--- /dev/null	2019-07-24 07:52:56.000000000 -0700
+++ new/src/hotspot/share/services/threadTable.cpp	2019-07-24 07:52:56.000000000 -0700
@@ -0,0 +1,253 @@
+
+/*
+* Copyright (c) 2019, 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 "runtime/interfaceSupport.inline.hpp"
+#include "runtime/timerTrace.hpp"
+#include "runtime/thread.hpp"
+#include "runtime/threadSMR.hpp"
+#include "services/threadTable.hpp"
+#include "utilities/concurrentHashTable.inline.hpp"
+#include "utilities/concurrentHashTableTasks.inline.hpp"
+
+
+// 2^24 is max size
+static const size_t END_SIZE = 24;
+// Default initial size 256
+static const size_t DefaultThreadTableSizeLog = 8;
+// Prefer short chains of avg 2
+static const double PREF_AVG_LIST_LEN = 2.0;
+
+typedef ConcurrentHashTable<ThreadTableConfig, mtInternal> ThreadTableHash;
+
+static ThreadTableHash* volatile _local_table = NULL;
+
+volatile bool ThreadTable::_has_work = false;
+volatile bool ThreadTable::_is_initialized = false;
+
+
+static volatile size_t _current_size = 0;
+static volatile size_t _items_count = 0;
+
+
+class ThreadTableEntry : public CHeapObj<mtInternal> {
+  private:
+    jlong _tid;
+    JavaThread* _java_thread;
+  public:
+    ThreadTableEntry(jlong tid, JavaThread* java_thread) :
+    _tid(tid),_java_thread(java_thread) {}
+
+    jlong tid() const { return _tid;}
+    JavaThread* thread() const {return _java_thread;}
+};
+
+class ThreadTableConfig : public AllStatic {
+  public:
+    typedef ThreadTableEntry* Value;
+
+    static uintx get_hash(Value const& value, bool* is_dead) {
+      jlong tid = value->tid();
+      return primitive_hash(tid);
+    }
+    static void* allocate_node(size_t size, Value const& value) {
+      ThreadTable::item_added();
+      return AllocateHeap(size, mtInternal);
+    }
+    static void free_node(void* memory, Value const& value) {
+      delete value;
+      FreeHeap(memory);
+      ThreadTable::item_removed();
+    }
+};
+
+static size_t ceil_log2(size_t val) {
+  size_t ret;
+  for (ret = 1; ((size_t)1 << ret) < val; ++ret);
+  return ret;
+}
+
+// Lazily creates the table and populates it with the given
+// thread list
+void ThreadTable::lazy_initialize(const ThreadsList *threads) {
+  if (!_is_initialized) {
+    MutexLocker ml(ThreadTableCreate_lock, Mutex::_no_safepoint_check_flag);
+    if (!_is_initialized) {
+      create_table(threads->length());
+      _is_initialized = true;
+    }
+    for (uint i = 0; i < threads->length(); i++) {
+      JavaThread* thread = threads->thread_at(i);
+      oop tobj = thread->threadObj();
+      if (tobj != NULL && !thread->is_exiting()) {
+        jlong java_tid = java_lang_Thread::thread_id(tobj);
+        add_thread(java_tid, thread);
+      }
+    }
+  }
+}
+
+void ThreadTable::create_table(size_t size) {
+  assert(_local_table == NULL, "Thread table is already created");
+  size_t size_log = ceil_log2(size);
+  size_t start_size_log = size_log > DefaultThreadTableSizeLog
+  ? size_log : DefaultThreadTableSizeLog;
+  _current_size = (size_t)1 << start_size_log;
+  _local_table = new ThreadTableHash(start_size_log, END_SIZE);
+}
+
+void ThreadTable::item_added() {
+  Atomic::inc(&_items_count);
+  log_trace(thread, table) ("Thread entry added");
+}
+
+void ThreadTable::item_removed() {
+  Atomic::dec(&_items_count);
+  log_trace(thread, table) ("Thread entry removed");
+}
+
+double ThreadTable::get_load_factor() {
+  return (double)_items_count/_current_size;
