[wtallis]

True. But as soon as your program wants to list two directories and knows both names ahead of time, you have an opportunity to fire off both operations for the kernel to work on simultaneously.

And even if your program doesn't have any opportunity for doing IO in parallel, being able to chain a sequence of IO operations together and issue them with at most one syscall may still get you improved latency.

[touisteur]

Yes and even clustering often-used-together syscalls... An interesting 2010 thesis https://os.itec.kit.edu/deutsch/2211.php and https://www2.cs.arizona.edu/~debray/Publications/multi-call.... for something called 'multi-calls'

Interesting times.