodeBlobClosure : public CodeBlobClosure {
  class HeapRegionGatheringOopClosure : public OopClosure {
    G1CollectedHeap* _g1h;
    OopClosure* _work;
    nmethod* _nm;

    template <typename T>
    void do_oop_work(T* p) {
      _work->do_oop(p);
      T oop_or_narrowoop = oopDesc::load_heap_oop(p);
      if (!oopDesc::is_null(oop_or_narrowoop)) {
        oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
        HeapRegion* hr = _g1h->heap_region_containing_raw(o);
        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");
        hr->add_strong_code_root(_nm);
      }
    }

  public:
    HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}

    void do_oop(oop* o) {
      do_oop_work(o);
    }

    void do_oop(narrowOop* o) {
      do_oop_work(o);
    }

    void set_nm(nmethod* nm) {
      _nm = nm;
    }
  };

  HeapRegionGatheringOopClosure _oc;
public:
  G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}

  void do_code_blob(CodeBlob* cb) {
    nmethod* nm = cb->as_nmethod_or_null();
    if (nm != NULL) {
      if (!nm->test_set_oops_do_mark()) {
        _oc.set_nm(nm);
        nm->oops_do(&_oc);
        nm->fix_oop_relocations();
      }
    }
  }
};


void G1RootProcessor::worker_has_discovered_all_strong_classes() {
  uint n_workers = _g1h->n_par_threads();
  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() {
  uint n_workers = _g1h->n_par_threads();
  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) :
    _g1h(g1h),
    _process_strong_tasks(new SubTasksDone(G1RP_PS_NumElements)),
    _srs(g1h),
    _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false),
    _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();

  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);

  // 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);

  // Now the CM ref_processor roots.
  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) {
    // 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.
    ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
  }

  // 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();

  G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
  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->mark_in_progress()) {
      JavaThread::satb_mark_queue_set().filter_thread_buffers();
    }
  }

  _process_strong_tasks->all_tasks_completed();
}

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

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

  _process_strong_tasks->all_tasks_completed();
}

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

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

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

  _process_strong_tasks->all_tasks_completed();
}

void G1RootProcessor::process_java_roots(OopClosure* strong_roots,
                                         CLDClosure* thread_stack_clds,
                                         CLDClosure* strong_clds,
                                         CLDClosure* weak_clds,
                                         CodeBlobClosure* strong_code) {
  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.

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
    ClassLoaderDataGraph::roots_cld_do(strong_clds, weak_clds);
  }

  Threads::possibly_parallel_oops_do(strong_roots, thread_stack_clds, strong_code);
}

void G1RootProcessor::process_vm_roots(OopClosure* strong_roots,
                                       OopClosure* weak_roots) {

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Universe_oops_do)) {
    Universe::oops_do(strong_roots);
  }

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_JNIHandles_oops_do)) {
    JNIHandles::oops_do(strong_roots);
  }

  if (!_process_strong_tasks-> is_task_claimed(G1RP_PS_ObjectSynchronizer_oops_do)) {
    ObjectSynchronizer::oops_do(strong_roots);
  }

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_FlatProfiler_oops_do)) {
    FlatProfiler::oops_do(strong_roots);
  }

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_Management_oops_do)) {
    Management::oops_do(strong_roots);
  }

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_jvmti_oops_do)) {
    JvmtiExport::oops_do(strong_roots);
  }

  if (!_process_strong_tasks->is_task_claimed(G1RP_PS_SystemDictionary_oops_do)) {
    SystemDictionary::roots_oops_do(strong_roots, weak_roots);
  }

  // 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);
  }
}

void G1RootProcessor::scan_remembered_sets(G1ParPushHeapRSClosure* scan_rs,
                                           OopClosure* scan_non_heap_weak_roots,
                                           uint worker_i) {
  // Now scan the complement of the collection set.
  G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);

  _g1h->g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
}

void G1RootProcessor::set_num_workers(int active_workers) {
  _process_strong_tasks->set_n_threads(active_workers);
}