Web Performance Matters

Managing Response Time for Web Sites and Web Applications

Human beings don’t like to wait. We don’t like waiting in line at a store, we don’t like waiting for our food at a restaurant, and we definitely don’t like waiting for Web pages to load.

Those words open Web Page Response Time 101, an excellent article by Alberto Savoia. Although it was published in July 2001, it remains every bit as relevant and useful today. It does a really good job of explaining and summarizing two fundamental aspects of Web performance -- human behavior and site behavior.

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Most hosted Web Analytics vendors charge you according to page views -- not unreasonable since each view is a call to their server and a new record in their database. But what happens when Ajax and other rich applications eliminate the notion of a "page"?

That's from Web 2.0 Changes Web Analytics Pricing Models, a recent post by Phil Kemelor in CMP's Intelligent Enterprise Weblog. Describing how he sees Web Analytics (WA) vendors adapting to Web 2.0, Phil continues ...

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Recent posts have discussed some insightful statements about the importance of measurements by Lord Kelvin, Grace Hopper, Tom DeMarco, and Tom Gilb.

In the last of these, I concluded that Gilb's observation (Anything you need to quantify can be measured in some way that is superior to not measuring it at all) gets across the value of measurements without making any claims that are too far-reaching or contentious.

A follow-up comment and the ensuing conversation with Ben Simo -- author of Quality Frog, a blog about software testing and software quality -- reminded me of this post, which I'd been meaning to complete and publish for a while. I'll explain the reasons for the delay below.

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Posts on The Importance of Measurements and Controlling Software Projects have reviewed the origin of the saying that "you can't manage what you can't (or don't) measure". Today I look more closely at its meaning and validity -- how true is it?

One apparent contradiction is that this much quoted fact of management is also widely viewed as a fallacy -- or at least, as an over-exaggerated claim -- especially by people in the software engineering profession, which seems (in the person of Tom DeMarco) to have coined the saying in the first place. That contradiction was highlighted in a 2003 book by Robert L. Glass, Facts and Fallacies of Software Engineering [Amazon].

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My post on The importance of measurements highlighted Lord Kelvin's famous statement that "if you cannot measure, then your knowledge is meagre and unsatisfactory", and the modern saying that "you can't manage what you can't (or don't) measure." Both advance the notion that measurements are indispensable.

I also discussed the origin of the second saying, which is very widely quoted, but rarely attributed to anyone. People sometimes cite Peter Drucker or W. Edwards Deming, but it seems fairly certain that both of those attributions are mistaken.

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Previous posts in this series described the influence of Moore's Law and Wirth's Law on application performance, how to balance hardware capacity and software demand with a systematic approach to performance tuning, and the five fundamental elements of computer system performance.

This post is the second of a small group devoted to the importance of measurements. Kelvin's dictum ("if you cannot measure, then your knowledge is meagre and unsatisfactory"), and the popular saying, "you can't manage what you can't (or don't) measure," each advance the idea that measurements are indispensable.

But such a sweeping claim may not actually be true in every instance, so I am now highlighting some slightly more focused statements about the value of measurements.

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Previous posts in this series described the influence of Moore's Law and Wirth's Law on application performance, how to balance hardware capacity and software demand with a systematic approach to performance tuning, and the five fundamental elements of computer system performance.

Today's post is the first of several that will review insights on the central importance of measurements. Previously I've described how I view measurements as the foundation of all performance management -- see, for example, The ABC's of Measurement Data and my review of Practical Service Level Management.

Today's quote by Lord Kelvin sums up my point of view. Unless you have measured something, your attempts at managing it, and maintaining or improving its performance, will be unscientific at best ...

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Performance Management (SLM) Challenges for Ajax and Rich Internet Applications (RIA's)

In my post on Ajax Wisdom, I reviewed the progress of Ajax against the Gartner Hype Cycle, concluding that Ajax had not yet advanced beyond the Trough of Disillusionment. I referred to Michael Mahemoff's recent post about Ajax concerns as just one piece of evidence.

Michael responded (see the comments) that the mere existence of concerns does not indicate anything, because any viable technology has outstanding problems to be solved. To judge Ajax I should really look at the progress that has already been made in solving problems. So let's do that ...

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A recent post by Tenni Theurer, who works in a performance team at Yahoo!, appeared in the Yahoo! User Interface Blog. The post begins with the claim that ... most of web page performance is affected by front-end engineering, that is, the user interface design and development.

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In a previous post, I discussed some complications of measuring Rich Internet Applications (RIAs). In particular, I concluded that to report useful measurements of the user experience of response times, …

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