Summary

Introduce a new JDK-specific monitoring and management interface named jdk.management.HotSpotAOTCacheMXBean.java to manage the creation of the AOT cache.

Problem

There is currently no tooling support for AOT cache creation that can be accessed from the Java application. When the command-line options -XX:AOTCacheOutput and/or -XX:AOTMode=create are given, the cache is created only when the current JVM exits. This is not suitable for application that never exits, or for applications that want to create the AOT cache before the JVM exits.

Solution

Add management interface jdk.management.HotSpotAOTCacheMXBean to the jdk.management module to provide an operation endRecording() that would end the AOT recording and create the AOT cache and/or configuration file. As with any MXBean, the operation can be invoked either from within the application, or from an externally tool such as JConsole.

Specification

package jdk.management;

import java.lang.management.ManagementFactory;
import java.lang.management.PlatformManagedObject;
import java.util.concurrent.ForkJoinPool;
import javax.management.MBeanServer;
import javax.management.ObjectName;

/**
 * Management interface for the JDK's Ahead of Time (AOT) Cache.
 *
 * <p> The management interface is registered with the platform {@link MBeanServer
 * MBeanServer}. The {@link ObjectName ObjectName} that uniquely identifies the management
 * interface within the {@code MBeanServer} is: "jdk.management:type=HotSpotAOTCache".
 *
 * <p> Direct access to the MXBean interface can be obtained with
 * {@link ManagementFactory#getPlatformMXBean(Class)}.
 *
 * {@code HotSpotAOTCacheMXBean} defines one operation at this time to
 * end the AOT recording. More operations and/or properties may be added in a
 * future release.
 *
 * @since 26
 */
public interface HotSpotAOTCacheMXBean extends PlatformManagedObject {
  /**
   * If an AOT recording is in progress, ends the recording. This operation completes
   * after the AOT artifacts have been completely written.
   *
   * <p>The JVM will start recording AOT artifacts upon start-up if certain JVM options are
   * given in the command-line. The recording will stop when the JVM exits, or when
   * the {@code endRecording} method is called. Examples:
   *
   * <p> java -XX:AOTCacheOutput=app.aot ....
   *
   * <blockquote>
   *    The JVM will record optimization information about the current application
   *    that will be used to generate the AOT cache file app.aot. In a future execution of this application,
   *    -XX:AOTCache=app.aot can be provided to improve the application's
   *    start-up and warm-up performance.
   * </blockquote>
   *
   * <p> java -XX:AOTMode=record -XX:AOTConfiguration=app.aotconfig ....
   *
   * <blockquote>
   *    The JVM will record optimization information about the current application
   *    into the AOT configuration file app.aotconfig. Subsequently, an AOT cache
   *    file can be created with the command:
   *
   *    <p>java -XX:AOTMode=create -XX:AOTConfiguration=app.aotconfig  -XX:AOTCache=app.aot ...
   *  </blockquote>
   *
   * <p>For more information about creating and using the AOT artifacts, and detailed
   * specification of the corresponding JVM command-line options, please refer
   * to <a href="https://openjdk.org/jeps/483">483</a> and <a href="https://openjdk.org/jeps/514">514</a>.
   *
   * <p>Note: Currently there are no APIs to start an AOT recording. AOT recordings must be
   * started using JVM command-line options such as -XX:AOTCacheOutput.
   *
   * <p> There are also no APIs to querying whether the AOT recording is in progress, or what AOT
   * artifacts are being recorded.
   *
   * <p> It is possible for an application to end its own AOT recording programatically, but that
   * would require a change to the application’s own logic.  Even when such a change would
   * be feasible, training-specific logic injected into the application reduces the necessary
   * similarity between training runs and production runs.  Therefore, some AOT training
   * procedures rely on an external agent to select the correct moment to end training.
   * In this way the selected length of training produces the correct set of AOT
   * optimizations in the AOT archive, without interfering with the application code.
   *
   * @return {@code true} if a recording was in progress and has been ended
   * successfully; {@code false} otherwise.
   */
   public boolean endRecording();
}