the multiple execution seems to be much slower with the empty executable than with /bin/true using the multitime tool https://tratt.net/laurie/src/multitime/
$ multitime -n 10 ./empty
===> multitime results
1: ./empty
Mean Std.Dev. Min Median Max
real 0.006 0.000 0.005 0.006 0.006
user 0.001 0.001 0.000 0.002 0.002
sys 0.000 0.001 0.000 0.000 0.002
$ multitime -n 10 /bin/true
===> multitime results
1: /bin/true
Mean Std.Dev. Min Median Max
real 0.002 0.000 0.001 0.002 0.003
user 0.001 0.000 0.001 0.001 0.001
sys 0.000 0.000 0.000 0.000 0.000
> What is also interesting is that while strace seems to report much less overhead in "./empty" compared to /bin/true
That's because it reports an error and does not actually execute the file.
>strace: exec: Erreur de format pour exec()
`strace` uses one of the exec()-style functions that don't automatically invoke a shell here. And if it did, it would invoke an entire shell (/bin/sh, typically), which might have more overhead.
----
You need to be very careful when measuring this, because what happens is that a shell executes the shebangless empty file.
If you try launching it from e.g. a C program using execlp(), it will have to first start that shell.
If you try launching it from e.g. bash, it might directly run that in-process or at least after a fork() or similar, skipping some of the shell setup.
