performance - JMeter understanding ramp-up

Question

This is the configuration of my test plan thread properties:

Number of Threads (users): 100
Ramp-up Period (in seconds): 10
Loop Count : Forever
Delay thread creation until needed: No
Scheduler: No

I ran the test overnight with the total duration of 14 hours and 7 minutes (approximately 50820 seconds). After loading the jtl file, The number of samples shown in summary report is 1050975. I tried to compute but I can't understand how it came up with that many sample.

If Ramp-up Period is the time taken by JMeter to create the number of threads per iteration and if the duration of the test is 50820 seconds, then I should have 508200 samples only ( 50820/10 * 100 ). I do not know how or if Loop Count affects this.

Answer 1

The ramp-up in the Thread Group is the time JMeter should take to start the total number of threads. In your situation this means that every 0.1 second a new thread starts giving 100 running threads after 10 seconds. These 100 threads perform your test iterations back-to-back, so after the ramp-up 100 threads run continously for the duration of the test.