If you are looking to get your performance back on linux playing minecraft, then you have to drop OpenJDK. If you are on Ubuntu or another Debian based distro here
is a tutorial to install Oracle's JDK, which is far superior to OpenJDK.
OpenJDK and Oracle JDK share 97% of their source code. I completely disagree with you about the "superiority" of Oracle JDK. Maybe Minecraft is slower with OpenJDK but it doesn't mean than OpenJDK is slower than Oracle JDK. There is still a known bug preventing from running Minecraft as an applet with Icedtea-web & OpenJDK but actually it comes from something else as you can see here
. Minecraft, an extremely famous game has a bad support of OpenJDK and you blame OpenJDK instead of blaming Minecraft itself, it's not fair. I have never noticed measurable performance differences when developing 3D applications in Java when running them both with OpenJDK and Oracle JDK.