How long is too long for a script to execute?

Question

What is the max time do you think is acceptable for a web script (PHP for example) to execute before it starts to become an annoyance for the user (on average)? I always thought that if the user has to wait more than 1 second for the page to load (this of course after images and css have been cached..this rule really only applies for subsequent requests) they would start to get annoyed.

Answer 1

Well default limit for a PHP script execution is 30 seconds. If you are just asking from the users perspective then the rule of thumb would be the faster the better...

Answer 2

Anything that takes more than a few seconds of process time should be handled differently, here are some examples

• Cache its output server side
• Run a Cron job that does the processing
• Spawn a faux process with PHP using system()

Answer 3

42 seconds.

Actually, truth is it more comes down to the age and expectations of the user you are catering to. My parents for example, might be much more tolerant of an extended wait, but are also much more likely to press the button again and again, like they will to a crosswalk or elevator button.

That said the real answer is, how long is too long for the user to go without feedback? Even kicking up a quick hourglass logo, or progress bar, can make all the difference in the world for a user. That said, if the service you are providing should be realtime and act like a desktop app, too long is basically "anything perceptible".

So, cop-out answer... it depends. That said, even a "too long" wait, can be overcome by proper UI design and customer interaction.

Answer 4

Take a look at this link:

http://www.simple-talk.com/dotnet/.net-tools/the-cost-of-poor-website-performance/

then just decide the level of frustration your users can reach.

Answer 5

My rule of thumb:

Keep server-side processing under a second in the average case scenario and definitely under 30s in the worst case.

Answer 6

I'd say a couple of seconds before you should call (PHP)ob_flush() and at least send SOMETHING to the client. Otherwise the elevator effect will take over and the user will refresh repeatedly. As for total page load, it doesn't matter as long as you keep the user posted. A progress bar will help with that.

Answer 7

The tried and true strategy is always to manage expectations. Don't make a user second guess you or your application. If, by your benchmarks, the average processing time for a particular page will go beyond, say a 6-second threshold, say so before the user clicks a button. It's much like waiting for a Web site to send you a confirmation e-mail, not knowing when it will arrive, because it was never mentioned that it could take several hours due to traffic beyond the control of the site.

Answer 8

Jacob Nielsen has done some research on this.

• 0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.
• 1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay. Normally, no special feedback is necessary during delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of operating directly on the data.
• 10 seconds is about the limit for keeping the user's attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect.

To serve as inspiration, you could look at how the NetBeans community interpret these values:

1. 0.1 second - navigation and edit actions (e.g. folder expansion, paste in editor, navigation in editor), and painting of all menu bars must finish within this limit
2. 1.0 second - all window and dialog openings must finish within this limit
3. 10 seconds - all actions which are finished later than after 1 second and usually take less than 10 seconds must show some sort of busy indication (e.g. hour glass cursor or "please wait..." text); all actions taking longer than this limit are required to provide progress bar using Progress APIs

Answer 9

From my experience, you should give the user at least some notice if something's gonna take more than few seconds. Possibly use AJAX with some fancy animation and notice like "This is gonna take a while".

If you cannot use AJAX and your PHP script is taking, for example, more than 10 seconds to load, try to think about a way to optimize it.