Set Netty pooled buffer size to 2MiB

proxy/src/main/java/com/velocitypowered/proxy/Velocity.java

@@ -12,6 +12,17 @@ public class Velocity {
     // We use BufferedImage for favicons, and on macOS this puts the Java application in the dock.
     // How inconvenient. Force AWT to work with its head chopped off.
     System.setProperty("java.awt.headless", "true");
+
+    // By default, Netty allocates 16MiB arenas for the PooledByteBufAllocator. This is too much
+    // memory for Minecraft, which imposes a maximum packet size of 2MiB! We'll use 2MiB as a more
+    // sane default.
+    //
+    // Note: io.netty.allocator.pageSize << io.netty.allocator.maxOrder is the formula used to
+    // compute the chunk size. We lower maxOrder from its default of 11 to 8. (We also use a null
+    // check, so that the user is free to choose another setting if need be.)
+    if (System.getProperty("io.netty.allocator.maxOrder") == null) {
+      System.setProperty("io.netty.allocator.maxOrder", "8");
+    }
   }
 
   /**