Hello, thanks for your patch!

Our documentation doesn't contain any mentions that fiber.create can fail.

Could you please file an issue (or may be doc bot request) with description in what cases user

can expect that fiber.create will fail. Usually users don't use pcall for fiber.create and this fact can

be quite unexpected for them.

Currently we use say_x to log if error happened.
Strictly speaking when madvise is used to relax
pressue on mm subsystem since we started to use
bigger stacks (due to libreadline increased memory
usage).

Same time mprotect usage is more sensitive -- we
setup guard pages with its help and when failing
it is definitely an error which we should not only
mention in logger but provide a caller diag error.
Here is an example from memcached

-- 
Oleg Babin