What should be the value of “parallel download” field in HTTP sampler of Jmeter

Question

I hit a URL through my browser and and check the Network tab of the browser, it showed me like: DOMContentLoad: 4 seconds (Just to load DOM) Load: 7 seconds(DOM + scripts + assets)

When I hit the same through J-Meter, it gave me a response time of ~seconds.

So, through, J-meter it's taking very long time to respond. Then, I enabled "Parallel downloads" and added a value to number field under the advanced option of HttpSampler. The response time reduced.But, still I am not sure what should be the value of that number.

Can anyone please help me out here in understanding on what factor we decide the value of the number field.

Answer 1

Modern browsers use ~6 parallel threads for downloading embedded resources so you should put 6 there. Adjust the value up or down to mimic browser(s) you would like to simulate.

Also don't forget to add HTTP Cache Manager as read browsers download embedded resources only once , on subsequent requests the resources (images, scripts and styles) are being returned from the browser's cache so you need to mimic this behaviour as well.

And finally make sure you are excluding external domains (3rd party banners, counters, maps, whatever) to focus solely on your application calls.

See Web Testing with JMeter: How To Properly Handle Embedded Resources in HTML Responses for more details.