--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/task.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 1997, 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
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_RUNTIME_TASK_HPP
+#define SHARE_VM_RUNTIME_TASK_HPP
+
+#include "memory/allocation.hpp"
+#include "runtime/timer.hpp"
+
+// A PeriodicTask has the sole purpose of executing its task
+// function with regular intervals.
+// Usage:
+//   PeriodicTask pf(10);
+//   pf.enroll();
+//   ...
+//   pf.disenroll();
+
+class PeriodicTask: public CHeapObj<mtInternal> {
+ public:
+  // Useful constants.
+  // The interval constants are used to ensure the declared interval
+  // is appropriate;  it must be between min_interval and max_interval,
+  // and have a granularity of interval_gran (all in millis).
+  enum { max_tasks     = 10,       // Max number of periodic tasks in system
+         interval_gran = 10,
+         min_interval  = 10,
+         max_interval  = 10000 };
+
+  static int num_tasks()   { return _num_tasks; }
+
+ private:
+  int _counter;
+  const int _interval;
+
+  static int _num_tasks;
+  static PeriodicTask* _tasks[PeriodicTask::max_tasks];
+  // Can only be called by the WatcherThread
+  static void real_time_tick(int delay_time);
+
+#ifndef PRODUCT
+  static elapsedTimer _timer;                      // measures time between ticks
+  static int _ticks;                               // total number of ticks
+  static int _intervalHistogram[max_interval];     // to check spacing of timer interrupts
+ public:
+  static void print_intervals();
+#endif
+  // Only the WatcherThread can cause us to execute PeriodicTasks
+  friend class WatcherThread;
+ public:
+  PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time
+  ~PeriodicTask();
+
+  // Make the task active
+  // For dynamic enrollment at the time T, the task will execute somewhere
+  // between T and T + interval_time.
+  void enroll();
+
+  // Make the task deactive
+  void disenroll();
+
+  void execute_if_pending(int delay_time) {
+    // make sure we don't overflow
+    jlong tmp = (jlong) _counter + (jlong) delay_time;
+
+    if (tmp >= (jlong) _interval) {
+      _counter = 0;
+      task();
+    } else {
+      _counter += delay_time;
+    }
+  }
+
+  // Returns how long (time in milliseconds) before the next time we should
+  // execute this task.
+  int time_to_next_interval() const {
+    assert(_interval > _counter,  "task counter greater than interval?");
+    return _interval - _counter;
+  }
+
+  // Calculate when the next periodic task will fire.
+  // Called by the WatcherThread's run method.
+  // Requires the PeriodicTask_lock.
+  static int time_to_wait();
+
+  // The task to perform at each period
+  virtual void task() = 0;
+};
+
+#endif // SHARE_VM_RUNTIME_TASK_HPP