changeset 51476:6c0ac4b4d761

8206467: Refactor G1ParallelCleaningTask into shared Summary: Refactored and moved G1ParllelCleaningTask to be shared among GCs Reviewed-by: rkennke, kbarrett
author zgu
date Tue, 21 Aug 2018 20:29:57 -0400
parents 492b366f8e57
children e77d7687c831
files src/hotspot/share/gc/g1/g1CollectedHeap.cpp src/hotspot/share/gc/shared/parallelCleaning.cpp src/hotspot/share/gc/shared/parallelCleaning.hpp
diffstat 3 files changed, 517 insertions(+), 325 deletions(-) [+]
line wrap: on
line diff
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Tue Aug 21 13:17:29 2018 -0700
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Tue Aug 21 20:29:57 2018 -0400
@@ -70,6 +70,7 @@
 #include "gc/shared/generationSpec.hpp"
 #include "gc/shared/isGCActiveMark.hpp"
 #include "gc/shared/oopStorageParState.hpp"
+#include "gc/shared/parallelCleaning.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
 #include "gc/shared/suspendibleThreadSet.hpp"
 #include "gc/shared/referenceProcessor.inline.hpp"
@@ -3254,334 +3255,12 @@
                undo_waste * HeapWordSize / K);
 }
 
-class G1StringCleaningTask : public AbstractGangTask {
-private:
-  BoolObjectClosure* _is_alive;
-  G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
-  OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
-
-  int _initial_string_table_size;
-
-  bool  _process_strings;
-  int _strings_processed;
-  int _strings_removed;
-
-  bool _process_string_dedup;
-
-public:
-  G1StringCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_string_dedup) :
-    AbstractGangTask("String Unlinking"),
-    _is_alive(is_alive),
-    _dedup_closure(is_alive, NULL, false),
-    _par_state_string(StringTable::weak_storage()),
-    _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
-    _process_string_dedup(process_string_dedup) {
-
-    _initial_string_table_size = (int) StringTable::the_table()->table_size();
-    if (process_strings) {
-      StringTable::reset_dead_counter();
-    }
-  }
-
-  ~G1StringCleaningTask() {
-    log_info(gc, stringtable)(
-        "Cleaned string table, "
-        "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
-        strings_processed(), strings_removed());
-    if (_process_strings) {
-      StringTable::finish_dead_counter();
-    }
-  }
-
-  void work(uint worker_id) {
-    int strings_processed = 0;
-    int strings_removed = 0;
-    if (_process_strings) {
-      StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
-      Atomic::add(strings_processed, &_strings_processed);
-      Atomic::add(strings_removed, &_strings_removed);
-    }
-    if (_process_string_dedup) {
-      G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
-    }
-  }
-
-  size_t strings_processed() const { return (size_t)_strings_processed; }
-  size_t strings_removed()   const { return (size_t)_strings_removed; }
-};
-
-class G1CodeCacheUnloadingTask {
-private:
-  static Monitor* _lock;
-
-  BoolObjectClosure* const _is_alive;
-  const bool               _unloading_occurred;
-  const uint               _num_workers;
-
-  // Variables used to claim nmethods.
-  CompiledMethod* _first_nmethod;
-  CompiledMethod* volatile _claimed_nmethod;
-
-  // The list of nmethods that need to be processed by the second pass.
-  CompiledMethod* volatile _postponed_list;
-  volatile uint            _num_entered_barrier;
-
- public:
-  G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
-      _is_alive(is_alive),
-      _unloading_occurred(unloading_occurred),
-      _num_workers(num_workers),
-      _first_nmethod(NULL),
-      _claimed_nmethod(NULL),
-      _postponed_list(NULL),
-      _num_entered_barrier(0)
-  {
-    CompiledMethod::increase_unloading_clock();
-    // Get first alive nmethod
-    CompiledMethodIterator iter = CompiledMethodIterator();
-    if(iter.next_alive()) {
-      _first_nmethod = iter.method();
-    }
-    _claimed_nmethod = _first_nmethod;
-  }
-
-  ~G1CodeCacheUnloadingTask() {
-    CodeCache::verify_clean_inline_caches();
-
-    CodeCache::set_needs_cache_clean(false);
-    guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
-
-    CodeCache::verify_icholder_relocations();
-  }
-
- private:
-  void add_to_postponed_list(CompiledMethod* nm) {
-      CompiledMethod* old;
-      do {
-        old = _postponed_list;
-        nm->set_unloading_next(old);
-      } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
-  }
-
-  void clean_nmethod(CompiledMethod* nm) {
-    bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
-
-    if (postponed) {
-      // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
-      add_to_postponed_list(nm);
-    }
-
-    // Mark that this nmethod has been cleaned/unloaded.