+}
+
+void ThreadTable::check_concurrent_work() {
+  if (_has_work) {
+    return;
+  }
+    
+  double load_factor = get_load_factor();
+  // Resize if we have more items than preferred load factor
+  if (load_factor > PREF_AVG_LIST_LEN) {
+    log_debug(thread, table)("Concurrent work triggered, load factor: %g",
+                             load_factor);
+    trigger_concurrent_work();
+  }
+}
+
+void ThreadTable::trigger_concurrent_work() {
+  MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
+  _has_work = true;
+  Service_lock->notify_all();
+}
+
+size_t ThreadTable::table_size() {
+  return (size_t)1 << _local_table->get_size_log2(Thread::current());
+}
+
+void ThreadTable::grow(JavaThread* jt) {
+  ThreadTableHash::GrowTask gt(_local_table);
+  if (!gt.prepare(jt)) {
+    return;
+  }
+  log_trace(thread, table)("Started to grow");
+  TraceTime timer("Grow", TRACETIME_LOG(Debug, membername, table, perf));
+  while (gt.do_task(jt)) {
+    gt.pause(jt);
+    {
+      ThreadBlockInVM tbivm(jt);
+    }
+    gt.cont(jt);
+  }
+  gt.done(jt);
+  _current_size = table_size();
+  log_info(thread, table)("Grown to size:" SIZE_FORMAT, _current_size);
+}
+
+class ThreadTableLookup : public StackObj {
+  private:
+    jlong          _tid;
+    uintx         _hash;
+  public:
+    ThreadTableLookup(jlong tid)
+    : _tid(tid), _hash(primitive_hash(tid)) {}
+    uintx get_hash() const {
+      return _hash;
+    }
+    bool equals(ThreadTableEntry **value, bool* is_dead) {
+      bool equals = primitive_equals(_tid, (*value)->tid());
+      if (!equals) {
+        return false;
+      }
+      return true;
+    }
+};
+
+class ThreadGet : public StackObj {
+  private:
+    JavaThread* _return;
+  public:
+    ThreadGet():_return(NULL) {}
+    void operator()(ThreadTableEntry** val) {
+      _return = (*val)->thread();
+    }
+    JavaThread* get_res_thread() {
+      return _return;
+    }
+};
+
+void ThreadTable::do_concurrent_work(JavaThread* jt) {
+   assert(_is_initialized, "Thread table is not initialized");
+  _has_work = false;
+  double load_factor = get_load_factor();
+  log_debug(thread, table)("Concurrent work, load factor: %g", load_factor);
+  if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
+    grow(jt);
+  }
+}
+
+JavaThread* ThreadTable::add_thread(jlong tid, JavaThread* java_thread) {
+  assert(_is_initialized, "Thread table is not initialized");
+  Thread* thread = Thread::current();
+  ThreadTableLookup lookup(tid);
+  ThreadGet tg;
+  while(true) {
+    if (_local_table->get(thread, lookup, tg)) {
+      return tg.get_res_thread();
+    }
+    ThreadTableEntry* entry = new ThreadTableEntry(tid,java_thread);
+    // The hash table takes ownership of the ThreadTableEntry,
+    // even if it's not inserted.
+    if (_local_table->insert(thread, lookup, entry)) {
+      check_concurrent_work();
+      return java_thread;
+    }
+  }
+}
+
+JavaThread* ThreadTable::find_thread_by_tid(jlong tid) {
+  assert(_is_initialized, "Thread table is not initialized");
+  Thread* thread = Thread::current();
+  ThreadTableLookup lookup(tid);
+  ThreadGet tg;
+  _local_table->get(thread, lookup, tg);
+  return tg.get_res_thread();
+}
+
+bool ThreadTable::remove_thread(jlong tid) {
+  assert(_is_initialized, "Thread table is not initialized");
+  Thread* thread = Thread::current();
+  ThreadTableLookup lookup(tid);
+  return _local_table->remove(thread,lookup);
+}