You are correct that all attempts at bringing scheduling out of kernel space have failed, even the L4 folks found the performance impact intolerable. However,

You are correct that all attempts at bringing scheduling out of kernel space have failed, even the L4 folks found the performance impact intolerable. However, this uses eBPF to perform logical operations within kernel space that are loaded from user space at runtime. See https://ebpf.io/ https://ebpf.io/ for more info.