--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/utilities/spinYield.cpp	Mon Apr 09 01:22:37 2018 -0400
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2018, 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/os.hpp"
+#include "utilities/ostream.hpp"
+#include "utilities/spinYield.hpp"
+#include "utilities/ticks.inline.hpp"
+
+SpinYield::SpinYield(uint spin_limit, uint yield_limit) :
+  _sleep_time(),
+  _spins(0),
+  _yields(0),
+  _spin_limit(os::is_MP() ? spin_limit : 0),
+  _yield_limit(yield_limit)
+{}
+
+void SpinYield::yield_or_sleep() {
+  if (_yields < _yield_limit) {
+    ++_yields;
+    os::naked_yield();
+  } else {
+    Ticks sleep_start = Ticks::now();
+    os::naked_short_sleep(1);
+    Ticks sleep_end = Ticks::now();
+    _sleep_time += (sleep_end - sleep_start);
+  }
+}
+
+static const char* print_separator(outputStream* s, const char* separator) {
+  s->print("%s", separator);
+  return ", ";
+}
+
+void SpinYield::report(outputStream* s) const {
+  const char* initial_separator = "";
+  const char* separator = initial_separator;
+  if (_spins > 0) {             // Report spins, if any.
+    separator = print_separator(s, separator);
+    s->print("spins = %u", _spins);
+  }
+  if (_yields > 0) {            // Report yields, if any.
+    separator = print_separator(s, separator);
+    s->print("yields = %u", _yields);
+  }
+  if (_sleep_time.value() != 0) { // Report sleep duration, if slept.
+    separator = print_separator(s, separator);
+    s->print("sleep = " JLONG_FORMAT " usecs",
+             TicksToTimeHelper::milliseconds(_sleep_time));
+  }
+  if (separator == initial_separator) {
+    s->print("no waiting");
+  }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/utilities/spinYield.hpp	Mon Apr 09 01:22:37 2018 -0400
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2018, 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_UTILITIES_SPINYIELD_HPP
+#define SHARE_UTILITIES_SPINYIELD_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/ticks.hpp"
+
+class outputStream;
+
+extern "C" int SpinPause();
+
+class SpinYield : public StackObj {
+  Tickspan _sleep_time;
+  uint _spins;
+  uint _yields;
+  uint _spin_limit;
+  uint _yield_limit;
+
+  void yield_or_sleep();
+
+public:
+  static const uint default_spin_limit = 4096;
+  static const uint default_yield_limit = 64;
+
+  // spin_limit is ignored (treated as zero) when !os::is_MP().
+  explicit SpinYield(uint spin_limit = default_spin_limit,
+                     uint yield_limit = default_yield_limit);
+
+  // Perform next round of delay.
+  void wait() {
+    // Simple policy: return immediately (spinning) configured number
+    // of times, then switch to yield/sleep.  Future work might
+    // provide other policies, such as (1) always spin if system is
+    // not saturated, or (2) sleeping if yielding is ineffective.
+    if (_spins < _spin_limit) {
+      ++_spins;
+      SpinPause();
+    } else {
+      yield_or_sleep();
+    }
+  }
+
+  // Write information about the wait duration to s.
+  void report(outputStream* s) const;
+};
+
+#endif // SHARE_UTILITIES_SPINYIELD_HPP

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/gtest/utilities/test_spinYield.cpp	Mon Apr 09 01:22:37 2018 -0400
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2018, 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/os.hpp"
+#include "utilities/ostream.hpp"
+#include "utilities/spinYield.hpp"
+#include "unittest.hpp"
+
+// Some basic tests of SpinYield, using comparison of report output with
+// expected results to verify state.  This is all very hard-wired to the
+// current implementation of SpinYield, esp. the report function.
+
+static void check_report(const SpinYield* spinner, const char* expected) {
+  char buffer[100];
+  stringStream s(buffer, sizeof(buffer));
+  spinner->report(&s);
+  ASSERT_STREQ(expected, buffer);
+}
+
+TEST(SpinYield, no_waiting) {
+  SpinYield spinner;
+  check_report(&spinner, "no waiting");
+}
+
+TEST(SpinYield, one_wait) {
+  SpinYield spinner(100);
+  spinner.wait();
+  check_report(&spinner, os::is_MP() ? "spins = 1" : "yields = 1");
+}
+
+TEST(SpinYield, ten_waits) {
+  SpinYield spinner(100, 100);
+  for (unsigned i = 0; i < 10; ++i) {
+    spinner.wait();
+  }
+  check_report(&spinner, os::is_MP() ? "spins = 10" : "yields = 10");
+}
+
+TEST(SpinYield, two_yields) {
+  SpinYield spinner(0, 10);
+  spinner.wait();
+  spinner.wait();
+  check_report(&spinner, "yields = 2");
+}
+
+TEST(SpinYield, one_sleep) {
+  SpinYield spinner(0, 0);
+  spinner.wait();
+
+  char buffer[100];
+  stringStream s(buffer, sizeof(buffer));
+  spinner.report(&s);
+
+  const char* expected = "sleep = ";
+  ASSERT_TRUE(strncmp(expected, buffer, strlen(expected)) == 0);
+}
+
+TEST(SpinYield, one_spin_one_sleep) {
+  SpinYield spinner(1, 0);
+  spinner.wait();
+  spinner.wait();
+
+  char buffer[100];
+  stringStream s(buffer, sizeof(buffer));
+  spinner.report(&s);
+
+  const char* expected_MP = "spins = 1, sleep = ";
+  const char* expected_UP = "sleep = ";
+  const char* expected = os::is_MP() ? expected_MP : expected_UP;
+  ASSERT_TRUE(strncmp(expected, buffer, strlen(expected)) == 0);
+}