I have been searching for an appropriate method to measure cost of various syscalls in the Linux OS. There have been many questions raised related to this topic in the past, none provide a detailed description of how to measure it accurately. Most of the answers arbitrarily claim the cost of the syscall is 1-2us or a few 100 cycles if it caches on the CPU.
The naive way I can think of measuring the syscall cost is to use rdtscp instruction across a syscall such as getpid(). However this is insufficient for measuring the cost of open(), read() or write() calls accurately. I do can modify the kernel and insert specific timer code across these functions and measure it but that would require changes in the kernel which I don't want to do. I wonder if there is a simpler solution that would allow me to measure it from the userspace itself.