-    // After this call, it will be safe to ask if this nmethod was unloaded or not.
-    nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
-  }
-
-  void clean_nmethod_postponed(CompiledMethod* nm) {
-    nm->do_unloading_parallel_postponed();
-  }
-
-  static const int MaxClaimNmethods = 16;
-
-  void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
-    CompiledMethod* first;
-    CompiledMethodIterator last;
-
-    do {
-      *num_claimed_nmethods = 0;
-
-      first = _claimed_nmethod;
-      last = CompiledMethodIterator(first);
-
-      if (first != NULL) {
-
-        for (int i = 0; i < MaxClaimNmethods; i++) {
-          if (!last.next_alive()) {
-            break;
-          }
-          claimed_nmethods[i] = last.method();
-          (*num_claimed_nmethods)++;
-        }
-      }
-
-    } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
-  }
-
-  CompiledMethod* claim_postponed_nmethod() {
-    CompiledMethod* claim;
-    CompiledMethod* next;
-
-    do {
-      claim = _postponed_list;
-      if (claim == NULL) {
-        return NULL;
-      }
-
-      next = claim->unloading_next();
-
-    } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
-
-    return claim;
-  }
-
- public:
-  // Mark that we're done with the first pass of nmethod cleaning.
-  void barrier_mark(uint worker_id) {
-    MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
-    _num_entered_barrier++;
-    if (_num_entered_barrier == _num_workers) {
-      ml.notify_all();
-    }
-  }
-
-  // See if we have to wait for the other workers to
-  // finish their first-pass nmethod cleaning work.
-  void barrier_wait(uint worker_id) {
-    if (_num_entered_barrier < _num_workers) {
-      MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
-      while (_num_entered_barrier < _num_workers) {
-          ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
-      }
-    }
-  }
-
-  // Cleaning and unloading of nmethods. Some work has to be postponed
-  // to the second pass, when we know which nmethods survive.
-  void work_first_pass(uint worker_id) {
-    // The first nmethods is claimed by the first worker.
-    if (worker_id == 0 && _first_nmethod != NULL) {
-      clean_nmethod(_first_nmethod);
-      _first_nmethod = NULL;
-    }
-
-    int num_claimed_nmethods;
-    CompiledMethod* claimed_nmethods[MaxClaimNmethods];
-
-    while (true) {
-      claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
-
-      if (num_claimed_nmethods == 0) {
-        break;
-      }
-
-      for (int i = 0; i < num_claimed_nmethods; i++) {
-        clean_nmethod(claimed_nmethods[i]);
-      }
-    }
-  }
-
-  void work_second_pass(uint worker_id) {
-    CompiledMethod* nm;
-    // Take care of postponed nmethods.
-    while ((nm = claim_postponed_nmethod()) != NULL) {
-      clean_nmethod_postponed(nm);
-    }
-  }
-};
-
-Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
-
-class G1KlassCleaningTask : public StackObj {
-  volatile int                            _clean_klass_tree_claimed;
-  ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
-
- public:
-  G1KlassCleaningTask() :
-      _clean_klass_tree_claimed(0),
-      _klass_iterator() {
-  }
-
- private:
-  bool claim_clean_klass_tree_task() {
-    if (_clean_klass_tree_claimed) {
-      return false;
-    }
-
-    return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
-  }
-
-  InstanceKlass* claim_next_klass() {
-    Klass* klass;
-    do {
-      klass =_klass_iterator.next_klass();
-    } while (klass != NULL && !klass->is_instance_klass());
-
-    // this can be null so don't call InstanceKlass::cast
-    return static_cast<InstanceKlass*>(klass);
-  }
-
-public:
-
-  void clean_klass(InstanceKlass* ik) {
-    ik->clean_weak_instanceklass_links();
-  }
-
-  void work() {
-    ResourceMark rm;
-
-    // One worker will clean the subklass/sibling klass tree.
-    if (claim_clean_klass_tree_task()) {
-      Klass::clean_subklass_tree();
-    }
-
-    // All workers will help cleaning the classes,
-    InstanceKlass* klass;
-    while ((klass = claim_next_klass()) != NULL) {
-      clean_klass(klass);
-    }
-  }
-};
-
-// To minimize the remark pause times, the tasks below are done in parallel.
