Add option to toggle Extended HCR capability

eclipse-openj9#1352 New option -XX:[+|-]EnableExtendedHCR added to the TOC. Closes eclipse-openj9#1352 Signed-off-by: Sreekala Gopakumar <[email protected]>
Sreekala-Gopakumar · Jun 28, 2024 · edb3c49 · edb3c49
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diff --git a/docs/version0.46.md b/docs/version0.46.md
@@ -29,6 +29,7 @@ The following new features and notable changes since version 0.45.0 are included
 - [MD5 message digest algorithm support for OpenSSL](#md5-message-digest-algorithm-support-for-openssl)
 - [Support added for the `com.sun.management.ThreadMXBean.getTotalThreadAllocatedBytes()` API](#support-added-for-the-comsunmanagementthreadmxbeangettotalthreadallocatedbytes-api)
 - [The JITServer AOT caching feature enabled by default at the JITServer server](#the-jitserver-aot-caching-feature-enabled-by-default-at-the-jitserver-server)
+- [New `-XX:[+|-]EnableExtendedHCR` option added](#new-xx-enableextendedhcr-option-added)
 
 ## Features and changes
 
@@ -56,6 +57,12 @@ Although this option is by default enabled at the server, it is still disabled f
 
 For more information, see [ `-XX:[+|-]JITServerUseAOTCache`](xxjitserveruseaotcache.md).
 
+### New `-XX:[+|-]EnableExtendedHCR` option added
+
+By default, the extended Hot Code Replace (HCR) capability in the VM is disabled for all OpenJDK versions. You can enable or disable the HCR capability by using the [`-XX:[+|-]EnableExtendedHCR`](xxenableextendedhcr.md) option.
+
+The extended HCR feature is deprecated in this release and will be removed in a future release. From OpenJDK 25 onwards, extended HCR will not be supported. Following that, the extended HCR support will be removed from other earlier OpenJDK versions also.
+
 ## Known problems and full release information
 
 To see known problems and a complete list of changes between Eclipse OpenJ9 v0.45.0 and v0.46.0 releases, see the [Release notes](https://github.com/eclipse-openj9/openj9/blob/master/doc/release-notes/0.46/0.46.md).

diff --git a/docs/xxenableextendedhcr.md b/docs/xxenableextendedhcr.md
@@ -0,0 +1,52 @@
+<!--
+* Copyright (c) 2017, 2024 IBM Corp. and others
+*
+* This program and the accompanying materials are made
+* available under the terms of the Eclipse Public License 2.0
+* which accompanies this distribution and is available at
+* https://www.eclipse.org/legal/epl-2.0/ or the Apache
+* License, Version 2.0 which accompanies this distribution and
+* is available at https://www.apache.org/licenses/LICENSE-2.0.
+*
+* This Source Code may also be made available under the
+* following Secondary Licenses when the conditions for such
+* availability set forth in the Eclipse Public License, v. 2.0
+* are satisfied: GNU General Public License, version 2 with
+* the GNU Classpath Exception [1] and GNU General Public
+* License, version 2 with the OpenJDK Assembly Exception [2].
+*
+* [1] https://www.gnu.org/software/classpath/license.html
+* [2] https://openjdk.org/legal/assembly-exception.html
+*
+* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
+-->
+
+# -XX:[+|-]EnableExtendedHCR
+
+This option enables or disables the extended Hot Code Replace (HCR) capability in the VM.
+
+## Syntax
+
+        -XX:[+|-]EnableExtendedHCR
+
+| Setting               | Effect  | Default                                                                            |
+|-----------------------|---------|:----------------------------------------------------------------------------------:|
+| `-XX:+EnableExtendedHCR` |  Enable   |                                               |
+| `-XX:-EnableExtendedHCR` |  Disable  |    :fontawesome-solid-check:{: .yes aria-hidden="true"}<span class="sr-only">yes</span>                          |
+
+## Explanation
+
+Supporting extended HCR has a maintenance cost and because only few users use this capability, the extended HCR feature is deprecated and will be removed in a future release. From OpenJDK 25 onwards, extended HCR will not be supported. Following that, the extended HCR support will be removed from other earlier OpenJDK versions also.
+
+If the extended HCR support is disabled (`-XX:-EnableExtendedHCR`), it might result in a JVMTI failure. In case of such a failure, the following warning message is displayed:
+
+```
+Warning: Extended HCR is disabled, enable with -XX:+EnableExtendedHCR. This feature is deprecated. In the future, the extended HCR capability, and the option to enable it, will be completely removed from all versions.
+```
+
+## See also
+
+- [What's new in version 0.46.0](version0.46.md#new-xx-enableextendedhcr-option-added)
+
+
+<!-- ==== END OF TOPIC ==== xxenableextendedhcr.md ==== -->
diff --git a/mkdocs.yml b/mkdocs.yml
@@ -399,6 +399,7 @@ nav:
             - "-XX:[+|-]Enable3164Interoperability"                              : xxenable3164interoperability.md
             - "-XX:[+|-]EnableCPUMonitor"                                        : xxenablecpumonitor.md
             - "-XX:[+|-]EnableDynamicAgentLoading"                               : xxenabledynamicagentloading.md
+            - "-XX:[+|-]EnableExtendedHCR"                                       : xxenableextendedhcr.md
             - "-XX:[+|-]EnsureHashed"                                            : xxensurehashed.md
             - "-XX:[+|-]ExitOnOutOfMemoryError"                                  : xxexitonoutofmemoryerror.md
             - "-XX:[+|-]GlobalLockReservation"                                   : xxgloballockreservation.md