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WAS PMI. servlet response time.

Hi, seems it isn't quite relevant group to ask but I don't know any better :).

So, I measure response time for a servlet with three tools: LR Web Page Diagnostics, LR transaction brackets and WAS MPI counter for servlet response time (via Sitescope). Results for first two are rather like, but WAS provides measurements with completely another curve.

My assumption is what difference between curves is result of algorithm (expression) which is used for average response time calculation.

Could somebody clarify what approach is actually used by WebSphere for calculation of servlet response time available via PMI.

Thanks,
Alexander

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Re: WAS PMI. servlet response time.

Hi,

The difference here is that the PMI metrics are gathered from your servlet container whereas your LR response times are from the perspective of your load generator. This means that even where you have a 1:1 mapping of LR transactions to servlets you should see that the PMI metrics show faster response times as they do not include any network time for example.

A second cause of difference is that as you say the samples from each monitor may not be exactly the same. With the PMI metrics you can get a sample which is already an average such as for average servlet latency. LR may then average that again depending on the granularity of the curve you are looking at. This compares with LR which will gather the individual LR transaction response times and then average them.

Hope that makes sense.
Steve
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Re: WAS PMI. servlet response time.

Thanks, for replay.
Yes, you are right, RT on LR should be always lower than on MPI, since network latency isn't counted. But in my case it wasn't always true, I assume, as a result of averaging in MPI.

And what I really would like to know is exact algorithm used to calculate servlet response time which .

Seems, accordingly to my observation, it just divide total time spent in servlet, since last restart, by the number of calls to it.

Alexander
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Re: WAS PMI. servlet response time.

According to network world there is a free response time monitoring tool http://www.real-user-monitoring.com
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