-class G1ParallelCleaningTask : public AbstractGangTask {
-private:
-  bool                          _unloading_occurred;
-  G1StringCleaningTask          _string_task;
-  G1CodeCacheUnloadingTask      _code_cache_task;
-  G1KlassCleaningTask           _klass_cleaning_task;
-
-public:
-  // The constructor is run in the VMThread.
-  G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
-      AbstractGangTask("Parallel Cleaning"),
-      _unloading_occurred(unloading_occurred),
-      _string_task(is_alive, true, G1StringDedup::is_enabled()),
-      _code_cache_task(num_workers, is_alive, unloading_occurred),
-      _klass_cleaning_task() {
-  }
-
-  // The parallel work done by all worker threads.
-  void work(uint worker_id) {
-    // Do first pass of code cache cleaning.
-    _code_cache_task.work_first_pass(worker_id);
-
-    // Let the threads mark that the first pass is done.
-    _code_cache_task.barrier_mark(worker_id);
-
-    // Clean the Strings.
-    _string_task.work(worker_id);
-
-    // Wait for all workers to finish the first code cache cleaning pass.
-    _code_cache_task.barrier_wait(worker_id);
-
-    // Do the second code cache cleaning work, which realize on
-    // the liveness information gathered during the first pass.
-    _code_cache_task.work_second_pass(worker_id);
-
-    // Clean all klasses that were not unloaded.
-    // The weak metadata in klass doesn't need to be
-    // processed if there was no unloading.
-    if (_unloading_occurred) {
-      _klass_cleaning_task.work();
-    }
-  }
-};
-
-
 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
                                         bool class_unloading_occurred) {
   uint n_workers = workers()->active_workers();
 
-  G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
+  G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false);
+  ParallelCleaningTask g1_unlink_task(is_alive, &dedup_closure, n_workers, class_unloading_occurred);
   workers()->run_task(&g1_unlink_task);
 }
 
@@ -3593,7 +3272,8 @@
     return;
   }
 
-  G1StringCleaningTask g1_unlink_task(is_alive, process_strings, process_string_dedup);
+  G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false);
+  StringCleaningTask g1_unlink_task(is_alive, process_string_dedup ? &dedup_closure : NULL, process_strings);
   workers()->run_task(&g1_unlink_task);
 }
 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/parallelCleaning.cpp	Tue Aug 21 20:29:57 2018 -0400
@@ -0,0 +1,337 @@
+/*
+ * Copyright (c) 2018, 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
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/symbolTable.hpp"
+#include "classfile/stringTable.hpp"
+#include "code/codeCache.hpp"
+#include "gc/shared/parallelCleaning.hpp"
+#include "memory/resourceArea.hpp"
+#include "prims/resolvedMethodTable.hpp"
+#include "logging/log.hpp"
+
+StringCleaningTask::StringCleaningTask(BoolObjectClosure* is_alive, StringDedupUnlinkOrOopsDoClosure* dedup_closure, bool process_strings) :
+  AbstractGangTask("String Unlinking"),
+  _is_alive(is_alive),
+  _dedup_closure(dedup_closure),
+  _par_state_string(StringTable::weak_storage()),
+  _initial_string_table_size((int) StringTable::the_table()->table_size()),
+  _process_strings(process_strings), _strings_processed(0), _strings_removed(0) {
+
+  if (process_strings) {
+    StringTable::reset_dead_counter();
+  }
+}
+
+StringCleaningTask::~StringCleaningTask() {
+  log_info(gc, stringtable)(
+      "Cleaned string table, "
+      "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
+      strings_processed(), strings_removed());
+  if (_process_strings) {
+    StringTable::finish_dead_counter();
+  }
+}
+
+void StringCleaningTask::work(uint worker_id) {
+  int strings_processed = 0;
+  int strings_removed = 0;
+  if (_process_strings) {
+    StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
+    Atomic::add(strings_processed, &_strings_processed);
+    Atomic::add(strings_removed, &_strings_removed);
+  }
+  if (_dedup_closure != NULL) {
+    StringDedup::parallel_unlink(_dedup_closure, worker_id);
+  }
+}
+
+CodeCacheUnloadingTask::CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
+      _is_alive(is_alive),
+      _unloading_occurred(unloading_occurred),
+      _num_workers(num_workers),
+      _first_nmethod(NULL),
+      _claimed_nmethod(NULL),
+      _postponed_list(NULL),
+      _num_entered_barrier(0) {
+  CompiledMethod::increase_unloading_clock();
+  // Get first alive nmethod
+  CompiledMethodIterator iter = CompiledMethodIterator();
+  if(iter.next_alive()) {
+    _first_nmethod = iter.method();
+  }
+  _claimed_nmethod = _first_nmethod;
+}
+
+CodeCacheUnloadingTask::~CodeCacheUnloadingTask() {
+  CodeCache::verify_clean_inline_caches();
+
+  CodeCache::set_needs_cache_clean(false);
+  guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
+
+  CodeCache::verify_icholder_relocations();
+}
+
+Monitor* CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
+
+void CodeCacheUnloadingTask::add_to_postponed_list(CompiledMethod* nm) {
+  CompiledMethod* old;
+  do {
+    old = _postponed_list;
+    nm->set_unloading_next(old);
+  } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
+}
+
+void CodeCacheUnloadingTask::clean_nmethod(CompiledMethod* nm) {
+  bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
+
+  if (postponed) {
+    // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
+    add_to_postponed_list(nm);
+  }
+
+  // Mark that this nmethod has been cleaned/unloaded.
