Document class metadata memory reservation impacts (#3266)

* Document class metadata memory reservation impacts

Signed-off-by: Daniel Widdis <widdis@gmail.com>

* Update index.md

* Address review comments

Signed-off-by: Daniel Widdis <widdis@gmail.com>

* Revise wording for more clarity

Signed-off-by: Daniel Widdis <widdis@gmail.com>

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Signed-off-by: Daniel Widdis <widdis@gmail.com>
Co-authored-by: Naarcha-AWS <97990722+Naarcha-AWS@users.noreply.github.com>

_install-and-configure/install-opensearch/index.md

@@ -73,6 +73,8 @@ The [sample docker-compose.yml]({{site.url}}{{site.baseurl}}/install-and-configu
 
   Disables swapping (along with `memlock`). Swapping can dramatically decrease performance and stability, so you should ensure it is disabled on production clusters.
 
+  Enabling the `bootstrap.memory_lock` setting will cause the JVM to reserve any memory it needs. The [Java SE Hotspot VM Garbage Collection Tuning Guide](https://docs.oracle.com/javase/9/gctuning/other-considerations.htm#JSGCT-GUID-B29C9153-3530-4C15-9154-E74F44E3DAD9) documents a default 1 gigabyte (GB) Class Metadata native memory reservation. Combined with Java heap, this may result in an error due to the lack of native memory on VMs with less memory than these requirements. To prevent errors, limit the reserved memory size using `-XX:CompressedClassSpaceSize` or `-XX:MaxMetaspaceSize` and set the size of the Java heap to make sure you have enough system memory.
+
 - `OPENSEARCH_JAVA_OPTS=-Xms512m -Xmx512m`
 
   Sets the size of the Java heap (we recommend half of system RAM).