[Matthias247]

You need to measure it for your application. A lot of people think „syscalls are expensive“ because that’s repeated for your years, but often it’s actually their implementation and not the overhead.

Eg a UDP syscall will do a whole lot of route lookups, iptable rule evaluations, potential eBPF program evaluations, copying data into other packets, splitting packets, etc. I measured this to be fare more than > 10x of the syscall overhead. But your mileage might vary depending on which calls you use.

As for the applications: these lessons where collected in a CDN data plane. There’s hardly any applications out there which are more async IO intense.