Does JMeter show the correct average response time for the first page it hits for many virtual users?

Question

I'm load testing a system with 500 virtual users. I've kept the "Ramp-Up period (in seconds)" option to zero. So, what I understand, JMeter will hit the system with 500 virtual users all at the same time. Please correct me if I'm wrong here.

Now, the summary report shows the average response time for the first page is ~100 seconds!. Which is more than a minute and a half of wait time. But while the JMeter is running, I manually went to the same page/url using a browser and didn't have to wait for that long. It was not even close, the page response was almost immediate for me.

My question is: is there any known issue for the average response time of the first page? Is it JMeter which is taking long to trigger that many users?

Thanks in advance. --Ishtiaque

Answer 1

There is no issue in Jmeter related to first page response time.

Summary Report shows all response time details in Milliseconds, the value "100" seconds have you converted milliseconds to seconds?

Also in order to make sure that 500 users hit concurrently, use Synchronizing Timer.

Hope this will help.

Answer 2

While the response times will be accurate, you need to consider the affect of starting so many threads at once on both your server and your client.

500 threads to start at once is not insignificant n the client. If your server has the connections, it will start 500 threads as well.

Ramping over a period of time is more realistic loadwise, but still not really indicative of server capability until the threads have all started and settled in.

Databases can also require a settling in period which can affect response times.

Alternative to ramping is introducing a random wait at the start of each thread before firing the first sample. You can then choose not to ramp over time, but still expect resources on the client to suddenly come under load and change the settings if you hit limits. This will make the entire run much more realistic of typical behaviour. However, you need to determine if your use cases are typical.

Answer 3

Although the heap size is increased, i notice there is still longer time as compared to actual response time. Later i realised it was the probe effect (the extra time a tool generates due to test execution)