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 is more dependent on the kind of performance testing you do(load, spike, endurance etc) on a specific server (a little on hardware dependency)

Keep in mind around these parameters - the client machine on which you are targeting the run of jmeter, there will be a certain amount of heap memory allocated, ensure to have a healthy allocation so that the script does not error out. The highest i had run on jmeter was 1500 on a local environment ( client - server arch), On a Web arch, the highest i had a run was based upon Non- functional requirement were limited to 250 threads,

so it ideally depends on the kinds of performance testing and deployment style and so on..

Answer 2

There is not standard number for this. The maximum number of threads that you can generate from one computer depends completely on the computer's hardware and the OS. The OS by default occupies certain amount of CPU and the RAM.

To find out the maximum threads your computer can handle you can prepare a sample test and run it with only a few threads. Then with each cycle of test run increase the number of threads gradually. During this you also need to monitor the CPU, RAM, Disk I/O and Network I/O of your computer. The moment any of these reach near or beyond 80% (Again for you to decide if near is okay for you or beyond), that is the maximum number of threads your computer can handle. To be on the safer side I would stop at the number when the resource utilization reaches 70%.

Answer 3

I have used JMeter a fair bit and found it is not great at generating really high load. On a 2Ghz Core2 Duo with 2Gb memory you can reasonably expect about 100 threads.

That being said, it is best to run it on your hardware so that the CPU of the PC does not peak at 100% - a stable 80%-90% is best otherwise the results are affected.

I have also tried WAPT 5 - it successfully ran 1000+ threads from the same PC. It is not free but it is more useable than JMeter but doesn't have all of the features.

Outdated answer since at least version 2.6 see https://stackoverflow.com/a/11922239/460802 for a more up to date one.