+  // After this call, it will be safe to ask if this nmethod was unloaded or not.
+  nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
+}
+
+void CodeCacheUnloadingTask::clean_nmethod_postponed(CompiledMethod* nm) {
+  nm->do_unloading_parallel_postponed();
+}
+
+void CodeCacheUnloadingTask::claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
+  CompiledMethod* first;
+  CompiledMethodIterator last;
+
+  do {
+    *num_claimed_nmethods = 0;
+
+    first = _claimed_nmethod;
+    last = CompiledMethodIterator(first);
+
+    if (first != NULL) {
+
+      for (int i = 0; i < MaxClaimNmethods; i++) {
+        if (!last.next_alive()) {
+          break;
+        }
+        claimed_nmethods[i] = last.method();
+        (*num_claimed_nmethods)++;
+      }
+    }
+
+  } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
+}
+
+CompiledMethod* CodeCacheUnloadingTask::claim_postponed_nmethod() {
+  CompiledMethod* claim;
+  CompiledMethod* next;
+
+  do {
+    claim = _postponed_list;
+    if (claim == NULL) {
+      return NULL;
+    }
+
+    next = claim->unloading_next();
+
+  } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
+
+  return claim;
+}
+
+void CodeCacheUnloadingTask::barrier_mark(uint worker_id) {
+  MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
+  _num_entered_barrier++;
+  if (_num_entered_barrier == _num_workers) {
+    ml.notify_all();
+  }
+}
+
+void CodeCacheUnloadingTask::barrier_wait(uint worker_id) {
+  if (_num_entered_barrier < _num_workers) {
+    MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
+    while (_num_entered_barrier < _num_workers) {
+        ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
+    }
+  }
+}
+
+void CodeCacheUnloadingTask::work_first_pass(uint worker_id) {
+  // The first nmethods is claimed by the first worker.
+  if (worker_id == 0 && _first_nmethod != NULL) {
+    clean_nmethod(_first_nmethod);
+    _first_nmethod = NULL;
+  }
+
+  int num_claimed_nmethods;
+  CompiledMethod* claimed_nmethods[MaxClaimNmethods];
+
+  while (true) {
+    claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
+
+    if (num_claimed_nmethods == 0) {
+      break;
+    }
+
+    for (int i = 0; i < num_claimed_nmethods; i++) {
+      clean_nmethod(claimed_nmethods[i]);
+    }
+  }
+}
+
+void CodeCacheUnloadingTask::work_second_pass(uint worker_id) {
+  CompiledMethod* nm;
+  // Take care of postponed nmethods.
+  while ((nm = claim_postponed_nmethod()) != NULL) {
+    clean_nmethod_postponed(nm);
+  }
+}
+
+
+KlassCleaningTask::KlassCleaningTask() :
+  _clean_klass_tree_claimed(0),
+  _klass_iterator() {
+}
+
+bool KlassCleaningTask::claim_clean_klass_tree_task() {
+  if (_clean_klass_tree_claimed) {
+    return false;
+  }
+
+  return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
+}
+
+InstanceKlass* KlassCleaningTask::claim_next_klass() {
+  Klass* klass;
+  do {
+    klass =_klass_iterator.next_klass();
+  } while (klass != NULL && !klass->is_instance_klass());
+
+  // this can be null so don't call InstanceKlass::cast
+  return static_cast<InstanceKlass*>(klass);
+}
+
+void KlassCleaningTask::work() {
+  ResourceMark rm;
+
+  // One worker will clean the subklass/sibling klass tree.
