--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1YoungRemSetSamplingThread.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2015, 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_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
+#define SHARE_VM_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
+
+#include "gc/shared/concurrentGCThread.hpp"
+
+// The G1YoungRemSetSamplingThread is used to re-assess the validity of
+// the prediction for the remembered set lengths of the young generation.
+//
+// At the end of the GC G1 determines the length of the young gen based on
+// how much time the next GC can take, and when the next GC may occur
+// according to the MMU.
+//
+// The assumption is that a significant part of the GC is spent on scanning
+// the remembered sets (and many other components), so this thread constantly
+// reevaluates the prediction for the remembered set scanning costs, and potentially
+// G1Policy resizes the young gen. This may do a premature GC or even
+// increase the young gen size to keep pause time length goal.
+class G1YoungRemSetSamplingThread: public ConcurrentGCThread {
+private:
+  Monitor _monitor;
+
+  void sample_young_list_rs_lengths();
+
+  void run_service();
+  void stop_service();
+
+  void sleep_before_next_cycle();
+
+  double _vtime_accum;  // Accumulated virtual time.
+
+public:
+  G1YoungRemSetSamplingThread();
+  double vtime_accum() { return _vtime_accum; }
+};
+
+#endif // SHARE_VM_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP