VSync and frame rate instability

[vlad0-0]

Request Description

Context and Problem Description

When VSync is enabled in Minecraft (likely standard double buffering), the frame rate consistently drops from an average of ~80-100 FPS (VSync disabled) to ~40 FPS (VSync enabled default/adaptive).

This behavior is characteristic of VSync dropping to a divisor (60/2 = 30 FPS, or similar) due to slight, transient spikes in frame time (frame pacing instability), even though the average FPS is high.

Troubleshooting Steps Attempted

1. Tested without VSync: FPS stable at 80-100.
2. Enabled VSync in Minecraft (default/adaptive): FPS drops to ~40.
3. Forced Triple Buffering via the AMD driver control panel (OpenGL setting): No noticeable change in FPS stability or VSync behavior.

Questions for Sodium Developers

1. VSync Overriding: Is it true that external driver settings (like Triple Buffering from AMD/NVIDIA panel) cannot reliably override the built-in VSync settings in Minecraft (Java Edition)?
2. Sodium's VSync: Does the Sodium mod specifically modify or replace the functionality of the built-in Minecraft VSync, or does it primarily rely on the vanilla implementation?
3. CPU Render-Ahead Limit: I understand the existing CPU Render-Ahead Limit addresses CPU-side load spikes and smooths the CPU $\to$ GPU pipeline. Is this correct, and does it not directly address GPU-side frame time spikes that cause VSync drops?
4. Future Feature Request: Are there any plans to integrate or enable settings for more advanced frame pacing controls, such as forcing OpenGL Triple Buffering or implementing alternatives like Fast Sync (NVIDIA)/Enhanced Sync (AMD) equivalents?

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Thank you for your hard work on Sodium

[douira]

Related: #2618