Jmeter browser concurrency

I was interested to see how well Jmeter emulated the number of concurrent requests made for resource in a web page. If you don’t know a browser like Chrome will make up to 6 concurrent requests for resources embedded in the webpage (images, css, javascript). The aim is that this will improve the performance of the webpage.

So, I configured Jmeter to download the embedded resource in the webpage. It is done by setting the options at the bottom of the HTTP sampler. Under “Optional Tasks” enable embedded resources and set the concurrency pool size. I used 6 to model a Chrome browser.

Next, I went to my test page and using fiddler (debugging proxy) cleared my browser cache and requested a webpage. The diagram below shows the timeline with the request made down the lefthand side and the time across the top.

Next, I configured Jmeter to playback through fiddler and ran my script which requested the same page.

What I wanted to see was near identical timelines. Alas, as you can see very different time lines. Not sure why this is happening but I did notice that many of the images are requested in the .CSS rather than the main webpage.


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