--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/workerManager.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2016, 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_WORKERMANAGER_HPP
+#define SHARE_VM_GC_SHARED_WORKERMANAGER_HPP
+
+#include "gc/shared/adaptiveSizePolicy.hpp"
+
+class WorkerManager : public AllStatic {
+ public:
+  // Create additional workers as needed.
+  //   active_workers - number of workers being requested for an upcoming
+  // parallel task.
+  //   total_workers - total number of workers.  This is the maximum
+  // number possible.
+  //   created_workers - number of workers already created.  This maybe
+  // less than, equal to, or greater than active workers.  If greater than
+  // or equal to active_workers, nothing is done.
+  //   worker_type - type of thread.
+  //   initializing - true if this is called to get the initial number of
+  // GC workers.
+  // If initializing is true, do a vm exit if the workers cannot be created.
+  // The initializing = true case is for JVM start up and failing to
+  // create all the worker at start should considered a problem so exit.
+  // If initializing = false, there are already some number of worker
+  // threads and a failure would not be optimal but should not be fatal.
+  template <class WorkerType>
+  static uint add_workers (WorkerType* holder,
+                           uint active_workers,
+                           uint total_workers,
+                           uint created_workers,
+                           os::ThreadType worker_type,
+                           bool initializing) {
+    uint start = created_workers;
+    uint end = MIN2(active_workers, total_workers);
+    for (uint worker_id = start; worker_id < end; worker_id += 1) {
+      WorkerThread* new_worker = NULL;
+      if (initializing || !InjectGCWorkerCreationFailure) {
+        new_worker = holder->install_worker(worker_id);
+      }
+      if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
+        log_trace(gc, task)("WorkerManager::add_workers() : "
+                            "creation failed due to failed allocation of native %s",
+                            new_worker == NULL ?  "memory" : "thread");
+        if (new_worker != NULL) {
+           delete new_worker;
+        }
+        if (initializing) {
+          vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create worker GC thread. Out of system resources.");
+        }
+        break;
+      }
+      created_workers++;
+      os::start_thread(new_worker);
+    }
+
+    log_trace(gc, task)("WorkerManager::add_workers() : "
+                        "created_workers: %u", created_workers);
+
+    return created_workers;
+  }
+
+  // Log (at trace level) a change in the number of created workers.
+  template <class WorkerType>
+  static void log_worker_creation(WorkerType* holder,
+                                  uint previous_created_workers,
+                                  uint active_workers,
+                                  uint created_workers,
+                                  bool initializing) {
+    if (previous_created_workers < created_workers) {
+      const char* initializing_msg =  initializing ? "Adding initial" : "Creating additional";
+      log_trace(gc, task)("%s %s(s) previously created workers %u active workers %u total created workers %u",
+                          initializing_msg, holder->group_name(), previous_created_workers, active_workers, created_workers);
+    }
+  }
+};
+#endif // SHARE_VM_GC_SHARED_WORKERMANAGER_HPP