It's well known that syscalls are expensive. And that software mitigations against CPU bugs (such as Meltdown) even have made them more expensive. But how expensive are they really? To begin to answer this question I wrote a small micro-benchmark in order to measure the minimal costs of a syscall. Meaning the cost of syscalls one always has to pay whether a context-switch happens or not, even when the work in the kernel is minuscule, i.e. the costs of switching from user-mode to kernel-mode and...