[portmanteaufu]

You may already be familiar with this and are specifically concerned with GC. However, for what it's worth, it's not just the absence of garbage collection that makes languages like Rust and C faster. A huge piece of their performance is the level of control that they offer over types' layout in memory and where things get stored. Rust's preference for stack allocations and the absence of a mandatory per-Object size overhead (a la Java) really allow it to shine.