High memory usage warning despite XMS = XMX with FAWE

[NoltoxGit]

Server Implementation

Paper

Server Version

1.21.8

Describe the bug

I regularly receive the error message High memory usage detected, FAWE will attempt to slow operations to prevent a crash. even though my Java startup flags have the same value for XMS and XMX. This seems abnormal as I expect FAWE to handle available memory correctly with this configuration.

To Reproduce

1. Start the Minecraft server with FAWE installed
2. Set Java startup flags with XMS = XMX
3. Use WorldEdit or FAWE normally
4. Observe the high memory usage warning message appearing in the console

Expected behaviour

I expect FAWE to not show a high memory usage message if I properly set XMX and XMS in my Java flags. I expect FAWE to properly use all available memory without unnecessarily displaying this alert or slowing operations.

Screenshots / Videos

No response

Error log (if applicable)

https://mclo.gs/iKvHP92

Fawe Debugpaste

https://athion.net/ISPaster/paste/view/cc8a76ca2da7434b87e5538724fab576

Fawe Version

FastAsyncWorldEdit-2.14.1-SNAPSHOT-1212

Checklist

• I have included a Fawe debugpaste.
• I am using the newest build from https://ci.athion.net/job/FastAsyncWorldEdit/ and the issue still persists.

Anything else?

Other users on forums and Discord reported similar messages even with proper memory flags. It may be a false positive or an internal memory management issue of FAWE.

[SirYwell]

Maybe we should switch to use https://docs.oracle.com/en/java/javase/25/docs/api/java.management/java/lang/management/MemoryPoolMXBean.html#CollectionThreshold instead, but this needs some exploration into which memory pools are affected then for typical GCs.

[NoltoxGit]

Maybe we should switch to use https://docs.oracle.com/en/java/javase/25/docs/api/java.management/java/lang/management/MemoryPoolMXBean.html#CollectionThreshold instead, but this needs some exploration into which memory pools are affected then for typical GCs.

Maybe due to usage of ZGC and Java GraalVM 25 🤔

[NoltoxGit]

Maybe we should switch to use https://docs.oracle.com/en/java/javase/25/docs/api/java.management/java/lang/management/MemoryPoolMXBean.html#CollectionThreshold instead, but this needs some exploration into which memory pools are affected then for typical GCs.

Re,
The method you are using checks the allocated memory against the maximum memory;
On the other hand, the minimum allocated memory is set to the same value as the maximum allowed memory.