From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 4 May 2020 01:08:56 -0400
Subject: [PATCH] Set cap on JDK per-thread native byte buffer cache

See: https://www.evanjones.ca/java-bytebuffer-leak.html

This is potentially a source of lots of native memory usage.

We are clearly seeing native usage upwards to 1-4GB which doesn't make sense.

Region File usage fixed in previous patch should of tecnically only been somewhat
temporary until GC finally gets it some time later, but between all the various
plugins doing IO on various threads, this hidden detail of the JDK could be
keeping long lived large direct buffers in cache.

Set system properly at server startup if not set already to help protect from this.

diff --git a/src/main/java/org/bukkit/craftbukkit/Main.java b/src/main/java/org/bukkit/craftbukkit/Main.java
index 093dbeae2784d51dae74f66e3e1ce5bf6a370428..93340e9470b23f2d8c91338e63e95c6465e69c3c 100644
--- a/src/main/java/org/bukkit/craftbukkit/Main.java
+++ b/src/main/java/org/bukkit/craftbukkit/Main.java
@@ -21,6 +21,7 @@ public class Main {
 
     public static void main(String[] args) {
         // Todo: Installation script
+        if (System.getProperty("jdk.nio.maxCachedBufferSize") == null) System.setProperty("jdk.nio.maxCachedBufferSize", "262144"); // Paper - cap per-thread NIO cache size
         OptionParser parser = new OptionParser() {
             {
                 acceptsAll(asList("?", "help"), "Show the help");