testserver/patches/server/0410-Set-cap-on-JDK-per-thread-native-byte-buffer-cache.patch

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 987bc4577190d827718b5144656aaddf22599cab..5b48047242e20c216b110502935763ea433c55cd 100644
--- a/src/main/java/org/bukkit/craftbukkit/Main.java
+++ b/src/main/java/org/bukkit/craftbukkit/Main.java
@@ -28,6 +28,7 @@ public class Main {
         }
         // Paper end
         // 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(Main.asList("?", "help"), "Show the help");