It depends on what you really want to do.

If it's just stressing nginx with a unique request, ab should be the
best option. And I think this is what you're looking for.

If you want to make some kind of more complex benchmarking, there is
many tools (free and commercial) for that.

I've tested :
- the free jmeter which is good to stress a webserver with differents
scenarios. The results are good if you keep them simple. Don't except
to make a huge bench with complex results easily.
- the commercial qaload which is very expensive and very complex but
very powerfull. You need to practice to get rid of it
- the commercial neoload which is powerfull and very simple. The
reports made after are amazing. I'm using it for 4 months and I'm very
happy with it.

But benchmarking isn't just easy.

2009/6/27 meto <nginx-forum@nginx.us>:
> good old ab from apache dev?
>
> Posted at Nginx Forum: http://forum.nginx.org/read.php?2,3434,3462#msg-3462
>
>
>