--- /dev/null	2018-11-26 11:49:18.255023023 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahPacer.hpp	2018-11-26 21:30:07.071073113 +0100
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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_SHENANDOAH_SHENANDOAHPACER_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHPACER_HPP
+
+#include "gc/shenandoah/shenandoahNumberSeq.hpp"
+#include "memory/allocation.hpp"
+
+class ShenandoahHeap;
+
+#define PACING_PROGRESS_UNINIT (-1)
+#define PACING_PROGRESS_ZERO   ( 0)
+
+/**
+ * ShenandoahPacer provides allocation pacing mechanism.
+ *
+ * Currently it implements simple tax-and-spend pacing policy: GC threads provide
+ * credit, allocating thread spend the credit, or stall when credit is not available.
+ */
+class ShenandoahPacer : public CHeapObj<mtGC> {
+private:
+  ShenandoahHeap* _heap;
+  BinaryMagnitudeSeq _delays;
+  TruncatedSeq* _progress_history;
+
+  // Set once per phase
+  volatile intptr_t _epoch;
+  volatile double _tax_rate;
+
+  // Heavily updated, protect from accidental false sharing
+  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile intptr_t));
+  volatile intptr_t _budget;
+  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
+
+  // Heavily updated, protect from accidental false sharing
+  DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile intptr_t));
+  volatile intptr_t _progress;
+  DEFINE_PAD_MINUS_SIZE(3, DEFAULT_CACHE_LINE_SIZE, 0);
+
+public:
+  ShenandoahPacer(ShenandoahHeap* heap) :
+          _heap(heap),
+          _progress_history(new TruncatedSeq(5)),
+          _epoch(0),
+          _tax_rate(1),
+          _budget(0),
+          _progress(PACING_PROGRESS_UNINIT) {}
+
+  void setup_for_idle();
+  void setup_for_mark();
+  void setup_for_evac();
+  void setup_for_updaterefs();
+  void setup_for_traversal();
+
+  inline void report_mark(size_t words);
+  inline void report_evac(size_t words);
+  inline void report_updaterefs(size_t words);
+
+  inline void report_alloc(size_t words);
+
+  bool claim_for_alloc(size_t words, bool force);
+  void pace_for_alloc(size_t words);
+  void unpace_for_alloc(intptr_t epoch, size_t words);
+
+  intptr_t epoch();
+
+  void print_on(outputStream* out) const;
+
+private:
+  inline void report_internal(size_t words);
+  inline void report_progress_internal(size_t words);
+
+  void restart_with(size_t non_taxable_bytes, double tax_rate);
+
+  size_t update_and_get_progress_history();
+};
+
+#endif //SHARE_VM_GC_SHENANDOAH_SHENANDOAHPACER_HPP