Latency

1 Oct 2007 - 6:15am
7 years ago
6 replies
436 reads
Jens Meiert
2004

Dear IxDA colleagues,

flanking my “vision” of a “latency-free world” [1], I'm interested in your assessment of the impact latency has on any user experience. I know that there is research showing that wait is a quite subjective thing, thus not necessarily having a negative impact, but what chances are there to raise more awareness for that issue? How critical do you judge it?

Best regards,
Jens.

[1] http://meiert.com/en/blog/20071001/the-vision-of-a-latency-free-world/

--
Jens Meiert
http://meiert.com/en/

Comments

1 Oct 2007 - 8:24am
Claude Knaus
2007

Hi Jens,

I rarely feel that I am wasting time when it takes several minutes to
wait. I carry around a book most of the time. In situations where
reading is inconvenient, I think about my pet project.

However, if the expected waiting time is short, like latency on a
mouse click, it is a problem if there is no prompt feedback. It is a
shame that today's operating systems did not adopt real-time
scheduling from operating systems like the Amiga OS. In my opinion,
user interaction imposes real-time constraints on feedback as a
requirement.

-- Claude

On 10/1/07, Jens Meiert <jens.meiert at erde3.com> wrote:
> Dear IxDA colleagues,
>
>
> flanking my "vision" of a "latency-free world" [1], I'm interested in your assessment of the impact latency has on any user experience. I know that there is research showing that wait is a quite subjective thing, thus not necessarily having a negative impact, but what chances are there to raise more awareness for that issue? How critical do you judge it?
>
>
> Best regards,
> Jens.
>
>
> [1] http://meiert.com/en/blog/20071001/the-vision-of-a-latency-free-world/
>
> --
> Jens Meiert
> http://meiert.com/en/
>
>
>
>
> ________________________________________________________________
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>

1 Oct 2007 - 10:20am
Jens Meiert
2004

Claude Knaus wrote:
> However, if the expected waiting time is short, like latency on a
> mouse click, it is a problem if there is no prompt feedback. It is a
> shame that today's operating systems did not adopt real-time
> scheduling from operating systems like the Amiga OS. In my opinion,
> user interaction imposes real-time constraints on feedback as a
> requirement.

True, but rather should /avoiding/ latency be a critical software design principle.

Yishay wrote:
> Gift wrapping is latency. But is it useless? No. we all love our gifts
> wrapped because this is the added value; we like to wait until we are
> allowed to open our gifts.

That's an interesting issue, gifts certainly mean an exception …!

--
Jens Meiert
http://meiert.com/en/

1 Oct 2007 - 10:33am
Claude Knaus
2007

On 10/1/07, Jens Meiert <jens.meiert at erde3.com> wrote:
> Claude Knaus wrote:
> > However, if the expected waiting time is short, like latency on a
> > mouse click, it is a problem if there is no prompt feedback. It is a
> > shame that today's operating systems did not adopt real-time
> > scheduling from operating systems like the Amiga OS. In my opinion,
> > user interaction imposes real-time constraints on feedback as a
> > requirement.
>
> True, but rather should /avoiding/ latency be a critical software design principle.

Both are important. What you are saying is best effort practice. What
I was mentioning was that unbounded waiting (like when my machine
starts to swap in/out memory after a mouse click) is a terrible
experience. At least the window system should continue to remain
responsive.

-- Claude

1 Oct 2007 - 10:37am
Jens Meiert
2004

> > > However, if the expected waiting time is short, like latency on a
> > > mouse click, it is a problem if there is no prompt feedback. It is a
> > > shame that today's operating systems did not adopt real-time
> > > scheduling from operating systems like the Amiga OS. In my opinion,
> > > user interaction imposes real-time constraints on feedback as a
> > > requirement.
> >
> > True, but rather should /avoiding/ latency be a critical software
> > design principle.
>
> Both are important. What you are saying is best effort practice. What
> I was mentioning was that unbounded waiting (like when my machine
> starts to swap in/out memory after a mouse click) is a terrible
> experience. At least the window system should continue to remain
> responsive.

Of course, I didn't want to disagree but rather emphasize the importance to design software so that it induces as few latency as possible.

--
Jens Meiert
http://meiert.com/en/

1 Oct 2007 - 11:23am
Claude Knaus
2007

---------- Forwarded message ----------
From: Claude Knaus <clyde7 at gmail.com>
Date: Oct 1, 2007 6:22 PM
Subject: Re: [IxDA Discuss] Latency
To: Jens Meiert <jens.meiert at erde3.com>

On 10/1/07, Jens Meiert <jens.meiert at erde3.com> wrote:
> > > > However, if the expected waiting time is short, like latency on a
> > > > mouse click, it is a problem if there is no prompt feedback. It is a
> > > > shame that today's operating systems did not adopt real-time
> > > > scheduling from operating systems like the Amiga OS. In my opinion,
> > > > user interaction imposes real-time constraints on feedback as a
> > > > requirement.
> > >
> > > True, but rather should /avoiding/ latency be a critical software
> > > design principle.
> >
> > Both are important. What you are saying is best effort practice. What
> > I was mentioning was that unbounded waiting (like when my machine
> > starts to swap in/out memory after a mouse click) is a terrible
> > experience. At least the window system should continue to remain
> > responsive.
>
> Of course, I didn't want to disagree but rather emphasize the importance to design software so that it induces as few latency as possible.

So, using a real-time system could be a solution for both designer and
engineer. The designer could specify a maximum tolerable latency. I am
only disappointed that real-time technology is not commonly used for
user interfaces.

-- Claude

2 Oct 2007 - 2:41am
Jeroen Arendsen
2007

"Real-time" is not as straightforward as it sounds. For how fast should a computer respond for you to feel like it is 'immediate'? I am studying this problem with regard to gesture recognition. When should the computer respond to a gesture to make it feel 'real-time'. It turns out that it should respond already during the gesture.

Jakob Nielsen has a good deal of info on the matter. Here are the famous rules:

The basic advice regarding response times has been about the same for thirty years [Miller 1968; Card et al. 1991]:

* 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. (more)

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