Update latest release section for 0.49.0

[Sreekala-Gopakumar]

What's New update for the website, for 0.49.0 (February 2025)

[Sreekala-Gopakumar]

First draft (0.48.0 content is live at https://www.eclipse.org/openj9). Note: this isn't an exhaustive list of all the changes, just the main ones:

Eclipse OpenJ9 version 0.49.0 released

February 2025

We're pleased to announce the availability of Eclipse OpenJ9™ v0.49.0.

This release supports OpenJDK 8,11, 17, 21, and 23. For more information about supported platforms and OpenJDK versions, see Supported environments.

Other updates in this release include the following:

• The shared classes cache generation number is incremented causing the VM to create new shared caches, rather than re-creating or reusing existing caches. To save space, all existing shared caches should be removed unless they are in use by an earlier release.
• A new shared classes cache suboption, -Xshareclasses:extraStartupHints=<number> is added to adjust the number of startup hints that can be stored in a shared cache.
• subAllocator related -Xgc options are added to control the compressed reference allocation.
• Support for JDK Flight Recorder (JFR) in the VM is provided as a technical preview for OpenJDK 11 and later running on Linux® x86 or Linux on AArch64 and the recording can be triggered with the jcmd tool.

To read more about these and other changes, see the OpenJ9 user documentation.

Performance highlights include:

• POWER11 CPU recognition and exploitation is added to achieve optimal performance on new hardware.

[Sreekala-Gopakumar]

@pshipton @vijaysun-omr - Are there any performance updates that you want to highlight in the website?
Any other what's new update to be added here? Thanks!

[Sreekala-Gopakumar]

@pshipton @vijaysun-omr - Are there any performance updates that you want to highlight in the website? Any other what's new update to be added here? Thanks!

Anything to be added here?

[pshipton]

Nothing from me.

[pshipton]

I think "A new option, -XX:[+|-]FlightRecorder is added to enable or disable the Java Flight Recorder (JFR) tool in the VM." should be phrased differently. It's not the option that is important, but that JFR preview support is available on the two platforms, and can be enabled via jcmd.

[pshipton]

Similarly the shared classes cache generation number item. Nobody cares why it was incremented, the important part is that obsolete shared caches should be deleted.

[Sreekala-Gopakumar]

I think "A new option, -XX:[+|-]FlightRecorder is added to enable or disable the Java Flight Recorder (JFR) tool in the VM." should be phrased differently. It's not the option that is important, but that JFR preview support is available on the two platforms, and can be enabled via jcmd.

@pshipton - I need a clarification. In the eclipse-openj9/openj9#20854 issue, it is mentioned that

Currently, JFR is enabled by default on all platforms that support it, and it cannot be disabled. We have been using -XX:+FlightRecorder to indicate if the JVM should start with recording enabled. This is not consistent with the RI. With this change -XX:[+|-]FlightRecorder toggles whether JFR is enabled. By default JFR will remain enabled, but we now have the ability to disable it. -XX:StartFlightRecording will be used to indicate that a recording should be begin at startup.

So, does that mean that JFR support was always there before this release but the ability to disable with this option was added in this release? If so, then would we have to emphasise the fact that JFR can be enabled via jcmd on these 2 platforms rather than that "JFR preview support is available on the two platforms"?

Thanks!

[pshipton]

@tajila fyi

This is the first release where JFR support is available (other than the special preview put out in Dec). It's enabled by default, although -XX:-FlightRecorder can be used to disable it. The "news" is that the JFR tech preview is available in this release.

[vijaysun-omr]

I don't have anything specific to call out, since we did a collection of smaller improvements is my sense. @mpirvu @0xdaryl @zl-wang @r30shah @jasonkatonica in case anything stands out for us to call out.

[zl-wang]

POWER11 CPU recognition and exploitation was added in 0.49

[Sreekala-Gopakumar]

Similarly the shared classes cache generation number item. Nobody cares why it was incremented, the important part is that obsolete shared caches should be deleted.

So, does this count as an update in this release that needs to be highlighted or can I delete it from this list? Thanks!

[Sreekala-Gopakumar]

POWER11 CPU recognition and exploitation was added in 0.49

Could you please provide a little more clarity about what exactly is the performance highlight here? Any other word that can replace "exploitation"? Thanks!

[zl-wang]

Rephrased as: In order to achieve optimal performance on new hardware, POWER11 CPU recognition and exploitation was added in 0.49

word exploitation is the right word in context (CPU feature exploitation .... that has been the expression we used ever).

[pshipton]

Re #369 (comment)

See https://eclipse-openj9.github.io/openj9-docs/version0.49/#change-to-the-shared-classes-cache-generation-number

The part we want to highlight is - To save space, all existing shared caches can be removed unless they are in use by an earlier release. For more information, see Housekeeping and -Xshareclasses.

[r30shah]

Nothing major on Z apart from the smaller improvement changes that recognizes and accelerate certain intrinsic candidates on Z.

[mpirvu]

Nothing special from the control point of view. A couple of changes are protected by options as they are experimental and not enabled by default (AOT support for method handles and AOT load based on dependencies).

[jasonkatonica]

There are no new openj9 updates for the semeru distributed security components.

[Sreekala-Gopakumar]

Re #369 (comment)

See https://eclipse-openj9.github.io/openj9-docs/version0.49/#change-to-the-shared-classes-cache-generation-number

The part we want to highlight is - To save space, all existing shared caches can be removed unless they are in use by an earlier release. For more information, see Housekeeping and -Xshareclasses.

Another clarification required :) Wasn't this removal of all existing shared caches unless they are in use by an earlier release an existing capability? So, is this specific to this release?

[pshipton]

It's not a capability or a new feature, it's something the user should do. The cache generation was incremented which will leave existing caches orphaned on the machines using disk space. The user should take action and remove them.

[Sreekala-Gopakumar]

Rephrased as: In order to achieve optimal performance on new hardware, POWER11 CPU recognition and exploitation was added in 0.49

word exploitation is the right word in context (CPU feature exploitation .... that has been the expression we used ever).

I have updated. Please check and confirm. Thanks!

[Sreekala-Gopakumar]

@pshipton - I have made the changes. Please check and confirm. Thanks!

[pshipton]

This seems awkward: The shared classes cache generation number is incremented because of which the VM creates a new shared classes cache, rather than re-creating or reusing an existing cache.

I suggest: The shared classes cache generation number is incremented causing the VM to create new shared caches, rather than re-creating or reusing existing caches.