--- /dev/null	2018-06-17 23:18:20.806999507 +0800
+++ new/src/share/classes/jdk/jfr/Period.java	2019-01-29 10:58:50.033010448 +0800
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2016, 2019, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package jdk.jfr;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Event annotation, specifies the default setting value for a periodic event.
+ *
+ * @since 9
+ */
+@MetadataDefinition
+@Retention(RetentionPolicy.RUNTIME)
+@Inherited
+@Target(ElementType.TYPE)
+public @interface Period {
+    /**
+     * Settings name {@code "period"} for configuring periodic events
+     */
+    public final static String NAME = "period";
+
+    /**
+     * Returns the default setting value for a periodic setting.
+     * <p>
+     * String representation of a positive {@code Long} value followed by an empty
+     * space and one of the following units:<br>
+     * <br>
+     * {@code "ns"} (nanoseconds)<br>
+     * {@code "us"} (microseconds)<br>
+     * {@code "ms"} (milliseconds)<br>
+     * {@code "s"} (seconds)<br>
+     * {@code "m"} (minutes)<br>
+     * {@code "h"} (hours)<br>
+     * {@code "d"} (days)<br>
+     * <p>
+     * Example values: {@code "0 ns"}, {@code "10 ms"}, and {@code "1 s"}.
+     * <p>
+     * A period may also bes <code>"everyChunk"</code> to specify that it occurs at
+     * least once for every recording file. The number of events that are emitted
+     * depends on how many times the file rotations occur when data is recorded.
+     *
+     * @return the default setting value, not {@code null}
+     */
+    String value() default "everyChunk";
+}