I am currently in the process of performance tuning a Web Application and have been doing some research into what is considered ‘Good’ performance. I know this depends often on the application being built, target audience, plus many other factors, but wondered if people follow a general set of rules.
There is always the risk with tuning that there is no end to the job, and one should at some point have to make a call one when to stop, but when is this? When can we be happy the job is done?
To kick off the discussion, I have been using the following rules, based on the Jakob Nielsen report (http://www.useit.com/alertbox/response-times.html), which says
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.Even a few
seconds’ delay is enough to create an
unpleasant user experience. Users are
no longer in control, and they’re
consciously annoyed by having to wait
for the computer. Thus, with repeated
short delays, users will give up
unless they’re extremely committed to
completing the task. The result? You
can easily lose half your sales (to
those less-committed customers) simply
because your site is a few seconds too
slow for each page.slow for each page.
The rules are pretty much sensible. Indeed one should aim to have response times in 1 second or less but sometimes the processing will really take longer (bad design, slow machines, waiting on 3rd parties, intense data processing, etc). In this case one can use various tips & tricks to improve the user experience:
etc etc