JMC 8 Binary Releases!

Two binary releases of JMC 8 are now available:

• Oracle JMC 8
• AdoptOpenJDK JMC 8

Since I could not find the project provided release notes at any of the vendor sites, I’ve taken the liberty of reproducing them below.

Mission Control 8.0 – New and Noteworthy

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General

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JMC 8.0 – Major New Release!
This is a major new release of Java Mission Control. All binary build of the JMC application using the Eclipse 2020-09 platform will now require JDK 11+ to run, but can be used with OpenJDK 8u272+ and Oracle JDK 7u40+. It can also open and visualize flight recordings from JDK 7 and 8.

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Eclipse 4.16 support
The Mission Control client is now built to run optimally on Eclipse 2020-06 and later. To install Java Mission Control into Eclipse, go to the update site (Help | Install New Software…). The URL to the update site will be vendor specific, and some vendors will instead provide an archive with the update site.

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JOverflow in the Base Distribution
JOverflow is now part of the base distribution of Mission Control, and has been converted to SWT. It also has a brand new TreeMap visualization of the heap occupied by type. To open the new view, go to Window | Show view | Other… and start typing JOverflow, and select JOverflow TreeMap.

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Minor bugfixes and improvements
There are over two hundred fixes and improvements in this release. Check out the JMC 8 Result Dashboard (https://bugs.openjdk.java.net/secure/Dashboard.jspa?selectPageId=19536″) for more information.

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Java Flight Recorder (JFR)

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Flame Graph View Improvements
The Flame Graph View is now available in the standard perspective. It can now be configured to be rendered either as an icicle graph or a flame graph, and the tool tips have been improved. Click on anything representing a selection of events to get the aggregate of stack traces represented by that selection rendered in the Flame Graph View.

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New Graph View
An early access version of a Graph View is now available. The Graph View will show a directed graph where the individual methods are nodes in the graphs, and the edges will represent calls from one method to another. The size of the node will represent the “self” contribution, and the thickness of an edge will correlate with the number of calls from one method to another in the events. To open up the graph view, go to Window | Show view | Other…, then select Mission Control / Graph View. Once the Graph View has opened, it can be docked where you want it to be, or dragged out into a new top level window which can be handled by your window manager. Currently there is no graph pruning, and large graph will take a very long time to layout and render, during which the UI will freeze. Therefore we’ve imposed a user configurable limit on the number of nodes a graph can have for now.

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Predecessors and Successors
The predecessors and successors tabs have been brought back to the Method Profiling page. This means that it is now easy to select a method and easily see wherever that method was called from, and to see what was then called from that method. This is a temporary solution until we have a separate Butterfly/Sandwich view where any selection of a method in a set of events can be rendered in a separately configured view.

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JMC Agent

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Agent 1.0.0
This is the first version where we build and release the JMC agent. The JMC agent is a byte code instrumentation agent, providing an easy way to declaratively generate JFR events from most methods, even methods for which the source code is not available. Either configure the agent with an XML configuration file, or use the MBean to dynamically change the instrumentation whilst the application is running.

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Converter Functions
Now any public static method can be used to convert objects of a specific type to one of the types supported by flight recorder. The converter to use must be explicitly declared per recorded data.

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Bug Fixes

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Area: JFR
Issue: 5734
Synopsis: Overflow in stacktrace tooltips fixed

On Mac, the tooltips shown for the stacktraces could overflow. This is now fixed.

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Known Issues

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Area: General
Issue: 4270
Synopsis: Hibernation and time

After the bugfix of https://bugs.openjdk.java.net/browse/JDK-6523160 in JDK 8, the RuntimeMXBean#getUptime() attribute was re-implemented to mean “Elapsed time of JVM process”, whilst it previously was implemented as time since start of the JVM process. The uptime attribute is used by JMC, together with RuntimeMXBean#getStartTime(), to estimate the actual server time. This means that time stamps, as well as remaining time for a flight recording, can be wrong for processes on machines that have been hibernated.

Area: JFR
Issue: 7122
Synopsis: Rules evaluation never complete

Sometimes the rules evaluation may never complete for the GC rules.

Area: JFR
Issue: 7071
Synopsis: JMC can’t attach to jlinked JVMs

This one is still under investigation, but it seems JMC can’t attach to certain jlinked images.

Area: JFR
Issue: 7068
Synopsis: JfrRecordingTest (uitest) hangs on the automated analysis page

Trying to run uitests on Fedora hangs on JfrRecordingTest.

Area: JFR
Issue: 7007
Synopsis: Unable to edit run configurations for eclipse project after installing JMC plugin

Avoid installing the experimental JMC launcher plug-in into Eclipse until this problem has been resolved.

Area: JFR
Issue: 7003
Synopsis: The graph view does not work on Windows

This is due to a bug in the chromium browser plug-in used by JMC on Windows. See the issue for more information.

Area: JFR
Issue: 6265
Synopsis: JMC crashes with Webkit2+GTK 4

See the issue for more information.

Area: JFR
Issue: 6265
Synopsis: JMC crashes with Webkit2+GTK 4

See the issue for more information.

Area: JFR
Issue: 5412
Synopsis: Dragging and dropping a JFR file into an open analysis page does not work

The expected behaviour would be to open the recording whenever a file is dropped in the editor area, but the behaviour will be defined by the embedded browser component, and not very useful.