Ixeris

Overview

Ixeris is a mod that optimizes the client performance by offloading event polling to a separate thread, making available more CPU time for the render thread.

You might have noticed a visible drop of the FPS when you move your mouse. Part of the FPS drop is because the game does have additional jobs to do when you turn the camera, like calculating the visibility of chunks. However, because of the inefficiency in the native code that polls events and the JNI upcall overhead, some of the CPU time, otherwize can be utilized for rendering, are unnecessarily spent on the call to glfwPollEvents(). This is most noticeable on Windows, especially when your mouse has a high polling rate.

This mod resolves this issue by calling glfwPollEvents() on the main thread, which means event polling no longer blocks the render thread. This way, the render thread can keep working while GLFW retrieves events from the operating system. FPS improvements while standing still are unlikely, but you will have a much smoother framerate when turning the camera.

Benchmarks

These tests are done after the world has fully loaded and the framerate has stabilized. The mouse has a polling rate of 1000Hz. F3+Esc is pressed to make sure the framerate change when moving the mouse is the result of event polling, not any other calculation.

The "Idle FPS" column shows the FPS when not moving the mouse. The next two columns show the FPS when moving the mouse quickly over the game window, without Ixeris and with Ixeris, respectively. The last column compares the FPS when Ixeris is and is not installed.

Thread Safety (Technical Detail)

In vanilla Minecraft, the render thread is synonymous with the main thread. Ixeris creates a new thread which becomes the render thread and does everything the game normally does, except event polling, which is done on the main thread.

In its current state Ixeris should not break thread safety. Callbacks registered with glfwSet*Callback are executed on the render thread. Calls to GLFW functions that are required to be called on the main thread, if made on other threads, are dispatched to the main thread. These calls may immediately return if they are safe to be delayed, or otherwise may block the caller until the call is finished.

As of version 3.1.0, the requirements of thread safety in the GLFW documentation are strictly obeyed.