How to increase limits on sockets on osx for load testing?

Question

I'm creating a load tester that uses libev to create lots of open tcp connections to an app i'm working on. Currently it bombs out at 256 connections, due to the nofiles limit:

ulimit -n 256 

I can increase this to 1024 by doing the below:

ulimit -n 1024 

But i cannot increase it further. Ideally i want to set it to 1048576. It gives the following error:

ulimit: open files: cannot modify limit: Invalid argument 

How can i increase the ulimit further on osx?

Answer 1

(answer updated to use -S as several commenters suggested)

$ sysctl kern.maxfiles kern.maxfiles: 12288 $ sysctl kern.maxfilesperproc kern.maxfilesperproc: 10240 $ sudo sysctl -w kern.maxfiles=1048600 kern.maxfiles: 12288 -> 1048600 $ sudo sysctl -w kern.maxfilesperproc=1048576 kern.maxfilesperproc: 10240 -> 1048576 $ ulimit -S -n 256 $ ulimit -S -n 1048576 $ ulimit -S -n 1048576