+  if (claim_clean_klass_tree_task()) {
+    Klass::clean_subklass_tree();
+  }
+
+  // All workers will help cleaning the classes,
+  InstanceKlass* klass;
+  while ((klass = claim_next_klass()) != NULL) {
+    clean_klass(klass);
+  }
+}
+
+bool ResolvedMethodCleaningTask::claim_resolved_method_task() {
+  if (_resolved_method_task_claimed) {
+    return false;
+  }
+  return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
+}
+
+// These aren't big, one thread can do it all.
+void ResolvedMethodCleaningTask::work() {
+  if (claim_resolved_method_task()) {
+    ResolvedMethodTable::unlink();
+  }
+}
+
+class ParallelCleaningTaskTimer {
+  volatile jint* _timer_us;
+  jlong start;
+public:
+  ParallelCleaningTaskTimer(jint* timer_us) : _timer_us(timer_us) {
+    start = os::javaTimeNanos();
+  }
+  ~ParallelCleaningTaskTimer() {
+    jlong ns = os::javaTimeNanos() - start;
+    jlong us = ns / 1000;
+    assert (us < max_jint, "overflow");
+    Atomic::add((jint) us, _timer_us);
+  }
+};
+
+
+ParallelCleaningTask::ParallelCleaningTask(BoolObjectClosure* is_alive,
+  StringDedupUnlinkOrOopsDoClosure* dedup_closure, uint num_workers, bool unloading_occurred) :
+  AbstractGangTask("Parallel Cleaning"),
+  _unloading_occurred(unloading_occurred),
+  _string_task(is_alive, StringDedup::is_enabled() ? dedup_closure : NULL, true),
+  _code_cache_task(num_workers, is_alive, unloading_occurred),
+  _klass_cleaning_task(),
+  _resolved_method_cleaning_task() {
+}
+
+// The parallel work done by all worker threads.
+void ParallelCleaningTask::work(uint worker_id) {
+  {
+    ParallelCleaningTaskTimer timer(&_times._codecache_work);
+    // Do first pass of code cache cleaning.
+    _code_cache_task.work_first_pass(worker_id);
+  }
+
+  {
+    ParallelCleaningTaskTimer timer(&_times._sync);
+    // Let the threads mark that the first pass is done.
+    _code_cache_task.barrier_mark(worker_id);
+  }
+
+  {
+    ParallelCleaningTaskTimer timer(&_times._tables_work);
+    // Clean the Strings and Symbols.
+    _string_task.work(worker_id);
+  }
+
+  {
+    ParallelCleaningTaskTimer timer(&_times._rmt_work);
+    // Clean unreferenced things in the ResolvedMethodTable
+    _resolved_method_cleaning_task.work();
+  }
+
+  {
+    ParallelCleaningTaskTimer timer(&_times._sync);
+    // Wait for all workers to finish the first code cache cleaning pass.
+    _code_cache_task.barrier_wait(worker_id);
+  }
+
+  {
+    ParallelCleaningTaskTimer timer(&_times._codecache_work);
+    // Do the second code cache cleaning work, which realize on
+    // the liveness information gathered during the first pass.
+    _code_cache_task.work_second_pass(worker_id);
+  }
+
+  // Clean all klasses that were not unloaded.
+  // The weak metadata in klass doesn't need to be
+  // processed if there was no unloading.
