How do threads and number of iterations impact test and what is JMeter’s max. thread limit

Question

1. Would you please tell me the max limit of no. of threads that i can use in JMeter 2.4 for conducting a load test?

2. Is there any difference in taking all threads in a single loop or by taking less no. of threads and initialize loop to achieve same no. of users/threads?

Example:

No. of threads=500 Ramp up=1000 Loop=1  

whether it is same as

No. of threads=50 Ramp up=100 Loop=10 

or is there any difference in terms of result?

Answer 1

1. The max number of threads is determined by a lot of factors, see this answer https://stackoverflow.com/a/11922239/460802

2. There is a big difference in what you are proposing.

   • "500 threads, Loop 1 " Means 500 threads AT THE SAME TIME doing the loop ONCE.
   • "50 threads, loop 10" Means only 50 threads AT THE SAME TIME doing the loop TEN TIMES.

In theory you get the same number of results (500), but you are hitting the server in a very different manner.

Answer 2

Maximum number of users depends of your OS,free RAM and connection. Win XP is limited to 3000 processes at the same time. On Linux is more than 3000 but I don't how much. Be careful that you test server and if you start 3000 thread on your machine require a lot of resources and the test will not be real. I pref fare to start maximum 300 users per machine. If you want to increase the number of users than use distributed testing (use more machine as DoS attack). In theory is the same number of request but the time complexity is not the same.