What is the highest number of threads that is reasonable to simultaneously run in Jmeter?

Question

I want to use the highest possible number of threads (to use less computers) but without making the bottleneck to be in the client.

Answer 1

It'll depend on the hardware you run on as well as the underlying script. I've always felt that this fuzziness is the biggest problem with traditional load testing tools. If you've got a small budget ($200 or so gets you a LOT of testing), check out my company's load testing service, BrowserMob.

Besides our Real Browser Users (RBUs) which control thousands on actual browsers for the purpose of performance and load testing, we also have traditional virtual users (VUs). Scripts are written in JavaScript and can make various HTTP calls.

The reason I bring it up is that I always felt that the game of trying to figure out how many VUs you can fit on your load gen hardware is dangerous. It's so easy to get bad results without realizing it.

To solve that for BrowserMob, we took an extremely conservative approach on the number of VUs and RBUs per CPU core: no more than 1 browser or 50 threads per CPU core, and sometimes much less. In the world of cloud computing, CPU cycles are so cheap that it just doesn't make sense to try to overload machines.