+  if (_unloading_occurred) {
+    ParallelCleaningTaskTimer timer(&_times._klass_work);
+    _klass_cleaning_task.work();
+  }
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/parallelCleaning.hpp	Tue Aug 21 20:29:57 2018 -0400
@@ -0,0 +1,175 @@
+/*
+ * Copyright (c) 2018, 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
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_SHARED_PARALLELCLEANING_HPP
+#define SHARE_VM_GC_SHARED_PARALLELCLEANING_HPP
+
+#include "gc/shared/oopStorageParState.hpp"
+#include "gc/shared/stringdedup/stringDedup.hpp"
+#include "gc/shared/workgroup.hpp"
+
+class ParallelCleaningTask;
+
+class StringCleaningTask : public AbstractGangTask {
+private:
+  BoolObjectClosure* _is_alive;
+  StringDedupUnlinkOrOopsDoClosure * const _dedup_closure;
+
+  OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
+
+  int _initial_string_table_size;
+
+  bool  _process_strings;
+  int   _strings_processed;
+  int   _strings_removed;
+
+public:
+  StringCleaningTask(BoolObjectClosure* is_alive, StringDedupUnlinkOrOopsDoClosure* dedup_closure, bool process_strings);
+  ~StringCleaningTask();
+
+  void work(uint worker_id);
+
+  size_t strings_processed() const { return (size_t)_strings_processed; }
+  size_t strings_removed()   const { return (size_t)_strings_removed; }
+};
+
+class CodeCacheUnloadingTask {
+private:
+  static Monitor* _lock;
+
+  BoolObjectClosure* const _is_alive;
+  const bool               _unloading_occurred;
+  const uint               _num_workers;
+
+  // Variables used to claim nmethods.
+  CompiledMethod* _first_nmethod;
+  CompiledMethod* volatile _claimed_nmethod;
+
+  // The list of nmethods that need to be processed by the second pass.
+  CompiledMethod* volatile _postponed_list;
+  volatile uint            _num_entered_barrier;
+
+public:
+  CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred);
+  ~CodeCacheUnloadingTask();
+
+private:
+  void add_to_postponed_list(CompiledMethod* nm);
+  void clean_nmethod(CompiledMethod* nm);
+  void clean_nmethod_postponed(CompiledMethod* nm);
+
+  static const int MaxClaimNmethods = 16;
+
+  void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods);
+  CompiledMethod* claim_postponed_nmethod();
+public:
+  // Mark that we're done with the first pass of nmethod cleaning.
+  void barrier_mark(uint worker_id);
+
+  // See if we have to wait for the other workers to
+  // finish their first-pass nmethod cleaning work.
+  void barrier_wait(uint worker_id);
+
+  // Cleaning and unloading of nmethods. Some work has to be postponed
+  // to the second pass, when we know which nmethods survive.
+  void work_first_pass(uint worker_id);
+  void work_second_pass(uint worker_id);
+};
+
+
+class KlassCleaningTask : public StackObj {
+  volatile int                            _clean_klass_tree_claimed;
+  ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
+
+public:
+  KlassCleaningTask();
+
+private:
+  bool claim_clean_klass_tree_task();
+  InstanceKlass* claim_next_klass();
+
+public:
+
+  void clean_klass(InstanceKlass* ik) {
+    ik->clean_weak_instanceklass_links();
+  }
+
+  void work();
+};
+
+class ResolvedMethodCleaningTask : public StackObj {
+  volatile int       _resolved_method_task_claimed;
+public:
+  ResolvedMethodCleaningTask() :
+      _resolved_method_task_claimed(0) {}
+
+  bool claim_resolved_method_task();
+
+  void work();
+};
+
+class ParallelCleaningTimes {
+  friend class ParallelCleaningTask;
+private:
+  // All times are in microseconds, making room for ~2 hrs in jint
+  jint _sync, _codecache_work, _tables_work, _rmt_work, _klass_work;
+
+public:
+  ParallelCleaningTimes() :
+          _sync(0),
+          _codecache_work(0),
+          _tables_work(0),
+          _rmt_work(0),
+          _klass_work(0) {};
+
+  jint sync_us()           const { return _sync; }
+  jint codecache_work_us() const { return _codecache_work; }
+  jint tables_work_us()    const { return _tables_work; }
+  jint rmt_work_us()       const { return _rmt_work; }
+  jint klass_work_us()     const { return _klass_work; }
+};
+
+// To minimize the remark pause times, the tasks below are done in parallel.
+class ParallelCleaningTask : public AbstractGangTask {
+private:
+  bool                        _unloading_occurred;
+  StringCleaningTask          _string_task;
+  CodeCacheUnloadingTask      _code_cache_task;
+  KlassCleaningTask           _klass_cleaning_task;
+  ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
+
+  ParallelCleaningTimes       _times;
+public:
+  // The constructor is run in the VMThread.
+  ParallelCleaningTask(BoolObjectClosure* is_alive, StringDedupUnlinkOrOopsDoClosure* dedup_closure,
+    uint num_workers, bool unloading_occurred);
+
+  void work(uint worker_id);
+
+  ParallelCleaningTimes times() const {
+    return _times;
+  }
+};
+
+#endif // SHARE_VM_GC_SHARED_PARALLELCLEANING_HPP