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--- | ||
layout: page | ||
title: BlueMap and RAM | ||
parent: Community Guides | ||
nav_order: 16 | ||
--- | ||
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# BlueMap and RAM | ||
{: .no_toc } | ||
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Do not be alarmed if you notice that BlueMap seems to be using a lot of RAM. | ||
This is actually perfectly normal and should not be an actual problem. | ||
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There are multiple things that contribute to this effect: | ||
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### 1. Unused RAM | ||
BlueMap is using **unused** heap-space (RAM) to cache some things | ||
like e.g. chunk-data and resources to improve performance. | ||
But as soon as your JVM (your server) needs this cache-space somewhere else, it can do so! | ||
BlueMap is not hard-reserving that space, so it can't cause an OOM because of this. | ||
*(Technically this is done using a [SoftValue-Cache](<https://www.baeldung.com/java-caching-caffeine#3-reference-based-eviction>))* | ||
After all, it is always said that unused RAM is wasted RAM. | ||
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### 2. Garbage Collection | ||
RAM/Heap management in your JVM is done using a Garbage Collector. | ||
Your JVM runs this GC in intervals to free up heap-space that is no-longer used. | ||
If you have a big heap of multiple GBs, depending on your GC-configuration, | ||
it can wait for a long time until it decides to run the GC and free some space. | ||
This has the effect that your RAM-Usage will keep climbing until the GC is ran. | ||
**Or:** until you restart the server. | ||
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So if you remove BlueMap to prove that it is using a lot of RAM, | ||
what you actually did is you restarted the server, | ||
resetting your heap that has risen to a higher amount | ||
and now it looks like you have much less heap-usage, | ||
but all it actually is just a freshly cleaned heap | ||
which will rise again if the server runs for a while, | ||
even if BlueMap is removed now. | ||
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## Conclusion | ||
If you are having OOM errors, it is usually unlikely that BlueMap is causing them. | ||
In fact, BlueMap has been tested to run fine with only 500MB of RAM! | ||
However, if you still believe it's BlueMap causing your OOM, | ||
then please use the Java startup flag `-XX:+HeapDumpOnOutOfMemoryError` | ||
to create a heap-dump the next time an OOM occurs, | ||
and send it in the [Discord](https://bluecolo.red/map-discord) in some way. | ||
(Heap-dumps are very big unfortunately, so you may need to use a cloud service) | ||
We are willing to analyse that heap-dump to check what actually has caused your OOM | ||
and if it really was BlueMap :) | ||
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Not entirely happy with this sentence yet. It is very long. Could use some splitting up.