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HPjmeter 4.1 User's Guide

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  HPjmeter 4.1 User's Guide > Chapter 5 Profiling Applications   

Scaling Comparison Data

At times it is not possible to run performance testing benchmarks under identical conditions. For example, the load may be slightly different, or the measurement duration may differ, or you may want to compare the same activity at different times of the day or week. To compensate for these differences, you can scale one set of data to more closely match the other set.

Scale and Scale Special are available from the Edit menu on the profiling viewer when comparing two profiling data files. Use these scale options when the data files that you are comparing are unequal in some way.

For example, imagine a scenario where you are able to generate a constant load on your systems, but one profile represents 10 minutes of application activity and the other only 5 minutes. You can use Edit ->Scale Special to set and apply a factor of 2 to the shorter time period, which normalizes the 5–minute data set to 10 minutes for easier presentation and interpretation.

Or, suppose that you want to look at activity for a particular application during peak business hours and compare it to a relatively quiet period at night. You know that the number of transactions will differ, so how do you compare the amount of work done for each transaction?

Open a profiling viewer with the peak time data. Open another viewer with the night data. In the peak time viewer, click File->Compare to open a profiling viewer with the comparison data.

In the comparison viewer, select Metrics->Code/CPU->Method Call Count. Click to select a known method that represents a unit of work or a transaction. Then click Edit ->Scale from the menu bar. HPjmeter automatically recalculates the call count for each method in the peak data with the result that each value is normalized to the ratio of the call counts for the selected method.

HPjmeter then sorts the data. By viewing the information that appears in the newly sorted list, you can compare differences in activity between the two data files. If you want to see how this works in detail, select View->Show Formula to display the calculations that HPjmeter uses.