What's the reasonable time for generating web page?

Question

I'm working on web app (Rails 3 based). And I really don't like the time it takes to generate the page - depending on the displayed data it takes up to 2.5 and even 4 seconds.

So I just was wondering what is the average reasonable time for generating page in your apps. Saying you check the generation time, e.g. it's 750ms and think "Ok, that should be fine even without caching". Or when you see 1.5sec you think "Oh my God, the user won't wait so long and leave the site"

Answer 1

There's a huge amount of research data regarding the time from query to rendering and user's experience. I'd recommend reading this useit.com article. After all Google integrated page speed in its results for a reason ;)

The 3 response-time limits are the same today as when I wrote about them in 1993 (based on 40-year-old research by human factors pioneers):

• 0.1 seconds gives the feeling of instantaneous response — that is, the outcome feels like it was caused by the user, not the computer. This level of responsiveness is essential to support the feeling of direct manipulation (direct manipulation is one of the key GUI techniques to increase user engagement and control — for more about it, see our Principles of Interface Design seminar).
• 1 second keeps the user's flow of thought seamless. Users can sense a delay, and thus know the computer is generating the outcome, but they still feel in control of the overall experience and that they're moving freely rather than waiting on the computer. This degree of responsiveness is needed for good navigation.
• 10 seconds keeps the user's attention. From 1–10 seconds, users definitely feel at the mercy of the computer and wish it was faster, but they can handle it. After 10 seconds, they start thinking about other things, making it harder to get their brains back on track once the computer finally does respond.

A 10-second delay will often make users leave a site immediately. And even if they stay, it's harder for them to understand what's going on, making it less likely that they'll succeed in any difficult tasks.

As a rule of thumb, think that you always should aim for a balance of optimization time vs time gained. Don't spend days optimizing the hell out of one routine when your images aren't compressed correctly, or your scripts/css not combined. Yes, faster is better, but a 90% gain in generating the page by setting up a smart cache beats a 10% gain after one week tweaking the algorithm.

Also don't look too much into the first-render-time when the framework has to load everything, but use stress-testing, cached or not, to simulate various situations.

Now, some data; some of the latest sites i worked on used DotNetNuke, a huge open-source CMS, and Asp.Net MVC where you nearer to the metal. Average page time with average db queries was 600-700 milliseconds for DotNetNuke. For Asp.net MVC, it's 70-100 milliseconds... Users really like the second one :)