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From Felix Frank>
Subject Re: Jmeter time vs User Percieved time
Date Mon, 23 Aug 2010 06:51:33 GMT
On 08/23/10 08:20, ankitR wrote:
> Hi,
> I am using Jmeter to stress the server with 50 concurrent users.At the same
> time I note down the manual time( i.e user perceived time as i am interested
> in the high level UI rendering time) by opening a browser and following the
> same steps as in Jmeter script. I am using three different machines for this
> ( app server, Jmeter scripts & for browser). when I note the time taken by
> Jmeter for loading the jsp i am interested in it shows - average time = 19s
> and 90% line = 35s, whereas the manual time for loading the same page is 7s.
> I have used cache manager in Jmeter and also am using download all embedded
> resources so that jmeter can emulate the browser behaviour to some extent.
> since Jmeter is not a browser and doesn't give the UI rendering time, I
> expected the manual time to be more than the jmeter time not vice-versa.
> (the times mentioned earlier are averages of multiple runs).
> Now I am thinking should I even compare the two times? 

You absolutely should, but your base assumption may be wrong.

I remember a stress test where Jmeter consistently reported overlong
times. The reason where background scripts. The web developer managed
site statistics by embedding a 1x1 transparent gif in each page, the
source being an elaborate call to a php script. When the load was high,
the web servers took several seconds to process that script. However,
the page was displayed fine way before that. So while Jmeter patiently
waited 20 seconds or more for each page, they were visible much sooner.

Use the excellent FireBug extension for Firefox (specifically, its "Net"
tab) to monitor loading times for DOM content and all embedded elements
respectively. Google's Chrome has a similar feature built in.


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