The article is not accurate. Pre-KPTI, the cost of a system call might have been hundreds of cycles total. On a modern chip, that’s ~50ns. Add kernel code for

The article is not accurate. Pre-KPTI, the cost of a system call might have been hundreds of cycles total. On a modern chip, that’s ~50ns. Add kernel code for relevant operation. A read on a pipe might be 500ns total. A read on a cached file would be similar. Add a few hundred cycles for KPTI. A typically function call will be tens of cycles, but with lots of copies and stack changes can easily be hundreds.