diff -r 2c3cc4b01880 -r c16ac7a2eba4 src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java
--- a/src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java	Wed Oct 30 16:14:56 2019 +0100
+++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java	Wed Oct 30 19:43:52 2019 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 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
@@ -81,7 +81,7 @@
      * @throws DCmdException if recording could not be started
      */
     @SuppressWarnings("resource")
-    public String execute(String name, String[] settings, Long delay, Long duration, Boolean disk, String path, Long maxAge, Long maxSize, Boolean dumpOnExit, Boolean pathToGcRoots) throws DCmdException {
+    public String execute(String name, String[] settings, Long delay, Long duration, Boolean disk, String path, Long maxAge, Long maxSize, Long flush, Boolean dumpOnExit, Boolean pathToGcRoots) throws DCmdException {
         if (Logger.shouldLog(LogTag.JFR_DCMD, LogLevel.DEBUG)) {
             Logger.log(LogTag.JFR_DCMD, LogLevel.DEBUG, "Executing DCmdStart: name=" + name +
                     ", settings=" + Arrays.asList(settings) +
@@ -90,6 +90,7 @@
                     ", disk=" + disk+
                     ", filename=" + path +
                     ", maxage=" + maxAge +
+                    ", flush=" + flush +
                     ", maxsize=" + maxSize +
                     ", dumponexit =" + dumpOnExit +
                     ", path-to-gc-roots=" + pathToGcRoots);
@@ -136,6 +137,12 @@
             }
         }
 
+        if (flush != null) {
+            if (Boolean.FALSE.equals(disk)) {
+                throw new DCmdException("Flush can only be set for recordings that are to disk.");
+            }
+        }
+
         if (!FlightRecorder.isInitialized() && delay == null) {
             initializeWithForcedInstrumentation(s);
         }
@@ -148,6 +155,7 @@
         if (disk != null) {
             recording.setToDisk(disk.booleanValue());
         }
+
         recording.setSettings(s);
         SafePath safePath = null;
 
@@ -177,6 +185,10 @@
             recording.setMaxAge(Duration.ofNanos(maxAge));
         }
 
+        if (flush != null) {
+            recording.setFlushInterval(Duration.ofNanos(flush));
+        }
+
         if (maxSize != null) {
             recording.setMaxSize(maxSize);
         }
@@ -222,6 +234,7 @@
             print("Use jcmd " + getPid() + " JFR." + cmd + " " + recordingspecifier + " " + fileOption + "to copy recording data to file.");
             println();
         }
+
         return getResult();
     }