Techniques to measure application performance

Question

I maintain an application which, during the course of two years, has constantly required new hardware to be even usable, due to the amount of new users / new data inserted. However, justifying the investiment is sometimes very hard to do.

I started to wonder - how can I establish the maximum number of users a web application currently suports?

I thought of using JMeter scripts but they can get really nasty to implement when having to simulate file transfers and decison trees. What do you guys use?

Answer 1

You can use this performance algorithm:

http://i.msdn.microsoft.com/cc500561.fig02_L(en-us).gif

R Response time. The total time from the user requesting a page (by clicking a link, and so on) to when the full page is rendered on the user's computer. Typically measured in seconds. Payload Total bytes sent to the browser, including markup and all resources (such as CSS, JS, and image files).

Bandwidth Rate of transfer to and from the browser. This may be asymmetrical and might represent multiple speeds if a given page is generated from multiple sources. Usually, it is averaged together to create a single bandwidth expressed in bytes per second.

AppTurns The number of resource files a given page needs. These resource files will include CSS, JS, images, and any other files retrieved by the browser in the process of rendering the page. In the equation, the HTML page is accounted for separately by adding in round-trip time (RTT) before the AppTurns expression.

RTT The time it takes to round-trip, regardless of bytes transferred. Every request pays a minimum of one RTT for the page itself. Typically measured in milliseconds.

Concurrent Requests Number of simultaneous requests a browser will make for resource files. By default, Internet Explorer performs two concurrent requests. This setting can be adjusted but rarely is.

Cs Compute time on the server. This is the time it takes for code to run, retrieve data from the database, and compose the response to be sent to the browser. Measured in milliseconds.

Cc Compute time on the client. This is the time it takes for a browser to actually render the HTML on the screen, execute JavaScript, implement CSS rules, and so on.

For more details:

http://msdn.microsoft.com/en-us/magazine/cc500561.aspx

Answer 2

We use HP's LoadRunner. But it's not cheap, and you still have to create scripts, test cases.